Enhanced weak superconductivity in trigonal γ-PtBi2

Abstract

Electrical resistivity experiments show superconductivity at Tc=1.1 K in a high-quality single crystal of trigonal γ-PtBi2, with an enhanced critical magnetic field μ0Hc2(0)≳1.5 Tesla and a low critical current-density Jc(0)≈40  A cm−2 at H = 0. Both Tc and Hc2(0) are the highest reported values for stoichiometric bulk samples at ambient pressure. We found a weak Hc2 anisotropy with Γ=Hc2ab/Hc2c<1 , which is unusual among superconductors. Under a magnetic field, the superconducting transition becomes broader and asymmetric. Along with the low critical currents, this observation suggests an inhomogeneous superconducting state. In fact, no trace of superconductivity is observed through field-cooling–zero-field-cooling magnetization experiments.