Odd-frequency Superconductivity Revealed by Thermopower

TL;DR

This paper proposes using thermopower measurements as a direct method to detect odd-frequency superconductivity, which has been elusive in experiments so far.

Contribution

It introduces thermopower as a novel, unambiguous probe for odd-frequency superconductivity, supported by a theoretical model involving a superconductor-quantum dot-ferromagnet hybrid.

Findings

Thermopower is finite only with odd-frequency superconductivity.

Theoretical demonstration with a superconductor-quantum dot-ferromagnet system.

Provides a new experimental approach to identify odd-frequency pairing.

Abstract

Superconductivity is characterized by a nonvanishing superconducting pair amplitude. It has a definite symmetry in spin, momentum and frequency (time). While the spin and momentum symmetry have been probed experimentally for different classes of superconductivity, the odd-frequency nature of certain superconducting correlations has not been demonstrated yet in a direct way. Here we propose the thermopower as an unambiguous way to assess odd-frequency superconductivity. This is possible since the thermoelectric coefficient given by Andreev-like processes is only finite in the presence of odd-frequency superconductivity. We illustrate our general findings with a simple example of a superconductor-quantum dot-ferromagnet hybrid.