Fully gapped superconductivity with preserved time reversal symmetry in noncentrosymmetric LaPdIn

TL;DR

This study reveals that LaPdIn is a fully gapped superconductor with preserved time-reversal symmetry, characterized by single-gap s-wave pairing and weak spin-orbit coupling effects, distinguishing it from similar compounds that do not superconduct.

Contribution

It provides the first detailed characterization of superconductivity in LaPdIn, showing fully gapped s-wave behavior and preserved time-reversal symmetry in a noncentrosymmetric compound.

Findings

Bulk superconductivity below 1.6 K confirmed by resistivity, heat capacity, and susceptibility.

Superconducting gap magnitude of 1.8k_B T_c consistent with single-gap s-wave model.

No evidence of spontaneous magnetic fields, indicating preserved time-reversal symmetry.

Abstract

We report an investigation of the superconducting properties of the hexagonal noncentrosymmetric compound LaPdIn. Electrical resistivity, specific heat and ac susceptibility measurements demonstrate the presence of bulk superconductivity below $T_c$ = 1.6 K. The specific heat, together with the penetration depth measured using transverse-field muon spin rotation and the tunnel diode oscillator based method, are well described by single gap $s$-wave superconductivity, with a gap magnitude of 1.8$k_BT_c$. From zero-field muon spin relaxation results no evidence is found for the spontaneous emergence of magnetic fields in the superconducting state, indicating that time-reversal symmetry is preserved. Band structure calculations reveal that there is a relatively weak effect of antisymmetric spin-orbit coupling on the electronic bands near the Fermi level, which is consistent with there being negligible singlet-triplet mixing due to broken inversion symmetry. On the other hand, isostructural LuPdIn and LaPtIn do not exhibit superconductivity down to 0.4 K, which may be due to these systems having a smaller density of states at the Fermi level.