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We investigate non-equilibrium transport properties of a quantum dot in the Coulomb blockade regime under the condition of negligible inelastic scattering during the dwelling time of the electrons in the dot. Using the quantum kinetic equation we show that the absence of thermalization leads to a double-step in the distribution function of electrons on the dot, provided that it is symmetrically coupled to the leads. This drastically changes nonlinear transport through the dot resulting in an additional (compared to the thermalized case) jump in the conductance at voltages close to the charging energy, which could serve as an experimental manifestation of the absence of thermalization., Comment: 5 pages, 3 figures, and Supplemental material

In recent experiments on conductance of one-dimensional (1D) channels in ultra-clean samples, a diverse set of plateaus were found at fractions of the quantum of conductance in zero magnetic field. We consider a discrete model of strongly interacting electrons in a clean 1D system where the current between weak tunneling contacts is carried by fractionally charged solutions. While in the spinless case conductance remains unaffected by the interaction, as is typical for the strongly interacting clean 1D systems, we demonstrate that in the spinful case the peak conductance takes fractional values that depend on the filling factor of the 1D channel., Comment: 5 pages, 3 figures

The nonlinear sigma model (NLSM) epitomises a field-theoretical approach to (interacting) electrons in disordered media. These lectures are aimed at the audience who might have vaguely heard about its existence but know very little of what is that, even less so of why it should be used and next to nothing of how it can be applied. These what, why and mainly how are the subject of the present lectures. In the first part, after a short description of why to be bothered, the NLSM is derived from scratch in a relatively simple (but still rather mathematical) way for non-interacting electrons in the presence of disorder, and some illustration of its perturbative usage is given. In the second part it is generalised, not without some leap of faith, to include the Coulomb repulsion and superconducting pairing., Comment: 21 pages, 5 eps figures. To appear in "Proceedings of the International School of Physics "Enrico Fermi" Course CLI, edited by B. Altshuler and V. Tognetti, IOS Press, Amsterdam 2003

Mohanty and Webb [Phys. Rev. Lett. 88, 146601 (2002), cond-mat/0204298] claim that their data on conductance fluctuations in gold wires contradict the one-parameter scaling. We show that flaws in extracting values of the cumulants (irreducible moments) <> of the conductance distribution (for n=3,4) invalidate all the conclusions made there. The actual values of the cumulants determined by us from the published raw data contained in Ref. [Phys. Rev. Lett. 88, 146601 (2002)] are orders of magnitude smaller than those claimed. Moreover, the limited applicability of the ergodicity hypothesis makes the higher order cumulants extracted from magnetofingerprints statistically unreliable. Thus, the data of Ref. [Phys. Rev. Lett. 88, 146601 (2002)] do not warrant any statement on the violation or validity of the one-parameter scaling., This is a revised version, where a misprint has been corrected and an explicit footnote added, helping the interested reader to make a visual inspection of the data in the commented Letter by P. Mohanty and R.A. Webb, Phys. Rev. Lett. 88, 146601 (2002); cond-mat/0204298

We suggest a novel nonlinear $��$-model for the description of disordered superconductors. The main distinction from existing models lies in the fact that the saddle point equation is solved non-perturbatively in the superconducting pairing field. It allows one to use the model both in the vicinity of the metal-superconductor transition and well below its critical temperature with full account for the self-consistency conditions. We show that the model reproduces a set of known results in different limiting cases, and apply it for a self-consistent description of the proximity effect at the superconductor-metal interface., Revised version, 8 pages, 1 fig., revtex; final version, as published, contains a few corrections in the summary