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119 results on '"Xavier Waintal"'

1. Opening the Black Box inside Grover’s Algorithm

Author

E. M. Stoudenmire and Xavier Waintal

Subjects
Physics, QC1-999
Abstract

Grover’s algorithm is one of the primary algorithms offered as evidence that quantum computers can provide an advantage over classical computers. It involves an “oracle” (external quantum subroutine), which must be specified for a given application and whose internal structure is not part of the formal scaling of the quadratic quantum speedup guaranteed by the algorithm. Grover’s algorithm also requires exponentially many calls to the quantum oracle (approximately sqrt[2^{n}] calls where n is the number of qubits) to succeed, raising the question of its implementation on both noisy and error-corrected quantum computers. In this work, we construct a quantum-inspired algorithm executable on a classical computer that performs Grover’s task in a linear number of calls to (simulations of) the oracle—an exponentially smaller number than Grover’s algorithm—and demonstrate this algorithm explicitly for Boolean satisfiability problems. The complexity of our algorithm depends on the cost to simulate the oracle once, which may or may not be exponential, depending on its internal structure. Indeed, Grover’s algorithm does not have an a priori quantum speedup as soon as one is given access to the “source code” of the oracle, which may reveal an internal structure of the problem. Our findings illustrate this point explicitly, as our algorithm exploits the structure of the quantum circuit used to program the quantum computer to speed up the search. There are still problems where Grover’s algorithm would provide an asymptotic speedup if it could be run accurately for large enough sizes. Our quantum-inspired algorithm provides lower bounds, in terms of the quantum-circuit complexity, for the quantum hardware to beat classical approaches for these problems. These estimates, combined with the unfavorable scaling of the success probability of Grover’s algorithm, which in the presence of noise decays as the exponential of the exponential of the number of qubits, makes a practical speedup unrealistic even under extremely optimistic assumptions of the evolution of both hardware quality and availability.

Published
2024
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2. Density-Matrix Renormalization Group Algorithm for Simulating Quantum Circuits with a Finite Fidelity

Author

Thomas Ayral, Thibaud Louvet, Yiqing Zhou, Cyprien Lambert, E. Miles Stoudenmire, and Xavier Waintal

Subjects
Physics, QC1-999, Computer software, QA76.75-76.765
Abstract

We develop a density-matrix renormalization group (DMRG) algorithm for the simulation of quantum circuits. This algorithm can be seen as the extension of the time-dependent DMRG from the usual situation of Hermitian Hamiltonian matrices to quantum circuits defined by unitary matrices. For small circuit depths, the technique is exact and equivalent to other matrix product state–based techniques. For larger depths, it becomes approximate in exchange for an exponential speed up in computational time. Like an actual quantum computer, the quality of the DMRG results is characterized by a finite fidelity. However, unlike a quantum computer, the fidelity depends strongly on the quantum circuit considered. For the most difficult possible circuit for this technique, the so-called “quantum supremacy” benchmark of Google LLC [Arute et al., Nature 574, 505 (2019)], we find that the DMRG algorithm can generate bit strings of the same quality as the seminal Google experiment on a single computing core. For a more structured circuit used for combinatorial optimization (quantum approximate optimization algorithm), we find a drastic improvement of the DMRG results with error rates dropping by a factor of 100 compared with random quantum circuits. Our results suggest that the current bottleneck of quantum computers is their fidelities rather than the number of qubits.

Published
2023
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3. Unveiling the charge distribution of a GaAs-based nanoelectronic device: A large experimental dataset approach

Author

Eleni Chatzikyriakou, Junliang Wang, Lucas Mazzella, Antonio Lacerda-Santos, Maria Cecilia da Silva Figueira, Alex Trellakis, Stefan Birner, Thomas Grange, Christopher Bäuerle, and Xavier Waintal

Subjects
Physics, QC1-999
Abstract

In quantum nanoelectronics, numerical simulations have become a ubiquitous tool. Yet the comparison with experiments is often done at a qualitative level or restricted to a single device with a handful of fitting parameters. In this work, we assess the predictive power of these simulations by comparing the results of a single model with a large experimental dataset of 110 devices with 48 different geometries. The devices are quantum point contacts of various shapes and sizes made with electrostatic gates deposited on top of a high mobility GaAs/AlGaAs two-dimensional electron gas. We study the pinch-off voltages applied on the gates to deplete the two-dimensional electron gas in various spatial positions. We argue that the pinch-off voltages are a very robust signature of the charge distribution in the device. The large experimental dataset allows us to critically review the modeling and arrive at a robust one-parameter model that can be calibrated in situ, a crucial step for making predictive simulations.

Published
2022
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4. Learning Feynman Diagrams with Tensor Trains

Author

Yuriel Núñez Fernández, Matthieu Jeannin, Philipp T. Dumitrescu, Thomas Kloss, Jason Kaye, Olivier Parcollet, and Xavier Waintal

Subjects
Physics, QC1-999
Abstract

We use tensor network techniques to obtain high-order perturbative diagrammatic expansions for the quantum many-body problem at very high precision. The approach is based on a tensor train parsimonious representation of the sum of all Feynman diagrams, obtained in a controlled and accurate way with the tensor cross interpolation algorithm. It yields the full time evolution of physical quantities in the presence of any arbitrary time-dependent interaction. Our benchmarks on the Anderson quantum impurity problem, within the real-time nonequilibrium Schwinger-Keldysh formalism, demonstrate that this technique supersedes diagrammatic quantum Monte Carlo by orders of magnitude in precision and speed, with convergence rates 1/N^{2} or faster, where N is the number of function evaluations. The method also works in parameter regimes characterized by strongly oscillatory integrals in high dimension, which suffer from a catastrophic sign problem in quantum Monte Carlo calculations. Finally, we also present two exploratory studies showing that the technique generalizes to more complex situations: a double quantum dot and a single impurity embedded in a two-dimensional lattice.

Published
2022
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5. Sound-driven single-electron transfer in a circuit of coupled quantum rails

Author

Shintaro Takada, Hermann Edlbauer, Hugo V. Lepage, Junliang Wang, Pierre-André Mortemousque, Giorgos Georgiou, Crispin H. W. Barnes, Christopher J. B. Ford, Mingyun Yuan, Paulo V. Santos, Xavier Waintal, Arne Ludwig, Andreas D. Wieck, Matias Urdampilleta, Tristan Meunier, and Christopher Bäuerle

Subjects
Science
Abstract

Surface acoustic waves are promising candidates to convey flying qubits through semiconductor circuits. The authors investigate the central building block of such a circuit in an experiment and present a route to realise quantum logic gates with flying electrons that are surfing on a sound-wave.

Published
2019
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6. Unveiling the bosonic nature of an ultrashort few-electron pulse

Author

Gregoire Roussely, Everton Arrighi, Giorgos Georgiou, Shintaro Takada, Martin Schalk, Matias Urdampilleta, Arne Ludwig, Andreas D. Wieck, Pacome Armagnat, Thomas Kloss, Xavier Waintal, Tristan Meunier, and Christopher Bäuerle

Subjects
Science
Abstract

Electronic excitations in low-dimensional quantum nanoelectronic devices are collective waves that are strongly affected by the Coulomb interaction. Here, the authors demonstrate that they are able to prepare these collective excitations down to the single electron level and control their propagation.

Published
2018
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7. Low-symmetry topological materials for large charge-to-spin interconversion: The case of transition metal dichalcogenide monolayers

Author

Marc Vila, Chuang-Han Hsu, Jose H. Garcia, L. Antonio Benítez, Xavier Waintal, Sergio O. Valenzuela, Vitor M. Pereira, and Stephan Roche

Subjects
Physics, QC1-999
Abstract

The spin polarization induced by the spin Hall effect (SHE) in thin films typically points out of the plane. This is rooted on the specific symmetries of traditionally studied systems, not in a fundamental constraint. Recently, experiments on few-layer MoTe_{2} and WTe_{2} showed that the reduced symmetry of these strong spin-orbit coupling materials enables a new form of canted spin Hall effect, characterized by concurrent in-plane and out-of-plane spin polarizations. Here, through quantum transport calculations on realistic device geometries, including disorder, we predict a very large gate-tunable SHE figure of merit λ_{s}θ_{xy}≈1–50 nm in MoTe_{2} and WTe_{2} monolayers that significantly exceeds values of conventional SHE materials. This stems from a concurrent long spin diffusion length (λ_{s}) and charge-to-spin interconversion efficiency as large as θ_{xy}≈80%, originating from momentum-invariant (persistent) spin textures together with large spin Berry curvature along the Fermi contour, respectively. Generalization to other materials and specific guidelines for unambiguous experimental confirmation are proposed, paving the way toward exploiting such phenomena in spintronic devices. These findings vividly emphasize how crystal symmetry and electronic topology can govern the intrinsic SHE and spin relaxation, and how they may be exploited to broaden the range and efficiency of spintronic materials and functionalities.

Published
2021
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8. Tkwant: a software package for time-dependent quantum transport

Author

Thomas Kloss, Joseph Weston, Benoit Gaury, Benoit Rossignol, Christoph Groth, and Xavier Waintal

Subjects
quantum nanoelectronics, non-equilibrium, real-time dynamics, tight binding, numerical simulation, Science, Physics, QC1-999
Abstract

T kwant is a Python package for the simulation of quantum nanoelectronics devices to which external time-dependent perturbations are applied. T kwant is an extension of the kwant package ( https://kwant-project.org/ ) and can handle the same types of systems: discrete tight-binding-like models that consist of an arbitrary central region connected to semi-infinite electrodes. The problem is genuinely many-body even in the absence of interactions and is treated within the non-equilibrium Keldysh formalism. Examples of Tkwant applications include the propagation of plasmons generated by voltage pulses, propagation of excitations in the quantum Hall regime, spectroscopy of Majorana fermions in semiconducting nanowires, current-induced skyrmion motion in spintronic devices, multiple Andreev reflection, Floquet topological insulators, thermoelectric effects, and more. The code has been designed to be easy to use and modular. T kwant is free software distributed under a BSD license and can be found at https://tkwant.kwant-project.org/ .

Published
2021
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9. What Limits the Simulation of Quantum Computers?

Author

Yiqing Zhou, E. Miles Stoudenmire, and Xavier Waintal

Subjects
Physics, QC1-999
Abstract

An ultimate goal of quantum computing is to perform calculations beyond the reach of any classical computer. It is therefore imperative that useful quantum computers be very difficult to simulate classically, otherwise classical computers could be used for the applications envisioned for the quantum ones. Perfect quantum computers are unarguably exponentially difficult to simulate: the classical resources required grow exponentially with the number of qubits N or the depth D of the circuit. This difficulty has triggered recent experiments on deep, random circuits that aim to demonstrate that quantum devices may already perform tasks beyond the reach of classical computing. These real quantum computing devices, however, suffer from many sources of decoherence and imprecision which limit the degree of entanglement that can actually be reached to a fraction of its theoretical maximum. They are characterized by an exponentially decaying fidelity F∼(1-ε)^{ND} with an error rate ε per operation as small as ≈1% for current devices with several dozen qubits or even smaller for smaller devices. In this work, we provide new insight on the computing capabilities of real quantum computers by demonstrating that they can be simulated at a tiny fraction of the cost that would be needed for a perfect quantum computer. Our algorithms compress the representations of quantum wave functions using matrix product states, which are able to capture states with low to moderate entanglement very accurately. This compression introduces a finite error rate ε so that the algorithms closely mimic the behavior of real quantum computing devices. The computing time of our algorithm increases only linearly with N and D in sharp contrast with exact simulation algorithms. We illustrate our algorithms with simulations of random circuits for qubits connected in both one- and two-dimensional lattices. We find that ε can be decreased at a polynomial cost in computing power down to a minimum error ε_{∞}. Getting below ε_{∞} requires computing resources that increase exponentially with ε_{∞}/ε. For a two-dimensional array of N=54 qubits and a circuit with control-Z gates, error rates better than state-of-the-art devices can be obtained on a laptop in a few hours. For more complex gates such as a swap gate followed by a controlled rotation, the error rate increases by a factor 3 for similar computing time. Our results suggest that, despite the high fidelity reached by quantum devices, only a tiny fraction (∼10^{-8}) of the system Hilbert space is actually being exploited.

Published
2020
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10. Pushing the limit of quantum transport simulations

Author

Mathieu Istas, Christoph Groth, and Xavier Waintal

Subjects
Physics, QC1-999
Abstract

Simulations of quantum transport in coherent conductors have evolved into mature techniques that are used in fields of physics ranging from electrical engineering to quantum nanoelectronics and material science. The most efficient general-purpose algorithms have a computational cost that scales as L^{6,⋯,7} in three dimensions (L: length of the device), which on the one hand is a substantial improvement over older algorithms, but on the other hand still severely restricts the size of the simulation domain, limiting the usefulness of simulations through strong finite-size effects. Here we present a class of algorithms that, for certain systems, allows us to directly access the thermodynamic limit. Our approach, based on the Green's function formalism for discrete models, targets systems that are mostly invariant by translation, i.e., invariant by translation up to a finite number of orbitals and/or quasi-one-dimensional electrodes and/or the presence of edges or surfaces. Our approach is based on an automatic calculation of the poles and residues of series expansions of the Green's function in momentum space. This expansion allows us to integrate analytically in one momentum variable. We illustrate our algorithms with several applications: devices with graphene electrodes that consist of half an infinite sheet, Friedel oscillation calculations of infinite two-dimensional systems in the presence of an impurity, quantum spin Hall physics in the presence of an edge, and the surface of a Weyl semimetal in the presence of impurities and electrodes connected to the surface. In this last example, we study the conduction through the Fermi arcs of the topological material and its resilience to the presence of disorder. Our approach provides a practical route for simulating three-dimensional bulk systems or surfaces as well as other setups that have so far remained elusive.

Published
2019
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11. Reconstructing Nonequilibrium Regimes of Quantum Many-Body Systems from the Analytical Structure of Perturbative Expansions

Author

Corentin Bertrand, Serge Florens, Olivier Parcollet, and Xavier Waintal

Subjects
Physics, QC1-999
Abstract

We propose a systematic approach to the nonequilibrium dynamics of strongly interacting many-body quantum systems, building upon the standard perturbative expansion in the Coulomb interaction. High-order series are derived from the Keldysh version of the determinantal diagrammatic quantum Monte Carlo algorithm, and the reconstruction beyond the weak-coupling regime of physical quantities is obtained by considering them as analytic functions of a complex-valued interaction U. Our advances rely on two crucial ingredients: (i) a conformal change of variable, based on the approximate location of the singularities of these functions in the complex U plane, and (ii) a Bayesian inference technique, that takes into account additional known nonperturbative relations, in order to control the amplification of noise occurring at large U. This general methodology is applied to the strongly correlated Anderson quantum impurity model and is thoroughly tested both in and out of equilibrium. In the situation of a finite voltage bias, our method is able to extend previous studies, by bridging with the regime of unitary conductance and by dealing with energy offsets from particle-hole symmetry. We also confirm the existence of a voltage splitting of the impurity density of states and find that it is tied to a nontrivial behavior of the nonequilibrium distribution function. Beyond impurity problems, our approach could be directly applied to Hubbard-like models, as well as other types of expansions.

Published
2019
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12. Kwant: a software package for quantum transport

Author

Christoph W Groth, Michael Wimmer, Anton R Akhmerov, and Xavier Waintal

Subjects
quantum transport, tight-binding model, numerical simulation, 73.23.-b, 72.20.-i, 72.15.Eb, Science, Physics, QC1-999
Abstract

Kwant is a Python package for numerical quantum transport calculations. It aims to be a user-friendly, universal, and high-performance toolbox for the simulation of physical systems of any dimensionality and geometry that can be described by a tight-binding model. Kwant has been designed such that the natural concepts of the theory of quantum transport (lattices, symmetries, electrodes, orbital/spin/electron-hole degrees of freedom) are exposed in a simple and transparent way. Defining a new simulation setup is very similar to describing the corresponding mathematical model. Kwant offers direct support for calculations of transport properties (conductance, noise, scattering matrix), dispersion relations, modes, wave functions, various Greenʼs functions, and out-of-equilibrium local quantities. Other computations involving tight-binding Hamiltonians can be implemented easily thanks to its extensible and modular nature. Kwant is free software available at http://kwant-project.org/ .

Published
2014
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13. Graphene-Based Heterojunction between Two Topological Insulators

Author

Oleksii Shevtsov, Pierre Carmier, Cyril Petitjean, Christoph Groth, David Carpentier, and Xavier Waintal

Subjects
Physics, QC1-999
Abstract

Quantum Hall (QH) and quantum spin Hall (QSH) phases have very different edge states and, when going from one phase to the other, the direction of one edge state must be reversed. We study this phenomenon in graphene in the presence of a strong perpendicular magnetic field on top of a spin-orbit (SO)-induced QSH phase. We show that, below the SO gap, the QSH phase is virtually unaffected by the presence of the magnetic field. Above the SO gap, the QH phase is restored. An electrostatic gate placed on top of the system allows the creation of a QSH-QH junction which is characterized by the existence of a spin-polarized chiral state, propagating along the topological interface. We find that such a setup naturally provides an extremely sensitive spin-polarized current switch which could pave the way to novel spin-based electronic devices.

Published
2012
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14. Unveiling the charge distribution of a GaAs-based nanoelectronic device: A large experimental data-set approach

Author

Eleni Chatzikyriakou, Junliang Wang, Lucas Mazzella, Antonio Lacerda-Santos, Maria Cecilia da Silva Figueira, Alex Trellakis, Stefan Birner, Thomas Grange, Christopher Bäuerle, Xavier Waintal, Laboratory of Quantum Theory (GT), PHotonique, ELectronique et Ingénierie QuantiqueS (PHELIQS), Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes (UGA)-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes (UGA), Circuits électroniques quantiques Alpes (NEEL - QuantECA), Institut Néel (NEEL), Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Nextnano GmbH, and Nextnano Lab

Subjects
[PHYS]Physics [physics], [SPI]Engineering Sciences [physics], Condensed Matter - Mesoscale and Nanoscale Physics, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), General Physics and Astronomy, FOS: Physical sciences
Abstract

In quantum nanoelectronics, numerical simulations have become an ubiquitous tool. Yet the comparison with experiments is often done at a qualitative level or restricted to a single device with a handful of fitting parameters. In this work, we assess the predictive power of these simulations by comparing the results of a single model with a large experimental data set of 110 devices with 48 different geometries. The devices are quantum point contacts of various shapes and sizes made with electrostatic gates deposited on top of a high mobility GaAs/GaAlAs two dimensional electron gas. We study the pinch-off voltages applied on the gates to deplete the two-dimensional electron gas in various spatial positions. We argue that the pinch-off voltages are a very robust signature of the charge distribution in the device. The large experimental data set allows us to critically review the modeling and arrive at a robust one-parameter model that can be calibrated in situ, a crucial step for making predictive simulations., 33 pages, 16 figures, journal submission, corrected author name typo, added references, corrected visibility of appendix table, to appear in Physical Review Research

Published
2022

15. Coulomb-mediated antibunching of an electron pair surfing on sound

Author

Junliang Wang, Hermann Edlbauer, Aymeric Richard, Shunsuke Ota, Wanki Park, Jeongmin Shim, Arne Ludwig, Andreas D. Wieck, Heung-Sun Sim, Matias Urdampilleta, Tristan Meunier, Tetsuo Kodera, Nobu-Hisa Kaneko, Hermann Sellier, Xavier Waintal, Shintaro Takada, Christopher Bäuerle, Circuits électroniques quantiques Alpes (NEEL - QuantECA), Institut Néel (NEEL), Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Tokyo Institute of Technology [Tokyo] (TITECH), National Institute of Advanced Industrial Science and Technology (AIST), Korea Advanced Institute of Science and Technology (KAIST), Ruhr-Universität Bochum [Bochum], Nano-Electronique Quantique et Spectroscopie (NEEL - QuNES), PHotonique, ELectronique et Ingénierie QuantiqueS (PHELIQS), Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes (UGA), Laboratory of Quantum Theory (GT), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes (UGA)-Institut de Recherche Interdisciplinaire de Grenoble (IRIG)

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Biomedical Engineering, FOS: Physical sciences, General Materials Science, Bioengineering, Electrical and Electronic Engineering, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], Condensed Matter Physics, Atomic and Molecular Physics, and Optics
Abstract

International audience; Electron flying qubits are envisioned as potential information link within a quantum computer, but also promise -- alike photonic approaches -- a self-standing quantum processing unit. In contrast to its photonic counterpart, electron-quantum-optics implementations are subject to Coulomb interaction, which provide a direct route to entangle the orbital or spin degree of freedom. However, the controlled interaction of flying electrons at the single particle level has not yet been established experimentally. Here we report antibunching of a pair of single electrons that is synchronously shuttled through a circuit of coupled quantum rails by means of a surface acoustic wave. The in-flight partitioning process exhibits a reciprocal gating effect which allows us to ascribe the observed repulsion predominantly to Coulomb interaction. Our single-shot experiment marks an important milestone on the route to realise a controlled-phase gate for in-flight quantum manipulations.

Published
2022
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16. Le problème à N corps qui se cache derrière l’ordinateur quantique

Author

Xavier Waintal, Laboratory of Quantum Theory (GT), PHotonique, ELectronique et Ingénierie QuantiqueS (PHELIQS), Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes (UGA)-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes (UGA)

Subjects
Physics, [PHYS]Physics [physics], [SPI]Engineering Sciences [physics], General Medicine
Abstract

Le concept d’ordinateur quantique recouvre deux réalités très différentes. Il y a d’une part de très belles expériences de physique qui se basent sur des systèmes appartenant à la nanoélectronique quantique (supraconducteurs, semi-conducteurs), l’optique quantique ou la physique atomique. D’autre part, il y a une promesse, celle que ces systèmes puissent être décrits avec grande précision par un modèle mathématique très épuré. Ce modèle est une instance d’un problème plus général, le problème quantique à N corps, que les physiciens étudient depuis des dizaines d’années. Dans cet article, nous verrons qu’envisager l’ordinateur quantique sous l’angle du problème quantique à N corps donne un éclairage utile pour comprendre à quoi il pourrait servir ou les diffi cultés liées à son élaboration.

Published
2021

17. Spin Hall effect and spin absorption in ferromagnetic materials

Author

Ariel Brenac, Cecile Grezes, Alain Marty, Jean-François Jacquot, Van Tuong Pham, Xavier Waintal, Patrick Warin, Laurent Vila, Jean-Philippe Attané, Sara Varotto, Yu Fu, Daria Gusakova, Maxen Cosset-Cheneau, Vincent Baltz, Paul Noël, Henri Jaffrès, Serge Gambarelli, SPINtronique et TEchnologie des Composants (SPINTEC), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes (UGA), Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), THALES-Centre National de la Recherche Scientifique (CNRS), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich), SYstèmes Moléculaires et nanoMatériaux pour l’Energie et la Santé (SYMMES), Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), PHotonique, ELectronique et Ingénierie QuantiqueS (PHELIQS), Institut de Recherche Interdisciplinaire de Grenoble (IRIG), and THALES [France]-Centre National de la Recherche Scientifique (CNRS)

Subjects
Materials science, Condensed matter physics, Spin valve, Conductance, 02 engineering and technology, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, 021001 nanoscience & nanotechnology, 01 natural sciences, Condensed Matter::Materials Science, Paramagnetism, Magnetization, Ferromagnetism, 0103 physical sciences, Spin Hall effect, Condensed Matter::Strongly Correlated Electrons, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], 010306 general physics, 0210 nano-technology, Absorption (electromagnetic radiation), ComputingMilieux_MISCELLANEOUS, Spin-½
Abstract

The link between magnetization and Spin Hall Effect (SHE) has remained mostly unclear for now. In a first part of this contribution, we study oh the presence of the magnetization affect the SHE, by performing in the weak ferromagnet NiCu Spin Pumping-FMR measurements across the ferromagnetic / paramagnetic critical temperature. We show that the high spin Hall effects which can be obtained in 3d ferromagnets seems to be independent of the magnetic phase. In a second part, we show that the spin absorption process in a ferromagnetic material depends on the spin orientation relative to the magnetization. Using a ferromagnet to absorb the pure spin current created within a lateral spin valve, we evidence and quantify a sizable orientation dependence of the spin absorption in Co, CoFe, and NiFe. These experiments allow us to determine the spin-mixing conductance, an elusive but fundamental parameter of the spin-dependent transport.

Published
2021

18. Measurement of the Spin Absorption Anisotropy in Lateral Spin Valves

Author

J. P. Attané, D. Gusakova, Henri Jaffrès, Maxen Cosset-Cheneau, Laurent Vila, Van Tuong Pham, Xavier Waintal, Alain Marty, G. Zahnd, C. Grèzes, SPINtronique et TEchnologie des Composants (SPINTEC), Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS), PHotonique, ELectronique et Ingénierie QuantiqueS (PHELIQS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes (UGA), Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), THALES-Centre National de la Recherche Scientifique (CNRS), ANR-17-CE24-0026,OISO,SPINORBITRONIQUE A BASE D'OXYDES.(2017), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), and THALES [France]-Centre National de la Recherche Scientifique (CNRS)

Subjects
Condensed Matter - Materials Science, Materials science, Condensed matter physics, Condensed Matter - Mesoscale and Nanoscale Physics, Spin valve, General Physics and Astronomy, Conductance, Materials Science (cond-mat.mtrl-sci), FOS: Physical sciences, 01 natural sciences, Magnetization, Condensed Matter::Materials Science, Ferromagnetism, 0103 physical sciences, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Spin diffusion, Condensed Matter::Strongly Correlated Electrons, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], 010306 general physics, Anisotropy, Absorption (electromagnetic radiation), Spin-½
Abstract

International audience; The spin absorption process in a ferromagnetic material depends on the spin orientation relative to the magnetization. Using a ferromagnet to absorb the pure spin current created within a lateral spin valve, we evidence and quantify a sizable orientation dependence of the spin absorption in Co, CoFe, and NiFe. These experiments allow us to determine the spin-mixing conductance, an elusive but fundamental parameter of the spin-dependent transport. We show that the obtained values cannot be understood within a model considering only the Larmor, transverse decoherence, and spin diffusion lengths, and rather suggest that the spin-mixing conductance is actually limited by the Sharvin conductance.

Published
2021

19. Quantum Quasi-Monte Carlo Technique for Many-Body Perturbative Expansions

Author

Philipp T. Dumitrescu, Corentin Bertrand, Bill Triggs, Xavier Waintal, Marjan Maček, Olivier Parcollet, PHotonique, ELectronique et Ingénierie QuantiqueS (PHELIQS), Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes (UGA), Flatiron Institute, Simons Foundation, Données, Apprentissage et Optimisation (DAO), Laboratoire Jean Kuntzmann (LJK), Institut National de Recherche en Informatique et en Automatique (Inria)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA)-Institut National de Recherche en Informatique et en Automatique (Inria)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Institut de Physique Théorique - UMR CNRS 3681 (IPHT), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Laboratory of Quantum Theory (GT), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes (UGA)-Institut de Recherche Interdisciplinaire de Grenoble (IRIG)

Subjects
Physics, Condensed Matter - Mesoscale and Nanoscale Physics, Strongly Correlated Electrons (cond-mat.str-el), Monte Carlo method, FOS: Physical sciences, General Physics and Astronomy, Orders of magnitude (numbers), Ridge (differential geometry), 01 natural sciences, Condensed Matter - Strongly Correlated Electrons, Orders of magnitude (time), [PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph], [STAT.ML]Statistics [stat]/Machine Learning [stat.ML], Quantum dot, 0103 physical sciences, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Perturbation theory (quantum mechanics), Statistical physics, Quasi-Monte Carlo method, Perturbation theory, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], [SPI.NANO]Engineering Sciences [physics]/Micro and nanotechnologies/Microelectronics, 010306 general physics, Scaling, Quantum
Abstract

High order perturbation theory has seen an unexpected recent revival for controlled calculations of quantum many-body systems, even at strong coupling. We adapt integration methods using low-discrepancy sequences to this problem. They greatly outperform state-of-the-art diagrammatic Monte Carlo. In practical applications, we show speed-ups of several orders of magnitude with scaling as fast as $1/N$ in sample number $N$; parametrically faster than $1/\sqrt{N}$ in Monte Carlo. We illustrate our technique with a solution of the Kondo ridge in quantum dots, where it allows large parameter sweeps., Comment: 16 pages; 12 figures; v2. updates title and text to reflect published version; expands discussion, adds additional appendices, corrects typos

Published
2020

20. Low-symmetry topological materials for large charge-to-spin interconversion: The case of transition metal dichalcogenide monolayers

Author

Marc Vila, Chuang-Han Hsu, Jose H. Garcia, L. Antonio Benítez, Xavier Waintal, Sergio O. Valenzuela, Vitor M. Pereira, Stephan Roche, European Commission, Ministerio de Ciencia, Innovación y Universidades (España), Generalitat de Catalunya, National Research Foundation Singapore, ICN2 - Institut Catala de Nanociencia i Nanotecnologia (ICN2), Universitat Autònoma de Barcelona (UAB), National University of Singapore (NUS), Laboratory of Quantum Theory (GT), PHotonique, ELectronique et Ingénierie QuantiqueS (PHELIQS), Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes (UGA)-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes (UGA), and Institució Catalana de Recerca i Estudis Avançats (ICREA)

Subjects
[PHYS]Physics [physics], Spin hall effect, Condensed Matter - Mesoscale and Nanoscale Physics, Topological materials, Thin-films, Interconversions, FOS: Physical sciences, 02 engineering and technology, Spin-polarization, 021001 nanoscience & nanotechnology, 01 natural sciences, Transition metal dichalcogenides (TMD), Transition metal dichalcogenides, New forms, Out-of-plane, [SPI]Engineering Sciences [physics], Mesoscale and Nanoscale Physics (cond-mat.mes-hall), 0103 physical sciences, Spin-orbit couplings, Condensed Matter::Strongly Correlated Electrons, Coupling materials, 010306 general physics, 0210 nano-technology, Fundamental constraints
Abstract

The spin polarization induced by the spin Hall effect (SHE) in thin films typically points out of the plane. This is rooted on the specific symmetries of traditionally studied systems, not in a fundamental constraint. Recently, experiments on few-layer ${\rm MoTe}_2$ and ${\rm WTe}_2$ showed that the reduced symmetry of these strong spin-orbit coupling materials enables a new form of {\it canted} spin Hall effect, characterized by concurrent in-plane and out-of-plane spin polarizations. Here, through quantum transport calculations on realistic device geometries, including disorder, we predict a very large gate-tunable SHE figure of merit $\lambda_s\theta_{xy}\sim 1\text{--}50$ nm in ${\rm MoTe}_2$ and ${\rm WTe}_2$ monolayers that significantly exceeds values of conventional SHE materials. This stems from a concurrent long spin diffusion length ($\lambda_s$) and charge-to-spin interconversion efficiency as large as $\theta_{xy} \approx 80$\%, originating from momentum-invariant (persistent) spin textures together with large spin Berry curvature along the Fermi contour, respectively. Generalization to other materials and specific guidelines for unambiguous experimental confirmation are proposed, paving the way towards exploiting such phenomena in spintronic devices. These findings vividly emphasize how crystal symmetry and electronic topology can govern the intrinsic SHE and spin relaxation, and how they may be exploited to broaden the range and efficiency of spintronic materials and functionalities., Comment: Published version, Phys. Rev. Reserach

Published
2020

21. Nonlocal Spin Dynamics in the Crossover from Diffusive to Ballistic Transport

Author

Marc Vila, Xavier Waintal, Stephen R. Power, Jose H. Garcia, Aron W. Cummings, Stephan Roche, Christoph Groth, ICN2 - Institut Catala de Nanociencia i Nanotecnologia (ICN2), Universitat Autònoma de Barcelona (UAB), Laboratory of Quantum Theory (GT), PHotonique, ELectronique et Ingénierie QuantiqueS (PHELIQS), Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes (UGA)-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes (UGA), Fundación 'la Caixa', Irish Research Council, Agence Nationale de la Recherche (France), European Commission, Generalitat de Catalunya, Ministerio de Ciencia, Innovación y Universidades (España), and Agencia Estatal de Investigación (España)

Subjects
Crossover, Spin valve, FOS: Physical sciences, General Physics and Astronomy, Theoretical framework, Two-dimensional materials, Spin manipulation, 01 natural sciences, law.invention, [SPI]Engineering Sciences [physics], Fabrication technique, Quantum simulations, law, Ballistic conduction, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), 0103 physical sciences, Spin-diffusion length, 010306 general physics, Quantum, Spin-½, Physics, [PHYS]Physics [physics], Condensed Matter - Materials Science, Condensed Matter - Mesoscale and Nanoscale Physics, Condensed matter physics, Graphene, Nonlocal spin valves, Materials Science (cond-mat.mtrl-sci), Charge (physics), Ballistic transports, Spin diffusion, Condensed Matter::Strongly Correlated Electrons
Abstract

Improved fabrication techniques have enabled the possibility of ballistic transport and unprecedented spin manipulation in ultraclean graphene devices. Spin transport in graphene is typically probed in a nonlocal spin valve and is analyzed using spin diffusion theory, but this theory is not necessarily applicable when charge transport becomes ballistic or when the spin diffusion length is exceptionally long. Here, we study these regimes by performing quantum simulations of graphene nonlocal spin valves. We find that conventional spin diffusion theory fails to capture the crossover to the ballistic regime as well as the limit of long spin diffusion length. We show that the latter can be described by an extension of the current theoretical framework. Finally, by covering the whole range of spin dynamics, our study opens a new perspective to predict and scrutinize spin transport in graphene and other two-dimensional material-based ultraclean devices., M. V. acknowledges support from “La Caixa” Foundation. S. R. P. acknowledges funding from the Irish Research Council under the Laureate awards programme. X. W. acknowledges the ANR GRANSPORT funding. All authors were supported by the European Union Horizon 2020 research and innovation programme under Grant Agreement No. 785219 (Graphene Flagship). ICN2 is funded by the CERCA Programme/Generalitat de Catalunya, and is supported by the Severo Ochoa program from Spanish MINECO (Grant No. SEV-2017-0706).

Published
2020

22. Canted persistent spin texture and quantum spin hall effect in WTe2

Author

Jose H. Garcia, Marc Vila, Chuang-Han Hsu, Stephan Roche, Vitor M. Pereira, Xavier Waintal, Fundación 'la Caixa', National University of Singapore, Agence Nationale de la Recherche (France), European Commission, Generalitat de Catalunya, Agencia Estatal de Investigación (España), Ministerio de Ciencia, Innovación y Universidades (España), National Research Foundation Singapore, ICN2 - Institut Catala de Nanociencia i Nanotecnologia (ICN2), Universitat Autònoma de Barcelona (UAB), National University of Singapore (NUS), Laboratory of Quantum Theory (GT), PHotonique, ELectronique et Ingénierie QuantiqueS (PHELIQS), Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes (UGA)-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes (UGA)

Subjects
Physics, [PHYS]Physics [physics], Condensed matter physics, Spin polarization, General Physics and Astronomy, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, 01 natural sciences, Hall conductivity, Quantization (physics), [SPI]Engineering Sciences [physics], Quantum spin Hall effect, 0103 physical sciences, Monolayer, Condensed Matter::Strongly Correlated Electrons, 010306 general physics, Low symmetry, Spin (physics), Quantum
Abstract

We report an unconventional quantum spin Hall phase in the monolayer WTe2, which exhibits hitherto unknown features in other topological materials. The low symmetry of the structure induces a canted spin texture in the yz plane, which dictates the spin polarization of topologically protected boundary states. Additionally, the spin Hall conductivity gets quantized (2e2/h) with a spin quantization axis parallel to the canting direction. These findings are based on large-scale quantum simulations of the spin Hall conductivity tensor and nonlocal resistances in multiprobe geometries using a realistic tight-binding model elaborated from first-principle methods. The observation of this canted quantum spin Hall effect, related to the formation of topological edge states with nontrivial spin polarization, demands for specific experimental design and suggests interesting alternatives for manipulating spin information in topological materials., M. V. acknowledges support from “La Caixa” Foundation and the Centre for Advanced 2D Materials at the National University of Singapore for its hospitality. X. W. acknowledges the ANR Flagera GRANSPORT funding. ICN2 authors were supported by the European Union Horizon 2020 research and innovation programme under Grant Agreement No. 881603 (Graphene Flagship) and No. 824140 (TOCHA, H2020-FETPROACT-01-2018). ICN2 is funded by the CERCA Programme/Generalitat de Catalunya, and is supported by the Severo Ochoa program from Spanish MINECO (Grant No. SEV2017-0706). V. M. P. acknowledges the support of the National Research Foundation (Singapore) under its Medium-Sized Centre Programme (R-723-000-001-281).

Published
2020

23. Sound-driven single-electron transfer in a circuit of coupled quantum rails

Author

Matias Urdampilleta, Giorgos Georgiou, C. J. B. Ford, Crispin H. W. Barnes, Shintaro Takada, Hugo V. Lepage, Arne Ludwig, Christopher Bäuerle, Pierre-André Mortemousque, Junliang Wang, Mingyun Yuan, Tristan Meunier, Paulo V. Santos, Hermann Edlbauer, Andreas D. Wieck, Xavier Waintal, Circuits électroniques quantiques Alpes (QuantECA ), Institut Néel (NEEL), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Cavendish Laboratory, University of Cambridge [UK] (CAM), Institut de Microélectronique, Electromagnétisme et Photonique - Laboratoire d'Hyperfréquences et Caractérisation (IMEP-LAHC ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Paul-Drude-Institut für Festkörperelektronik (PDI), PHotonique, ELectronique et Ingénierie QuantiqueS (PHELIQS), Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Ruhr University Bochum (RUB), Circuits électroniques quantiques Alpes (NEEL - QuantECA), Takada, Shintaro [0000-0002-7831-585X], Edlbauer, Hermann [0000-0002-0236-3265], Lepage, Hugo V. [0000-0002-7363-4165], Wang, Junliang [0000-0002-7164-1644], Ford, Christopher J. B. [0000-0002-4557-3721], Wieck, Andreas D. [0000-0001-9776-2922], Bäuerle, Christopher [0000-0001-7393-0346], Apollo - University of Cambridge Repository, Lepage, Hugo V [0000-0002-7363-4165], Ford, Christopher JB [0000-0002-4557-3721], and Wieck, Andreas D [0000-0001-9776-2922]

Subjects
electron, 147/135, 120, General Physics and Astronomy, 02 engineering and technology, Integrated circuit, 01 natural sciences, 5108 Quantum Physics, Quantum logic, law.invention, sound, Computer Science::Hardware Architecture, Computer Science::Emerging Technologies, law, 639/766/483/2802, electron transport, lcsh:Science, Quantum, Physics, 639/766/119/995, Quantum Physics, Multidisciplinary, 142/126, quantum mechanics, article, quantum dot, 021001 nanoscience & nanotechnology, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, Optoelectronics, 639/766/25/3927, 0210 nano-technology, 51 Physical Sciences, Qubits, adiabaticity, scanning electron microscopy, Electronic properties and materials, Quantum information, 144, Science, 639/925/927/481, FOS: Physical sciences, General Biochemistry, Genetics and Molecular Biology, Quantum circuit, electric potential, 0103 physical sciences, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Hardware_INTEGRATEDCIRCUITS, 010306 general physics, [PHYS.COND.CM-MSQHE]Physics [physics]/Condensed Matter [cond-mat]/Mesoscopic Systems and Quantum Hall Effect [cond-mat.mes-hall], acoustic wave, Condensed Matter - Mesoscale and Nanoscale Physics, electrical conductivity, piezoelectricity, business.industry, General Chemistry, Acoustics, 5104 Condensed Matter Physics, Quantum dot, Qubit, Power dividers and directional couplers, lcsh:Q, business, Quantum Physics (quant-ph), Hardware_LOGICDESIGN
Abstract

Surface acoustic waves (SAWs) strongly modulate the shallow electric potential in piezoelectric materials. In semiconductor heterostructures such as GaAs/AlGaAs, SAWs can thus be employed to transfer individual electrons between distant quantum dots. This transfer mechanism makes SAW technologies a promising candidate to convey quantum information through a circuit of quantum logic gates. Here we present two essential building blocks of such a SAW-driven quantum circuit. First, we implement a directional coupler allowing to partition a flying electron arbitrarily into two paths of transportation. Second, we demonstrate a triggered single-electron source enabling synchronisation of the SAW-driven sending process. Exceeding a single-shot transfer efficiency of 99 %, we show that a SAW-driven integrated circuit is feasible with single electrons on a large scale. Our results pave the way to perform quantum logic operations with flying electron qubits., Comment: Accepted for Publication in Nature Communications

Published
2019

25. The self-consistent quantum-electrostatic problem in strongly non-linear regime

Author

Christoph Groth, Pacome Armagnat, A. Lacerda-Santos, Xavier Waintal, Benoit Rossignol, Laboratory of Quantum Theory (GT), PHotonique, ELectronique et Ingénierie QuantiqueS (PHELIQS), Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), and ANR-16-CE30-0015,FullyQuantum,Manipulation tout-quantique de pulses de charges entières et non-entières dans des fils quantiques(2016)

Subjects
[PHYS]Physics [physics], Physics, Condensed Matter - Mesoscale and Nanoscale Physics, Quantum point contact, FOS: Physical sciences, General Physics and Astronomy, Computational Physics (physics.comp-ph), Quantum Hall effect, 01 natural sciences, lcsh:QC1-999, 010305 fluids & plasmas, [SPI]Engineering Sciences [physics], Nonlinear system, Nanoelectronics, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), 0103 physical sciences, Density of states, Compressibility, Statistical physics, 010306 general physics, Physics - Computational Physics, Quantum, lcsh:Physics, Integer (computer science)
Abstract

The self-consistent quantum-electrostatic (also known as Poisson-Schr\"odinger) problem is notoriously difficult in situations where the density of states varies rapidly with energy. At low temperatures, these fluctuations make the problem highly non-linear which renders iterative schemes deeply unstable. We present a stable algorithm that provides a solution to this problem with controlled accuracy. The technique is intrinsically convergent including in highly non-linear regimes. We illustrate our approach with (i) a calculation of the compressible and incompressible stripes in the integer quantum Hall regime and (ii) a calculation of the differential conductance of a quantum point contact geometry. Our technique provides a viable route for the predictive modeling of the transport properties of quantum nanoelectronics devices., Comment: 28 pages. 14 figures. Added solution to a potential failure mode of the algorithm

Published
2019

26. Proximity magnetoresistance in graphene induced by magnetic insulators

Author

Xavier Waintal, Mairbek Chshiev, Ali Hallal, D. A. Solis, SPINtronique et TEchnologie des Composants (SPINTEC), Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), PHotonique, ELectronique et Ingénierie QuantiqueS (PHELIQS), Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Laboratory of Quantum Theory (GT), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG)

Subjects
Materials science, Magnetoresistance, Yttrium iron garnet, Spin valve, chemistry.chemical_element, FOS: Physical sciences, 02 engineering and technology, 01 natural sciences, law.invention, chemistry.chemical_compound, law, 0103 physical sciences, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), 010306 general physics, ComputingMilieux_MISCELLANEOUS, Condensed Matter - Materials Science, Condensed matter physics, Spin polarization, Condensed Matter - Mesoscale and Nanoscale Physics, Graphene, Conductance, Materials Science (cond-mat.mtrl-sci), 021001 nanoscience & nanotechnology, chemistry, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Curie temperature, 0210 nano-technology, Europium
Abstract

We demonstrate the existence of Giant proximity magnetoresistance (PMR) effect in a graphene spin valve where spin polarization is induced by a nearby magnetic insulator. PMR calculations were performed for yttrium iron garnet (YIG), cobalt ferrite (CFO), and two europium chalcogenides EuO and EuS. We find a significant PMR (up to 100%) values defined as a relative change of graphene conductance with respect to parallel and antiparallel alignment of two proximity induced magnetic regions within graphene. Namely, for high Curie temperature (Tc) CFO and YIG insulators which are particularly important for applications, we obtain 22% and 77% at room temperature, respectively. For low Tc chalcogenides, EuO and EuS, the PMR is 100% in both cases. Furthermore, the PMR is robust with respect to system dimensions and edge type termination. Our findings show that it is possible to induce spin polarized currents in graphene with no direct injection through magnetic materials., 6 pages, 5 figures

Published
2019

27. What determines the ultimate precision of a quantum computer

Author

Xavier Waintal, Laboratory of Quantum Theory (GT), PHotonique, ELectronique et Ingénierie QuantiqueS (PHELIQS), Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)

Subjects
Discrete mathematics, Physics, Quantum Physics, Code (set theory), FOS: Physical sciences, 01 natural sciences, 010305 fluids & plasmas, Quantum state, Quantum error correction, [PHYS.COND.CM-GEN]Physics [physics]/Condensed Matter [cond-mat]/Other [cond-mat.other], Qubit, 0103 physical sciences, Limit (mathematics), Quantum Physics (quant-ph), 010306 general physics, Quantum, ComputingMilieux_MISCELLANEOUS, Quantum computer, Event (probability theory)
Abstract

A quantum error correction (QEC) code uses $N_{\rm c}$ quantum bits to construct one "logical" quantum bits of better quality than the original "physical" ones. QEC theory predicts that the failure probability $p_L$ of logical qubits decreases exponentially with $N_{\rm c}$ provided the failure probability $p$ of the physical qubit is below a certain threshold $p, Comment: Published version. New discussion added at the end

Published
2019

28. Reconstructing non-equilibrium regimes of quantum many-body systems from the analytical structure of perturbative expansions

Author

Olivier Parcollet, Serge Florens, Corentin Bertrand, Xavier Waintal, Flatiron Institute, Simons Foundation, Théorie Quantique des Circuits (NEEL - ThQC), Institut Néel (NEEL), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Institut de Physique Théorique - UMR CNRS 3681 (IPHT), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Laboratory of Quantum Theory (GT), PHotonique, ELectronique et Ingénierie QuantiqueS (PHELIQS), Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)

Subjects
[PHYS]Physics [physics], Physics, Strongly Correlated Electrons (cond-mat.str-el), Condensed Matter - Mesoscale and Nanoscale Physics, QC1-999, Quantum dynamics, Structure (category theory), FOS: Physical sciences, General Physics and Astronomy, Non-equilibrium thermodynamics, 01 natural sciences, Many body, 010305 fluids & plasmas, [SPI]Engineering Sciences [physics], Condensed Matter - Strongly Correlated Electrons, Classical mechanics, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), 0103 physical sciences, Mathematics::Metric Geometry, 010306 general physics, Quantum
Abstract

We propose a systematic approach to the non-equilibrium dynamics of strongly interacting many-body quantum systems, building upon the standard perturbative expansion in the Coulomb interaction. High order series are derived from the Keldysh version of determinantal diagrammatic Quantum Monte Carlo, and the reconstruction beyond the weak coupling regime of physical quantities is obtained by considering them as analytic functions of a complex-valued interaction $U$. Our advances rely on two crucial ingredients: i) a conformal change of variable, based on the approximate location of the singularities of these functions in the complex $U$-plane; ii) a Bayesian inference technique, that takes into account additional known non-perturbative relations, in order to control the amplification of noise occurring at large $U$. This general methodology is applied to the strongly correlated Anderson quantum impurity model, and is thoroughly tested both in- and out-of-equilibrium. In the situation of a finite voltage bias, our method is able to extend previous studies, by bridging with the regime of unitary conductance, and by dealing with energy offsets from particle-hole symmetry. We also confirm the existence of a voltage splitting of the impurity density of states, and find that it is tied to a non-trivial behavior of the non-equilibrium distribution function. Beyond impurity problems, our approach could be directly applied to Hubbard-like models, as well as other types of expansions., 16 pages, 18 figures, added comparison with Bethe Ansatz, appendix B and some discussion

Published
2019

29. Role of Quasiparticles in an Electric Circuit with Josephson Junctions

Author

Thomas Kloss, Xavier Waintal, Benoit Rossignol, Laboratory of Quantum Theory (GT), PHotonique, ELectronique et Ingénierie QuantiqueS (PHELIQS), Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), and ANR-16-CE30-0015,FullyQuantum,Manipulation tout-quantique de pulses de charges entières et non-entières dans des fils quantiques(2016)

Subjects
Superconductivity, Physics, Josephson effect, Condensed matter physics, Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Superconductivity, General Physics and Astronomy, FOS: Physical sciences, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, 01 natural sciences, law.invention, Andreev reflection, [PHYS.COND.CM-S]Physics [physics]/Condensed Matter [cond-mat]/Superconductivity [cond-mat.supr-con], Superconductivity (cond-mat.supr-con), law, Condensed Matter::Superconductivity, 0103 physical sciences, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quasiparticle, RLC circuit, Resistor, 010306 general physics, RC circuit, ComputingMilieux_MISCELLANEOUS, Electronic circuit
Abstract

While Josephson junctions can be viewed as highly non-linear impedances for superconducting quantum technologies, they also possess internal dynamics that may strongly affect their behavior. Here, we construct a computational framework that includes a microscopic description of the junction (full fledged treatment of both the superconducting condensate and the quasi-particles) in presence of a surrounding electrical circuit. Our approach generalizes the standard ResistorCapacitor-Josephson model (RCJ) to arbitrary junctions (including e.g. multi-terminal geometries and/or junctions that embed topological or magnetic elements) and arbitrary electric circuits treated at the classical level. By treating the superconducting condensate and quasi-particles on equal footings, we capture non-equilibrium phenomena such as Multiple Andreev Reflection. We show that the interplay between the quasi-particle dynamics and the electrical environment leads to the emergence of new phenomena. In a RC circuit connected to single channel Josephson junction, we find out-of-equilibrium current-phase relations that are strongly distorted with respect to the (almost sinusoidal) equilibrium one, revealing the presence of high harmonic AC Josephson effect. In an RLC circuit connected to a junction, we find that the shape of the resonance is strongly modified by the quasi-particle dynamics: close to resonance, the current can be smaller than without the resonator. Our approach provides a route for the quantitative modeling of superconducting based circuits., Comment: 5 pages, 4 figures

Published
2019

30. Unveiling multiferroic proximity effect in graphene

Author

Daniel Solis Lerma, Ali Hallal, Fatima Ibrahim, Mairbek Chshiev, Xavier Waintal, Evgeny Y. Tsymbal, SPINtronique et TEchnologie des Composants (SPINTEC), Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Laboratory of Quantum Theory (GT), PHotonique, ELectronique et Ingénierie QuantiqueS (PHELIQS), Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), University of Nebraska–Lincoln, University of Nebraska System, ANR-18-CE24-0017,FEOrgSpin,Contrôle ferroélectrique de la spinterface organique/ferromagnétique(2018), and University of Nebraska [Lincoln]

Subjects
Materials science, FOS: Physical sciences, 02 engineering and technology, Electronic structure, 01 natural sciences, law.invention, Condensed Matter::Materials Science, chemistry.chemical_compound, symbols.namesake, law, 0103 physical sciences, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), General Materials Science, Multiferroics, 010306 general physics, Electronic band structure, ComputingMilieux_MISCELLANEOUS, Bismuth ferrite, Condensed Matter - Materials Science, Condensed Matter - Mesoscale and Nanoscale Physics, Spintronics, Condensed matter physics, Condensed Matter::Other, Graphene, Mechanical Engineering, Materials Science (cond-mat.mtrl-sci), General Chemistry, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Polarization density, chemistry, Mechanics of Materials, symbols, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], 0210 nano-technology, Hamiltonian (quantum mechanics)
Abstract

We demonstrate that electronic and magnetic properties of graphene can be tuned via proximity of multiferroic substrate. Our first-principles calculations performed both with and without spin-orbit coupling clearly show that by contacting graphene with bismuth ferrite BiFeO$_3$ (BFO) film, the spin-dependent electronic structure of graphene is strongly impacted both by the magnetic order and by electric polarization in the underlying BFO. Based on extracted Hamiltonian parameters obtained from the graphene band structure, we propose a concept of six-resistance device based on exploring multiferroic proximity effect giving rise to significant proximity electro- (PER), magneto- (PMR), and multiferroic (PMER) resistance effects. This finding paves a way towards multiferroic control of magnetic properties in two dimensional materials., Comment: 20 pages, 4 figures

Published
2019
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31. Reprint of : A computational approach to quantum noise in time-dependent nanoelectronic devices

Author

Xavier Waintal and Benoit Gaury

Subjects
Physics, Quantum network, Quantum noise, Shot noise, 02 engineering and technology, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, 021001 nanoscience & nanotechnology, Condensed Matter Physics, 01 natural sciences, Atomic and Molecular Physics, and Optics, Electronic, Optical and Magnetic Materials, Quantum technology, Open quantum system, Quantum error correction, Quantum mechanics, Quantum process, 0103 physical sciences, Quantum operation, Statistical physics, 010306 general physics, 0210 nano-technology
Abstract

We derive simple expressions that relate the noise and correlation properties of a general time-dependent quantum conductor to the wave functions of the system. The formalism provides a practical route for numerical calculations of quantum noise in an externally driven system. We illustrate the approach with numerical calculations of the noise properties associated to a voltage pulse applied on a one-dimensional conductor. The methodology is however fully general and can be used for a large class of mesoscopic conductors.

Published
2016

32. Reprint of : Probing (topological) Floquet states through DC transport

Author

David Carpentier, Xavier Waintal, Pierre Delplace, Michel Fruchart, and Joseph Weston

Subjects
Floquet theory, Physics, Mesoscopic physics, Operator (physics), Spectrum (functional analysis), Dissipation, Condensed Matter Physics, Topology, 01 natural sciences, Atomic and Molecular Physics, and Optics, 010305 fluids & plasmas, Electronic, Optical and Magnetic Materials, Topological insulator, Quantum mechanics, 0103 physical sciences, Scattering theory, 010306 general physics, Differential (mathematics)
Abstract

We consider the differential conductance of a periodically driven system connected to infinite electrodes. We focus on the situation where the dissipation occurs predominantly in these electrodes. Using analytical arguments and a detailed numerical study we relate the differential conductances of such a system in two and three terminal geometries to the spectrum of quasi-energies of the Floquet operator. Moreover these differential conductances are found to provide an accurate probe of the existence of gaps in this quasi-energy spectrum, being quantized when topological edge states occur within these gaps. Our analysis opens the perspective to describe the intermediate time dynamics of driven mesoscopic conductors as topological Floquet filters.

Published
2016

33. Reconciling edge states with compressible stripes in a ballistic mesoscopic conductor

Author

Pacome Armagnat, Xavier Waintal, Laboratory of Quantum Theory (GT), PHotonique, ELectronique et Ingénierie QuantiqueS (PHELIQS), Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes (UGA)-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes (UGA), and ANR-16-CE30-0015,FullyQuantum,Manipulation tout-quantique de pulses de charges entières et non-entières dans des fils quantiques(2016)

Subjects
[PHYS]Physics [physics], Physics, Mesoscopic physics, Condensed Matter - Mesoscale and Nanoscale Physics, Condensed matter physics, Field (physics), Electric potential energy, Phase (waves), FOS: Physical sciences, Fermi energy, Landau quantization, Quantum Hall effect, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, Condensed Matter Physics, Atomic and Molecular Physics, and Optics, Conductor, [SPI]Engineering Sciences [physics], Mesoscale and Nanoscale Physics (cond-mat.mes-hall), General Materials Science
Abstract

The well-known Landauer-Buttiker (LB) picture used to explain the quantum Hall effect uses the concept of (chiral) edge states that carry the current. In their seminal 1992 article, Chklovskii, Shklovskii and Glazman (CSG) showed that the LB picture does not account for some very basic properties of the gas, such as its density profile, as it lacks a proper treatment of the electrostatic energy. They showed that, instead, one should consider alternated stripes of compressible and incompressible phases. In this letter, we revisit this issue using a full solution of the quantum-electrostatic problem of a narrow ballistic conductor, beyond the CSG approach. We recover the LB channels at low field and the CSG compressible/incompressible stripes at high field. Our calculations reveal the existence of a third "hybrid" phase at intermediate field. This hybrid phase has well defined LB type edge states, yet possesses a Landau level pinned at the Fermi energy as in the CSG picture. We calculate the magneto-conductance which reveals the interplay between the LB and CSG regimes. Our results have important implications for the propagation of edge magneto-plasmons., Comment: 6 pages, 3 figures

Published
2020

34. Coherent control of single electrons: a review of current progress

Author

Christopher Bäuerle, D. Christian Glattli, Shintaro Takada, Preden Roulleau, Tristan Meunier, Xavier Waintal, Fabien Portier, Patrice Roche, Circuits électroniques quantiques Alpes (QuantECA ), Institut Néel (NEEL), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Groupe Nano-Electronique (GNE), Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology (AIST), Laboratory of Quantum Theory (GT), PHotonique, ELectronique et Ingénierie QuantiqueS (PHELIQS), Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), ANR-16-CE30-0015,FullyQuantum,Manipulation tout-quantique de pulses de charges entières et non-entières dans des fils quantiques(2016), and Circuits électroniques quantiques Alpes (NEEL - QuantECA)

Subjects
Field (physics), FOS: Physical sciences, General Physics and Astronomy, Electrons, 02 engineering and technology, Electron, 01 natural sciences, 2D electron systems, Quantum state, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), 0103 physical sciences, Limit (music), Electronic engineering, 010306 general physics, Electronic circuit, Physics, Quantum optics, [PHYS]Physics [physics], Condensed Matter - Mesoscale and Nanoscale Physics, flying qubits, quantum interference, 021001 nanoscience & nanotechnology, Coherent control, Qubit, Quantum Theory, 0210 nano-technology, single-electron electronics
Abstract

In this report we review the present state of the art of the control of propagating quantum states at the single-electron level and its potential application to quantum information processing. We give an overview of the different approaches which have been developed over the last ten years in order to gain full control over a propagating single electron in a solid state system. After a brief introduction of the basic concepts, we present experiments on flying qubit circuits for ensemble of electrons measured in the low frequency (DC) limit. We then present the basic ingredients necessary to realise such experiments at the single-electron level. This includes a review of the various single electron sources which are compatible with integrated single electron circuits. This is followed by a review of recent key experiments on electron quantum optics with single electrons. Finally we will present recent developments about the new physics that emerges using ultrashort voltage pulses. We conclude our review with an outlook and future challenges in the field., Comment: 35 pages, 24 figures, This is an author-created, un-copyedited version of an article accepted for publication in Rep. Prog. Phys. (references added)

Published
2018

35. Cooperative Charge Pumping and Enhanced Skyrmion Mobility

Author

Aurelien Manchon, Joseph Weston, Adel Abbout, Xavier Waintal, King Abdullah University of Science and Technology (KAUST), Laboratory of Quantum Theory (GT), PHotonique, ELectronique et Ingénierie QuantiqueS (PHELIQS), Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)

Subjects
Physics, [PHYS]Physics [physics], Condensed Matter - Materials Science, Condensed matter physics, Condensed Matter - Mesoscale and Nanoscale Physics, Skyrmion, Time evolution, General Physics and Astronomy, Semiclassical physics, Materials Science (cond-mat.mtrl-sci), FOS: Physical sciences, Context (language use), 02 engineering and technology, 021001 nanoscience & nanotechnology, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, 01 natural sciences, Hall effect, 0103 physical sciences, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Scattering theory, 010306 general physics, 0210 nano-technology, Adiabatic process, Spin-½
Abstract

International audience; It is well known that moving magnetic textures may pump spin and charge currents along the direction ofmotion, a phenomenon called electronic pumping. Here, the electronic pumping arising from the steadymotion of ferromagnetic skyrmions is investigated by solving the time evolution of the Schrödingerequation implemented on a tight-binding model with the statistical physics of the many-body problem. Incontrast with rigid one-dimensional magnetic textures, we show that steadily moving magnetic skyrmionsare able to pump large dc currents. This ability arises from their nontrivial magnetic topology, i.e., thecoexistence of the spin-motive force and the topological Hall effect. Based on an adiabatic scatteringtheory, we compute the pumped current and demonstrate that it scales with the reflection coefficient of theconduction electrons against the skyrmion. In other words, in the semiclassical limit, reducing the size ofthe skyrmion and the width of the nanowire enhances this effect, making it scalable. We propose that such aphenomenon can be exploited in the context of racetrack devices, where the electronic pumping enhancesthe collective motion of the train of skyrmions.

Published
2018

36. Transient and Sharvin resistances of Luttinger liquids

Author

Thomas Kloss, Xavier Waintal, Joseph Weston, Laboratory of Quantum Theory (GT), PHotonique, ELectronique et Ingénierie QuantiqueS (PHELIQS), Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Kavli Institute of Nanosciences [Delft] (KI-NANO), Delft University of Technology (TU Delft), and ANR-16-CE30-0015,FullyQuantum,Manipulation tout-quantique de pulses de charges entières et non-entières dans des fils quantiques(2016)

Subjects
FOS: Physical sciences, 02 engineering and technology, 01 natural sciences, Measure (mathematics), Renormalization, symbols.namesake, Luttinger liquid, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), 0103 physical sciences, 010306 general physics, Quantum, ComputingMilieux_MISCELLANEOUS, Physics, Condensed Matter::Quantum Gases, [PHYS]Physics [physics], Condensed matter physics, Condensed Matter - Mesoscale and Nanoscale Physics, Contact resistance, Conductance, 021001 nanoscience & nanotechnology, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, Boltzmann constant, symbols, Condensed Matter::Strongly Correlated Electrons, Fermi liquid theory, 0210 nano-technology
Abstract

Although the intrinsic conductance of an interacting one-dimensional system is renormalized by the electron-electron correlations, it has been known for some time that this renormalization is washed out by the presence of the (non-interacting) electrodes to which the wire is connected. Here, we study the transient conductance of such a wire: a finite voltage bias is suddenly applied across the wire and we measure the current before it has enough time to reach its stationary value. These calculations allow us to extract the Sharvin (contact) resistance of Luttinger and Fermi liquids. In particular, we find that a perfect junction between a Fermi liquid electrode and a Luttinger liquid electrode is characterized by a contact resistance that consists of half the quantum of conductance in series with half the intrinsic resistance of an infinite Luttinger liquid. These results were obtained using two different methods: a dynamical Hartree-Fock approach and a self-consistent Boltzmann approach. Although these methods are formally approximate we find a perfect match with the exact results of Luttinger/Fermi liquid theory., 6 pages, 3 figures, final version

Published
2018

37. A general algorithm for computing bound states in infinite tight-binding systems

Author

Mathieu Istas, Xavier Waintal, Christoph Groth, Anton R. Akhmerov, Michael Wimmer, Service de Physique Statistique, Magnétisme et Supraconductivité (SPSMS - UMR 9001), Institut Nanosciences et Cryogénie (INAC), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Delft University of Technology (TU Delft), Laboratory of Quantum Theory (GT), PHotonique, ELectronique et Ingénierie QuantiqueS (PHELIQS), Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)

Subjects
Matching (graph theory), Edge states, Continuous spectrum, Bound states, Superconducting nanowires, Phase (waves), Majorana fermions, General Physics and Astronomy, FOS: Physical sciences, 01 natural sciences, 010305 fluids & plasmas, Tight binding, Quantum mechanics, 0103 physical sciences, Bound state, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Weyl semimetals, 010306 general physics, Quantum, Physics, Fermi arcs, [PHYS]Physics [physics], Quantum billiards, Condensed Matter - Mesoscale and Nanoscale Physics, Scattering, Tight-binding models, Topological materials, Quantum spin Hall effect, lcsh:QC1-999, 3. Good health, MAJORANA, lcsh:Physics
Abstract

We propose a robust and efficient algorithm for computing bound states of infinite tight-binding systems that are made up of a finite scattering region connected to semi-infinite leads. Our method uses wave matching in close analogy to the approaches used to obtain propagating states and scattering matrices. We show that our algorithm is robust in presence of slowly decaying bound states where a diagonalization of a finite system would fail. It also allows to calculate the bound states that can be present in the middle of a continuous spectrum. We apply our technique to quantum billiards and the following topological materials: Majorana states in 1D superconducting nanowires, edge states in the 2D quantum spin Hall phase, and Fermi arcs in 3D Weyl semimetals., Comment: 21 pages, 13 figures, minors changes according to the referees comments, https://scipost.org/submissions/1711.08250v1/

Published
2018

38. Toward flying qubit spectroscopy

Author

Xavier Waintal, Benoit Rossignol, Pacome Armagnat, Thomas Kloss, Laboratory of Quantum Theory (GT), PHotonique, ELectronique et Ingénierie QuantiqueS (PHELIQS), Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), ANR-16-CE30-0015,FullyQuantum,Manipulation tout-quantique de pulses de charges entières et non-entières dans des fils quantiques(2016), and ANR-15-CE24-0007,QTERA,Electronique quantique terahertz(2015)

Subjects
Physics, Floquet theory, Condensed Matter - Mesoscale and Nanoscale Physics, Continuum (topology), FOS: Physical sciences, 02 engineering and technology, 021001 nanoscience & nanotechnology, Topology, 01 natural sciences, Interferometry, Coherent control, Qubit, 0103 physical sciences, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], 010306 general physics, 0210 nano-technology, Spectroscopy, Quantum, Voltage
Abstract

While the coherent control of two level quantum systems ---qubits--- is now standard, their continuum electronic equivalents ---flying qubits--- are much less developed. A first step in this direction has been achieved in DC interferometry experiments. Here, we propose a simple setup to perform the second step, the spectroscopy of these flying qubits, by measuring the DC response to a high frequency AC voltage drive. Using two different concurring approaches --- Floquet theory and time-dependent simulations --- and three different models --- an analytical model, a simple microscopic model and a realistic microscopic model --- we predict the power-frequency map of the multi-terminal device. We argue that this spectroscopy provides a direct measurement of the flying qubit characteristic frequencies and a key validation for more advanced quantum manipulations., 9 pages, 10 figures

Published
2018

39. Robust spin transfer torque in antiferromagnetic tunnel junctions

Author

Aurelien Manchon, Xavier Waintal, Hamed Ben Mohamed Saidaoui, King Abdullah University of Science and Technology (KAUST), Laboratory of Quantum Theory (GT), PHotonique, ELectronique et Ingénierie QuantiqueS (PHELIQS), Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)

Subjects
Physics, [PHYS]Physics [physics], Condensed Matter - Mesoscale and Nanoscale Physics, Condensed matter physics, Spin-transfer torque, FOS: Physical sciences, Order (ring theory), 02 engineering and technology, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, 021001 nanoscience & nanotechnology, 01 natural sciences, Out of plane, In plane, Ferromagnetism, Condensed Matter::Superconductivity, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), 0103 physical sciences, Antiferromagnetism, Condensed Matter::Strongly Correlated Electrons, 010306 general physics, 0210 nano-technology, Quantum tunnelling, ComputingMilieux_MISCELLANEOUS, Spin-½
Abstract

We theoretically study the current-induced spin torque in antiferromagnetic tunnel junctions, composed of two semi-infinite antiferromagnetic layers separated by a tunnel barrier, in both clean and disordered regimes. We find that the torque enabling the electrical manipulation of the N\'eel antiferromagnetic order parameter is out of plane $\sim {\bf n}\times{\bf p}$, while the torque competing with the antiferromagnetic exchange is in-plane $\sim {\bf n}\times({\bf p}\times{\bf n})$. Here, ${\bf { p}}$ and ${\bf { n}}$ are the N\'eel order parameter direction of the reference and free layers, respectively. Their bias dependence shows similar behavior as in ferromagnetic tunnel junctions, the in-plane torque being mostly linear in bias while the out-of-plane torque is quadratic. Most importantly, we find that the spin transfer torque in antiferromagnetic tunnel junctions is much more robust against disorder than in antiferromagnetic metallic spin-valves due to the tunneling nature of spin transport., Comment: 7 pages, 7 figures

Published
2017

40. Control of the Oscillatory Interlayer Exchange Interaction with Terahertz Radiation

Author

Xavier Waintal, Géraldine Haack, Christoph Groth, Uta Meyer, Service de Physique Statistique, Magnétisme et Supraconductivité (SPSMS - UMR 9001), Institut Nanosciences et Cryogénie (INAC), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Laboratory of Quantum Theory (GT), PHotonique, ELectronique et Ingénierie QuantiqueS (PHELIQS), Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)

Subjects
Materials science, Terahertz radiation, Spin valve, FOS: Physical sciences, General Physics and Astronomy, 02 engineering and technology, ddc:500.2, 01 natural sciences, Condensed Matter::Materials Science, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), 0103 physical sciences, Antiferromagnetism, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], 010306 general physics, ComputingMilieux_MISCELLANEOUS, [PHYS]Physics [physics], Condensed Matter - Materials Science, Range (particle radiation), Condensed Matter - Mesoscale and Nanoscale Physics, Condensed matter physics, Exchange interaction, Materials Science (cond-mat.mtrl-sci), Macroscopic quantum phenomena, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, 021001 nanoscience & nanotechnology, Amplitude, Ferromagnetism, Condensed Matter::Strongly Correlated Electrons, 0210 nano-technology
Abstract

The oscillatory interlayer exchange interaction between two magnetic layers separated by a metallic spacer is one of the few coherent quantum phenomena that persist at room temperature. Here we show that this interaction can be controlled dynamically by illuminating the sample (e.g. a spin valve) with radiation in the 10-100 THz range. We predict that the exchange interaction can be changed from ferromagnetic to anti-ferromagnetic (and vice versa) by tuning the amplitude and/or the frequency of the radiation. Our chief theoretical result is an expression that relates the dynamical exchange interaction to the static one that has already been extensively measured., 5 pages, 3 figures

Published
2017

42. Linear-scaling source-sink algorithm for simulating time-resolved quantum transport and superconductivity

Author

Joseph Weston, Xavier Waintal, Service de Physique Statistique, Magnétisme et Supraconductivité (SPSMS - UMR 9001), Institut Nanosciences et Cryogénie (INAC), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Laboratory of Quantum Theory (GT), PHotonique, ELectronique et Ingénierie QuantiqueS (PHELIQS), Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), and European Project: 257241,EC:FP7:ERC,ERC-2010-StG_20091028,MESOQMC(2011)

Subjects
Josephson effect, FOS: Physical sciences, 02 engineering and technology, 01 natural sciences, Schrödinger equation, Superconductivity (cond-mat.supr-con), symbols.namesake, Condensed Matter::Superconductivity, Quantum mechanics, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), 0103 physical sciences, Quantum system, Linear scale, 010306 general physics, Wave function, [PHYS]Physics [physics], Superconductivity, Physics, Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Superconductivity, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, 021001 nanoscience & nanotechnology, symbols, 0210 nano-technology, Hamiltonian (quantum mechanics), Algorithm, Long Josephson junction
Abstract

We report on a "source-sink" algorithm which allows one to calculate time-resolved physical quantities from a general nanoelectronic quantum system (described by an arbitrary time-dependent quadratic Hamiltonian) connected to infinite electrodes. Although mathematically equivalent to the non equilibrium Green's function formalism, the approach is based on the scattering wave functions of the system. It amounts to solving a set of generalized Schr\"odinger equations which include an additional "source" term (coming from the time dependent perturbation) and an absorbing "sink" term (the electrodes). The algorithm execution time scales linearly with both system size and simulation time allowing one to simulate large systems (currently around $10^6$ degrees of freedom) and/or large times (currently around $10^5$ times the smallest time scale of the system). As an application we calculate the current-voltage characteristics of a Josephson junction for both short and long junctions, and recover the multiple Andreev reflexion (MAR) physics. We also discuss two intrinsically time-dependent situations: the relaxation time of a Josephson junction after a quench of the voltage bias, and the propagation of voltage pulses through a Josephson junction. In the case of a ballistic, long Josephson junction, we predict that a fast voltage pulse creates an oscillatory current whose frequency is controlled by the Thouless energy of the normal part. A similar effect is found for short junctions, a voltage pulse produces an oscillating current which, in the absence of electromagnetic environment, does not relax., Comment: 13 pages, 12 figures

Published
2016

43. Towards Realistic Time-Resolved Simulations of Quantum Devices

Author

Joseph Weston, Xavier Waintal, Service de Physique Statistique, Magnétisme et Supraconductivité (SPSMS - UMR 9001), Institut Nanosciences et Cryogénie (INAC), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Laboratory of Quantum Theory (GT), PHotonique, ELectronique et Ingénierie QuantiqueS (PHELIQS), Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)

Subjects
FOS: Physical sciences, 02 engineering and technology, 01 natural sciences, symbols.namesake, Pauli exclusion principle, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), 0103 physical sciences, Time domain, Statistical physics, Electrical and Electronic Engineering, 010306 general physics, Physics, [PHYS]Physics [physics], Condensed Matter - Mesoscale and Nanoscale Physics, Scattering, Fermi level, Bandwidth (signal processing), 021001 nanoscience & nanotechnology, Atomic and Molecular Physics, and Optics, Electronic, Optical and Magnetic Materials, Interferometry, Modeling and Simulation, Qubit, symbols, 0210 nano-technology, Hamiltonian (quantum mechanics)
Abstract

We report on our recent efforts to perform realistic simulations of large quantum devices in the time domain. In contrast to d.c. transport where the calculations are explicitly performed at the Fermi level, the presence of time-dependent terms in the Hamiltonian makes the system inelastic so that it is necessary to explicitly enforce the Pauli principle in the simulations. We illustrate our approach with calculations for a flying qubit interferometer, a nanoelectronic device that is currently under experimental investigation. Our calculations illustrate the fact that many degrees of freedom (16,700 tight-binding sites in the scattering region) and long simulation times (80,000 times the inverse Bandwidth of the tight-binding model) can be easily achieved on a local computer., 8 pages, 6 figures

Published
2016

44. A computational approach to quantum noise in time-dependent nanoelectronic devices

Author

Xavier Waintal, Benoit Gaury, Service de Physique Statistique, Magnétisme et Supraconductivité (SPSMS - UMR 9001), Institut Nanosciences et Cryogénie (INAC), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Laboratory of Quantum Theory (GT), PHotonique, ELectronique et Ingénierie QuantiqueS (PHELIQS), Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), and European Project: 257241,EC:FP7:ERC,ERC-2010-StG_20091028,MESOQMC(2011)

Subjects
FOS: Physical sciences, 02 engineering and technology, 01 natural sciences, Open quantum system, Quantum error correction, Quantum mechanics, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), 0103 physical sciences, Quantum operation, Statistical physics, 010306 general physics, Physics, [PHYS]Physics [physics], Quantum network, Condensed Matter - Mesoscale and Nanoscale Physics, Quantum noise, Shot noise, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, Atomic and Molecular Physics, and Optics, 3. Good health, Electronic, Optical and Magnetic Materials, Quantum process, Quantum algorithm, 0210 nano-technology
Abstract

We derive simple expressions that relate the noise and correlation properties of a general time-dependent quantum conductor to the wave functions of the system. The formalism provides a practical route for numerical calculations of quantum noise in an externally driven system. We illustrate the approach with numerical calculations of the noise properties associated to a voltage pulse applied on a one-dimensional conductor. The methodology is however fully general and can be used for a large class of mesoscopic conductors., 7 pages, 4 figures

Published
2016

45. Probing (topological) Floquet states through DC transport

Author

Xavier Waintal, Joseph Weston, David Carpentier, Pierre Delplace, Michel Fruchart, Laboratoire de Physique de l'ENS Lyon (Phys-ENS), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), Service de Physique Statistique, Magnétisme et Supraconductivité (SPSMS - UMR 9001), Institut Nanosciences et Cryogénie (INAC), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Laboratory of Quantum Theory (GT), PHotonique, ELectronique et Ingénierie QuantiqueS (PHELIQS), Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), École normale supérieure - Lyon (ENS Lyon)-Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon, and Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)

Subjects
Floquet theory, Physics, [PHYS]Physics [physics], Mesoscopic physics, Condensed Matter - Mesoscale and Nanoscale Physics, Operator (physics), Spectrum (functional analysis), FOS: Physical sciences, 02 engineering and technology, Dissipation, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Topology, 01 natural sciences, Atomic and Molecular Physics, and Optics, Electronic, Optical and Magnetic Materials, Topological insulator, Quantum mechanics, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), 0103 physical sciences, Scattering theory, 010306 general physics, 0210 nano-technology, Differential (mathematics)
Abstract

We consider the differential conductance of a periodically driven system connected to infinite electrodes. We focus on the situation where the dissipation occurs predominantly in these electrodes. Using analytical arguments and a detailed numerical study we relate the differential conductances of such a system in two and three terminal geometries to the spectrum of quasi-energies of the Floquet operator. Moreover these differential conductances are found to provide an accurate probe of the existence of gaps in this quasi-energy spectrum, being quantized when topological edge states occur within these gaps. Our analysis opens the perspective to describe the intermediate time dynamics of driven mesoscopic conductors as topological Floquet filters., Comment: 8 pages, 6 figures, invited contribution to the special issue of Physica E on "Frontiers in quantum electronic transport" in memory of Markus Buttiker

Published
2016

46. The a.c. Josephson effect without superconductivity

Author

Joseph Weston, Xavier Waintal, Benoit Gaury, Service de Physique Statistique, Magnétisme et Supraconductivité (SPSMS - UMR 9001), Institut Nanosciences et Cryogénie (INAC), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Laboratory of Quantum Theory (GT), PHotonique, ELectronique et Ingénierie QuantiqueS (PHELIQS), Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), European Project: 257241,EC:FP7:ERC,ERC-2010-StG_20091028,MESOQMC(2011), Institut de Recherche Interdisciplinaire de Grenoble (IRIG), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut de Recherche Interdisciplinaire de Grenoble (IRIG)

Subjects
Josephson effect, Terahertz gap, General Physics and Astronomy, FOS: Physical sciences, Nanotechnology, Electron, General Biochemistry, Genetics and Molecular Biology, Article, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Wave function, Interferometer, Quantum, Superconductivity, Physics, [PHYS]Physics [physics], Mesoscopic physics, States, Multidisciplinary, Condensed matter physics, Condensed Matter - Mesoscale and Nanoscale Physics, General Chemistry, Nanotube, Qubit, Electron, States, Interferometer, Interference, Nanotube, Interference, Coherence (physics)
Abstract

Superconductivity derives its most salient features from the coherence of its macroscopic wave function. The associated physical phenomena have now moved from exotic subjects to fundamental building blocks for quantum circuits such as qubits or single photonic modes. Here, we theoretically find that the AC Josephson effect---which transforms a DC voltage $V_b$ into an oscillating signal $cos(2eV_b t/ \hbar)$---has a mesoscopic counterpart in normal conductors. We show that on applying a DC voltage $V_b$ to an electronic interferometer, there exists a universal transient regime where the current oscillates at frequency $eV_b/h$. This effect is not limited by a superconducting gap and could, in principle, be used to produce tunable AC signals in the elusive $0.1-10$ THz "terahertz gap"., Comment: 4 pages, 2 figures, 5 equations

Published
2015

47. Existe-t-il des métaux à deux dimensions ?

Author

Geneviève Fleury and Xavier Waintal

Subjects
General Medicine
Abstract

Les proprietes de conduction des systemes bidimensionnels d’electrons que l’on trouve par exemple dans les transistors de nos ordinateurs, font depuis plus de quinze ans l’objet d’un debat qui divise les physiciens de la matiere condensee. Alors que l’on pensait qu’en dimension deux il ne pouvait exister que des isolants a cause du desordre inevitable dans les echantillons, des experiences, menees depuis 1994 dans des transistors de nouvelle generation, ont montre d’etranges comportements metalliques.Par une approche numerique, nous montrons que les interactions coulombiennes entre electrons, considerables dans ces nouveaux echantillons, sont a l’origine de ces observations experimentales.

Published
2010

48. Graphene spintronics

Author

Marcos H. D. Guimarães, Jaroslav Fabian, Stephan Roche, Bart J. van Wees, Xavier Waintal, Pierre Seneor, Bruno Dlubak, Christian Schönenberger, Albert Fert, Jean-Christophe Charlier, Mairbek Chshiev, Sergio O. Valenzuela, Bernd Beschoten, Francisco Guinea, Christoph Stampfer, Saroj P. Dash, Johan Åkerman, Irina V. Grigorieva, Institut Català de Nanociència i Nanotecnologia (ICN2), Universitat Autònoma de Barcelona (UAB), Institució Catalana de Recerca i Estudis Avançats (ICREA), University of Gothenburg (GU), I. Physikalisches Institut [Aachen], Rheinisch-Westfälische Technische Hochschule Aachen (RWTH), Institut de la matière condensée et des nanosciences / Institute of Condensed Matter and Nanosciences (IMCN), Université Catholique de Louvain = Catholic University of Louvain (UCL), SPINtronique et TEchnologie des Composants (SPINTEC), Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Chalmers University of Technology [Göteborg], Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), Centre National de la Recherche Scientifique (CNRS)-THALES, Universität Regensburg (UR), Cornell University [New York], School of Physics and Astronomy [Manchester], University of Manchester [Manchester], University of Basel (Unibas), Forschungszentrum Jülich GmbH | Centre de recherche de Juliers, Helmholtz-Gemeinschaft = Helmholtz Association, Laboratory of Quantum Theory (GT), PHotonique, ELectronique et Ingénierie QuantiqueS (PHELIQS), Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Rheinisch-Westfälische Technische Hochschule Aachen University (RWTH), THALES [France]-Centre National de la Recherche Scientifique (CNRS), and Physics of Nanodevices

Subjects
Engineering, Work package, Nanotechnology, Context (language use), Spin current, 7. Clean energy, law.invention, SPIN INJECTION, law, MAGNETORESISTANCE, General Materials Science, DEPOSITION, [PHYS]Physics [physics], Spintronics, business.industry, Graphene, Mechanical Engineering, General Chemistry, Condensed Matter Physics, TRANSPORT, ROOM-TEMPERATURE, SINGLE, Mechanics of Materials, Spin Hall effect, business, Spin injection
Abstract

International audience; We review current challenges and perspectives in graphene spintronics, which is one of the most promising directions of innovation, given its room-temperature long-spin lifetimes and the ability of graphene to be easily interfaced with other classes of materials (ferromagnets, magnetic insulators, semiconductors, oxides, etc), allowing proximity effects to be harvested. The general context of spintronics is first discussed together with open issues and recent advances achieved by the Graphene Spintronics Work Package consortium within the Graphene Flagship project. Based on such progress, which establishes the state of the art, several novel opportunities for spin manipulation such as the generation of pure spin current (through spin Hall effect) and the control of magnetization through the spin torque phenomena appear on the horizon. Practical applications are within reach, but will require the demonstration of wafer-scale graphene device integration, and the realization of functional prototypes employed for determined applications such as magnetic sensors or nano-oscillators. This is a specially commissioned editorial from the Graphene Flagship Work Package on Spintronics. This editorial is part of the 2D Materials focus collection on 'Progress on the science and applications of two-dimensional materials,' published in association with the Graphene Flagship. It provides an overview of key recent advances of the spintronics work package as well as the mid-term objectives of the consortium.

Published
2015

49. Manipulating Andreev and Majorana bound states with microwaves

Author

Xavier Waintal, Joseph Weston, Benoit Gaury, Service de Physique Statistique, Magnétisme et Supraconductivité (SPSMS - UMR 9001), Institut Nanosciences et Cryogénie (INAC), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Laboratory of Quantum Theory (GT), PHotonique, ELectronique et Ingénierie QuantiqueS (PHELIQS), Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), European Project: 257241,EC:FP7:ERC,ERC-2010-StG_20091028,MESOQMC(2011), Institut de Recherche Interdisciplinaire de Grenoble (IRIG), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut de Recherche Interdisciplinaire de Grenoble (IRIG)

Subjects
Physics, Superconductivity, [PHYS]Physics [physics], Condensed Matter - Mesoscale and Nanoscale Physics, Condensed matter physics, Phase (waves), Boundary (topology), FOS: Physical sciences, Condensed Matter Physics, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, Electronic, Optical and Magnetic Materials, Andreev reflection, Differential conductance, MAJORANA, Quantum mechanics, Condensed Matter::Superconductivity, Bound state, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Microwave
Abstract

We study the interplay between Andreev (Majorana) bound states that form at the boundary of a (topological) superconductor and a train of microwave pulses. We find that the extra dynamical phase coming from the pulses can shift the phase of the Andreev reflection, resulting in the appear- ance of dynamical Andreev states. As an application we study the presence of the zero bias peak in the differential conductance of a normal-topological superconductor junction - the simplest, yet somehow ambiguous, experimental signature for Majorana states. Adding microwave radiation to the measuring electrodes provides an unambiguous probe of the Andreev nature of the zero bias peak., Comment: 4 pages, 4 figures

Published
2015

50. Control of spin current by a magnetic YIG substrate in NiFe/Al nonlocal spin valves

Author

J. van Wees, David Luc, J. Ben Youssef, Xavier Waintal, Fasil Kidane Dejene, N. Vlietstra, Groningen Biomolecular Sciences and Biotechnology Institute & Zernike Institute for Advanced Materials, University of Groningen [Groningen], Zernike Institute for Advanced Materials, Service de Physique Statistique, Magnétisme et Supraconductivité (SPSMS - UMR 9001), Institut Nanosciences et Cryogénie (INAC), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Laboratory of Quantum Theory (GT), PHotonique, ELectronique et Ingénierie QuantiqueS (PHELIQS), Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Laboratoire de magnétisme de Bretagne (LMB), Université de Brest (UBO)-Institut Brestois du Numérique et des Mathématiques (IBNM), Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), European Project: 612759,EC:FP7:ICT,FP7-ICT-2013-X,INSPIN(2014), Physics of Nanodevices, and Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)

Subjects
Materials science, Spin valve, Yttrium iron garnet, FOS: Physical sciences, 02 engineering and technology, Surface finish, 01 natural sciences, Magnetization, chemistry.chemical_compound, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), 0103 physical sciences, Thermal, 010306 general physics, ACCUMULATION, [PHYS]Physics [physics], Condensed Matter - Mesoscale and Nanoscale Physics, Condensed matter physics, Spin polarization, Magnon, Conductance, 021001 nanoscience & nanotechnology, Condensed Matter Physics, 3. Good health, Electronic, Optical and Magnetic Materials, chemistry, Condensed Matter::Strongly Correlated Electrons, 0210 nano-technology
Abstract

We study the effect of a magnetic insulator (Yttrium Iron Garnet - YIG) substrate on the spin transport properties of Ni$_{80}$Fe$_{20}$/Al nonlocal spin valve (NLSV) devices. The NLSV signal on the YIG substrate is about 2 to 3 times lower than that on a non magnetic SiO$_2$ substrate, indicating that a significant fraction of the spin-current is absorbed at the Al/YIG interface. By measuring the NLSV signal for varying injector-to-detector distance and using a three dimensional spin-transport model that takes spin current absorption at the Al/YIG interface into account we obtain an effective spin-mixing conductance $G_{\uparrow\downarrow}\simeq 5 - 8\times 10^{13}~\Omega^{-1}$m$^{-2}$. We also observe a small but clear modulation of the NLSV signal when rotating the YIG magnetization direction with respect to the fixed spin polarization of the spin accumulation in the Al. Spin relaxation due to thermal magnons or roughness of the YIG surface may be responsible for the observed small modulation of the NLSV signal., Comment: 9 pages, 6 figures, including supplementary information

Published
2015

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