Odd-frequency superconducting pairing in multi-band superconductors

TL;DR

This paper demonstrates that all multi-band superconductors inherently possess an odd-frequency pairing component, which arises from band hybridization and non-identical intraband order parameters, highlighting a fundamental symmetry relation.

Contribution

It provides a general symmetry analysis showing the universal presence of odd-frequency pairing in multi-band superconductors under minimal conditions.

Findings

Odd-frequency pairing is present in all multi-band superconductors.

Band hybridization and differing intraband gaps are sufficient conditions.

A symmetry reciprocity between band parity and frequency is established.

Abstract

We point out that essentially all multi-band superconductors have an odd-frequency pairing component, as follows from a general symmetry analysis of even- and odd-frequency pairing states. We show that odd-frequency superconducting pairing requires only a finite band hybridization, or scattering, and non-identical intraband order parameters, of which only one band needs to be superconducting. Under these conditions odd-frequency odd-interband pairing is always present. From a symmetry analysis we establish a complete reciprocity between parity in band-index and frequency.