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1. Epsilon iron as a spin-smectic state

Author

Alain Polian, P. Munsch, Amélie Juhin, Tommaso Gorni, Blair W. Lebert, James M. Ablett, François Baudelet, Thomas C. Hansen, Matteo d'Astuto, Jean-Pascal Rueff, Michele Casula, Stefan Klotz, Gilles Le Marchand, Zailan Zhang, Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), 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), Laboratoire de Physique et d'Etude des Matériaux (UMR 8213) (LPEM), Ecole Superieure de Physique et de Chimie Industrielles de la Ville de Paris (ESPCI Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institut Laue-Langevin (ILL), Institut de Génétique et Développement de Rennes (IGDR), Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS)-Structure Fédérative de Recherche en Biologie et Santé de Rennes ( Biosit : Biologie - Santé - Innovation Technologique ), Laboratoire de Chimie Physique - Matière et Rayonnement (LCPMR), Institut de Chimie du CNRS (INC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Magnétisme et Supraconductivité (NEEL - MagSup), 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]), ANR-11-IDEX-0004-02, Agence Nationale de la Recherche, ANR-11-IDEX-0004,SUPER,Sorbonne Universités à Paris pour l'Enseignement et la Recherche(2011), ILL, Structure Fédérative de Recherche en Biologie et Santé de Rennes ( Biosit : Biologie - Santé - Innovation Technologique )-Centre National de la Recherche Scientifique (CNRS)-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES), Magnétisme et Supraconductivité (MagSup ), Université de Rennes 1 (UR1), and Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)-Structure Fédérative de Recherche en Biologie et Santé de Rennes ( Biosit : Biologie - Santé - Innovation Technologique )

Subjects
Neutron powder diffraction, Materials science, Magnetism, media_common.quotation_subject, FOS: Physical sciences, Frustration, 02 engineering and technology, 01 natural sciences, iron, Lattice (order), 0103 physical sciences, Antiferromagnetism, Emission spectrum, 010306 general physics, ComputingMilieux_MISCELLANEOUS, media_common, Superconductivity, Condensed Matter - Materials Science, Multidisciplinary, Condensed matter physics, Magnetic moment, superconductivity, Materials Science (cond-mat.mtrl-sci), 021001 nanoscience & nanotechnology, [PHYS.COND.CM-S]Physics [physics]/Condensed Matter [cond-mat]/Superconductivity [cond-mat.supr-con], high pressure, magnetism, Physical Sciences, Condensed Matter::Strongly Correlated Electrons, [PHYS.COND.CM-SCE]Physics [physics]/Condensed Matter [cond-mat]/Strongly Correlated Electrons [cond-mat.str-el], 0210 nano-technology
Abstract

Using X-ray emission spectroscopy, we find appreciable local magnetic moments until 30 GPa to 40 GPa in the high-pressure phase of iron; however, no magnetic order is detected with neutron powder diffraction down to 1.8 K, contrary to previous predictions. Our first-principles calculations reveal a “spin-smectic” state lower in energy than previous results. This state forms antiferromagnetic bilayers separated by null spin bilayers, which allows a complete relaxation of the inherent frustration of antiferromagnetism on a hexagonal close-packed lattice. The magnetic bilayers are likely orientationally disordered, owing to the soft interlayer excitations and the near-degeneracy with other smectic phases. This possible lack of long-range correlation agrees with the null results from neutron powder diffraction. An orientationally disordered, spin-smectic state resolves previously perceived contradictions in high-pressure iron and could be integral to explaining its puzzling superconductivity.

Published
2019
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2. A high performance self-driven photodetector based on a graphene/InSe/MoS2 vertical heterostructure

Author

Zailan Zhang, Johan Biscaras, Zhesheng Chen, and Abhay Shukla

Subjects
Photocurrent, Materials science, business.industry, Graphene, Photodetector, Heterojunction, 02 engineering and technology, General Chemistry, 010402 general chemistry, 021001 nanoscience & nanotechnology, 01 natural sciences, 7. Clean energy, 0104 chemical sciences, law.invention, Semiconductor, Stack (abstract data type), Transition metal, law, Materials Chemistry, Optoelectronics, 0210 nano-technology, business, Self driven
Abstract

Hybrid van der Waals heterostructures comprising ultrathin layers of different materials and offering the possibility of novel properties and unusual charge transport characteristics have become a reality in recent years. Here, we vertically stack graphene, a transition metal dichalcogenide and a III–VI semiconductor together and report a novel self-driven photodetector based on a graphene/InSe/MoS2 heterostructure. The device shows rectifying and bipolar behavior. In the self-driven mode it exhibits high photoresponsivity (110 mA W−1), fast photo-response (less than 1 ms) and high detectivity (over 1010 Jones). It also shows ambient operational stability over one month of operation and nearly uniform photocurrent distribution because of the efficient electron–hole pair separation arising from the large built-in potential at the interface of MoS2 and InSe. Our graphene/InSe/MoS2 heterostructure holds promise for novel self-driven optoelectronics based on III–VI/transition metal dichalcogenide heterojunctions.

Published
2018
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3. Spectroscopy of buried states in black phosphorus with surface doping

Author

Evangelos Papalazarou, Marino Marsi, Yingchun Cheng, Bingbing Tian, Zailan Zhang, Armina Taleb-Ibrahimi, Christine Giorgetti, Jean-Pascal Rueff, Zhesheng Chen, Jingwei Dong, Luca Perfetti, Qingwei Ma, Laboratoire des Solides Irradiés (LSI), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X), Laboratoire de Physique des Solides (LPS), Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Shenzhen University [Shenzhen], Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), Laboratoire de Chimie Physique - Matière et Rayonnement (LCPMR), Institut de Chimie du CNRS (INC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Materials science, Band gap, Angle-resolved photoemission spectroscopy, 02 engineering and technology, Electronic structure, 01 natural sciences, Molecular physics, law.invention, Condensed Matter::Materials Science, band gap engineering, law, 0103 physical sciences, General Materials Science, 010306 general physics, Electronic band structure, Graphene, business.industry, electron doping, Mechanical Engineering, Doping, Black phosphorus, General Chemistry, 021001 nanoscience & nanotechnology, Condensed Matter Physics, electronic structure, Semimetal, Semiconductor, Mechanics of Materials, [PHYS.COND.CM-GEN]Physics [physics]/Condensed Matter [cond-mat]/Other [cond-mat.other], time-resolved ARPES, 0210 nano-technology, business
Abstract

International audience; Electrostatic gating or alkali metal evaporation can be successfully employed to tune the interface of layered black phosphorus (BP) from a semiconductor to a 2D Dirac semimetal. Although Angle Resolved Photoelectron Spectroscopy (ARPES) experiments have captured the collapse of the band gap in the inversion layer, a quantitative estimation of band structure evolution has been hindered by the short escape depth and matrix elements of the probed photoelectrons. Here, we precisely monitor the evolution of electronic states using time-resolved ARPES at a photon energy of 6.3 eV. The probing depth of laser-based ARPES is long enough to observe the buried electronic states originating from the valence band maximum. Our data shows that the band gap has a maximal value of 0.32 eV in the pristine sample, and that it shrinks down monotonically by increasing the carrier concentration in the topmost layer. Most interestingly, the band velocity of the valence band increases by a factor of two along the armchair direction, surpassing the value reported in graphene on silicon carbide (SiC). This control of band structure via external gating will be of interest with regard to the design of optoelectronic devices.

Published
2020
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4. Direct Observation of Band Gap Renormalization in Layered Indium Selenide

Author

Abhay Shukla, Luca Perfetti, Hemian Yi, Dianyuan Fan, José Avila, Zailan Zhang, Meryem Bouaziz, Zhesheng Chen, Christine Giorgetti, Ying Li, Azzedine Bendounan, Bingbing Tian, Laboratoire des Solides Irradiés (LSI), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Materials science, Band gap, General Physics and Astronomy, chemistry.chemical_element, Angle-resolved photoemission spectroscopy, 02 engineering and technology, Electronic structure, 010402 general chemistry, 7. Clean energy, 01 natural sciences, Condensed Matter::Materials Science, chemistry.chemical_compound, Selenide, General Materials Science, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], ComputingMilieux_MISCELLANEOUS, business.industry, Doping, General Engineering, 021001 nanoscience & nanotechnology, 0104 chemical sciences, Semiconductor, chemistry, [PHYS.COND.CM-GEN]Physics [physics]/Condensed Matter [cond-mat]/Other [cond-mat.other], Optoelectronics, Direct and indirect band gaps, 0210 nano-technology, business, Indium
Abstract

Manipulation of intrinsic electronic structures by electron or hole doping in a controlled manner in van der Waals layered materials is the key to control their electrical and optical properties. Two-dimensional indium selenide (InSe) semiconductor has attracted attention due to its direct band gap and ultrahigh mobility as a promising material for optoelectronic devices. In this work, we manipulate the electronic structure of InSe by in situ surface electron doping and obtain a significant band gap renormalization of ∼120 meV directly observed by high-resolution angle resolved photoemission spectroscopy. This moderate doping level (carrier concentration of 8.1 × 1012 cm-2) can be achieved by electrical gating in field effect transistors, demonstrating the potential to design of broad spectral response devices.

Published
2019
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5. Band Gap Renormalization, Carrier Multiplication, and Stark Broadening in Photoexcited Black Phosphorus

Author

Luca Perfetti, Zailan Zhang, Amina Taleb-Ibrahimi, Evangelos Papalazarou, Marino Marsi, Zhesheng Chen, Christine Giorgetti, Bingbing Tian, Jingwei Dong, Jean-Pascal Rueff, 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), Laboratoire de Physique des Solides (LPS), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Solides Irradiés (LSI), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), College of Information Engineering, Shenzhen University, Centre National de la Recherche Scientifique (CNRS), Laboratoire de Chimie Physique - Matière et Rayonnement (LCPMR), Institut de Chimie du CNRS (INC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X), and Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Physics, Band gap, Mechanical Engineering, Bioengineering, Angle-resolved photoemission spectroscopy, 02 engineering and technology, General Chemistry, Electron, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Multiple exciton generation, Photoexcitation, symbols.namesake, Stark effect, Excited state, [PHYS.COND.CM-GEN]Physics [physics]/Condensed Matter [cond-mat]/Other [cond-mat.other], symbols, General Materials Science, Atomic physics, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], 0210 nano-technology, Excitation
Abstract

International audience; We investigate black phosphorus by time- and angle-resolved photoelectron spectroscopy. The electrons excited by 1.57 eV photons relax down to a conduction band minimum within 1 ps. Despite the low band gap value, no relevant amount of carrier multiplication could be detected at an excitation density 3–6 × 1019 cm–3. In the thermalized state, the band gap renormalization is negligible up to a photoexcitation density that fills the conduction band by 150 meV. Astonishingly, a Stark broadening of the valence band takes place at an early delay time. We argue that electrons and holes with a high excess energy lead to inhomogeneous screening of near surface fields. As a consequence, the chemical potential is no longer pinned in a narrow impurity band.

Published
2018
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6. Ultrafast electron dynamics reveal the high potential of InSe for hot-carrier optoelectronics

Author

Luca Perfetti, Evangelos Papalazarou, Christine Giorgetti, Jelena Sjakste, Valérie Véniard, Marino Marsi, Raphael Cabouat, Zailan Zhang, Jacques Peretti, Zhesheng Chen, Amina Taleb-Ibrahimi, Abhay Shukla, Laboratoire des Solides Irradiés (LSI), École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Institut de minéralogie, de physique des matériaux et de cosmochimie (IMPMC), Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS)-Institut de recherche pour le développement [IRD] : UR206, CASSIOPEE, Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique des Solides (LPS), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique Théorique de la Matière Condensée (LPTMC), Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Muséum national d'Histoire naturelle (MNHN)-Institut de recherche pour le développement [IRD] : UR206-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X), College of Information Engineering, Shenzhen University, Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11), Muséum national d'Histoire naturelle (MNHN)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de recherche pour le développement [IRD] : UR206-Centre National de la Recherche Scientifique (CNRS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), and Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Phonon, FOS: Physical sciences, 02 engineering and technology, Electron, 7. Clean energy, 01 natural sciences, Ab initio quantum chemistry methods, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), 0103 physical sciences, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], 010306 general physics, ComputingMilieux_MISCELLANEOUS, [PHYS]Physics [physics], Physics, Condensed Matter - Materials Science, Condensed Matter - Mesoscale and Nanoscale Physics, Condensed matter physics, Momentum transfer, Relaxation (NMR), Materials Science (cond-mat.mtrl-sci), 021001 nanoscience & nanotechnology, Coupling (probability), Thermalisation, [PHYS.COND.CM-GEN]Physics [physics]/Condensed Matter [cond-mat]/Other [cond-mat.other], Excited state, 0210 nano-technology
Abstract

We monitor the dynamics of hot carriers in InSe by means of two-photon photoelectron spectroscopy (2PPE). The electrons excited by photons of 3.12 eV experience a manifold relaxation. First, they thermalize to electronic states degenerate with the $\overline{M}$ valley. Subsequently, the electronic cooling is dictated by Fr\"ohlich coupling with phonons of small momentum transfer. Ab initio calculations predict cooling rates that are in good agreement with the observed dynamics. We argue that electrons accumulating in states degenerate with the $\overline{M}$ valley could travel through a multilayer flake of InSe with a lateral size of 1 $\ensuremath{\mu}\mathrm{m}$. The hot carriers pave a viable route to the realization of below-band-gap photodiodes and Gunn oscillators. Our results indicate that these technologies may find a natural implementation in future devices based on layered chalcogenides.

Published
2018
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7. Superconductivity, pseudo-gap, and stripe correlations in high-T c cuprates

Author

Amina Taleb-Ibrahimi, Matteo d'Astuto, Blair W. Lebert, Yvan Sidis, Luca Perfetti, Claudia Decorse, Patrick Le Fèvre, Vincent Jacques, Patrick Berthet, François Bertran, Sylvain Denis, Zailan Zhang, David Le Bolloc'h, John-Paul Castellan, Benoit Baptiste, Institut de minéralogie et de physique des milieux condensés (IMPMC), Université Pierre et Marie Curie - Paris 6 (UPMC)-IPG PARIS-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Conception, Ingénierie et Développement de l'Aliment et du Médicament (CIDAM), Université d'Auvergne - Clermont-Ferrand I (UdA), Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), CASSIOPEE, Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Léon Brillouin (LLB - UMR 12), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Saclay, Laboratoire de Physique des Solides (LPS), Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11), Groupe 3 axes (G3A), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Saclay-Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Chimie et Biologie des Membranes et des Nanoobjets (CBMN), École Nationale d'Ingénieurs des Travaux Agricoles - Bordeaux (ENITAB)-Institut de Chimie du CNRS (INC)-Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Physicochimique Etat Solide, UMR 8648,CNRS (LPCES, ICMMO), Université Paris-Sud - Paris 11 (UP11), Institut de Chimie Moléculaire et des Matériaux d'Orsay (ICMMO), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Laboratoire des Solides Irradiés (LSI), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X), Magnétisme et Supraconductivité (MagSup ), 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]), Université de Bordeaux (UB)-École Nationale d'Ingénieurs des Travaux Agricoles - Bordeaux (ENITAB)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Université Paris-Sud - Paris 11 (UP11)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Paris Diderot - Paris 7 (UPD7)-Institut de Physique du Globe de Paris (IPG Paris)-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), Université Paris-Sud - Paris 11 (UP11)-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)-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), Laboratoire de Physico-Chimie de l'Etat Solide (CHIMSOL), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), and Magnétisme et Supraconductivité (NEEL - MagSup)

Subjects
Context (language use), Angle-resolved photoemission spectroscopy, 02 engineering and technology, 01 natural sciences, cuprates, pseudo-gap, Tight binding, 0103 physical sciences, Cuprate, Electrical and Electronic Engineering, 010306 general physics, Electronic band structure, Superconductivity, Physics, Condensed matter physics, superconductivity, Fermi surface, 021001 nanoscience & nanotechnology, Condensed Matter Physics, ARPES, Electronic, Optical and Magnetic Materials, [PHYS.COND.CM-S]Physics [physics]/Condensed Matter [cond-mat]/Superconductivity [cond-mat.supr-con], stripes, [PHYS.COND.CM-SCE]Physics [physics]/Condensed Matter [cond-mat]/Strongly Correlated Electrons [cond-mat.str-el], 0210 nano-technology, Charge density wave
Abstract

International audience; Under-doped La-214 cuprates show a charge-and spin-modulation known as " stripes " [1]. These stripe modulations are (quasi)-static close to 1/8 hole doping where superconductivity is suppressed. The pseudo-gap phase of other cuprate compounds recently also revealed charge modulation, but interpreted rather as a charge density wave (CDW) [2, 3, 4], that possibly competes with superconductivity. In this context, to better understand the interplay between the stripe phase and the superconductivity, we use angle-resolved photoemission spectroscopy to study the electronic band structure and gap in La-214 cuprates near 1/8 doping (La 2−x−y Nd y Sr x CuO 4 (x = 0.12; y = 0.0 & 0.4)) and compare with the previous results in the same system [5] and La 1.86 Ba 0.14 CuO 4 [6]. Our data shows a loss of spectral intensity towards the end of the Fermi arcs, that is possibly due to a strong renormalisation, as already pointed out elsewhere * matteo.dastuto@neel.cnrs.fr-Institut Néel CNRS-25, av des Martyrs-38042 Grenoble cedex 9; tel: (+33)(0)4 76 88 12 84 [5], with a noisy but still measurable gap. On the nodal direction no gap is observed within our statistics, but a sizeable decrease in intensity with temperature. Moreover, we do not see any shadow band, but our Fermi surface can be well modelled with a single electron band calculation in the tight binding approximation, even very close to the 1/8 doping La 2−x−y Nd y Sr x CuO 4 with and without Nd substitution.

Published
2018
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8. Electronic structure and dynamics of CH3NH3PbI3 hybrid organic-inorganic perovskite

Author

Min-I Lee, Zhesheng Chen, Ana Barragan, Zailan Zhang, Lédée, F., Maya Narayanan Nair, Jemli, K., Gaëlle Trippé-Allard, Hiba Diab, Pierre Fertey, Garrot, D., Papalazarou, E., Carlito Ponseca, Jacques, V., David Le Bolloc'H, Marsi, M., Emmanuelle Deleporte, Luca Perfetti, Taleb-Ibrahimi, A., Antonio Tejeda, Tejeda, Antonio, Laboratoire de Physique des Solides (LPS), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Solides Irradiés (LSI), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), Institut de minéralogie, de physique des matériaux et de cosmochimie (IMPMC), Muséum national d'Histoire naturelle (MNHN)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de recherche pour le développement [IRD] : UR206-Centre National de la Recherche Scientifique (CNRS), Laboratoire Aimé Cotton (LAC), École normale supérieure - Cachan (ENS Cachan)-Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), Groupe d'Etude de la Matière Condensée (GEMAC), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS), Lund University [Lund], Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X), Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11)-École normale supérieure - Cachan (ENS Cachan), and Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de recherche pour le développement [IRD] : UR206-Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], [PHYS.COND.CM-MS] Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci]
Abstract

International audience; Organic-inorganic hybrid perovskites are promising absorber materials for low-cost photovoltaic solar cells or optoelectronic devices [1-4]. Among these perovskites, methylammonium triiodideplumbate (CH 3 NH 3 PbI 3 , MAPbI 3 or MAPI) exhibits currently the highest efficiency. Here we have analyzed the structural transition in MAPI by X-ray diffraction at the β phase and we have correlated it to its electronic properties. Despite all the extensive work on hybrid organic-inorganic halide perovskites, their experimental band structure measured with k-resolution has remained elusive. Such an experimental determination is a necessary requirement for an accurate theoretical description and understanding of the system. The impact of the structural phase transitions on the band structure in the operation temperature range of solar cells needed also to be elucidated. Herein, we present the experimental determination of the band structure of MAPI with k resolution by angle-resolved photoemission at 170 K [5]. Our results show that the spectral weight is strongly affected by the cubic symmetry although traces of the tetragonal band structure are appreciated. Some deviations with respect to theoretical calculations are observed, which may help to reach a more precise description of this paradigmatic system of the hybrid perovskite family. On a second step, we have studied the relaxation dynamics after photoexcitation, particularly important in a photovoltaic material. Time-resolved two-photon photoemission spectroscopy allows to directly visualize the electronic cooling at early delay times. It follows that photoexcited carriers thermalize on a subpicosecond timescale, presumably because of the coupling to the vibrations of organic cations [6]. The project leading to this application has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 687008 (GOTSolar). [1] S.D. Stranks and H.J. Snaith, Nature Nanotech 10, 391 (2015).[2] M. Grätzel, Nature Materials 13, 838 (2014).[3] Y. Wei et al., J. Phys. D: Appl. Phys. 46, 135105 (2013).[4] H. Diab, G. Trippé-Allard, F. Ledee, K. Jemli, C. Vilar, G. Bouchez, V. L. R. Jacques, A. Tejeda, J. Even, J.S. Lauret, E. Deleporte, and D. Garrot, J. Phys. Chem. Lett. 7, 5093 (2016). [5] M.-I. Lee, A. Barragán, M. N. Nair, V. L. R. Jacques, D. Le Bolloc’h, P. Fertey, K. Jemli, F. Ledee, G. Trippé-Allard, E. Deleporte, A. Taleb-Ibrahimi, and A. Tejeda, J. Phys. D: Appl. Phys. 50, 26LT02 (2017). [6] Z. Chen, M.-I. Lee, Z. Zhang, H. Diab, D. Garrot, F. Ledee, P. Fertey, E. Papalazarou, M. Marsi, C. Ponseca, E. Deleporte, A. Tejeda, and L. Perfetti, Phys. Rev. Mat. 1, 045402 (2017).

Published
2017

10. Phase coherence and pairing amplitude in photo-excited superconductors

Author

Luca Perfetti, Zailan Zhang, and Christian Piovera

Subjects
Superconductivity, Physics, Superconducting coherence length, Phase transition, High-temperature superconductivity, Condensed matter physics, Scattering, 02 engineering and technology, Inelastic scattering, 021001 nanoscience & nanotechnology, 01 natural sciences, law.invention, law, Condensed Matter::Superconductivity, Pairing, 0103 physical sciences, Quasiparticle, 010306 general physics, 0210 nano-technology
Abstract

New data on Bi 2 Sr 2 CaCu 2 O 8+δ (Bi2212) reveal interesting aspects of photoexcited superconductors. The electrons dynamics show that inelastic scattering by nodal quasiparticles decreases when the temperature is lowered below the critical value of the superconducting phase transition. This drop of electronic dissipation is astonishingly robust and survives to photoexcitation densities much larger than the value sustained by long-range superconductivity. The unconventional behavior of quasiparticle scattering is ascribed to superconducting correlations extending on a length scale comparable to the inelastic mean-free path. Our measurements indicate that strongly driven superconductors enter in a regime without phase coherence but finite pairing amplitude.

Published
2016
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11. Erratum: Quasiparticle dynamics in high-temperature superconductors far from equilibrium: An indication of pairing amplitude without phase coherence [Phys. Rev. B91, 224509 (2015)]

Author

Zailan Zhang, Marino Marsi, E. Papalazarou, A. Taleb-Ibrahimi, Matteo d'Astuto, Z. Z. Li, Luca Perfetti, H. Raffy, and C. Piovera

Subjects
Physics, High-temperature superconductivity, Condensed matter physics, Dynamics (mechanics), Electronic structure, Condensed Matter Physics, Electronic, Optical and Magnetic Materials, law.invention, Amplitude, Phase coherence, law, Quantum mechanics, Pairing, Quasiparticle, Autocatalytic reaction
Published
2015
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13. Epsilon iron as a spin-smectic state.

Author

Lebert, Blair W., Gorni, Tommaso, Casula, Michele, Klotz, Stefan, Baudelet, François, Ablett, James M., Hansen, Thomas C., Juhin, Amélie, Polian, Alain, Munsch, Pascal, Le Marchand, Gilles, Zailan Zhang, Rueff, Jean-Pascal, and d'Astuto, Matteo

Subjects
X-ray emission spectroscopy, IRON, NEUTRON diffraction, MAGNETIC moments, ANTIFERROMAGNETISM
Abstract

Using X-ray emission spectroscopy, we find appreciable local magnetic moments until 30 GPa to 40 GPa in the high-pressure phase of iron; however, no magnetic order is detected with neutron powder diffraction down to 1.8 K, contrary to previous predictions. Our first-principles calculations reveal a "spinsmectic" state lower in energy than previous results. This state forms antiferromagnetic bilayers separated by null spin bilayers, which allows a complete relaxation of the inherent frustration of antiferromagnetism on a hexagonal close-packed lattice. The magnetic bilayers are likely orientationally disordered, owing to the soft interlayer excitations and the neardegeneracy with other smectic phases. This possible lack of long-range correlation agrees with the null results from neutron powder diffraction. An orientationally disordered, spinsmectic state resolves previously perceived contradictions in highpressure iron and could be integral to explaining its puzzling superconductivity. [ABSTRACT FROM AUTHOR]

Published
2019
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14. Spin-polarized transport in zigzag graphene nanoribbons adsorbing nonmagnetic atomic chain

Author

Ya Qin Wang, Yuanping Chen, Yuee Xie, Zailan Zhang, and Y. Zhang

Subjects
Materials science, Spin polarization, Condensed matter physics, Solid-state physics, Fermi level, Condensed Matter Physics, Electronic, Optical and Magnetic Materials, Condensed Matter::Materials Science, Magnetization, symbols.namesake, Zigzag, symbols, Condensed Matter::Strongly Correlated Electrons, Density functional theory, Physics::Chemical Physics, Spin (physics), Graphene nanoribbons
Abstract

The spin-polarized transport properties of nonmagnetic (metallic Al and nonmetallic C) atomic chains adsorbed on zigzag graphene nanoribbons (ZGNRs) are investigated by the density functional theory (DFT) combined with the nonequilibrium Green’s function method. We find that the spin polarization of ZGNRs is sensitive to the adsorption sites and atomic types of the chains. As an Al chain is adsorbed on the middle of ZGNR, no spin-polarized transport arises. As the Al chain is adsorbed on the edge of ZGNR, high spin polarization is produced around the Fermi level. The different transport behaviors are originated from the fact that the edge adsorption of Al chain breaks the magnetization symmetry of two edges while the middle adsorption of Al chain only modifies the magnetizations of two edges equally. More prominent spin polarization is generated as a C chain is adsorbed on the edge of ZGNR. The complete spin polarization emerges not only around the Fermi level but also far from the Fermi level, owing to the edge states and the localized states. These results indicate that one can effectively modulate the spin-polarized transports of ZGNRs through adsorbing different nonmagnetic atomic chains.

Published
2013
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15. Spin-polarized transport properties of Fe atomic chain adsorbed on zigzag graphene nanoribbons

Author

Zailan Zhang, Jianxin Zhong, Min Zhang, Yuee Xie, and Yuanping Chen

Subjects
Acoustics and Ultrasonics, Condensed matter physics, Spin polarization, Chemistry, Fermi level, Conductance, Electronic structure, Condensed Matter Physics, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials, symbols.namesake, Zigzag, Atom, symbols, Condensed Matter::Strongly Correlated Electrons, Physics::Chemical Physics, Spin (physics), Graphene nanoribbons
Abstract

The spin-polarized transport properties of Fe atomic chain adsorbed on zigzag graphene nanoribbons (ZGNRs) are investigated using the density-functional theory in combination with the nonequilibrium Green's function method. We find that the Fe chain has drastic effects on spin-polarized transport properties of ZGNRs compared with a single Fe atom adsorbed on the ZGNRs. When the Fe chain is adsorbed on the centre of the ZGNR, the original semiconductor transforms into metal, showing a very wide range of spin-polarized transport. Particularly, the spin polarization around the Fermi level is up to 100%. This is because the adsorbed Fe chain not only induces many localized states but also has effects on the edge states of ZGNR, which can effectively modulate the spin-polarized transports. The spin polarization of ZGNRs is sensitive to the adsorption site of the Fe chain. When the Fe chain is adsorbed on the edge of ZGNR, the spin degeneracy of conductance is completely broken. The spin polarization is found to be more pronounced because the edge state of one edge is destroyed by the additional Fe chain. These results have direct implications for the control of the spin-dependent conductance in ZGNRs with the adsorption of Fe chains.

Published
2011
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