Conductivity of superconductors in the flux flow regime

TL;DR

This paper presents a new theoretical model for the conductivity of type-II superconductors in the flux flow regime, highlighting a dominant contribution from Debye-type relaxation related to inelastic processes.

Contribution

It introduces a novel contribution to flux flow conductivity accounting for spatial fluctuations and inelastic relaxation, surpassing traditional models in certain regimes.

Findings

New conductivity contribution proportional to inelastic relaxation time

Dominance of the new contribution in clean, low-temperature superconductors

Significant increase over conventional flux flow conductivity

Abstract

We develop a theory of conductivity of type-II superconductors in the flux flow regime taking into account random spatial fluctuations of the system parameters, such as the gap magnitude $\Delta$(r) and the diffusion coefficient D(r). We find a contribution to the conductivity that is proportional to the inelastic relaxation time $\tau_{in}$, which is much longer than the elastic relaxation time. This new contribution is due to Debye-type relaxation, and it can be much larger than the conventional flux flow conductivity due to Bardeen and Stephen. The new contribution is expected to dominate in clean superconductors at low temperatures and in magnetic fields much smaller than $H_{c2}$.