Nodeless superconductivity and preserved time-reversal symmetry in the noncentrosymmetric Mo3P superconductor

Abstract

We report a comprehensive study of the noncentrosymmetric superconductor Mo${}_3$P. Its bulk superconductivity, with $T_c=5.5$ K, was characterized via electrical resistivity, magnetization, and heat-capacity measurements, while its microscopic electronic properties were investigated by means of muon-spin rotation/relaxation ($\hat{I}¼$SR) and nuclear magnetic resonance (NMR) techniques. In the normal state, NMR relaxation data indicate an almost ideal metallic behavior, confirmed by band-structure calculations, which suggest a relatively high electron density of states, dominated by the Mo $4d$-orbitals. The low-temperature superfluid density, determined via transverse-field $\hat{I}¼$SR and electronic specific heat, suggest a fully-gapped superconducting state in Mo${}_3$P, with $\hat{I}{”}_0=0.83$ meV, the same as the BCS gap value in the weak-coupling case, and a zero-temperature magnetic penetration depth $\hat{I}{»}_0=126$ nm. The absence of spontaneous magnetic fields below the onset of superconductivity, as determined from zero-field $\hat{I}¼$SR measurements, indicates a preserved time-reversal symmetry in the superconducting state of Mo${}_3$P and, hence, spin-singlet pairing.

13 pages, 16 figures, accepted by Phys. Rev. B