Nonlinear Seebeck Effect in a Model Granular Superconductor

TL;DR

This paper models the nonlinear Seebeck effect in granular superconductors, showing how thermal gradients influence supercurrent density and thermopower in Josephson junction arrays, with implications for high-temperature ceramic superconductors.

Contribution

It introduces a model for the nonlinear Seebeck effect in 3D Josephson junction arrays, predicting strong dependence of thermopower on thermal gradients in granular superconductors.

Findings

Thermopower becomes strongly dT/dx-dependent above a critical gradient.

Critical gradient estimated to be around 10^4 K/m for YBCO ceramics.

Model predicts significant nonlinear thermoelectric behavior in granular superconductors.

Abstract

The change of the Josephson supercurrent density of a weakly-connected granular superconductor in response to externally applied arbitrary thermal gradient dT/dx (nonlinear Seebeck effect) is considered within a model of 3D Josephson junction arrays. For dT/dx>(dT/dx)_c, where (dT/dx)_c is estimated to be of the order of 10^4 K/m for YBCO ceramics with an average grain's size of 10 microns, the weak-links-dominated thermopower S (Seebeck coefficient) is predicted to become strongly dT/dx-dependent.