Dissipative mechanisms in SNS junctions and magnetic vortex lattices

Abstract

When a normal metal is subject to an external field and a transport current is induced, the dissipation rate is typically controlled by the elastic scattering time of the quasiparticles. In superconductors, the presence of the superfluid condensate complicates quasi-particle dynamics, and as a result the dissipation rate can depend on additional time scales. In particular, when the condensate is accelerated by the external field, a spectral flow of quasi-particle energy levels are induced, resulting in a mechanism of dissipation which is controlled by the inelastic relaxation time. In this work I theoretically investigate the role of this mechanism in two experimentally relevant superconducting systems: superconductor-normal metal-superconductor junctions and magnetic vortex lattices formed in type-II superconducting films. In the former, I develop a theory of current-voltage characteristics and show that there is a regime at small voltages/currents with features that are distinct from the large voltage/current regime, which is described by the conventional theory. In the latter, I calculate the microwave absorption coefficient and show that there is a broad range of parameters where the mechanism of dissipation related to spectral flow gives the dominant contribution.