Anomalous Nernst effect and heat transport by vortex vacancies in granular superconductors

TL;DR

This paper investigates the anomalous Nernst effect in granular superconductors, revealing how vortex vacancies can cause heat and vortex transport from colder to hotter regions, leading to a sign reversal of the Nernst signal.

Contribution

It introduces a simulation-based analysis of vortex-induced heat transport and the anomalous Nernst effect in granular superconductors, highlighting the role of vortex vacancies and geometric frustration.

Findings

Vortex vacancies can drive heat and vortex transport from cold to hot regions.

Geometric frustration causes sign reversal of the Nernst signal.

Heat transport by mobile vacancies explains the anomalous behavior.

Abstract

We study the Nernst effect due to vortex motion in two-dimensional granular superconductors using simulations with Langevin or resistively shunted Josephson-junction dynamics. In particular, we show that the geometric frustration of both regular and irregular granular materials can lead to thermally driven transport of vortices from colder to hotter regions, resulting in a sign reversal of the Nernst signal. We discuss the underlying mechanisms of this anomalous behavior in terms of heat transport by mobile vacancies in an otherwise pinned vortex lattice.