Evidence for triplet superconductivity near an antiferromagnetic instability in CrAs

Abstract

Superconductivity was recently observed in CrAs as the helimagnetic order is suppressed by applying pressure, suggesting possible unconventional superconductivity. To reveal the nature of the superconducting order parameter of CrAs, here we report the angular dependence of the upper critical field under pressure. Upon rotating the field by ${360}^{\ensuremath{\circ}}$ in the $bc$ plane, six maxima are observed in the upper critical field, where the oscillations have both sixfold- and twofold-symmetric components. Our analysis suggests the presence of an unconventional odd-parity spin-triplet state.