I-V characteristics of SNS junctions with a multivalley normal region

Abstract

In multivalley conductors the inter-valley relaxation time ${\tau }_v$ and the inelastic relaxation time ${\tau }_{in}$ may be significantly longer than the intra-valley momentum relaxation time $\tau$. We show that this separation of time scales has dramatic effects on the I-V characteristics of SNS junctions with a multivalley normal region. We generalize the Larkin-Ovchinnikov equations describing superconducting kinetics to the case of multivalley superconductors. We use this generalization to obtain a kinetic description of multivalley SNS junctions. We find that at constant voltage bias $V$, the current $I(V)$ is nonmonotonic; it exhibits two peaks of similar magnitude $I_{\text{max,1}}\sim I_{\text{max,2}}$ at $V_1\sim \hslash (e{\tau }_{in}{)}^{-1}$ and $V_2\sim \hslash (e{\tau }_v{)}^{-1}$, which may greatly exceed the critical current $I_c(T)$. At constant current bias $I$ we find that in a wide interval, $I_c(T)<I\lesssim I_{\text{jump}}$, the nonlinear resistance of the junction is controlled by the long relaxation times and may be several orders of magnitude smaller than the normal state resistance.