Distributions of Conductance and Shot Noise and Associated Phase Transitions

For a chaotic cavity with two indentical leads each supporting N channels, we compute analytically, for large N, the full distribution of the conductance and the shot noise power and show that in both cases there is a central Gaussian region flanked on both sides by non-Gaussian tails. The distribution is weakly singular at the junction of Gaussian and non-Gaussian regimes, a direct consequence of two phase transitions in an associated Coulomb gas problem.Comment: 5 pages, 3 figures include

Ballistic thermal conductance limited by phonon roughness scattering: A comparison of power-law and Gaussian roughness

In this work, we have investigated the influence of power-law roughness on the ballistic thermal conductance KTH for a nanosized beam adiabatically connected between two heat reservoirs. The sideways wall beam roughness is assumed to be power-law type, which is described by the roughness amplitude w, the in-plane roughness correlation length ξ and the roughness exponent 0≤H≤1. Distinct differences occur in between power-law and Gaussian wall roughness. For power-law roughness with low roughness exponents H (<0.5), the influence of phonon scattering can be rather destructive leading to significant deviations from the universal conductance value for flat beam walls. On the other hand for large roughness exponents (H>0.5) the conductance drop is significantly smaller than that of Gaussian roughness assuming similar roughness ratios w/ξ.

Hall Voltage with the Spin Hall Effect

The spin Hall effect does not generally result in a charge Hall voltage. We predict that in systems with inhomogeneous electron density in the direction perpendicular to main current flow, the spin Hall effect is instead accompanied by a Hall voltage. Unlike the ordinary Hall effect, we find that this Hall voltage is quadratic in the longitudinal electric field for a wide range of parameters accessible experimentally. We also predict spin accumulation in the bulk and sharp peaks of spin-Hall induced charge accumulation near the edges. Our results can be readily tested experimentally, and would allow the electrical measurement of the spin Hall effect in non-magnetic systems and without injection of spin-polarized electrons

Spin polarization in a T-shape conductor induced by strong Rashba spin-orbit coupling

We investigate numerically the spin polarization of the current in the presence of Rashba spin-orbit interaction in a T-shaped conductor proposed by A.A. Kiselev and K.W. Kim (Appl. Phys. Lett. {\bf 78} 775 (2001)). The recursive Green function method is used to calculate the three terminal spin dependent transmission probabilities. We focus on single-channel transport and show that the spin polarization becomes nearly 100 % with a conductance close to $e^{2}/h$ for sufficiently strong spin-orbit coupling. This is interpreted by the fact that electrons with opposite spin states are deflected into an opposite terminal by the spin dependent Lorentz force. The influence of the disorder on the predicted effect is also discussed. Cases for multi-channel transport are studied in connection with experiments

Effective medium theory for superconducting layers: A systematic analysis including space correlation effects

We investigate the effects of mesoscopic inhomogeneities on the metal-superconductor transition occurring in several two-dimensional electron systems. Specifically, as a model of systems with mesoscopic inhomogeneities, we consider a random-resistor network, which we solve both with an exact numerical approach and by the effective medium theory. We find that the width of the transition in these two-dimensional superconductors is mainly ruled by disorder rather than by fluctuations. We also find that "tail" features in resistivity curves of interfaces between LaAlO3 or LaTiO3 and SrTiO3 can arise from a bimodal distribution of mesoscopic local Tc's and/or substantial space correlations between the mesoscopic domains.Comment: 12 pages, 10 figure

Transport Statistics of Bistable Systems

We consider the transport statistics of classical bistable systems driven by noise. The stochastic path integral formalism is used to investigate the dynamics and distribution of transmitted charge. Switching rates between the two stable states are found from an instanton calculation, leading to an effective two-state system on a long time scale. In the bistable current range, the telegraph noise dominates the distribution, whose logarithm is found to be universally described by a tilted ellipse.Comment: 4 pages, 3 figures, version to appear in Phys. Rev. Let

Quantum transport and momentum conserving dephasing

We study numerically the influence of momentum-conserving dephasing on the transport in a disordered chain of scatterers. Loss of phase memory is caused by coupling the transport channels to dephasing reservoirs. In contrast to previously used models, the dephasing reservoirs are linked to the transport channels between the scatterers, and momentum conserving dephasing can be investigated. Our setup provides a model for nanosystems exhibiting conductance quantization at higher temperatures in spite of the presence of phononic interaction. We are able to confirm numerically some theoretical predictions.Comment: 7 pages, 4 figure

Wigner Function Description of the A.C.-Transport Through a Two-Dimensional Quantum Point Contact

We have calculated the admittance of a two-dimensional quantum point contact (QPC) using a novel variant of the Wigner distribution function (WDF) formalism. In the semiclassical approximation, a Boltzman-like equation is derived for the partial WDF describing both propagating and nonpropagating electron modes in an effective potential generated by the adiabatic QPC. We show that this quantum kinetic approach leads to the well-known stepwise behavior of the real part of the admittance (the conductance), and of the imaginary part of the admittance (the emittance), in agreement with the latest results, which is determined by the number of propagating electron modes. It is shown, that the emittance is sensitive to the geometry of the QPC, and can be controlled by the gate voltage. We established that the emittance has contributions corresponding to both quantum inductance and quantum capacitance. Stepwise oscillations in the quantum inductance are determined by the harmonic mean of the velocities for the propagating modes, whereas the quantum capacitance is a significant mesoscopic manifestation of the non-propagating (reflecting) modes.Comment: 23 pages (latex), 3 figure

On the validity of entropy production principles for linear electrical circuits

We discuss the validity of close-to-equilibrium entropy production principles in the context of linear electrical circuits. Both the minimum and the maximum entropy production principle are understood within dynamical fluctuation theory. The starting point are Langevin equations obtained by combining Kirchoff's laws with a Johnson-Nyquist noise at each dissipative element in the circuit. The main observation is that the fluctuation functional for time averages, that can be read off from the path-space action, is in first order around equilibrium given by an entropy production rate. That allows to understand beyond the schemes of irreversible thermodynamics (1) the validity of the least dissipation, the minimum entropy production, and the maximum entropy production principles close to equilibrium; (2) the role of the observables' parity under time-reversal and, in particular, the origin of Landauer's counterexample (1975) from the fact that the fluctuating observable there is odd under time-reversal; (3) the critical remark of Jaynes (1980) concerning the apparent inappropriateness of entropy production principles in temperature-inhomogeneous circuits.Comment: 19 pages, 1 fi

Landauer Conductance of Luttinger Liquids with Leads

We show that the dc conductance of a quantum wire containing a Luttinger liquid and attached to non-interacting leads is given by $e^2/h$ per spin orientation, regardless of the interactions in the wire. This explains the recent observations of the absence of conductance renormalization in long high-mobility $GaAs$ wires by Tarucha, Honda and Saku (Solid State Communications {\bf 94}, 413 (1995)).Comment: 4 two-column pages, RevTeX + 1 uuencoded figure