We calculate the corrections to the Sharvin conductance of ballistic multimode microcontacts that result from electron--electron scattering in the leads. Using a semiclassical Boltzmann equation, we obtain that these corrections are {\it positive} and scale with temperature as $T^2\ln(E_F/T)$ for three-dimensional contacts and as $T$ for two-dimensional ones. These results are relevant to recent experiments on 2DEG contacts.
Quantum corrections to the conductivity and Hall coefficient of a 2D electron gas in a dirty AlGaAs/GaAs/AlGaAs quantum well: transition from diffusive to ballistic regime
本文报道了AlGaAs/GaAs/AlGaAs量子阱中低迁移率、高密度二维电子气在宽温度范围（1.5 K - 110 K）内纵向电导率和霍尔系数的量子修正实验研究。这个温度范围涵盖了我们的样品的扩散和弹道相互作用制度。因此，可以研究纵向电导率和霍尔效应的交叉区域。
The coherent charge transport through an illuminated graphene ribbon is studied as function of electronic doping, frequency and strength of the electromagnetic driving, for monochromatic circularly polarized light. We focus on the DC current carried by 2D bulk carriers which is dominant (over edge transport) for short and wide enough samples. Broad dips in conductance are predicted for one-photon and multi-photon resonances between the valence and conductance bands. The residual conductance can be associated with evanescent states and related to dynamical gaps in the Floquet quasi-energy spect…
Understanding ballistic phonon transport effects in transient thermoreflectance experiments and explaining the observed deviations from classical theory remains a challenge. Diffusion equations are simple and computationally efficient but are widely believed to break down when the characteristic length scale is similar or less than the phonon mean-free-path. Building on our prior work, we demonstrate how well-known diffusion equations, namely the hyperbolic heat equation and the Cattaneo equation, can be used to model ballistic phonon effects in frequency-dependent periodic steady-state therma…
Quantum corrections to the conductivity and Hall coefficient of a two-dimensional electron gas in a dirty AlGaAs/GaAs/AlGaAs quantum well: from the diffusive to the ballistic regime
Influence of e-e scattering on the temperature dependence of the resistance of a classical ballistic point contact in a two-dimensional electron system
The bulk photovoltaic effect (BPVE) -- generation of electric currents by light in noncentrosymmetric materials in the absence of electric fields and gradients -- has been intensively investigated in the end of the last century. The outcomes including all main aspects of this phenomenon were summarized in review and books. A new upsurge of interest to the BPVE occurred recently and resulted in a flux of misleading theoretical and experimental publications centered around the so-called shift current. Numerous top-rated recent publications ignore the basic principles of charge-transport phenomen…
We investigate the Josephson critical current $I_c(Φ)$ of a wide superconductor-normal metal-superconductor (SNS) junction as a function of the magnetic flux $Φ$ threading it. Electronic trajectories reflected from the side edges alter the function $I_c(Φ)$ as compared to the conventional Fraunhofer-type dependence. At weak magnetic fields, $B\lesssim Φ_0/d^2$, the edge effect lifts zeros in $I_c(Φ)$ and gradually shifts the minima of that function toward half-integer multiples of the flux quantum. At $B>Φ_0/d^2$, the edge effect leads to an accelerated decay of the critical current $I_c(Φ)$ w…
We report an experimental study of quantum conductivity corrections for two-dimensional electron gas in a GaAs/InGaAs/GaAs single and double quantum wells in a wide temperature range (1.8-100) K. We perform a comparison of our experimental data for the longitudinal conductivity at zero magnetic field to the theory of interaction-induced corrections to th transport coefficients. In the temperature range from 10 K up to (45-60) K, wich covers the ballistic interaction regimes for our samples, a rather good agreement between the theory and our experimental results has been found.
Gallium nitride (GaN) is a typical wide-bandgap semiconductor with a critical role in a wide range of electronic applications. Ballistic thermal transport at nanoscale hotspots will greatly reduce the performance of a device when its characteristic length reaches the nanometer scale, due to heat dissipation. In this work, we developed a tip-enhanced Raman thermometry approach to study ballistic thermal transport within the range of 10 nm in GaN, simultaneously achieving laser heating and measuring the local temperature. The Raman results showed that the temperature increase from an Au-coated t…
Gate-controllable spin-orbit coupling is often one requisite for spintronic devices. For practical spin field-effect transistors, another essential requirement is ballistic spin transport, where the spin precession length is shorter than the mean free path such that the gate-controlled spin precession is not randomized by disorder. In this letter, we report the observation of a gate-induced crossover from weak localization to weak anti-localization in the magneto-resistance of a high-mobility two-dimensional hole gas in a strained germanium quantum well. From the magneto-resistance, we extract…
In the "ballistic" regime, the transport across a normal metal (N)/superconductor (S) point-contact is dominated by a quantum process called Andreev reflection. Andreev reflection causes an enhancement of the conductance below the superconducting energy gap, and the ratio of the low-bias and the high-bias conductance cannot be greater than 2 when the superconductor is conventional in nature. In this regime, the features associated with Andreev reflection also provide energy and momentum-resolved spectroscopic information about the superconducting phase. Here we theoretically consider various t…
We study the temperature-dependent corrections to the conductance due to electron-electron (e-e) interactions in clean two-dimensional conductors, such as lightly doped graphene or other Dirac matter. We use semiclassical Boltzmann kinetic theory to solve the problem of collision-dominated transport between reflection-free contacts. Time-reversal symmetry and the kinematic constraints of scattering in two dimensions (2D) ensure that inversion-odd and inversion-even distortions of the quasiparticle distribution relax with parametrically different rates at low temperature. This entails the surpr…
We study the magnetoconductance of topological insulator nanowires in a longitudinal magnetic field, including Aharonov-Bohm, Altshuler-Aronov-Spivak, perfectly conducting channel, and universal conductance fluctuation effects. Our focus is on predicting experimental behavior in single wires in the quantum limit where temperature is reduced to zero. We show that changing the Fermi energy $E_F$ can tune a wire from from ballistic to diffusive conduction and to localization. In both ballistic and diffusive single wires we find both Aharonov-Bohm and Altshuler-Aronov-Spivak oscillations with simi…
Facet-selective ballistic supercurrent in a weak topological insulator
Chalmers University of Technology（查尔姆斯理工大学）；University of Gothenburg（哥德堡大学）；Max-Planck-Institut für Festkörperforschung（马克斯·普朗克固体研究所）；Universität Würzburg（维尔茨堡大学）；Radboud University（拉德堡德大学）；Tohoku University（东北大学）
The anomalous Hall and Nernst effects are considered theoretically within Matsubara-Green's function formalism. The effective Hamiltonian of a magnetized two-dimensional electron gas with cubic Rashba spin-orbit interaction may describe transport properties of electronic states at the interfaces or surfaces of perovskite oxides or another type of heterostructures that, due to symmetry, may be described by the same effective model. In the quasi-ballistic limit, both effects are determined by the topological (Fermi sea) contribution whereas the states at the Fermi level gives a negligibly small …
Magnetoresistance ratio of a point-like contact with a 1 nm wide domain wall at different MFP asymmetries
International College of Semiconductor Technology, National Yang Ming Chiao Tung University（国立阳明交通大学半导体科技学院）；Indian Institute of Technology, Delhi（德里印度理工学院）；Unknown University（未知大学）
Equilibration to the steady state for a wide class of Luttinger liquid ballistic weakly linked tunnel contacts is extensively studied. Quantum fluctuations of tunnel current are considered in all orders in tunnel coupling and out of the equilibrium in the time domain. Especially, two important mathematical statements: Self-equilibration (SE-)theorem and Self-equilibration (SE-)lemma on the exact re-exponentiation of thermal average from the Keldysh-contour-ordered evolution operator for arbitrary weakly linked Luttinger liquid tunnel contact are proven. Demonstrated proof of SE-theorem and SE-…
