Fate of Time-Reversal Symmetry Breaking in UTe_{2}

Abstract

Topological superconductivity is a long-sought state of matter in bulk materials, and the odd-parity superconductor UTe_{2} is a prime candidate. The recent observation of a field-trainable spontaneous Kerr signal in UTe_{2} 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 UTe_{2} 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 UTe_{2} 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 UTe_{2} samples and place strong constraints on the superconducting order parameter of UTe_{2}.