Nodeless superconductivity in noncentrosymmetric LaRhSn

The superconducting order parameter of the noncentrosymmetric superconductor LaRhSn is investigated by means of low temperature measurements of the specific heat, muon-spin relaxation/rotation (\(\mu\)SR) and the tunnel-diode oscillator (TDO) based method. The specific heat and magnetic penetration depth [\(\lambda(T)\)] show an exponentially activated temperature dependence, demonstrating fully gapped superconductivity in LaRhSn. The temperature dependence of \(\lambda^{-2}(T)\) deduced from the TDO based method and \(\mu\)SR show nearly identical behavior, which can be well described by a single-gap \(s\)-wave model, with a zero temperature gap value of \(\Delta(0)=1.77(4)k_BT_c\). The zero-field \(\mu\)SR spectra do not show detectable changes upon cooling below \(T_c\), and therefore there is no evidence for time-reversal-symmetry breaking in the superconducting state.