160 research outputs found
Current fluctuations in composite conductors: Beyond the second cumulant
Employing the non-linear -model we analyze current fluctuations in
coherent composite conductors which contain a diffusive element in-between two
tunnel barriers. For such systems we explicitly evaluate the
frequency-dependent third current cumulant which also determines the leading
Coulomb interaction correction to shot noise. Our predictions can be directly
tested in future experiments.Comment: 6 pages, 1 figur
The influence of interstitial impurity atom – vacancy complex on diffusivity of interstitial atom in alpha-iron
Coherent Electron Transport in Superconducting-Normal Metallic Films
We study the transport properties of a quasi-two-dimensional diffusive normal
metal film attached to a superconductor. We demonstrate that the properties of
such films can essentially differ from those of quasi-one-dimensional systems:
in the presence of the proximity induced superconductivity in a sufficiently
wide film its conductance may not only increase but also decrease with
temperature. We develop a quantitative theory and discuss the physical nature
of this effect. Our theory provides a natural explanation for recent
experimental findings referred to as the ``anomalous proximity effect''.Comment: 4 Pages RevTex, 4 Postscript figures; submitted to Phys. Rev. Let
Diffusion under a stress in interstitial alloys and simulation of atom redistribution near the crack tip
Coulomb Interaction and Quantum Transport through a Coherent Scatterer
An interplay between charge discreteness, coherent scattering and Coulomb
interaction yields nontrivial effects in quantum transport. We derive a real
time effective action and an equivalent quantum Langevin equation for an
arbitrary coherent scatterer and evaluate its current-voltage characteristics
in the presence of interactions. Within our model, at large conductances
and low (but outside the instanton-dominated regime) the interaction
correction to saturates and causes conductance suppression by a universal
factor which depends only on the type of the conductor.Comment: 4 pages, no figure
Capacitance of a quantum dot from the channel-anisotropic two-channel Kondo model
We investigate the charge fluctuations of a large quantum dot coupled to a
two-dimensional electron gas via a quantum point contact following the work of
Matveev. We limit our discussion to the case where exactly two channels enter
the dot and we discuss the role of an anisotropy between the transmission
coefficients (for these two channels) at the constriction. Experimentally, a
channel-anisotropy can be introduced applying a relatively weak in-plane
magnetic field to the system when only one ``orbital'' channel is open. The
magnetic field leads to different transmission amplitudes for spin-up and
spin-down electrons.
In a strong magnetic field the anisotropic two-channel limit corresponds to
two (spin-polarized) orbital channels entering the dot.
The physics of the charge fluctuations can be captured using a mapping on the
channel-anisotropic two-channel Kondo model. For the case of weak reflection at
the point contact this has already briefly been stressed by one of us in PRB
{\bf 64}, 161302R (2001). This mapping is also appropriate to discuss the
conductance behavior of a two-contact set-up in strong magnetic field.
Here, we elaborate on this approach and also discuss an alternative solution
using a mapping on a channel-isotropic Kondo model. In addition we consider the
limit of weak transmission.
We show that the Coulomb-staircase behavior of the charge in the dot as a
function of the gate voltage, is already smeared out by a small
channel-anisotropy both in the weak- and strong transmission limits.Comment: 17 pages, 4 figures, 1 Table; Expands cond-mat/0101126; Sec. VI on
2-contact setup added (Final version for PRB
Bragg resonances for tunneling between edges of a 2D Quantum Hall system
A theory is presented for tunneling between compressible regions on the sides
of a narrow incompressible Quantum Hall strip. Assuming that electron
interactions lead to formation of a Wigner crystal on the edges of the
compressible regions, we consider the situation when the non-conservation of
electron momentum required for transport is provided, in the absence of
disorder, by umklapp scattering on the crystal. The momentum given to the
crystal is quantized due to the Bragg condition, which leads to resonances in
tunneling conductivity as a function of the incompressible strip width, similar
to those reported recently by N. Zhitenev, M. Brodsky, R. Ashoori, and M.
Melloch.Comment: 4 pages RevTex, 2 figure
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