Large Thermoelectric Effects in Unconventional Superconductors

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.