788 results on '"Range (particle radiation)"'
Search Results
2. Uniform structural phase transition in V2O3 without short-range distortions of the local structure
- Author
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Benjamin A. Frandsen, Hiroshi Kageyama, Ethan R. A. Fletcher, Yoav Kalcheim, and Kentaro Higashi
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Range (particle radiation) ,Structural phase ,Materials science ,Condensed matter physics ,Local structure - Published
- 2021
3. Weak adhesion between deposited rough films: Relation to dispersion forces
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I. A. Soldatenkov, Georgios Palasantzas, Vitaly B. Svetovoy, Nanostructured Materials and Interfaces, and Nanotechnology and Biophysics in Medicine (NANOBIOMED)
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Range (particle radiation) ,Materials science ,Condensed matter physics ,Dispersion (optics) ,Surface finish ,Adhesion ,Thin film ,Contact theory ,London dispersion force - Abstract
Although the contact theory between rough surfaces is designed for adhesion energies ≳100mJ/m2, microsystems are controlled by much weaker adhesion ≲100μJ/m2, which is critical for their operation. The weakest adhesion is related to the omnipresent fluctuation-induced dispersion forces. We develop a theory for such a weak adhesion emphasizing that the adhesion energy as a function of the average distance separating the bodies is almost entirely defined by the dispersion interaction. This dependence can be evaluated using the Lifshitz theory, but the effects of contact interaction or plastic deformations give only small contribution to the adhesion. Such a behavior is explained by a specific roughness of the deposited thin films used in microtechnologies. The films deposited on cold substrates have a much larger number of high asperities than is predicted by the Gaussian distribution and the contact occurs over a few asperities with heights much larger than the root-mean-square roughness. Finally, we discuss application of the effect for more precise determination of the distance upon contact, which is crucial for precise measurements of the dispersion forces especially at short separations in the range 5
- Published
- 2021
4. Tuning of electronic and optical properties of a predicted silicon allotrope: Hexagonal silicon h10 -Si
- Author
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Haiyang Niu, Yan-Ling Li, Peng Jiang, Yunguo Li, Hong-Mei Huang, and Deju Zhang
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Range (particle radiation) ,Materials science ,Silicon ,business.industry ,Silicene ,Band gap ,chemistry.chemical_element ,Electron ,Photon energy ,Semiconductor ,chemistry ,Optoelectronics ,Direct and indirect band gaps ,business - Abstract
The indirect band gap of the diamondlike silicon does not allow direct travel of electrons between valence band and conduction band edges, which has limited its application and performance in optoelectronic devices. Searching new silicon allotropes with highly tunable or direct band gap becomes more and more urgent with the increasing demand on clean energy. Here, we predict a silicon allotrope, $h10$-Si, which is an indirect-gap semiconductor with a band gap of about 0.96 eV. Furthermore, the electronic and optical properties exhibit a strong dependence on strain. In particular, the indirect band gap of the predicted silicon allotrope can be switched to a direct band gap at a uniaxial tensile strain of about 8% and the light absorption can be tuned continuously in a wide range of photon energy. Besides, the single-layer counterpart of this allotrope is confirmed to be dynamically stable and more stable in energy than silicene, endowing it with potential applications in nanoscale devices.
- Published
- 2021
5. Spacer layer thickness and temperature dependence of interlayer exchange coupling in Co/Ru/Co trilayer structures
- Author
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Erol Girt, Tommy McKinnon, and Bret Heinrich
- Subjects
Condensed Matter::Materials Science ,Range (particle radiation) ,Materials science ,Condensed matter physics ,Oscillation ,Perpendicular ,Order (ring theory) ,Electron ,Coupling (probability) ,Inductive coupling ,Layer (electronics) - Abstract
In this paper, we measure the bilinear interlayer magnetic coupling ${J}_{1}$ between two Co layers coupled across a Ru spacer layer over a wide range of spacer layer thicknesses from 0.4 to 3.4 nm and temperatures from 5 to 300 K. These measurements are fit using the interface-reflection interlayer magnetic coupling model in order to determine coupling strengths and electron Fermi velocities within the spacer layer in the direction perpendicular to the film interface for each of the critical spanning vectors. We find that there is a significant contribution to ${J}_{1}$ from several different critical spanning vectors, all with different periods of oscillation with respect to the spacer layer thickness. The results indicate that there is likely no exponential superexchangelike contribution to coupling in our samples. The nonoscillatory antiferromagnetic coupling bias of ${J}_{1}$ seen in thinner Ru spacer layers can be explained solely by a linear combination of oscillatory Ruderman-Kittel-Kasuya-Yosida-like coupling from several different critical spanning vectors, all with different periods of oscillation. The experimentally determined electron Fermi velocities are found to be within the range expected from theoretical calculations. The results also indicate that the interface-reflection model is capable of describing the bilinear interlayer exchange coupling in our samples over the entire range of spacer layer thicknesses and temperatures measured in this paper.
- Published
- 2021
6. Acoustic properties of metallic glasses at low temperatures: Tunneling systems and their dephasing
- Author
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Arnold Meißner, Uta Kühn, Saskia M. Meißner, Alexander Shnirman, S. Schneider, Georg Weiss, and Tim Voigtländer
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Superconductivity ,Range (particle radiation) ,Amorphous metal ,Materials science ,Condensed matter physics ,Dephasing ,FOS: Physical sciences ,Disordered Systems and Neural Networks (cond-mat.dis-nn) ,02 engineering and technology ,Electron ,Condensed Matter - Disordered Systems and Neural Networks ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,021001 nanoscience & nanotechnology ,Thermal conduction ,01 natural sciences ,0103 physical sciences ,Quasiparticle ,010306 general physics ,0210 nano-technology ,Quantum tunnelling - Abstract
The low temperature acoustic properties of bulk metallic glasses measured over a broad range of frequencies rigorously test the predictions of the standard tunneling model. The strength of these experiments and their analyses is mainly based on the interaction of the tunneling states with conduction electrons or quasiparticles in the superconducting state. A new series of experiments at kHz and GHz frequencies on the same sample material essentially confirms previous measurements and their discrepancies with theoretical predictions. These discrepancies can be lifted by considering more correctly the line widths of the dominating two-level atomic-tunneling systems. In fact, dephasing caused or mediated by interaction with conduction electrons may lead to particularly large line widths and destroy the tunneling sytems' two-level character in the normal conducting state.
- Published
- 2021
7. Role of NiO in the nonlocal spin transport through thin NiO films on Y3Fe5O12
- Author
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Timo Kuschel, Geert-Jan N. Sint Nicolaas, Inga Ennen, Olga Kuschel, Andreas Alexander, Geert R. Hoogeboom, Bart J. van Wees, and Joachim Wollschläger
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Range (particle radiation) ,Materials science ,Condensed matter physics ,Non-blocking I/O ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Magnetic field ,Conductor ,Thermal conductivity ,0103 physical sciences ,Thermal ,Antiferromagnetism ,Condensed Matter::Strongly Correlated Electrons ,010306 general physics ,0210 nano-technology ,Spin-½ - Abstract
In spin-transport experiments with spin currents propagating through an antiferromagnetic (AFM) material, the antiferromagnet is mainly treated as a passive spin conductor not generating nor adding any spin current to the system. The spin current transmissivity of the AFM NiO is affected by magnetic fluctuations, peaking at the N\'eel temperature and decreasing by lowering the temperature. To study the role of antiferromagnetism in local and nonlocal spin-transport experiments, we send spin currents through NiO of various thicknesses placed on ${\mathrm{Y}}_{3}{\mathrm{Fe}}_{5}{\mathrm{O}}_{12}$. The spin currents are injected either electrically or by thermal gradients and measured at a wide range of temperatures and magnetic field strengths. The transmissive role is reflected in the sign change of the local electrically injected signals and the decrease in signal strength of all other signals by lowering the temperature. The thermally generated signals, however, show an additional upturn below $100\phantom{\rule{4pt}{0ex}}\mathrm{K}$ that is unaffected by an increased NiO thickness. A change in the thermal conductivity could affect these signals. The temperature and magnetic field dependence are similar to those for bulk NiO, indicating that NiO itself contributes to thermally induced spin currents.
- Published
- 2021
8. Thermoelectric cooling properties of a quantum Hall Corbino device
- Author
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Werner Wegscheider, Liliana Arrachea, Mariano A. Real, Juan Herrera Mateos, Werner Dietsche, Alejandra Tonina, and Christian Reichl
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Condensed Matter - Materials Science ,Range (particle radiation) ,Thermoelectric cooling ,Materials science ,Condensed Matter - Mesoscale and Nanoscale Physics ,Condensed matter physics ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences ,Conductance ,02 engineering and technology ,Electron ,Quantum Hall effect ,Coefficient of performance ,021001 nanoscience & nanotechnology ,01 natural sciences ,Electrical resistance and conductance ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,0103 physical sciences ,Thermal ,010306 general physics ,0210 nano-technology - Abstract
We analyze the thermoelectric cooling properties of a Corbino device in the quantum Hall regime on the basis of experimental data of electrical conductance. We focus on the cooling power and the coefficient of performance within and beyond linear response. Thermovoltage measurements in this device reported in {\em Phys. Rev. Applied, {\bf 14} 034019 (2020)} indicated that the transport takes place in the diffusive regime, without signatures of effects due to the electron-phonon interaction in a wide range of temperatures and filling factors. In this regime, the heat and charge currents by electrons can be described by a single transmission function. We infer this function from experimental data of conductance measurements and we calculate the cooling power and the coefficient of performance for a wide range of filling factors and temperatures, as functions of the thermal and electrical biases. We predict an interesting cooling performance in several parameter regimes., 10 pages, 8 figures
- Published
- 2021
9. Domain-wall dynamics in multisegmented Ni/Co nanowires
- Author
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Voicu Dolocan, Institut des Matériaux, de Microélectronique et des Nanosciences de Provence (IM2NP), Université de Toulon (UTLN)-Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU), and Aix Marseille Université (AMU)-Université de Toulon (UTLN)-Centre National de la Recherche Scientifique (CNRS)
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Range (particle radiation) ,Materials science ,Condensed matter physics ,Polarity (physics) ,Nanowire ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Pulse (physics) ,0103 physical sciences ,Boundary value problem ,Domain wall dynamics ,[PHYS.COND]Physics [physics]/Condensed Matter [cond-mat] ,Current (fluid) ,010306 general physics ,0210 nano-technology ,ComputingMilieux_MISCELLANEOUS ,Phase diagram - Abstract
The current-induced motion of transverse magnetic domain walls (DWs) in a multisegmented Co/Ni nanowire is investigated numerically. We find that the phase diagram current pulse length magnitude presents a rare diversity of behaviors depending on the segment's length and material parameters. We show that by changing only the pulse shape, in a range of parameters we obtain the controlled motion of the DW with or without polarity change. The polarity change arises in the simplest case from the birth and propagation of an antivortex along the width of the nanowire. The antivortex can be displaced over long distances depending on the pulse characteristics and boundary conditions. The systematic motion of the DW with polarity flip is found to be stable at room temperature. Moreover, by modifying the material parameters through alloying, the phase diagram can be engineered, decreasing the depinning current and paving the way for storage or logic applications.
- Published
- 2021
10. Plasmons and magnetoplasmon resonances in nanorings
- Author
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Thomas Garm Pedersen
- Subjects
Range (particle radiation) ,Materials science ,Condensed matter physics ,Physics::Optics ,Nanoparticle ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Magnetic field ,Planar ,Homogeneous ,0103 physical sciences ,010306 general physics ,0210 nano-technology ,Plasmon - Abstract
Plasmonic sensors based on metallic nanorings benefit from resonances covering a wide spectral range and homogeneous cavity fields. Here, we explore the potential for nanorings in active plasmonics by examining the tunability of plasmon resonances due to external magnetic fields. Within the electrostatic approximation, we compute plasmon resonances and their shifts in magnetic fields for both solid and planar nanorings. In particular, solid nanorings of circular, elliptical, and disk-shaped cross sections are critically examined and compared to planar rings. Overall, we find that magnetoplasmon shifts in nanorings are greatly reduced compared to standard nanoparticles. However, flat geometries are found to be preferable and allow for relatively large shifts.
- Published
- 2021
11. Ba(Ti1−x,Zrx)O3 relaxors: Dynamic ferroelectrics in the gigahertz frequency range
- Author
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Sergey Lisenkov, A. Ladera, and Inna Ponomareva
- Subjects
Range (particle radiation) ,Materials science ,Condensed matter physics ,02 engineering and technology ,Frequency dependence ,Dielectric ,021001 nanoscience & nanotechnology ,Polarization (waves) ,01 natural sciences ,Ferroelectricity ,Condensed Matter::Materials Science ,Molecular dynamics ,0103 physical sciences ,Polar ,Curie temperature ,010306 general physics ,0210 nano-technology - Abstract
Relaxor ferroelectrics are of great scientific and technological significance as they exhibit large and unusual responses to external stimuli. Their hallmark features are broadness and frequency dispersion of the peak in the temperature dependence of the dielectric constant. Both are believed to originate from the dynamics of polar nanoregions. We apply first-principles-based molecular dynamics to resolve the gigahertz electric response of dynamically poled $\mathrm{Ba}({\mathrm{Ti}}_{1\ensuremath{-}x},{\mathrm{Zr}}_{x}){\mathrm{O}}_{3}$ ferroelectric relaxors that remained overlooked so far. We find that (i) the hallmark relaxor features continue to persist even in the dynamically poled structures, but do not necessarily originate from the polar nanoregions dynamics; (ii) dynamically poled samples exhibit polarization aging which leads to the frequency dependence of both remnant polarization and the Curie temperature; (iii) ``dynamical'' nature of the latter naturally explains the frequency dependence of the dielectric susceptibility maximum in dynamically poled $\mathrm{Ba}({\mathrm{Ti}}_{1\ensuremath{-}x},{\mathrm{Zr}}_{x}){\mathrm{O}}_{3}$; and (iv) incorporation of the polarization aging into dielectric susceptibility expression explains its enhancing contribution in an intuitive way.
- Published
- 2020
12. Phase-matched optical second harmonic generation in a hyperbolic metamaterial based on silver nanorods
- Author
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Tatiana V. Murzina, V. B. Novikov, I. V. Malysheva, Kirill S. Napolskii, Irina A. Kolmychek, and A. P. Leontiev
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Range (particle radiation) ,Materials science ,Field (physics) ,business.industry ,Phase (waves) ,Physics::Optics ,Metamaterial ,Resonance ,Second-harmonic generation ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Condensed Matter::Materials Science ,Wavelength ,0103 physical sciences ,Optoelectronics ,010306 general physics ,0210 nano-technology ,Anisotropy ,business - Abstract
Artificial hyperbolic metamaterials (HMM) are perspective for the nonlinear optical applications, their exciting functionality being due to the hyperbolic dispersion induced by a strong shape anisotropy. Here we study the second harmonic generation (SHG) in HMM formed by arrays of silver nanorods in anodic alumina. In the hyperbolic dispersion regime, giant SHG is observed associated with the fulfillment of the phase-matching conditions supported by the epsilon-near-pole resonance at the SHG wavelength, and an increase in the pump field in the epsilon-near-zero (ENZ) spectral range. We predict a strong increase in the SHG efficiency for metamaterials with the ENZ resonance at the second harmonic frequency.
- Published
- 2020
13. Imaging of nearly flat band induced atomic-scale negative differential conductivity in ABC -stacked trilayer graphene
- Author
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Xiaoshuai Fu, Li-Zhen Yang, Lijie Zhang, Qilong Wu, Zhihui Qin, Long-Jing Yin, Ling-Hui Tong, Li Zhang, Yuan Tian, and Guang Yang
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Range (particle radiation) ,Materials science ,Condensed matter physics ,Graphene ,Scanning tunneling spectroscopy ,Macroscopic quantum phenomena ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Atomic units ,law.invention ,law ,Condensed Matter::Superconductivity ,0103 physical sciences ,Dispersion (optics) ,Surface layer ,010306 general physics ,0210 nano-technology ,Quantum tunnelling - Abstract
Despite recent transport studies of ABC-stacked multilayer graphene systems revealed various unusual quantum phenomena which arise from the nearly flat electronic bands, their quantum tunneling properties have rarely been addressed. Here we investigate the local tunneling characteristics of a gapped ABC-stacked trilayer graphene (TLG) and report the experimental observation of the nearly flat band induced atomic-site-dependent negative differential conductivity (NDC, characterized by a current drop with increasing voltage) via scanning tunneling spectroscopy (STS) measurements. We show that strong NDC emerges in the gap region next to a sharp STS peak induced by the very flat low-energy dispersion of ABC TLG. The NDC is found to mainly reside on one atomic sublattice of the surface layer due to the strong sublattice and layer localization of the nearly flat bands. The observed NDC behavior is explained by the tunnel-diode mechanism, namely, the coexistence of a sharp flat-dispersion STS peak in which tunneling is strongly enhanced and a subsequent gap region in which tunneling is forbidden. Furthermore, we also find that a local defect could effectively switch off the NDC over a large spatial range. Our result highlights a quantum tunneling effect unique to the graphene-based nearly flat band system and expands the potential application scope of ABC TLG.
- Published
- 2020
14. Short-range magnetic order in the paramagnetic phase of cubic SrMnO3−x ( x<0.005 ): An O17 and Sr87 NMR study
- Author
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A. Gerashenko, A. Trokiner, K. N. Mikhalev, Z. N. Volkova, A. Yakubovskii, Alexander Yu. Germov, and S. V. Verkhovskii
- Subjects
Paramagnetism ,Range (particle radiation) ,Materials science ,Magnetic order ,Phase (matter) ,Analytical chemistry - Published
- 2020
15. Anisotropy and temperature dependence of the spin-wave stiffness in Nd2Fe14B : An inelastic neutron scattering investigation
- Author
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C. Rado, H. Naser, Stéphane Raymond, and Gérard Lapertot
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Range (particle radiation) ,Materials science ,Condensed matter physics ,Isotropy ,02 engineering and technology ,021001 nanoscience & nanotechnology ,7. Clean energy ,01 natural sciences ,Inelastic neutron scattering ,Tetragonal crystal system ,Spin wave ,Magnet ,0103 physical sciences ,Dispersion (optics) ,010306 general physics ,0210 nano-technology ,Anisotropy - Abstract
The anisotropy and the temperature dependence of the spin-wave stiffness constants of the permanent magnet ${\mathrm{Nd}}_{2}{\mathrm{Fe}}_{14}\mathrm{B}$ are determined in the range 160--440 K using single-crystal inelastic neutron scattering technique. It is found that the deviation from isotropic spin-wave dispersion, between the $a$ and the $c$ axis of the tetragonal structure, is small and eventually the anisotropy decreases when the temperature increases. The softening of the stiffness constants can be described by a linear temperature variation with an average rate of about $\ensuremath{-}0.46$ meV ${\AA{}}^{2}/\mathrm{K}$. These results are compared with the most recent atomistic and multiscale calculations.
- Published
- 2020
16. Tunneling mechanism in a (Ga,Mn)As/GaAs-based spin Esaki diode investigated by bias-dependent shot noise measurements
- Author
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Dieter Schuh, Yasuhiro Niimi, Kensuke Kobayashi, Makoto Kohda, Tomonori Arakawa, Junsaku Nitta, M. Maeda, Junichi Shiogai, Martin Utz, Mariusz Ciorga, Dominique Bougeard, and Dieter Weiss
- Subjects
Fano factor ,Range (particle radiation) ,Materials science ,Condensed matter physics ,ddc:530 ,Shot noise ,Biasing ,02 engineering and technology ,530 Physik ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,021001 nanoscience & nanotechnology ,Thermal conduction ,01 natural sciences ,0103 physical sciences ,Tunnel diode ,010306 general physics ,0210 nano-technology ,Quantum tunnelling ,Spin-½ - Abstract
Electron transport across a tunneling barrier is governed by intricate and diverse causes such as interface conditions, material properties, and device geometries. Here, by measuring the shot noise, we investigate electron transport in a (Ga,Mn)As/GaAs-based spin Esaki diode junction over a wide range of bias voltage. The asymmetric electronic band profile across the junction allows us to tune the types of tunneling process. By changing the bias voltage in a single device, we successively address the conventional direct tunneling, the excess current conduction through the mid-gap localized states, and the thermal excitation current conduction. These observations lead to a proper comparison of the bias dependent Fano factors. While the Fano factor is unity for the direct tunneling, it is pronouncedly reduced in the excess current region. Thus, we have succeeded in evaluating several types of conduction process with the Fano factor in a single junction.
- Published
- 2020
17. Phonon traces in glassy vibrations
- Author
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S. N. Taraskin, Stephen R. Elliott, J. D. Wiles, Nikita S. Shcheblanov, and Mikhail E. Povarnitsyn
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Condensed Matter::Soft Condensed Matter ,Vibration ,Range (particle radiation) ,Materials science ,Condensed matter physics ,Phonon ,Crystallite ,Condensed Matter::Disordered Systems and Neural Networks ,Symmetry (physics) - Abstract
A numerical approach, based on a local comparative projectional analysis onto symmetry modes of elementary structural units of glasses and their crystalline counterparts, is developed and used for the analysis of atomic vibrations in glasses in terms of phonons for the entire frequency range. The results of such an analysis shed light on the origin of the modes in the controversial low-frequency range, including the boson-peak region. Comparative analyses undertaken for glass, lattice-glass, and polycrystalline models reveal the role of different types of disorder in atomic vibrations.
- Published
- 2020
18. Photoexcited elastic waves in free-standing GaAs films
- Author
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Daniel Gammon, Brian H. Houston, A. S. Bracker, Samuel G. Carter, M. Zalalutdinov, and Douglas M. Photiadis
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Coupling ,Range (particle radiation) ,Materials science ,business.industry ,Phonon ,Physics::Optics ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,High strain ,Condensed Matter::Materials Science ,Semiconductor ,0103 physical sciences ,Femtosecond ,Optoelectronics ,Electronics ,010306 general physics ,0210 nano-technology ,business ,Excitation - Abstract
The ability to generate transversely propagating elastic waves on free-standing semiconductor films in the 10+ GHz frequency range is a critical element in the effort to achieve phonon-based coupling to on-chip electronic devices. The results of this joint experimental and theoretical study show that such phonons are created by the excitation of free-standing optically subwavelength thickness GaAs films with highly focused femtosecond optical pulses. With sufficiently high strain levels, this approach could become enabling for applications in nano-optomechanics.
- Published
- 2020
19. Transient optics of gold during laser irradiation: From first principles to experiment
- Author
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Tobias Zier, Jürgen Ihlemann, F. Kleinwort, Baerbel Rethfeld, Andreas Blumenstein, Eeuwe S. Zijlstra, Peter Šimon, S. T. Weber, D. S. Ivanov, and Martin E. Garcia
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Work (thermodynamics) ,Range (particle radiation) ,Materials science ,business.industry ,Physics::Optics ,02 engineering and technology ,Electron ,Dissipation ,021001 nanoscience & nanotechnology ,Laser ,01 natural sciences ,Fluence ,law.invention ,Optics ,law ,0103 physical sciences ,Irradiation ,Transient (oscillation) ,010306 general physics ,0210 nano-technology ,business - Abstract
The reflectivity of noble metals can dramatically change upon ultrashort laser irradiation due to the heating of $d$ electrons to high temperatures. Knowledge of the resulting transient optics is fundamental for determining and controlling the absorbed energy. In this work, high-accuracy self-reflectivity measurements are performed and interpreted using a theory for the space-resolved and time-resolved energy absorption and dissipation. The combined approach yields the reflectivity of gold in dependence on the incident laser fluence for a wide spectral range.
- Published
- 2020
20. Extraction of Dzyaloshinskii-Moriya interaction from propagating spin waves
- Author
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B Bert Koopmans, Sabine Wurmehl, Marcel A. Verheijen, Henk J. M. Swagten, Juriaan Lucassen, Reinoud Lavrijsen, EJ Erik Jan Geluk, Patrizia Fritsch, B Barcones, Casper F. Schippers, Rembert A. Duine, Physics of Nanostructures, Plasma & Materials Processing, Photonic Integration, NanoLab@TU/e, Center for Care & Cure Technology Eindhoven, Atomic scale processing, and Eindhoven Hendrik Casimir institute
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Range (particle radiation) ,Materials science ,Condensed matter physics ,Magnetism ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Stack (abstract data type) ,Spin wave ,0103 physical sciences ,Magnetic layer ,010306 general physics ,0210 nano-technology ,Spectroscopy ,Anisotropy ,Spin-½ - Abstract
The interfacial Dzyaloshinskii-Moriya interaction (iDMI) is of great interest in thin-film magnetism because of its ability to stabilize chiral spin textures. It can be quantified by investigating the frequency nonreciprocity of oppositely propagating spin waves. However, as the iDMI is an interface interaction, the relative effect reduces when the films become thicker, making quantification more difficult. Here, we utilize all-electrical propagating spin-wave spectroscopy to disentangle multiple contributions to spin wave frequency nonreciprocity to determine the iDMI. This is done by investigating nonreciprocities across a wide range of magnetic layer thicknesses (from 4 to 26 nm) in Pt/Co/Ir, Pt/Co/Pt, and Ir/Co/Pt stacks. We find the expected sign change in the iDMI when inverting the stack order and a negligible iDMI for the symmetric Pt/Co/Pt. We additionally extract a difference in surface anisotropies and find a large contribution due to the formation of different crystalline phases of the Co, which is corroborated using nuclear magnetic resonance and high-resolution transmission-electron-microscopy measurements. These insights will open up avenues to investigate, quantify, and disentangle the fundamental mechanisms governing the iDMI, and pave a way toward engineered large spin-wave nonreciprocities for magnonic applications.
- Published
- 2020
21. Semiempirical van der Waals method for two-dimensional materials with incorporated dielectric functions
- Author
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Jiabao Yang, Xiaofei Liu, and Wanlin Guo
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Range (particle radiation) ,Materials science ,Heterojunction ,02 engineering and technology ,Dielectric ,021001 nanoscience & nanotechnology ,01 natural sciences ,Molecular physics ,Condensed Matter::Materials Science ,symbols.namesake ,Planar ,0103 physical sciences ,Physics::Atomic and Molecular Clusters ,symbols ,Density functional theory ,van der Waals force ,010306 general physics ,0210 nano-technology ,Adiabatic process ,Dispersion (chemistry) - Abstract
A density functional theory based semiempirical van der Waals (vdW) method with dielectric functions being incorporated is developed for two-dimensional materials. The coefficients of interatomic pairwise potentials are derived from atomic polarizabilities obtained via a Clausius-Mossotti relation dedicated for layered crystals. The method not only can efficiently describe the dispersion energy for a range of planar graphene-like materials at nearly the same accuracy as the adiabatic connection fluctuation-dissipation theorem, but also rationalizes experimentally measured relative interfacial strengths of heterostructures and interlayer registry of hexagonal boron nitride that have plagued other vdW methods.
- Published
- 2020
22. Determination of the melting curve of gold up to 110 GPa
- Author
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Gunnar Weck, Mohamed Mezouar, Frédéric Datchi, Jean-Antoine Queyroux, Paul Loubeyre, S. Ninet, V. Recoules, J. Bouchet, Gaston Garbarino, DAM Île-de-France (DAM/DIF), Direction des Applications Militaires (DAM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Institut de minéralogie, de physique des matériaux et de cosmochimie (IMPMC), Muséum national d'Histoire naturelle (MNHN)-Institut de recherche pour le développement [IRD] : UR206-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Département de Physique Théorique et Appliquée (DPTA), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction des Applications Militaires (DAM), European Synchrotron Radiation Facility (ESRF), and ANR-13-BS04-0015,MOFLEX,Structure et dynamique des fluides moléculaires simples sous conditions extrêmes de pression et température(2013)
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Diffraction ,Range (particle radiation) ,Materials science ,Diamond ,Thermodynamics ,02 engineering and technology ,engineering.material ,021001 nanoscience & nanotechnology ,01 natural sciences ,Temperature measurement ,Melting curve analysis ,Synchrotron ,Diamond anvil cell ,law.invention ,law ,0103 physical sciences ,[PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci] ,engineering ,010306 general physics ,0210 nano-technology ,Pyrometer - Abstract
International audience; The melting curve of gold has been measured up to 110 GPa using laser-heated diamond anvil cells and synchrotron x-ray diffraction techniques. Accurate pyrometry temperature measurements and a homogeneous heating of the gold sample were achieved by implementing a sample assembly consisting of two boron-doped diamond cupped disks sandwiching the gold sample. In the investigated pressure range, the fcc solid gold remains stable up to melting. A clear structural signature of bulk melting is observed. Ab initio molecular dynamics simulations within the two-phase approach give a melting curve in good agreement with the experimental one. We discuss the validity of calculations based on the Lindemann criteria of melting which have been up to now used to obtain the melting line of Au in the 100 GPa range.
- Published
- 2020
23. Generation of phonon-induced resistance oscillations by terahertz radiation
- Author
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H. W. Schumacher, Thomas Heinzel, L. Freise, Beate Horn-Cosfeld, M. Cerchez, and Klaus Pierz
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Range (particle radiation) ,Materials science ,business.industry ,Terahertz radiation ,Phonon ,Physics::Optics ,02 engineering and technology ,Electron ,021001 nanoscience & nanotechnology ,01 natural sciences ,0103 physical sciences ,Optoelectronics ,010306 general physics ,0210 nano-technology ,business - Abstract
Terahertz radiation is demonstrated to generate phonon-induced resistance oscillations in two-dimensional electron gases. This effect dominates over microwave-induced resistance oscillations in the low terahertz range, but could not be detected in the gigahertz regime. Possible mechanisms for phonon generation are discussed.
- Published
- 2019
24. Pressure-induced densification of vitreous silica: Insight from elastic properties
- Author
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Coralie Weigel, René Vacher, Marouane Mebarki, Sébastien Clément, Marie Foret, Benoit Ruffle, Laboratoire Charles Coulomb (L2C), and Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
Condensed Matter - Materials Science ,Range (particle radiation) ,Equation of state ,Materials science ,Coordination number ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences ,Thermodynamics ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Light scattering ,Brillouin zone ,Hysteresis ,0103 physical sciences ,Dispersion (optics) ,[PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci] ,Compressibility ,010306 general physics ,0210 nano-technology ,ComputingMilieux_MISCELLANEOUS - Abstract
\textit{In situ} high-pressure Brillouin light scattering experiments along loading-unloading paths are used to investigate the compressibility of vitreous silica. An accurate equation of state is obtained below \SI{9}{GPa} using sound velocities corrected for dispersion. Conversely, huge inelastic effects are observed in the range \SIrange{10}{60}{GPa}, unveiling the reversible transformation from the fourfold-coordinated structure to the sixfold one. We find that the associated density changes fully correlate with the average Si coordination number. Decompression curves from above \SI{20}{GPa} reveal abrupt backward coordination changes around \SIrange{10}{15}{GPa} and significant hysteresis. Further, contrary to common wisdom, the residual densification of recovered silica samples can be figured out from the pressure cycles., 5 pages, 4 figures, revised version
- Published
- 2019
25. Intrinsic point defects and the n - and p -type dopability of the narrow gap semiconductors GaSb and InSb
- Author
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John Buckeridge, David O. Scanlon, C. R. A. Catlow, and Tim D. Veal
- Subjects
Coupling ,Range (particle radiation) ,Materials science ,Condensed matter physics ,02 engineering and technology ,Narrow-gap semiconductor ,021001 nanoscience & nanotechnology ,01 natural sciences ,Crystallographic defect ,Condensed Matter::Materials Science ,Ionization ,0103 physical sciences ,Density functional theory ,Physics::Chemical Physics ,010306 general physics ,0210 nano-technology ,Fermi Gamma-ray Space Telescope - Abstract
The presence of defects in the narrow gap semiconductors GaSb and InSb affects their dopability and hence applicability for a range of optoelectronic applications. Here, we report hybrid density functional theory (DFT)-based calculations of the properties of intrinsic point defects in the two systems, including spin-orbit coupling effects, which influence strongly their band structures. With the hybrid DFT approach adopted, we obtain excellent agreement between our calculated band dispersions and structural, elastic, and vibrational properties and available measurements. We compute point defect formation energies in both systems, finding that antisite disorder tends to dominate, apart from in GaSb under certain conditions, where cation vacancies can form in significant concentrations. Calculated self-consistent Fermi energies and equilibrium carrier and defect concentrations confirm the intrinsic n- and p-type behavior of both materials under anion-rich and anion-poor conditions. Moreover, by computing the compensating defect concentrations due to the presence of ionized donors and acceptors, we explain the observed dopability of GaSb and InSb.
- Published
- 2019
26. Magnetoelectric coupling without long-range magnetic order in the spin- 12 multiferroic Rb2Cu2Mo3O12
- Author
-
H. Luetkens, A. Mannig, Jonathan S. White, Ch. Niedermayer, A. Fujimura, C. Baines, Tatsuo Goko, Yukio Yasui, Marek Bartkowiak, Robert Scheuermann, N. Reynolds, and Lukas Keller
- Subjects
Coupling ,Range (particle radiation) ,Materials science ,Condensed matter physics ,Magnetic order ,0103 physical sciences ,Multiferroics ,010306 general physics ,Spin (physics) ,01 natural sciences ,010305 fluids & plasmas - Published
- 2019
27. Optical spectroscopy of SmN: Locating the 4f conduction band
- Author
-
R. G. Buckley, Ben J. Ruck, W. F. Holmes-Hewett, Franck Natali, and H. J. Trodahl
- Subjects
Superconductivity ,Range (particle radiation) ,Materials science ,Condensed matter physics ,chemistry.chemical_element ,02 engineering and technology ,Nitride ,021001 nanoscience & nanotechnology ,01 natural sciences ,Samarium ,chemistry ,0103 physical sciences ,Free carrier absorption ,010306 general physics ,0210 nano-technology ,Electronic band structure ,Ground state ,Spectroscopy - Abstract
The rare-earth nitride ferromagnetic semiconductors owe their varying magnetic properties to the progressive filling of the $4f$ shell across the series. Recent electrical transport measurements on samarium nitride, including the observation of superconductivity, have been understood in terms of a contribution from a $4f$ transport channel. Band structure calculations generally locate an empty majority-spin $4f$ band within the conduction band although over a wide range of possible energies. Here we report optical reflection and transmission measurements on samarium nitride from 0.01 to 4 eV that demonstrate clearly that the $4f$ band forms the bottom of the conduction band. Results at the lowest energies show no free carrier absorption, indicating a semiconducting ground state, and support earlier conclusions based on transport measurements.
- Published
- 2019
28. Enhanced Gilbert damping in Re-doped FeCo films: Combined experimental and theoretical study
- Author
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Nilamani Behera, Daniel Primetzhofer, Carmine Autieri, Rudra Banerjee, Ankit Kumar, Peter Svedlindh, Raquel Esteban-Puyuelo, Vijayaharan A. Venugopal, Biplab Sanyal, Mauricio A. Sortica, Serkan Akansel, Swaraj Basu, Mark Anthony Gubbins, and Rimantas Brucas
- Subjects
Condensed Matter - Materials Science ,Range (particle radiation) ,Materials science ,Condensed matter physics ,Doping ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences ,chemistry.chemical_element ,02 engineering and technology ,Electron ,Rhenium ,021001 nanoscience & nanotechnology ,01 natural sciences ,Condensed Matter::Materials Science ,chemistry ,Condensed Matter::Superconductivity ,0103 physical sciences ,Physics::Chemical Physics ,Thin film ,010306 general physics ,0210 nano-technology - Abstract
The effects of rhenium doping in the range 0 to 10 atomic percent on the static and dynamic magnetic properties of Fe65Co35 thin films have been studied experimentally as well as with first principles electronic structure calculations focusing on the change of the saturation magnetization and the Gilbert damping parameter. Both experimental and theoretical results show that the saturation magnetization decreases with increasing Re doping level, while at the same time Gilbert damping parameter increases. The experimental low temperature saturation magnetic induction exhibits a 29 percent decrease, from 2.31 T to 1.64 T, in the investigated doping concentration range, which is more than predicted by the theoretical calculations. The room temperature value of the damping parameter obtained from ferromagnetic resonance measurements, correcting for extrinsic contributions to the damping, is for the undoped sample 0.0027, which is close to the theoretically calculated Gilbert damping parameter. With 10 atomic percent Re doping, the damping parameter increases to 0.0090, which is in good agreement with the theoretical value of 0.0073. The increase in damping parameter with Re doping is explained by the increase in density of states at Fermi level, mostly contributed by the spin-up channel of Re. Moreover, both experimental and theoretical values for the damping parameter are observed to be weakly decreasing with decreasing temperature., 13 pages, 8 figures, 5 tables, Materials for spin-logic circuits
- Published
- 2019
29. First-principles investigations of the magnetic phase diagram of Gd1−xCaxMnO3
- Author
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Martin Hoffmann, Petriina Paturi, Hichem Ben Hamed, Kalevi Kokko, Waheed A. Adeagbo, Teemu Hynninen, Wolfram Hergert, and Arthur Ernst
- Subjects
Range (particle radiation) ,Materials science ,Condensed matter physics ,Monte Carlo method ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Magnetic phase diagram ,01 natural sciences ,Ferromagnetism ,0103 physical sciences ,Antiferromagnetism ,Condensed Matter::Strongly Correlated Electrons ,Density functional theory ,010306 general physics ,0210 nano-technology ,Ground state ,Solid solution - Abstract
We studied the magnetic phase diagram of the rare-earth manganites series ${\mathrm{Gd}}_{1\ensuremath{-}x}{\mathrm{Ca}}_{x}{\mathrm{MnO}}_{3}$ (GCMO) over the full concentration range based on density functional theory. GCMO has been shown to form solid solutions. We take into account this disordered character by adapting special quasi-random structures at different concentration steps. The magnetic phase diagram is mainly described by means of the magnetic exchange interactions between the Mn sites, and Monte Carlo simulations were performed to estimate the corresponding transition temperatures. They agree very well with recent experiments. The hole-doped region $xl0.5$ shows a strong ferromagnetic ground state, which competes with A-type antiferromagnetism at higher Ca concentrations $xg0.6$.
- Published
- 2019
30. Differential anharmonicity and thermal expansion coefficient in3C-SiC nanowires
- Author
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Zubaer M. Hossain, Zhaocheng Zhang, and Fazle Elahi
- Subjects
Surface (mathematics) ,Range (particle radiation) ,Materials science ,Condensed matter physics ,Anharmonicity ,Nanowire ,Inverse ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Power law ,Thermal expansion ,Core (optical fiber) ,0103 physical sciences ,010306 general physics ,0210 nano-technology - Abstract
Surface and core are two essential but distinct structural parts of a nanowire---but their individual effects on overall thermal expansion coefficient of a nanowire have never been quantified. Here we present an average bond-length based framework to determine the effects of the surface and core regimes of $3C$-SiC nanowires on their effective volumetric thermal expansion coefficient over a wide range of temperatures. Our results suggest that the surface and core atoms exhibit differential anharmonic response at finite temperatures, which makes the surface regime exhibit disparate expansion behavior compared to the core. While at lower temperatures the differential anharmonicity is negligible, at temperatures higher than the room temperature there is a pronounced differential anharmonicity in the nanowire. Furthermore, temperature-dependent expansion coefficients of the nanowire and the surface and core regimes qualitatively follow the behavior of the bulk---but they vary substantially quantitatively, with the maximum coefficient exhibited by the surface at higher temperatures. The diameter-dependent expansion coefficients follow inverse power laws with their exponents varying from 0.95 to 2.5. In thinner nanowires the expansion coefficient is controlled by an intricate combination of mass inertia and bond stiffness at the surface and core, whereas the expansion of thicker nanowires is dominated by the anharmonic motion of the core atoms alone. The surface effects saturate with increasing diameter, but the core effects decay nonlinearly with increasing diameter and approaches the bulk value as $d\ensuremath{\rightarrow}\ensuremath{\infty}$.
- Published
- 2019
31. Effect of anharmonicity on the hcp to bcc transition in beryllium at high-pressure and high-temperature conditions
- Author
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Xing-Yu Gao, Jun Yan, Tao Sun, Jiawei Xian, Gongmu Zhang, Hai-Feng Song, and Haifeng Liu
- Subjects
Phase transition ,Range (particle radiation) ,Materials science ,Condensed matter physics ,Condensed Matter::Other ,Triple point ,Anharmonicity ,chemistry.chemical_element ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Condensed Matter::Materials Science ,Molecular dynamics ,chemistry ,High pressure ,0103 physical sciences ,Beryllium ,010306 general physics ,0210 nano-technology ,Energy (signal processing) - Abstract
We investigate the hcp to bcc phase transition in beryllium (Be) at high-pressure and -temperature ($PT$) conditions. A recently developed hybrid approach that combines first-principles molecular dynamics and lattice dynamics is used to account for anharmonic contributions to the free energy. Anharmonic effects are shown to be strong at high $T$ in both hcp and bcc Be. They are stronger in hcp Be than in bcc Be, as evidenced by the larger anharmonic vibrational entropy of hcp Be. We find that anharmonicity has a significant influence on the hcp to bcc transition at high-$PT$ conditions. It substantially enlarges the stability domain of hcp Be at high $T$ compared with that calculated under the quasiharmonic approximation (QHA), as a result bringing theoretical predictions into good consistency with recent experimental observations. After considering anharmonic effects, the calculated pressure and temperature of the hcp/bcc/liquid triple point increase from about 85 to 165 GPa, and from about 3300 to 4200 K, respectively, and the predicted Clapeyron slope at the triple point takes a value of $\ensuremath{-}7.4\ifmmode\pm\else\textpm\fi{}0.7\phantom{\rule{0.28em}{0ex}}\mathrm{K}/\mathrm{GPa}$, noticeably larger in magnitude than previous QHA results in the range of $\ensuremath{-}3$ to 2 K/GPa.
- Published
- 2019
32. Energy losses and transition radiation in graphene traversed by a fast charged particle under oblique incidence
- Author
-
Silvina Segui, Kamran Akbari, N. R. Arista, J.L. Gervasoni, and Zoran L. Mišković
- Subjects
GRAPHENE ,EELS ,Materials science ,Terahertz radiation ,Ciencias Físicas ,Physics::Optics ,02 engineering and technology ,7. Clean energy ,01 natural sciences ,Molecular physics ,law.invention ,purl.org/becyt/ford/1 [https] ,law ,0103 physical sciences ,Scanning transmission electron microscopy ,PLASMONS ,010306 general physics ,Range (particle radiation) ,Graphene ,Electron energy loss spectroscopy ,purl.org/becyt/ford/1.3 [https] ,021001 nanoscience & nanotechnology ,Charged particle ,Transverse mode ,Transition radiation ,RETARDATION EFFECTS ,0210 nano-technology ,CIENCIAS NATURALES Y EXACTAS ,Física de los Materiales Condensados - Abstract
We perform fully relativistic calculations of the energy loss channels for a charged particle traversing a single layer of graphene under oblique incidence in a setting pertinent to a Scanning Transmission Electron Microscope (STEM), where we distinguish between the energy deposited in graphene in the form of electronic excitations (Ohmic loss) and the energy emitted in the far field in the form of transition radiation (TR). Our formulation of the problem uses a definition of two in-plane, dielectric functions of graphene, which describe the longitudinal and transverse excitation processes that contribute separately to those two energy loss channels. Using several models for the electric conductivity of graphene as the input in those dielectric functions enables us to discuss the effects of oblique incidence on several processes in a broad range of frequencies, from the terahertz (THz) to the ultraviolet (UV). In particular, at the THz frequencies, we demonstrate that the nonlocal effect in the graphene?s conductivity is not important in the retarded regime, and we show that the longitudinal and transverse contributions to the emitted TR spectra exhibit strongly anisotropic angular patterns that are readily distinguishable in a cathodoluminescence measurement in a STEM. Moreover, we explore the possibility of exciting the so-called transverse mode in the optical response of graphene at the mid-infrared (MIR) range of frequencies by means of a fast charged particle under oblique incidence. Finally, we demonstrate that, besides the usual high-energy peaks in the longitudinal contribution to the Ohmic energy loss in the MIR to the UV frequency range, there may arise strongly directional features in the in-plane distribution of the transverse contribution to the Ohmic energy loss for an oblique trajectory, which could be possibly observed via momentum- and angle-resolved electron energy loss spectroscopy of graphene in STEM. Fil: Akbari, Kamran. University of Waterloo; Canadá Fil: Segui Osorio, Silvina Inda Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Miskovic, Zoran L.. University of Waterloo; Canadá Fil: Gervasoni, Juana Luisa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Comisión Nacional de Energía Atómica; Argentina Fil: Arista, Nestor Ricardo. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Comisión Nacional de Energía Atómica; Argentina
- Published
- 2018
33. Coexistence of superconductivity and short-range double-stripe spin correlations in Te-vapor annealed FeTe1−xSex ( x≤0.2 )
- Author
-
Masaaki Matsuda, Songxue Chi, Guangyong Xu, Genda Gu, J. Schneeloch, Zhijun Xu, John M. Tranquada, Ming Yi, Yang Zhao, Robert J. Birgeneau, and Daniel M. Pajerowski
- Subjects
Superconductivity ,Range (particle radiation) ,Materials science ,Condensed matter physics ,Resonance ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Inelastic neutron scattering ,Ion ,Character (mathematics) ,Condensed Matter::Superconductivity ,0103 physical sciences ,Antiferromagnetism ,010306 general physics ,0210 nano-technology ,Spin-½ - Abstract
Author(s): Xu, Z; Schneeloch, JA; Yi, M; Zhao, Y; Matsuda, M; Pajerowski, DM; Chi, S; Birgeneau, RJ; Gu, G; Tranquada, JM; Xu, G | Abstract: In as-grown bulk crystals of Fe1+yTe1-xSex with x≲0.3, excess Fe (yg0) is inevitable and correlates with a suppression of superconductivity. At the same time, there remains the question as to whether the character of the antiferromagnetic correlations associated with the enhanced anion height above the Fe planes in Te-rich samples is compatible with superconductivity. To test this, we have annealed as-grown crystals with x=0.1 and 0.2 in Te vapor, effectively reducing the excess Fe and inducing bulk superconductivity. Inelastic neutron scattering measurements reveal low-energy magnetic excitations consistent with short-range correlations of the double-stripe type; nevertheless, cooling into the superconducting state results in a spin gap and a spin resonance, with the extra signal in the resonance being short range with a mixed single-stripe/double-stripe character, which is different than other iron-based superconductors. The mixed magnetic character of these superconducting samples does not appear to be trivially explainable by inhomogeneity.
- Published
- 2018
34. Subnanosecond magnetization reversal of a magnetic nanoparticle driven by a chirp microwave field pulse
- Author
-
M. T. Islam, X. R. Wang, Xiansi Wang, and Yunyan Zhang
- Subjects
010302 applied physics ,Range (particle radiation) ,Materials science ,Condensed Matter - Mesoscale and Nanoscale Physics ,Field (physics) ,Condensed matter physics ,01 natural sciences ,Pulse (physics) ,Magnetic field ,Amplitude ,0103 physical sciences ,Chirp ,010306 general physics ,Microwave ,Spin-½ - Abstract
We investigate the magnetization reversal of a single-domain magnetic nanoparticle driven by a linear down-chirp microwave magnetic field pulse. Numerical simulations based on the Landau-Lifshitz-Gilbert equation reveal that a down-chirp microwave pulse is solely capable of inducing subnanosecond magnetization reversal. With a certain range of initial frequency and chirp rate, the required field amplitude is much smaller than that of a constant-frequency microwave field. The fast reversal is due to the fact that the down-chirp microwave field pulse triggers stimulated microwave absorptions (emissions) by (from) the spin before (after) it crosses over the energy barrier. Applying a spin-polarized current additively to the system further reduces the microwave field amplitude. Our findings provide a way to realize low-cost and fast magnetization reversal.
- Published
- 2018
35. Characterization of the isolated [Co3Ni(EtOH)]+ cluster by IR spectroscopy and spin-dynamics calculations
- Author
-
M. Becherer, Daniel Bellaire, F. Dietrich, Wolfgang Hübner, Markus Gerhards, Dibyajyoti Dutta, and Georgios Lefkidis
- Subjects
Range (particle radiation) ,Materials science ,Infrared spectroscopy ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Quantum chemistry ,Molecular physics ,0103 physical sciences ,Atom ,Cluster (physics) ,Laser detuning ,010306 general physics ,0210 nano-technology ,Molecular beam ,Ultrashort pulse - Abstract
We experimentally and theoretically study the geometry, as well as the electronic and vibrational properties, of the heterotetranuclear magnetic cluster ${[{\mathrm{Co}}_{3}\mathrm{Ni}(\mathrm{EtOH})]}^{+}$, which is prepared in the gas phase with molecular beam expansion. We characterize the cluster and identify possible isomers through the comparison of experimentally observed infrared spectra with state-of-the-art quantum chemistry calculations, more specifically by focusing on the OH stretching frequency. Furthermore, we suggest ultrafast, laser-induced, local spin-flip scenarios on every Co atom, and report a cooperative effect, in which the spin density is localized on one Co atom, gets transiently transferred to another, and then bounces back pointing in the opposite direction. Finally, we predict a tolerance of the suggested scenarios with respect to the laser detuning of about 20 meV, which lies within an experimentally applicable range. Our joint investigation is an additional step toward the implementation of laser-controlled nanospintronic devices.
- Published
- 2018
36. Hybrid k·p tight-binding model for intersubband optics in atomically thin InSe films
- Author
-
Adrian Ceferino, Vladimir I. Fal'ko, Samuel Magorrian, and Viktor Zólyomi
- Subjects
Range (particle radiation) ,Materials science ,Infrared ,business.industry ,Bilayer ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Condensed Matter::Materials Science ,Tight binding ,Optics ,0103 physical sciences ,Thermal ,010306 general physics ,0210 nano-technology ,business - Abstract
We propose atomic films of $n$-doped $\ensuremath{\gamma}$-InSe as a platform for intersubband optics in the infrared and far-infrared range, coupled to out-of-plane polarized light. Depending on the film thickness (number of layers) and the amount of $n$-doping of the InSe film, these transitions span from $\ensuremath{\sim}0.7$ eV for bilayer to $\ensuremath{\sim}0.05$ eV for 15-layer InSe. We use a hybrid $\mathbf{k}\ifmmode\cdot\else\textperiodcentered\fi{}\mathbf{p}$ theory and tight-binding model, fully parametrized using density-functional theory, to predict their oscillator strengths and thermal linewidths at room temperature.
- Published
- 2018
37. Probing long-range structural order in SnPc/Ag(111) by umklapp process assisted low-energy angle-resolved photoelectron spectroscopy
- Author
-
Julian Falke, Stephan Jauernik, Petra Hein, Michael Bauer, and Max Gurgel
- Subjects
Range (particle radiation) ,Materials science ,Low energy ,X-ray photoelectron spectroscopy ,0103 physical sciences ,02 engineering and technology ,021001 nanoscience & nanotechnology ,010306 general physics ,0210 nano-technology ,01 natural sciences ,Molecular physics - Published
- 2018
38. Superconductivity induced by interfacial coupling to magnons
- Author
-
Eirik Løhaugen Fjærbu, Arne Brataas, and Niklas Rohling
- Subjects
Materials science ,Yttrium iron garnet ,FOS: Physical sciences ,02 engineering and technology ,Electron ,01 natural sciences ,Superconductivity (cond-mat.supr-con) ,Metal ,Condensed Matter::Materials Science ,chemistry.chemical_compound ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,0103 physical sciences ,010306 general physics ,Superconductivity ,Coupling ,Range (particle radiation) ,Condensed Matter - Mesoscale and Nanoscale Physics ,Condensed matter physics ,Condensed Matter - Superconductivity ,Magnon ,021001 nanoscience & nanotechnology ,chemistry ,Ferromagnetism ,visual_art ,visual_art.visual_art_medium ,Condensed Matter::Strongly Correlated Electrons ,0210 nano-technology - Abstract
We consider a thin normal metal sandwiched between two ferromagnetic insulators. At the interfaces, the exchange coupling causes electrons within the metal to interact with magnons in the insulators. This electron-magnon interaction induces electron-electron interactions, which, in turn, can result in p-wave superconductivity. In the weak-coupling limit, we solve the gap equation numerically and estimate the critical temperature. In YIG-Au-YIG trilayers, superconductivity sets in at temperatures somewhere in the interval between 1 and 10 K. EuO-Au-EuO trilayers require a lower temperature, in the range from 0.01 to 1 K., 6 pages, 3 figures
- Published
- 2018
39. Anharmonic model for the elastic constants of bulk metallic glass across the glass transition
- Author
-
John J. Lewandowski, Yong-Wei Zhang, Mehdi Jafary-Zadeh, and Zachary H. Aitken
- Subjects
Range (particle radiation) ,Materials science ,Amorphous metal ,Condensed matter physics ,Anharmonicity ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Moduli ,law.invention ,Shear (sheet metal) ,Molecular dynamics ,law ,0103 physical sciences ,Hydrostatic equilibrium ,010306 general physics ,0210 nano-technology ,Glass transition - Abstract
Here we examine the role of anharmonicity in the elastic constants of bulk metallic glasses and develop an anharmonic model to consider the effects of both pressure and temperature across the glass transition. By comparing against reported experimental data and elastic constants obtained from molecular dynamics simulations, we show that the model is able to capture reported elastic constants from cryogenic temperatures through the glass transition and under hydrostatic pressures up to 18 GPa. Microstructural indicators based on short-range order analysis also display strong correlations with the bulk and shear moduli across the range of pressures and temperatures studied. These results not only greatly expand our understanding in the physical origins of elastic properties of bulk metallic glasses but are also of practical interest for application to processing routes for bulk metallic glass materials.
- Published
- 2018
40. Interband absorption edge in the topological insulators Bi2(Te1−xSex)3
- Author
-
H. Steiner, Ondřej Caha, Pavel Friš, Adam Dubroka, Gerrit E. W. Bauer, Milan Orlita, Václav Holý, Josef Humlíček, Miloš Hronček, and G. Springholz
- Subjects
Range (particle radiation) ,Materials science ,Condensed matter physics ,Infrared ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Brillouin zone ,Absorption edge ,Ellipsometry ,Topological insulator ,0103 physical sciences ,Direct and indirect band gaps ,010306 general physics ,0210 nano-technology ,Absorption (electromagnetic radiation) - Abstract
We have investigated the optical properties of thin films of topological insulators Bi2Te3, Bi2Se3, and their alloys Bi-2(Te1-x Se-x)(3) on BaF2 substrates by a combination of infrared ellipsometry and reflectivity in the energy range from 0.06 to 6.5 eV. For the onset of interband absorption in Bi2Se3, after the correction for the Burstein-Moss effect, we find the value of the direct band gap of 215 +/- 10 meV at 10 K. Our data support the picture that Bi2Se3 has a direct band gap located at the Gamma point in the Brillouin zone and that the valence band reaches up to the Dirac point and has the shape of a downward-oriented paraboloid, i.e., without a camel-back structure. In Bi2Te3, the onset of strong direct interband absorption at 10 K is at a similar energy of about 200 meV, with a weaker additional feature at about 170 meV. Our data support the recent GW band-structure calculations suggesting that the direct interband transition does not occur at the Gamma point but near the Z-F line of the Brillouin zone. In the Bi-2(Te1-x Se-x)(3) alloy, the energy of the onset of direct interband transitions exhibits a maximum near x = 0.3 (i.e., the composition of Bi2Te2Se), suggesting that the crossover of the direct interband transitions between the two points in the Brillouin zone occurs close to this composition.
- Published
- 2017
41. Spin-dependent phase shift at ferromagnetic film interfaces from the reflectivity of slow electrons
- Author
-
Ryszard Zdyb and Ernst Bauer
- Subjects
Range (particle radiation) ,Materials science ,Condensed matter physics ,Nanotechnology ,02 engineering and technology ,Substrate (electronics) ,Electron ,021001 nanoscience & nanotechnology ,01 natural sciences ,Interferometry ,Ferromagnetism ,0103 physical sciences ,Vacuum level ,010306 general physics ,0210 nano-technology ,Electronic band structure ,Spin (physics) - Abstract
We report on spin-dependent phase shift of the electron wave reflected at the film/vacuum and film/substrate interfaces for electrons with energies above the vacuum level. The phase shift is determined within the Fabry-P\'erot interferometer model of an absorbing medium, which takes into account the band structure of film and substrate. The results obtained for the model system Fe/W(110) indicate that the phase shift has nonzero values in the entire investigated energy range (up to 20 eV), including the energies of the allowed states in the substrate. This is in contrast to the available models which give zero phase shift for those energy ranges. It is also shown that the spin dependence is much stronger for the Fe/vacuum than for the Fe/W interface.
- Published
- 2017
42. Robust short-range-ordered nematicity in FeSe evidenced by high-pressure NMR
- Author
-
Weiqiang Yu, Hechang Lei, S. S. Sun, P. S. Wang, Ziqiang Wang, Tianrun Li, P. Zhou, and Yi Cui
- Subjects
Superconductivity ,Range (particle radiation) ,Materials science ,Strongly Correlated Electrons (cond-mat.str-el) ,Condensed matter physics ,Magnetism ,Condensed Matter - Superconductivity ,FOS: Physical sciences ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Space (mathematics) ,01 natural sciences ,Magnetic field ,Superconductivity (cond-mat.supr-con) ,Condensed Matter - Strongly Correlated Electrons ,Tetragonal crystal system ,Laser linewidth ,0103 physical sciences ,010306 general physics ,0210 nano-technology ,Ground state - Abstract
We report high-pressure $^{77}$Se NMR studies on FeSe single crystals that reveal a prominent inhomogeneous NMR linewidth broadening upon cooling, with the magnetic field applied along the tetragonal [110] direction. The data indicate the existence of short-range-ordered, inhomogeneous electronic nematicity, which has surprisingly long time scales over milliseconds. The short-range order survives temperatures up to $8$ times the structural transition temperature, and remains robust against pressure, in contrast to the strong pressure-dependence of the orbital ordering, structural transition, and the ground state magnetism. Such an extended region of static nematicity in the ($P$,$T$) space of FeSe indicates an enormously large fluctuating regime, and provide fresh insights and constraints to the understanding of electronic nematicity in iron-based superconductors., To appear in PRB
- Published
- 2017
43. Combined effect of doping and temperature on the anisotropy of low-energy plasmons in monolayer graphene
- Author
-
V. M. Silkin, Godfrey Gumbs, and Antonios Balassis
- Subjects
Condensed Matter - Materials Science ,Range (particle radiation) ,Materials science ,Condensed Matter - Mesoscale and Nanoscale Physics ,Condensed matter physics ,Doping ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Dispersion relation ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,0103 physical sciences ,Dispersion (optics) ,Density functional theory ,010306 general physics ,0210 nano-technology ,Anisotropy ,Excitation ,Plasmon - Abstract
We compare the two-dimensional (2D) plasmon dispersion relations for monolayer graphene when the sample is doped with carriers in the conduction band and the temperature $T$ is zero with the case when the temperature is finite and there is no doping. Additionally, we have obtained the plasmon excitations when there is doping at finite temperature. The results were obtained in the random-phase approximation which employs energy electronic bands calculated using ab initio density functional theory. We found that in the undoped case the finite temperature results in appearance in the low-energy region of a 2D plasmon which is absent for the $T=0$ case. Its energy is gradually increased with increasing $T$. It is accompanied by expansion in the momentum range where this mode is observed as well. The 2D plasmon dispersion in the $\Gamma$M direction may differ in substantial ways from that along the $\Gamma$K direction at sufficiently high temperature and doping concentrations. Moreover, at temperatures exceeding $\approx300$ meV a second mode emerges along the $\Gamma$K direction at lower energies like it occurs at a doping level exceeding $\approx 300$ meV. Once the temperature exceeds $\approx 0.75$ eV this mode ceases to exit whereas the 2D plasmon exists as a well-defined collective excitation up to $T=1.5$ eV, a maximal temperature investigated in this work., Comment: 11 pages, 8 figures
- Published
- 2017
44. Frequency-dependent mechanical damping in alloys
- Author
-
Raghavan Ranganathan, Pawel Keblinski, and Yunfeng Shi
- Subjects
Range (particle radiation) ,Materials science ,Condensed matter physics ,Terahertz radiation ,Alloy ,02 engineering and technology ,engineering.material ,021001 nanoscience & nanotechnology ,01 natural sciences ,Glassy alloy ,Condensed Matter::Materials Science ,Oscillatory shear ,0103 physical sciences ,Dynamic modulus ,engineering ,Deformation (engineering) ,010306 general physics ,0210 nano-technology - Abstract
We perform oscillatory shear simulations to determine the loss modulus for three solids with identical interaction yet distinct structures: ordered, random, and glassy alloys. Random and glassy alloys show more pronounced high-frequency loss in the THz regime than the ordered alloy. Ordered and random alloys exhibit a power-law decay in damping strength as frequency decreases over nearly five decades. Glassy alloy, with a limited frequency range of power-law decay, retains significant damping at low frequencies extending down to $\ensuremath{\sim}100\phantom{\rule{0.16em}{0ex}}\mathrm{MHz}$ due to slow irreversible deformation of local clusters.
- Published
- 2017
45. Phase-separated magnetic ground state in Mn3Ga0.45Sn0.55C
- Author
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E. T. Dias, Giuliana Aquilanti, Ripandeep Singh, K. R. Priolkar, A. K. Nigam, and A. K. Das
- Subjects
Range (particle radiation) ,Materials science ,Neutron diffraction ,02 engineering and technology ,Type (model theory) ,021001 nanoscience & nanotechnology ,01 natural sciences ,X-ray absorption fine structure ,Magnetization ,Crystallography ,Phase (matter) ,0103 physical sciences ,Cluster (physics) ,010306 general physics ,0210 nano-technology ,Ground state - Abstract
Existence of non-ergodic ground states is considered as a precursor to a first order long range magnetostructural transformation. Mn$_3$Ga$_{0.45}$Sn$_{0.55}$C lies compositionally between two compounds, Mn$_3$GaC and Mn$_3$SnC, undergoing first order magnetic transformation. Mn$_3$Ga$_{0.45}$Sn$_{0.55}$C though crystallizes in single phase cubic structure, exhibits more than one long range magnetic transitions. Using a combination of magnetization, ac susceptibility, neutron diffraction and XAFS techniques it is shown that, though Mn$_3$Ga$_{0.45}$Sn$_{0.55}$C exhibits long range magnetic order, it presents a cluster glassy ground state due to formation of magnetically ordered Ga rich and Sn rich clusters. The clusters are big enough to present signatures of long range magnetic order but are distributed in such way that it limits interactions between two clusters of the same type leading to a frozen magnetic state at low temperatures. The main reason for such a cluster glass state is the difference in local structure of Mn atoms that find themselves in Ga rich and Sn rich clusters.
- Published
- 2017
46. Energy-dependent relaxation time in quaternary amorphous oxide semiconductors probed by gated Hall effect measurements
- Author
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Henning Sirringhaus, Pedro Barquinha, Rita Branquinho, Elvira Fortunato, Christopher Warwick, Josephine Socratous, Kulbinder K. Banger, Shun Watanabe, and Rodrigo Martins
- Subjects
010302 applied physics ,Range (particle radiation) ,Materials science ,Condensed matter physics ,business.industry ,02 engineering and technology ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,021001 nanoscience & nanotechnology ,01 natural sciences ,Electron transport chain ,Amorphous solid ,Ionized impurity scattering ,Condensed Matter::Materials Science ,Semiconductor ,Hall effect ,0103 physical sciences ,Charge carrier ,0210 nano-technology ,business ,Ternary operation - Abstract
Despite the success of exploiting the properties of amorphous oxide semiconductors for device applications, the charge transport in these materials is still not clearly understood. The observation of a definite Hall voltage suggests that electron transport in the conduction band is free-electron-like. However, the temperature dependence of the Hall and field-effect mobilities cannot be explained using a simple bandlike model. Here, we perform gated Hall effect measurements in field-effect transistors, which allow us to make two independent estimates of the charge carrier concentration and determine the Hall factor providing information on the energy dependence of the relaxation time. We demonstrate that the Hall factor in a range of sputtered and solution-processed quaternary amorphous oxides, such as a-InGaZnO, is close to two, while in ternary oxides, such as InZnO, it is near unity. This suggests that quaternary elements like Ga act as strong ionized impurity scattering centers in these materials.
- Published
- 2017
47. Competition between homogeneous and inhomogeneous broadening of orbital transitions in Si:Bi
- Author
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B. N. Murdin, C. R. Pidgeon, Britta Redlich, P. T. Greenland, K. Saeedi, N. Stavrias, Nikolai V. Abrosimov, Mike L. W. Thewalt, and Helge Riemann
- Subjects
Range (particle radiation) ,Materials science ,Dephasing ,Relaxation (NMR) ,Phonon energy ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Impurity ,Homogeneous ,Frequency domain ,0103 physical sciences ,FELIX ,Atomic physics ,010306 general physics ,0210 nano-technology ,Energy (signal processing) - Abstract
We present results for the lifetime of the orbital transitions of Bi donors in Si, measured using both frequency domain and time-domain techniques, allowing us to distinguish between homogeneous and inhomogeneous processes. The proximity of the energy of the optically allowed transitions to the optical phonon energy means that there is an unusually wide variation in the lifetimes and broadening mechanisms for this impurity, from fully homogeneous lifetime-broadened transitions to fully inhomogeneously broadened lines. The relaxation lifetime (T1) of the states range from the low 10’s to 100’s of ps, and we find that there is little extra dephasing (so that T1 is of the order of T2/2) in each case.
- Published
- 2017
48. Zero-bias anomaly in homogeneously disordered MoGe nanowires undergoing a superconductor-insulator transition
- Author
-
Hyunjeong Kim and Andrey Rogachev
- Subjects
Superconductivity ,Range (particle radiation) ,Amorphous metal ,Materials science ,Condensed matter physics ,Nanowire ,Physics::Optics ,02 engineering and technology ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,021001 nanoscience & nanotechnology ,01 natural sciences ,Condensed Matter::Materials Science ,Superconductor Insulator Transition ,0103 physical sciences ,Electrode ,Anomaly (physics) ,Zero bias ,010306 general physics ,0210 nano-technology - Abstract
Nanowires made of superconducting Mo-Ge alloys undergo a superconductor-insulator transition when their cross-sectional area is reduced. On the insulating side of the transition, the differential resistance of the nanowires drops with voltage and displays a positive zero-bias anomaly (ZBA). To reveal the origin of this ZBA, we fabricated and studied a series of nanowires made of amorphous alloys with composition $\mathrm{M}{\mathrm{o}}_{50}\mathrm{G}{\mathrm{e}}_{50}$. The length of wires was in the range 150 nm--11 \ensuremath{\mu}m and width was in the range 10--20 nm. We also fabricated and measured several more complex nanowire-based structures: (i) a nanowire gated by a nearby film electrode, (ii) a nanowire connected to film electrodes with an ``adiabatically reduced'' width, (iii) a nanowire with a multielectrode configuration which allowed comparison of different sections of the same nanowire, and (iv) a nanowire with different sizes of film electrodes. We found that for $\mathrm{M}{\mathrm{o}}_{50}\mathrm{G}{\mathrm{e}}_{50}$ nanowires all experimental parameters of the ZBA and their dependence on nanowire length can be explained by electron heating. Several physical processes thought to be responsible for the ZBA have been analyzed and rejected.
- Published
- 2016
49. Melting temperature of water: DFT-based molecular dynamics simulations with D3 dispersion correction
- Author
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Ari P. Seitsonen and Taras Bryk
- Subjects
Range (particle radiation) ,Materials science ,010304 chemical physics ,Melting temperature ,Ab initio ,01 natural sciences ,Molecular physics ,Molecular dynamics ,0103 physical sciences ,Melting point ,Molecule ,Density functional theory ,Physics::Chemical Physics ,010306 general physics ,Dispersion (chemistry) - Abstract
Extensive ab initio simulations of ice-water basal interface at seven temperatures in the range 250--400 K were performed in NVT and NPT ensembles with a collection of 389 water molecules in order to estimate the melting point of ice from direct liquid-solid two-phase coexistence. Density functional theory with the BLYP (Becke-Lee-Yang-Parr) exchange-correlation functional and the D3 dispersion correction were used in the expression of total energy. Analysis of density profiles and the evolution of the total potential, or Kohn-Sham plus D3, energy in the simulations at different temperatures resulted in an estimate for melting temperature of ice of 325 K.
- Published
- 2016
50. Boundary scattering effects on magnetotransport of narrow metallic wires and films
- Author
-
P. M. Ostrovsky and Eslam Khalaf
- Subjects
Range (particle radiation) ,Electron mobility ,Materials science ,Condensed Matter - Mesoscale and Nanoscale Physics ,Condensed matter physics ,Scattering ,FOS: Physical sciences ,02 engineering and technology ,Surface finish ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,021001 nanoscience & nanotechnology ,01 natural sciences ,Weak localization ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,0103 physical sciences ,Boundary value problem ,010306 general physics ,0210 nano-technology ,Fermi gas ,Electron scattering - Abstract
Electron transport in thin metallic wires and films is strongly influenced by the quality of their surface. Weak localization and magnetoconductivity are also sensitive to the electron scattering at the edges of the sample. We study weak localization effects in a two-dimensional electron gas patterned in the form of a narrow quasi-one-dimensional channel in transverse magnetic field. The most general boundary conditions interpolating between the limits of mirror and diffuse edge scattering are assumed. We calculate magnetoconductivity for an arbitrary width of the sample including the cases of diffusive and ballistic lateral transport as well as the crossover between them. We find that in a broad range of parameters, the electron mobility is limited by the boundary roughness while the magnetotransport is only weakly influenced by the quality of the edges. In addition, we calculate magnetoconductivity for a metallic cylinder in the transverse field and a quasi-two-dimensional metallic film in the parallel field., Comment: 18 pages, 11 figures
- Published
- 2016
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