Spontaneously polarized half-gapped superconductivity

TL;DR

This paper reports the discovery of nonunitary spin-triplet superconductivity in UTe2, characterized by high critical fields, spin-polarized pairing, and potential for quantum information applications.

Contribution

It presents the first observation of nonunitary spin-triplet superconductivity with unique spin-polarized properties in UTe2, expanding understanding of unconventional superconductors.

Findings

Superconductivity in UTe2 with Tc of 1.6 K and critical fields over 40 T.

Electrons with parallel spins form a spin-polarized condensate.

Superconducting state coexists with a spin-polarized metal.

Abstract

Nonunitary superconductivity is a rare and striking phenomenon in which spin up and spin down electrons segregate into two different quantum condensates. Because they support topological excitations, such superconductors are being seriously considered for potential quantum information applications. We report the discovery of nonunitary spin-triplet superconductivity in UTe2, featuring the high transition temperature of 1.6 K and a remarkably large and anisotropic upper critical field exceeding 40 T. In this unusual superconducting state, electrons with parallel spins pair, yet only half of the available electrons participate, yielding a spin-polarized condensate that coexists with a spin-polarized metal. The superconducting order parameter, which breaks both gauge and time reversal symmetries, arises from strong ferromagnetic fluctuations, placing UTe2 as the paramagnetic end member of the ferromagnetic superconductor series. This discovery yields a new platform for encoding information using topological excitations and for manipulation of spinpolarized currents.