Divergent Vortex Mass in a Superconducting Film in Proximity to a Metal

TL;DR

This paper derives a general expression for the vortex mass in a 2D superconductor near a metal, showing it diverges when close to the metal and is small when far, impacting vortex dynamics and resistance.

Contribution

It provides a microscopic derivation of the vortex mass dependence on the distance to a metallic overlayer, revealing divergent behavior at small distances.

Findings

Vortex mass is small at large distances due to Coulomb screening.

Vortex mass diverges logarithmically as the superconductor approaches the metal.

Proximity to metal significantly affects vortex dynamics and resistance.

Abstract

We consider a moving vortex in a two dimensional superconductor located at a distance $d$ from a metallic overlayer. Starting from the microscopic imaginary time action we integrate out the electronic degrees of freedom to obtain a low energy, long wavelength effective action for the vortex. We focus our attention on the vortex kinetic energy and derive a general expression for the vortex mass. We find that in the limit $d\to \infty$ the Coulomb screening of the density fluctuations, associated with vortex motion, results in a very small vortex mass as has been obtained in earlier studies. In the opposite limit of $d\ll \xi $ where $\xi$ is the coherence length of the superconductor we find that the vortex mass diverges logarithmically with the size of the system as the proximity to the metal makes the screening processes, that usually make the mass small, ineffective. We comment on the relevance of our results to recent experiments which show a dramatic fall in resistance when a metallic gate is placed near a supeconducting film in a magnetic field at low temperature.