Large Thermoelectric Effects in Unconventional Superconductors

TL;DR

This paper investigates the thermoelectric effect in unconventional superconductors with impurities, showing that small deviations from ideal scattering limits can produce significant thermoelectric responses, especially in clean systems.

Contribution

It provides analytic and numerical analysis of thermoelectric effects in superconductors with impurities, highlighting the impact of phase shift deviations from Born and unitary limits.

Findings

Thermoelectric response is linearly dependent on temperature at low T.

Small deviations from ideal impurity scattering cause large thermoelectric effects.

Potential measurement of thermoelectric flux in SQUID setups at low temperatures.

Abstract

We present analytic and numerical results for the thermoelectric effect in unconventional superconductors with a dilute random distribution of impurities, each scattering isotropically but with a phase shift intermediate between the Born and unitary limits. The thermoelectric response function has a linear temperature dependence at low temperatures, with a slope that depends on the impurity concentration and phase shift. Although the thermoelectric effect vanishes identically in the strict Born and unitary limits, even a small deviation of the phase shift from these limits leads to a large response, especially in clean systems. We also discuss possibilities of measuring counter-flowing supercurrents in a SQUID-setup. The non-quantized thermoelectrically induced flux can easily be of the order of a percent of the flux quantum in clean systems at 4He temperatures.