The fate of time-reversal symmetry breaking in UTe2
Abstract
Topological superconductivity is a long-sought state of matter in bulk materials, and 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.
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