Fate of Time-Reversal Symmetry Breaking in UTe2

Topological superconductivity is a long-sought state of matter in bulk materials, and the odd-parity superconductor UTe2 is a prime candidate. The recent observation of a field-trainable spontaneous Kerr signal in UTe2 at the onset of superconductivity provides strong evidence that the superconducting order parameter is multicomponent and breaks time-reversal symmetry. Here, we perform Kerr effect measurements on a number of UTe2 samples—grown via both chemical vapor transport and the molten-salt-flux methods—that show a single superconducting transition between 1.6 K and 2.1 K. Our results show no evidence for a spontaneous Kerr signal in zero-field measurements. This implies that the superconducting state of UTe2 does not intrinsically break time-reversal symmetry. Instead, we observe a field-trainable signal that varies in magnitude between samples and between different locations on a single sample, which is a sign of inhomogeneous magnetic regions. Our results provide an examination of representative UTe2 samples and place strong constraints on the superconducting order parameter of UTe2.Received 18 May 2023Revised 13 September 2023Accepted 28 September 2023DOI:https://doi.org/10.1103/PhysRevX.13.041019Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasMagneto-optical Kerr effectSuperconductivityTopological superconductorsVortex latticesPhysical SystemsStrongly correlated systemsTechniquesAC susceptibility measurementsCondensed Matter, Materials & Applied Physics