Observation of odd-parity superconductivity in UTe2

TL;DR

This study provides direct experimental evidence that UTe2, a heavy fermion superconductor, exhibits an odd-parity, spin-triplet pairing symmetry, confirmed through Josephson coupling experiments and surface state observations.

Contribution

First direct evidence of odd-parity pairing in UTe2 at zero magnetic field using Josephson coupling and surface state analysis.

Findings

UTe2 exhibits odd-parity, B_1u pairing symmetry.

Josephson coupling shows strong orientation dependence.

Andreev surface bound states observed on (1-10) surface.

Abstract

Symmetry properties of the order parameter are among the most fundamental characteristics of a superconductor. The pairing symmetry of recently discovered heavy fermion superconductor UTe2 featuring an exceedingly large upper critical field has attracted a great deal of attention. Even though it is widely believed that UTe2 possesses an odd-parity, spin-triplet pairing symmetry, direct evidence for it is lacking, especially at zero or low magnetic fields. We report here the selection-rule results of Josephson coupling between In, an s-wave superconductor, and UTe2. The orientation dependence of the Josephson coupling suggests very strongly that UTe2 possess an odd-parity pairing state of B_1u in zero magnetic fields. We also report the formation of Andreev surface bound states on the (1-10) surface of UTe2.