Transport properties of a two-dimensional electron liquid at high magnetic field

The chiral Luttinger liquid model for the edge dynamics of a two-dimensional electron gas in a strong magnetic field is derived from coarse-graining and a lowest Landau level projection procedure at arbitrary filling factors $\nu<1$ -- without reference to the quantum Hall effect. Based on this model, we develop a formalism to calculate the Landauer-B\"uttiker conductances in generic experimental set-ups including multiple leads and voltage probes. In the absence of tunneling between the edges the "ideal" Hall conductances ($G_{ij}= \frac{e^2 \nu}{h}$ if lead $j$ is immediately upstream of lead $i$, and $G_{ij}=0$ otherwise) are recovered. Tunneling of quasiparticles of fractional charge $e^*$ between different edges is then included as an additional term in the Hamiltonian. In the limit of weak tunneling we obtain explicit expressions for the corrections to the ideal conductances. As an illustration of the formalism we compute the current- and temperature-dependent resistance $R_{xx}(I,T)$ of a quantum point contact localized at the center of a gate-induced constriction in a quantum Hall bar. The exponent $\alpha$ in the low-current relation $R_{xx}(I,0) \sim I^{\alpha -2}$ shows a nontrivial dependence on the strength of the inter-edge interaction, and its value changes as $e^*V_H$, where $V_H = \frac{h I}{\nu e^2}$ is the Hall voltage, falls below a characteristic crossover energy $\frac{\hbar c}{d}$, where $c$ is the edge wave velocity and $d$ is the length of the constriction. The consequences of this crossover are discussed vis-a-vis recent experiments in the weak tunneling regime.Comment: 20 pages, 8 figures, Revtex4, adjourned with referee's comments, added references and typos correcte

Resonant Andreev Tunneling in Strongly Interacting Quantum Dots

We study resonant Andreev tunneling through a strongly interacting quantum dot connected to a normal and to a superconducting lead. We obtain a formula for the Andreev current and apply it to discuss the linear and non-linear transport in the nonperturbative regime, where the effects of the Kondo resonance on the two particle tunneling arise. In particular we notice an enhancement of the Kondo anomaly in the $I-V$ characteristics due to the superconducting electrode.Comment: 13 pages Revtex, 3 figures .p

Spin Hall effects due to phonon skew scattering

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 skew scattering, which is expected to be of foremost experimental relevance, is investigated. In particular, the phonon skew scattering spin Hall conductivity is found to be practically $T$-independent for temperatures above the Debye temperature $T_D$. As a consequence, in Rashba-like systems a high-$T$ linear behavior of the spin Hall angle demonstrates the dominance of extrinsic spin-orbit scattering only if the intrinsic spin splitting is smaller than the temperature.Comment: Accepted version, 4 (+1) pages, 2 figure

Quantum noise in the spin transfer torque effect

Describing the microscopic details of the interaction of magnets and spin-polarized currents is key to achieve control of such systems at the microscopic level. Here we discuss a description based on the Keldysh technique, casting the problem in the language of open quantum systems. We reveal the origin of noise in the presence of both field-like and damping like terms in the equation of motion arising from spin conductance

Nonlinear Inverse Spin Galvanic Effect in Anisotropic Disorder-free Systems

Spin transport phenomena in solid materials suffer limitations from spin relaxation associated to disorder or lack of translational invariance. Ultracold atoms, free of that disorder, can provide a platform to observe phenomena beyond the usual two-dimensional electron gas. By generalizing the approach used for isotropic two-dimensional electron gases, we theoretically investigate the inverse spin galvanic effect in the two-level atomic system in the presence of anisotropic Rashba-Dresselhaus spin-orbit couplings (SOC) and external magnetic field. We show that the combination of the SOC results in an asymmetric case: the total spin polarization considered for a small momentum has a longer spin state than in a two-dimensional electron gas when the SOC field prevails over the external electric field. Our results can be relevant for advancing experimental and theoretical investigations in spin dynamics as a basic approach for studying spin state control

Specific Heat Anomaly and Adiabatic Hysteresis in Disordered Electron Systems in a Magnetic Field

We consider the thermodynamic behavior of a disordered interacting electron system in two dimensions. We show that the corrections to the thermodynamic potential in the weakly localized regime give rise to a non monotonic behavior of the specific heat both in temperature and magnetic field. From this effect we predict the appearance of adiabatic hysteresis in the magnetoconductance. Our results can be interpreted as precursor effect of formation of local moments in disordered electron systems. We also comment on the relevance of our analysis in three dimensional systems.Comment: 4 pages, RevTeX, 3 figures, accepted by EPJ

Theory of charge-spin conversion at oxide interfaces: The inverse spin-galvanic effect

We evaluate the non-equilibrium spin polarization induced by an applied electric field for a tight-binding model of electron states at oxides interfaces in LAO/STO heterostructures. By a combination of analytic and numerical approaches we investigate how the spin texture of the electron eigenstates due to the interplay of spin-orbit coupling and inversion asymmetry determines the sign of the induced spin polarization as a function of the chemical potential or band filling, both in the absence and presence of local disorder. With the latter, we find that the induced spin polarization evolves from a non monotonous behavior at zero temperature to a monotonous one at higher temperature. Our results may provide a sound framework for the interpretation of recent experiments.Comment: Submitted to Proceedings of SPIE Nanoscience + Engineering 2018, Spintronics XI, 23 pages, 9 figure

Intrinsic spin Hall effect in systems with striped spin-orbit coupling

The Rashba spin-orbit coupling arising from structure inversion asymmetry couples spin and momentum degrees of freedom providing a suitable (and very intensively investigated) environment for spintronic effects and devices. Here we show that in the presence of strong disorder, non-homogeneity in the spin-orbit coupling gives rise to a finite spin Hall conductivity in contrast with the corresponding case of a homogeneous linear spin-orbit coupling. In particular, we examine the inhomogeneity arising from a striped structure for a two-dimensional electron gas, affecting both density and Rashba spin-orbit coupling. We suggest that this situation can be realized at oxide interfaces with periodic top gating.Comment: 9 pages, 8 figure

Electronic thermal conductivity of disordered metals

We calculate the thermal conductivity of interacting electrons in disordered metals. In our analysis we point out that the interaction affects thermal transport through two distinct mechanims, associated with quantum interference corrections and energy exchange of the quasi particles with the electromagnetic environment, respectively. The latter is seen to lead to a violation of the Wiedemann-Franz law. Our theory predicts a strong enhancement of the Lorenz ratio $\kappa /\sigma T$ over the value which is predicted by the Wiedemann-Franz law, when the electrons encounter a large environmental impedance.Comment: 4 page

Quasiclassical approach and spin-orbit coupling

We discuss the quasiclassical Green function method for a two-dimensional electron gas in the presence of spin-orbit coupling, with emphasis on the meaning of the $\xi$-integration procedure. As an application of our approach, we demonstrate how the spin-Hall conductivity, in the presence of spin-flip scattering, can be easily obtained from the spin-density continuity equation.Comment: 3 pages, Submitted to Physica