Flux-induced Nernst effect in a superconducting loop

TL;DR

This paper investigates a flux-induced Nernst effect in superconducting loops caused by thermal fluctuations, analyzing how various parameters influence the voltage generated when magnetic flux is enclosed.

Contribution

It provides a detailed theoretical analysis of the flux-induced Nernst effect in superconducting rings, highlighting the dependence on multiple physical parameters and comparing with field-induced effects.

Findings

Largest voltages occur near flux $0.3\Phi_0$ and temperatures just below critical.

Thermal coherence length comparable to the ring perimeter enhances the effect.

Comparison with 2D samples shows differences in flux-induced and field-induced effects.

Abstract

When a superconducting ring encloses a magnetic flux that is not an integer multiple of half the quantum of flux, a voltage arises in the direction perpendicular to the temperature gradient. This effect is entirely due to thermal fluctuations. We study the dependence of this voltage on the temperature gradient, flux, position, average temperature, BCS coherence length, thermal coherence length, and the Kramer--Watts-Tobin parameter. The largest voltages were obtained for fluxes close to $0.3\Phi_0$, average temperatures slightly below the critical temperature, thermal coherence length of the order of the perimeter of the ring and BCS coherence length that is not negligible in comparison to the thermal coherence length. As a rough comparison between the flux-induced and the field-induced effects, we also considered a two dimensional sample.