Anisotropic upper critical field in pressure-induced CrAs superconductor

Abstract

We report the upper critical field (Hc2) and its anisotropy in the pressure-induced superconductor CrAs. At ambient pressure, CrAs shows an antiferromagnetic phase transition at TN ∼ 264 K, where magnetostriction occurs simultaneously. TN is rapidly suppressed with increasing pressure and bulk superconductivity is induced near 7 kbar, above which the signature associated with TN is not visible in electrical resistivity measurements. With further increasing pressure, the superconducting phase shows a broad dome shape centered at the optimal pressure of 12.2 kbar. The Hc2 anisotropy of CrAs at 12.2 kbar, γHc2 = H//a/H⊥a, increases with decreasing temperature and becomes saturated at lower temperatures. Taken together with the positive curvature in Hc2 near Tc, these results suggest that the pressure-induced superconductor CrAs possesses multiple superconducting gaps.