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

TL;DR

This study uses NMR and NQR techniques to investigate the superconducting gap structure and the effects of inversion symmetry breaking in non-centrosymmetric superconductors Re7B3, LaBiPt, and BiPd, revealing diverse gap behaviors.

Contribution

It provides new insights into how inversion symmetry breaking influences superconducting properties and spin-orbit coupling in heavy-element non-centrosymmetric superconductors.

Findings

Re7B3 and LaBiPt exhibit isotropic superconducting gaps.

BiPd shows evidence of nodal gap components.

Inversion symmetry breaking affects the superconducting state.

Abstract

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