We present a theory for the current shot noise in long diffusive SNS structures with low-resistive interfaces at arbitrary temperatures. In such structures, the noise is mostly generated by normal electron scattering in the N-region. Whereas the $I$-
$V$ characteristics are approximately described by Ohms law, the current noise reveals all characteristic features of the MAR regime: giant enhancement at low voltages, pronounced SGS, and excess noise at large voltages. The most spectacular feature of the noise in the incoherent MAR regime is a universal finite noise level at zero voltage and at zero temperature, $S= 4Delta/3R$. This effect can be understood as the result of the enhancement of the effective charge of the carriers, $q^{it eff}=2Delta/V$, or, alternatively, as the effect of strongly non-equilibrium quasiparticle population in the energy gap region with the effective temperature $T_0=Delta/3$. Under the condition of dominant electron-electron scattering, the junction undergoes crossover to the hot electron regime, with the effective temperature of the subgap electrons decreasing logarithmically with the voltage. Calculation of the noise power has been done on the basis of circuit theory of the incoherent MAR.
We present numerical solution of equations by Aslamazov and Lempitskiy (AL) for the distribution of the transport current density in thin superconducting films in the absence of external magnetic field, in both the Meissner and the vortex states. Thi
s solution describes smooth transition between the regimes of a wide film and a narrow channel and enables us to find the critical currents and current-voltage characteristics within a wide range of the film width and temperatures. We propose simple approximating formulas for the current density distributions and critical currents.
We solve the coherent multiple Andreev reflection (MAR) problem and calculate current-voltage characteristics (IVCs) for Josephson SINIS junctions, where S are local-equilibrium superconducting reservoirs, I denotes tunnel barriers, and N is a short
diffusive normal wire, the length of which is much smaller than the coherence length, and the resistance is much smaller than the resistance of the tunnel barriers. The charge transport regime in such junctions qualitatively depends on a characteristic value gamma = Delta tau_d of relative phase shifts between the electrons and retro-reflected holes accumulated during the dwell time tau_d. In the limit of small electron-hole dephasing gamma << 1, our solution recovers a known formula for a short mesoscopic connector extended to the MAR regime. At large dephasing, the subharmonic gap structure in the IVC scales with 1/ gamma, which thus plays the role of an effective tunneling parameter. In this limit, the even gap subharmonics are resonantly enhanced, and the IVC exhibits portions with negative differential resistance.
This paper is devoted to the investigation of electron sound -- oscillations of the electron distribution function coupled with elastic deformation and propagating with the Fermi velocity. The amplitude-phase relations characterizing the behavior of
the electron sound in Ga single crystals are determined experimentally. A model problem of excitation of electron sound in a compensated metal with equivalent bands is solved for a finite sample with diffusive scattering of electrons at the interfaces. It was found that the displacement amplitude of the receiving interface is two orders of magnitude larger than the elastic amplitude of the wave due to electron pressure. It was established that the changes occurring in the amplitude and phase of the electron sound waves at a superconducting transition do not depend on the path traversed by the wave, i.e. they refer only to the behavior of the transformation coefficient.
