880 research outputs found
Quantum Decoherence in Disordered Mesoscopic Systems
We point out that the low temperature saturation of the electron phase
decoherence time in a disordered conductor can be explained within the existing
theory of weak localization provided the effect of quantum (high frequency)
fluctuations is taken into account. Making use of the fluctuation-dissipation
theorem we evaluate the quantum decoherence time, the crossover temperature
below which thermal effects become unimportant, and the weak localization
correction at T=0. For 1d systems the latter is found to be
, where is the number of conducting
channels.Comment: RevTeX, 3 page
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
Parity-Affected Superconductivity in Ultrasmall Metallic Grains
We investigate the breakdown of BCS superconductivity in {\em ultra}\/small
metallic grains as a function of particle size (characterized by the mean
spacing between discrete electronic eigenstates), and the parity ( =
even/odd) of the number of electrons on the island. Assuming equally spaced
levels, we solve the parity-dependent BCS gap equation for the order parameter
. Both the critical level spacing and the
critical temperature at which are parity
dependent, and both are so much smaller in the odd than the even case that
these differences should be measurable in current experiments.Comment: 4 pages RevTeX, 1 encapsulated postscript figure, submitted to
Physical Review Letter
Tunneling through a multigrain system: deducing the sample topology from the nonlinear conductance
We study a current transport through a system of a few grains connected with
tunneling links. The exact solution is given for an arbitrarily connected
double-grain system with a shared gate in the framework of the orthodox model.
The obtained result is generalized for multigrain systems with strongly
different tunneling resistances. We analyse the large-scale nonlinear
conductance and demonstrate how the sample topology can be unambiguously
deduced from the spectroscopy pattern (differential conductance versus
gate-bias plot). We present experimental data for a multigrain sample and
reconstruct the sample topology. A simple selection rule is formulated to
distinguish samples with spectral patterns free from spurious disturbance
caused by recharging of some grains nearby. As an example, we demonstrate
experimental data with additional peaks in the spectroscopy pattern, which can
not be attributed to coupling to additional grains. The described approach can
be used to judge the sample topology when it is not guaranteed by fabrication
and direct imaging is not possible.Comment: 13 pages (including 8 figures
Reply to the Comment on 'Quantum Phase Slips and Transport in Ultra-Thin Superconducting Wires'
We reply to the recent Comment [cond-mat/9702231] by J.-M. Duan. Our point of
view is markedly different on every issue raised. Much of the disagreement can
be traced to a different preception of experimentally relevant length scales.
i) We explain the difference between our formulation, which rests on a
microscopic basis, and the phenomenological one of the author. ii) Our
renormalization scheme is fundamentally right, as the "log(log)" interaction
appears only in wires of astronomical lengths. iii) The tunneling barrier is
profoundly reduced by the kinetic inductance. iv) We do make an appropriate
comparison to the data on the thinnest available wires.Comment: 1 page Revte
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