Nonreciprocal superconductivity

TL;DR

This paper introduces the concept of nonreciprocal superconductors, where broken symmetries lead to asymmetric energy dispersion, and proposes a detection method via asymmetric Andreev reflection in junctions.

Contribution

The paper defines nonreciprocal superconductivity, explains how to detect it through asymmetric current-voltage characteristics, and discusses potential material candidates.

Findings

Asymmetric current-voltage characteristic as a signature of nonreciprocal superconductivity

Detection method avoids large critical currents associated with superconducting diode effects

Potential candidates include graphene, UTe2, and engineered platforms

Abstract

We introduce the notion of nonreciprocal superconductors where inversion and time-reversal symmetries are broken, giving rise to an asymmetric energy dispersion. We demonstrate that nonreciprocal superconductivity can be detected by Andreev reflection. In particular, a transparent junction between a normal metal and a nonreciprocal superconductor generally exhibits an asymmetric current-voltage characteristic, which serves as a defining feature of nonreciprocal superconductivity. Unlike the superconducting diode effects, our detection scheme has the advantage of avoiding large critical currents that turn the superconducting state to normal. Finally, we discuss candidates for nonreciprocal superconductivity, including graphene, UTe2, as well as engineered platforms.