Jeff Sonier – Simon Fraser University
Title: Muon Studies of Superconducting UTe2

Abstract: Recently discovered UTe2 is believed to be a long-sought spin-triplet superconductor, but its magnetic properties and superconducting order parameter are matters of controversy. The observation of a nonzero polar Kerr effect in the superconducting state of UTe2 single crystals exhibiting two phase transitions in the specific heat has been taken as evidence of a time-reversal symmetry (TRS) breaking order parameter and chiral superconductivity. Yet a more recent study of the polar Kerr effect in single crystals exhibiting a single-phase transition found no evidence for TRS breaking. Zero-field muon spin relaxation (SR) is an ideal tool for independently determining whether TRS symmetry is spontaneously broken at the superconducting transition temperature, Tc, but until recently it has not been possible to investigate this in UTe2 due to the presence of slowly fluctuating spins. I will first explain what SR has revealed about the magnetic interactions in UTe2, which potentially play a role in the pairing mechanism that gives rise to spin-triplet superconductivity. I will then describe recent SR studies of a new generation of UTe2 single crystals, which shed light on the role disorder plays in the magnetic fluctuations and have provided an opportunity to look into whether TRS is broken.

Speaker bio: Jeff Sonier is a Professor at Simon Fraser University.