Low field magnetic response of the non-centrosymmetric superconductor YPtBi

Abstract

The low-field magnetic response of the non-centrosymmetric superconductor YPtBi ($T_c=0.77$ K) is investigated. Ac-susceptibility and dc-magnetization measurements provide solid evidence for bulk superconductivity with a volume fraction of $\sim 70\%$. The lower critical field is surprisingly small: $B_{c1}=0.008$ mT $(T\to 0)$. Muon spin rotation experiments in a transverse magnetic field of 0.01 T show a weak increase of the Gaussian damping rate $\ddot{I}{ƒ}_{TF}$ below $T_c$, which yields a London penetration depth $\hat{I}»=1.6\pm 0.2\hat{I}¼$m. The zero-field Kubo-Toyabe relaxation rate $\ddot{I}{ƒ}_{KT}$ equals $0.129\pm 0.004\hat{I}¼$s${}^{-1}$ and does not show a significant change below $T_c$. This puts an upper bound of 0.04 mT on the spontaneous magnetic field associated with a possible odd-parity component in the superconducting order parameter.

preprint 10 pages, including 8 figures; accepted for publication in Solid State Communications