Low field magnetic response of the non-centrosymmetric superconductor YPtBi

• We study the magnetic response of the non-centrosymmetric superconductor YPtBi.
• DC and ac magnetization demonstrate YPtBi is a bulk superconductor.
• We have determined the lower critical field by ac susceptibility.
• We have determined the London penetration depth by muon spin rotation.
• μSRμSR gives an upper bound on the internal field due to a mixed parity state.

The low-field magnetic response of the non-centrosymmetric superconductor YPtBi (Tc=0.77K) 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: Bc1=0.008mT (T→0T→0). Muon spin rotation experiments in a transverse magnetic field of 0.01 T show a weak increase of the Gaussian damping rate σTFσTF below Tc, which yields a London penetration depth λ=1.6±0.2μm. The zero-field Kubo–Toyabe relaxation rate σKTσKT equals 0.129±0.004μs−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.