MANIFESTATION OF QUASI-PARTICLE BRANCH IMBALANCE IN RESISTIVE MEASUREMENTS OF MESOSCOPIC SUPERCONDUCTORS

A model of the resistive state for mesoscopic superconductors has been proposed. It is considered that the frequency of thermally induced di screte phase-slip events is equal to the rate of thermally driven fluc tuations, Gamma(T). After each phase slippage the nonequilibrium distr ibution of chemical potentials for pairs mu(p) and quasiparticles mu(q ) relaxes on a time scale tau(Q). The measured time-averaged voltage across the mesoscopic sample with dimensions compared to a single phas e-slip center is found to be proportional to the spatial difference of the corresponding chemical potential (mu(p) for superconducting probe s and mu(q) for normal probes) and should be multiplied by the time av eraging weight similar to tau(Q)<Gamma(>)T. The resulting effective r esistance ratio [R(T)]/R(normal) for mesoscopic objects may be noticea bly greater than unity sufficiently close to the critical temperature; it displays a strong nonlinear dependence on the bias current and is greatly suppressed by an external magnetic field.