A5043331662- Quantum and electron transport phenomena
- Topological Materials and Phenomena
- Magnetic properties of thin films
- Physics of Superconductivity and Magnetism
- Advanced Thermoelectric Materials and Devices
- Graphene research and applications
- Surface and Thin Film Phenomena
- Electronic and Structural Properties of Oxides
- Semiconductor materials and devices
- Thermal properties of materials
- Cold Atom Physics and Bose-Einstein Condensates
- Quantum optics and atomic interactions
- Molecular Junctions and Nanostructures
- Advancements in Semiconductor Devices and Circuit Design
- Advanced Thermodynamics and Statistical Mechanics
- Magnetic and transport properties of perovskites and related materials
- Atomic and Subatomic Physics Research
- Advanced Physical and Chemical Molecular Interactions
- Random lasers and scattering media
- Thermal Radiation and Cooling Technologies
- Mechanical and Optical Resonators
- Terahertz technology and applications
- Advanced Chemical Physics Studies
- Quantum many-body systems
- Spectral Theory in Mathematical Physics
Université Paris-Saclay
2017-2025
University of Regensburg
2016-2025
Centre National de la Recherche Scientifique
2012-2024
CEA Paris-Saclay
2014-2024
Service de Physique de l'État Condensé
2014-2024
Commissariat à l'Énergie Atomique et aux Énergies Alternatives
2014-2024
Institut Rayonnement-Matière de Saclay
2014-2016
Université de Strasbourg
2011-2014
Institut de Physique et Chimie des Matériaux de Strasbourg
2011-2014
University of Augsburg
2006-2014
We put forward a concept to create highly collimated, nondispersive electron beams in pseudorelativistic Dirac materials such as graphene or topological insulator surfaces. Combining negative refraction and Klein collimation at parabolic $pn$ junction, the proposed lens generates beams, narrow focal length, that stay focused over scales of several microns can be steered by magnetic field without losing collimation. demonstrate capabilities applying it two paradigmatic settings optics:...
Nanowires with helical surface states represent key prerequisites for observing and exploiting phase-coherent topological conductance phenomena, such as spin-momentum locked quantum transport or superconductivity. We demonstrate in a joint experimental theoretical study that gated nanowires fabricated from high-mobility strained HgTe, known bulk insulator, indeed preserve the nature of states, moreover extend phase-coherently across entire wire geometry. The phase-coherence lengths are...
Abstract In the last decade, graphene has become an exciting platform for electron optical experiments, in some aspects superior to conventional two-dimensional gases (2DEGs). A major advantage, besides ultra-large mobilities, is fine control over electrostatics, which gives possibility of realising gap-less and compact p-n interfaces with high precision. The latter host non-trivial states, e.g. , snake states moderate magnetic fields, serve as building blocks complex interferometers. Thanks...
We study the spin-charge coupled transport in a two-dimensional electron system using method of quasiclassical ($\xi$-integrated) Green's functions. In particular we derive Eilenberger equation presence generic spin-orbit field. The allows us to spin and charge from ballistic diffusive regimes continuity equations for are automatically incorporated. clean limit establish connection between spin-Hall conductivity Berry phase momentum space. For finite systems solve numerically special case...
We present a microscopic derivation of the generalized Boltzmann and Eilenberger equations in presence non-Abelian gauges for case nonrelativistic disordered Fermi gas. A unified symmetric treatment charge $[U(1)]$ spin $[SU(2)]$ degrees freedom is achieved. Within this framework, just as $U(1)$ Lorentz force generates Hall effect, so does its $SU(2)$ counterpart gives rise to effect. Considering elastic spin-independent disorder we obtain diffusion densities show how interplay between an...
We study magneto-transport through topological insulator nanowires shaped in the form of a constriction, as can be obtained by etching techniques. The magnetic field is coaxial, potentially turning nanowire into magneto-chiral junction. show detailed analytical and numerical that two main transport regimes emerge, depending on central narrow region being short or long compared to length at junction entrance exit. In both cases hosts Dirac-particle-in-a-box states due confinement, whose...
We explore electrical transport through a point contact in strained HgTe, three-dimensional topological insulator. In the absence of magnetic field <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mi>B</a:mi></a:math>, there is no quantization. However, under higher fields, we observe distinct noninteger conductance steps. Based on numerical tight-binding calculations and phenomenological Landauer-Büttiker approach, attribute these atypical, quantized plateaus to significant...
A systematic theory of the conductance measurements noninvasive (weak probe) scanning gate microscopy is presented that provides an interpretation what precisely being measured. scattering approach used to derive explicit expressions for first- and second-order changes due perturbation by tip potential in terms states unperturbed structure. In case a quantum point contact, first-order correction dominates at steps vanishes on plateaux where term dominates. Both corrections are nonlocal...
We derive the Bloch equations for spin dynamics of a two-dimensional electron gas in presence spin-orbit coupling. For latter we consider both intrinsic mechanisms structure inversion asymmetry (Rashba) and bulk (Dresselhaus), extrinsic ones arising from scattering impurities. The derivation is based on SU(2) gauge-field formulation Rashba-Dresselhaus Our main result identification new spin-generation torque Elliot-Yafet process, which opposes similar term Dyakonov-Perel process. contributes...
Spin-orbit interaction is usefully classified as extrinsic or intrinsic depending on its origin: the potential due to random impurities (extrinsic), crystalline associated with band device structure (intrinsic). In this paper we will show how by using a SU(2) formulation two sources of spin-orbit may be described in an elegant and unified way. As result obtain simple description interplay types interaction, physically transparent explanation vanishing d.c. spin Hall conductivity Rashba...
Theory predicts for the two-dimensional electron gas with only a Rashba spin-orbit interaction vanishing spin Hall conductivity and at same time finite inverse effect. We show how these seemingly contradictory results are compatible Onsager relations: The latter do hold particle (charge) currents in gas, although (i) their form depends on experimental setup (ii) bulk does not necessarily imply also discuss situation which extrinsic orbit from impurities is present can be different zero.
A normal metallic film sandwiched between two insulators may have strong spin-orbit coupling near the metal-insulator interfaces, even if is negligible in bulk of film. In this paper, we study technologically important and deeply interconnected effects that arise from interfacial films. The first spin Hall effect, whereby a charge current plane partially converted into an orthogonal same plane. second Edelstein which produces in-plane, transverse polarization. At variance with strictly...
A diversity of spin Hall effects in metallic systems is known to rely on Mott skew scattering. In this work its high-temperature counterpart, phonon scattering, which expected be foremost experimental relevance, investigated. particular, the scattering conductivity found practically $T$ independent for temperatures above Debye temperature ${T}_{D}$. As a consequence, Rashba-like high-$T$ linear behavior angle demonstrates dominance extrinsic spin-orbit only if intrinsic splitting smaller...
We study the thermopower of a disordered nanowire in field effect transistor configuration. After first paper devoted to elastic coherent regime (Bosisio, Fleury and Pichard 2014 New J. Phys. 16 035004), we consider here inelastic activated taking place at higher temperatures. In case where charge transport is thermally assisted by phonons (Mott Variable Range Hopping regime), use Miller–Abrahams random resistor network model as recently adapted Jiang et al for thermoelectric transport. This...
We measure and analyze the effective spin Hall angle of platinum in low residual resistivity regime by second harmonic measurements spin-orbit torques for a multilayer Pt/Co/AlO$_x$. An angular dependent study allows us to extract responsible damping-like torque system. observe strikingly non-monotonic reproducible temperature dependence torques. This behavior is compatible with recent theoretical predictions which include both intrinsic extrinsic (impurities phonons) contributions effect at...
How does an initially homogeneous spin polarization in a confined two-dimensional electron gas with Rashba spin-orbit coupling evolve time? the relaxation time depend on system size? We study these questions for systems of size that is much larger than Fermi wavelength, but comparable and even shorter length. Depending confinement may become faster or slower bulk. An homogeneously polarized evolves into spiral pattern.
We consider a two-dimensional electron gas in the presence of Rashba spin-orbit coupling, and study effects magnetic $s$-wave long-range nonmagnetic impurities on spin-charge dynamics system. focus voltage induced spin polarizations their relation to Hall currents. Our results are obtained using quasiclassical Green function technique, hold full range disorder parameter $\ensuremath{\alpha}{p}_{F}\ensuremath{\tau}$.
We derive a kinetic equation for the electrons moving on surface of three-dimensional topological insulator. Due to helical nature excitations backward scattering is suppressed in collision integral, and spin dynamics entirely constrained by that charge. further analyze tunneling between conventional metal or ferromagnet. find tunnel resistance strongly depends angle magnetization ferromagnet current metal. A nonmagnetic layer top amplifies current-induced polarization.
We study the coupled dynamics of spin and charge currents in a two-dimensional electron gas transport diffusive regime. For systems with inversion symmetry there are established relations between Hall effect, anomalous effect inverse effect. However, gases semiconductors like GaAs, is broken so that standard arguments do not apply. demonstrate presence Rashba type spin-orbit coupling (broken structural symmetry) substantially different effects. Furthermore we discuss for Dresselhaus...
We study a thermoelectric ratchet consisting of an array disordered nanowires arranged in parallel on top insulating substrate and contacted asymmetrically to two electrodes. Transport is investigated the Mott hopping regime, when localized electrons can propagate through via thermally assisted hops. When electronic temperature different from phononic one substrate, we show that finite electrical current generated even absence driving forces between discuss device performance both as energy...
Presently much research is devoted to recapturing waste heat for improved energy efficiency. Here the authors study an array of parallel ``dirty'' semiconductor nanowires, configured as a field-effect transistor. For temperatures at which electrons move in phonon-assisted hops, large figures merit and output powers are obtained if impurity bands nanowires depleted by applying gate voltage. Synergy between phonon activation gate-tunable particle-hole asymmetry predicts versatile...
Magnetotransport through cylindrical topological insulator (TI) nanowires is governed by the interplay between quantum confinement and geometric (Aharonov-Bohm Berry) phases. Here, we argue that much broader class of TI with varying radius—for which a homogeneous coaxial magnetic field induces Aharonov-Bohm flux gives rise to nontrivial masslike potential along wire—is accessible studying its simplest member, nanocone. Such nanocones allow us observe intriguing mesoscopic transport...
Electrons in a lattice exhibit time-periodic motion, known as Bloch oscillation, when subject to an additional static electric field. Here, we show that corresponding dynamics can occur upon replacing the spatially periodic potential by driving: Floquet oscillations of charge carriers homogeneous system. The time driving gives rise bands take on role usual bands. For two different drivings (harmonic and kicking through pulses) systems with linear dispersion demonstrate existence such...