Weyl Superconductivity in UTe2

TL;DR

This paper investigates UTe2, an unconventional superconductor with potential for topological quantum computing, revealing it hosts Weyl superconductivity with broken time-reversal symmetry and chiral surface states.

Contribution

It provides experimental evidence that UTe2 is a Weyl superconductor with a two-component order parameter breaking time-reversal symmetry.

Findings

Observation of non-zero polar Kerr effect

Detection of two specific heat transitions

Evidence of Weyl superconductivity with chiral surface states

Abstract

The search for a material platform for topological quantum computation has recently focused on unconventional superconductors. Such material systems, where the superconducting order parameter breaks a symmetry of the crystal point group, are capable of hosting novel phenomena, including emergent Majorana quasiparticles. Unique among unconventional superconductors is the recently discovered UTe2, where spin-triplet superconductivity emerges from a paramagnetic normal state. Although UTe2 could be considered a relative of a family of known ferromagnetic superconductors, the unique crystal structure of this material and experimentally suggested zero Curie temperature pose a great challenge to determining the symmetries, magnetism, and topology underlying the superconducting state. These emergent properties will determine the utility of UTe2 for future spintronics and quantum information applications. Here, we report observations of a non-zero polar Kerr effect and of two transitions in the specific heat upon entering the superconducting state, which together show that the superconductivity in UTe2 is characterized by an order parameter with two components that breaks time reversal symmetry. These data allow us to place firm constraints on the symmetries of the order parameter, which strongly suggest that UTe2 is a Weyl superconductor that hosts chiral Fermi arc surface states.