NMR and NQR Studies on Non-centrosymmetric Superconductors Re₇B₃, LaBiPt, and BiPd

Abstract

We report the nuclear magnetic resonance (NMR) and nuclear quadrupole\nresonance (NQR) measurements for non-centrosymmetric superconductors Re7B3,\nLaBiPt, and BiPd containing heavy elements. For all three compounds, the\nspin-lattice relaxation rate 1/T1 shows a coherence peak just below Tc and\ndecreases exponentially at low temperatures, which indicates that an isotropic\nsuperconducting gap is dominant in these compounds. In BiPd, the height of the\ncoherence peak just below Tc is much suppressed, which suggests that there\nexists a substantial component of gap with nodes in this compound. Our results\nindicate that heavy element is not the only factor, but the extent of inversion\nsymmetry breaking is also important to induce a large spin-orbit coupling and\nan unconventional superconducting state.\n