Abrikosov vortex escape from a columnar defect as a topological electronic transition in vortex core

TL;DR

This paper investigates how vortices escape from columnar defects in superconductors, revealing that the process involves two topological electronic transitions in the vortex core driven by increasing current.

Contribution

It introduces a microscopic model showing that vortex depinning occurs via two distinct topological electronic transitions, a novel insight into vortex dynamics in superconductors.

Findings

Depinning involves two topological electronic transitions.

First transition creates vortex-antivortex pairs bound to the defect.

Second transition leads to free vortex motion.

Abstract

We study microscopic scenario of vortex escape from a columnar defect under the influence of a transport current. For defect radii smaller than the superconducting coherence length the depinning process is shown to be a consequence of two subsequent topological electronic transitions in a trapped vortex core. The first transition at a critical current $j_L$ is associated with the opening of Fermi surface segments corresponding to the creation of a vortex--antivortex pair bound to the defect. The second transition at a certain current $j_d > j_L$ is caused by merging of different Fermi surface segments, which accompanies the formation of a freely moving vortex.