Role of Impurities in Core Contribution to Vortex Friction

TL;DR

This paper provides a microscopic analysis of how impurities affect vortex friction in type II superconductors at zero temperature, revealing that core states dominate the friction and are influenced by impurity levels.

Contribution

It introduces a microscopic calculation method for vortex core state contributions to friction, highlighting the role of impurities and contrasting with previous relaxation time approximation results.

Findings

Vortex friction is proportional to normal state resistivity in weak impurity limit.

Core state contribution depends only on Fermi energy and energy gap in dirty limit.

Transverse force remains insensitive to impurities.

Abstract

We present a microscopic calculation of core states contribution to vortex friction in a type II superconductor at zero temperature. In weak impurity limit, a perturbative calculation leads to a vortex friction proportional to the normal state resistivity. With the aid of random matrix theory, vortex friction due to core states is determined only by the Fermi energy and the energy gap in dirty limit, similar to the phenomenological results of Bardeen and Stephen, but disagrees with the results obtained under the relaxation time approximation. In addition, an explicit demonstration is given on the the insensitivity of transverse force to impurities.