Thermally activated Hall creep of flux lines from a columnar defect

TL;DR

This paper investigates the thermally activated depinning of flux lines from columnar defects in superconductors, deriving an effective Hamiltonian and analyzing the decay rate's dependence on temperature and force.

Contribution

It introduces a new 1D field Hamiltonian to describe Hall-driven flux line depinning and provides a detailed analysis of the decay rate under thermal activation.

Findings

Decay rate proportional to F^{5/2} T^{-1/2} at high temperatures

Activation energy scales as (ε V_0)^{1/2} V_0 / F

Results applicable to vortex pinning in superclean superconductors

Abstract

We analyse the thermally activated depinning of an elastic string (line tension $\epsilon$) governed by Hall dynamics from a columnar defect modelled as a cylindrical potential well of depth $V_{0}$ for the case of a small external force $F.$ An effective 1D field Hamiltonian is derived in order to describe the 2D string motion. At high temperatures the decay rate is proportional to $F^{{5}/{2}}T^{-{1}/{2}} \exp{\left [{F_{0}}/{F}-{U(F)}/{T}\right ]},$ with $F_{0}$ a constant of order of the critical force and $U(F) \sim{\left ({\epsilon V_{0}})}^{{1}/{2}}{V_{0}/{F}}$ the activation energy. The results are applied to vortices pinned by columnar defects in superclean superconductors.