The Superfluidity and Experimental Properties of Odd-Energy-Gap Superconductors

TL;DR

This paper explores the properties of superconductors with an odd energy gap within a BCS framework, revealing two classes with distinct low-energy behaviors and stability features, including weak impurity effects.

Contribution

It introduces a theoretical analysis of odd-energy-gap superconductors, highlighting their stability and classification into two distinct low-energy behavior classes.

Findings

Superconductors with odd energy gaps are stable to finite supercurrents.

They are weakly affected by non-magnetic impurities.

Two distinct classes of odd-gap superconductors exhibit different low-energy properties.

Abstract

We consider the experimental properties of superconductors with a gap which is an odd function of energy $\bepsk=\epsk - \mu$, i.e.\ , a gap which vanishes everywhere on the Fermi surface; this is done within a in a BCS framework. Apart from the standard phenomenology (density of states, penetration depth, NMR, $C_V(T)$, $B_{c2}(T)$), we also look at the stability of the superconducting state. It is stable to finite supercurrents (although with a normal fluid density which increases with the supercurrent density), and is also very weakly affected by non-magnetic impurities. We find two classes of odd-gap superconductors, which strongly differ in their low-energy properties. For a certain parameter range, most of the results resemble those for d-wave superconductors (except for the effect of impurities).