Vortex Variable Range Hopping in a Conventional Superconducting Film

TL;DR

This study investigates vortex behavior in a disordered superconducting film, revealing a vortex variable-range hopping mechanism that explains resistance behavior near the superconductor-insulator transition.

Contribution

It introduces a model of vortex hopping in a granular superconducting film, applying Mott variable-range hopping theory to vortices, which is a novel approach.

Findings

Resistance follows 2D Mott variable-range hopping of vortices.

Superconductor-insulator transition observed without isotherm crossing.

Vortex hopping parameters estimated using granular model.

Abstract

The behavior of a disordered amorphous thin film of superconducting Indium Oxide has been studied as a function of temperature and magnetic field applied perpendicular to its plane. A superconductor-insulator transition has been observed, though the isotherms do not cross at a single point. The curves of resistance vs. temperature on the putative superconducting side of this transition, where the resistance decreases with decreasing temperature, obey two-dimensional Mott variable-range hopping of vortices over wide ranges of temperature and resistance. To estimate the parameters of hopping, the film is modeled as a granular system and the hopping of vortices is treated in a manner analogous to hopping of charges. The reason the long range interaction between vortices over the range of magnetic fields investigated does not lead to a stronger variation of resistance with temperature than that of two-dimensional Mott variable-range hopping remains unresolved.