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 ~70%. The lower critical field is surprisingly small: B c 1 = 0.008 mT ( T → 0 ). Muon spin rotation experiments in a transverse magnetic field of 0.01 T show a weak increase of the Gaussian damping rate σ TF below Tc, which yields a London penetration depth λ = 1.6 ± 0.2 μ m . The zero-field Kubo–Toyabe relaxation rate σ KT equals 0.129 ± 0.004 μ s − 1 and does not show a significant change below Tc. 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.
