Nodeless superconductivity in the noncentrosymmetric Mo${}_3$Rh${}_2$N superconductor: a $\hat{I}¼$SR study

Abstract

The noncentrosymmetric superconductor Mo${}_3$Rh${}_2$N, with $T_c=4.6$ K, adopts a ${\hat{I}}^2$-Mn-type structure (space group $P$4${}_1$32), similar to that of Mo${}_3$Al${}_2$C. Its bulk superconductivity was characterized by magnetization and heat-capacity measurements, while its microscopic electronic properties were investigated by means of muon-spin rotation and relaxation ($\hat{I}¼$SR). The low-temperature superfluid density, measured via transverse-field (TF)-$\hat{I}¼$SR, evidences a fully-gapped superconducting state with $\hat{I}{”}_0=1.73k_{\mathrm{B}}{T}_c$, very close to 1.76 $k_{\mathrm{B}}{T}_c$ - the BCS gap value for the weak coupling case, and a magnetic penetration depth $\hat{I}{»}_0=586$ nm. The absence of spontaneous magnetic fields below the onset of superconductivity, as determined by zero-field (ZF)-$\hat{I}¼$SR measurements, hints at a preserved time-reversal symmetry in the superconducting state. Both TF-and ZF-$\hat{I}¼$SR results evidence a spin-singlet pairing in Mo${}_3$Rh${}_2$N.

5 figures and 5 pages. Accepted for publication as a Rapid Communication in Phys. Rev. B