Symmetric and asymmetric states in a mesoscopic superconducting wire in the voltage-driven regime

Abstract

The response of a mesoscopic homogeneous superconducting wire, connected with bulk normal metal reservoirs, is theoretically investigated as function of the applied voltage. The finite relaxation length of the nonequilibrium quasiparticle distribution function $\bar{L_E}$ is included where we assumed that our wire is in the dirty limit. We found that {\it both} symmetric and asymmetric states can exist which are characterized by a stationary symmetric and asymmetric distribution of the order parameter with respect to the center of the wire. Current voltage characteristics of the wire with length $L>\bar{L_E}$ being in the symmetric state show a pronounced S-behavior. The asymmetric state may exist only for voltages larger than some critical value and coexist with the symmetric state in a finite voltage interval. For wires with $L \sim \bar{L_E}$ the asymmetric state survives up to higher values of the voltage than the symmetric one and may exist both in the voltage and the current driven regimes. We propose an experiment to observe reversible switching between those stationary symmetric and asymmetric states.