arXiv subjects

G. B. Lesovik

Publications and source records attributed to G. B. Lesovik.

61 records · Page 4Linked to original sources

arXiv1998

Finite voltage shot noise in normal-metal - superconductor junctions

We express the low-frequency shot noise in a disordered normal-metal - superconductor (NS) junction at finite (subgap) voltage in terms of the normal scattering amplitudes and the Andreev reflection amplitude. In the multichannel limit, the conductance exhibits resonances which are accompanied by an enhancement of the (differential) shot noise. In the study of multichannel single and double barrier junctions we discuss the noise properties of coherent transport at low versus high voltage with respect to the Andreev level spacing.

cond-mat.mes-hall↗

arXiv1996

Nonlinearity in NS transport: scattering matrix approach

A general formula for the current through a disordered normal--superconducting junction is derived, which is valid at finite temperature and includes the full voltage dependence. The result depends on a multichannel scattering matrix, which describes elastic scattering in the normal region, and accounts for the Andreev scattering at the NS interface. The symmetry of the current with respect to sign reversal in the subgap regime is discussed. The Andreev approximation is used to derive a spectral conductance formula, which applies to voltages both below and above the gap. In a case study the spectral conductance formula is applied to the problem of an NINIS double barrier junction.

cond-mat.mes-hall↗

arXiv1996

Electron Counting Statistics and Coherent States of Electric Current

A theory of electron counting statistics in quantum transport is presented. It involves an idealized scheme of current measurement using a spin 1/2 coupled to the current so that it precesses at the rate proportional to the current. Within such an approach, counting charge without breaking the circuit is possible. As an application, we derive the counting statistics in a single channel conductor at finite temperature and bias. For a perfectly transmitting channel the counting distribution is gaussian, both for zero-point fluctuations and at finite temperature. At constant bias and low temperature the distribution is binomial, i.e., it arises from Bernoulli statistics. Another application considered is the noise due to short current pulses that involve few electrons. We find the time-dependence of the driving potential that produces coherent noise-minimizing current pulses, and display analogies of such current states with quantum-mechanical coherent states.

cond-mat↗

arXiv1996

Hall Voltage Fluctuations as a Diagnostic of Internal Magnetic Field Fluctuations in High Temperature Superconductors and the Half-filled Landau Level

Fluctuations of the Hall voltage reveal information about long wavelength magnetic field fluctuations. If gauge theories of strongly correlated electrons are correct, such fluctuations are particularly large in the half-filled Landau level and in high $T_c$ superconductors. We present estimates for the magnitude, system size and frequency dependence of these fluctuations. The frequency dependence contains information about instantons in the gauge field.

cond-mat↗

arXiv1995

Quantum conductance fluctuations in 3D ballistic adiabatic wires.

Quantum conductance of 3D ballistic wires with idealy flat boundaries obeys fluctuations with the properties quite distinguishable from those of universal conductance fluctuations: Both their amplitude and the sensitivity to the magnetic field flux $Φ=HS$ penetrated into the sample cross-sectional area $S$ are different and depend on details of the cross-sectioanl shape of the wire. When the latter is integrable, conductance fluctuations have the enlarged amplitude $δG\sim\left[(e^2/h)^3G\right]^{1/4}$. When the cross-sectional shape of a wire is non-integrable, the irregular part of a conductance has the $e^ 2/h$ scale, whereas the correlation field is reduced to the value of $H_S\sim (λ_F/\sqrt S)^{1/2}(Φ_0/S)$ and the correlation voltage of the nonlinear conductance fluctuations has the scale of $eV_c\sim\hbar^2/mS\sim E_F/(S/λ_F)$, where $λ_F=1/p_F$ is the Fermi wavelength.

cond-mat↗

arXiv1994

Quantum Measurement in Electric Circuit

We study fluctuations of electric current in a quantum resistor and derive a general quantum-mechanical formula for the distribution of transmitted charge. For that we introduce a scheme of current measurement that involves a spin $1/2$ coupled to the current so that it precesses at the rate proportional to the current. Our approach allows the study of charge transfer without breaking the circuit. We analyze a single channel conductor and derive electron counting statistics for arbitrary relation between temperature and voltage. For a perfectly transmitting channel the counting distribution is gaussian, both for zero-point fluctuations and at finite temperature. At constant voltage and low temperature the distribution is binomial, i.e., it arises from Bernoulli statistics.

cond-mat↗

arXiv1993

Noise in an ac biased junction. Non-stationary Aharonov-Bohm effect

We study excess noise in a quantum conductor in the presence of constant voltage and alternating external field. Due to a two particle interference effect caused by Fermi correlations the noise is sensitive to the phase of the time dependent transmission amplitude. We compute spectral density and show that at T=0 the noise has singular dependence on the {\rm dc} voltage $V$ and the {\rm ac} frequency $Ω$ with cusplike singularities at integer $eV/\hbarΩ$. For a metallic loop with an alternating flux the phase sensitivity leads to an oscillating dependence of the strengths of the cusps on the flux amplitude.

cond-mat↗