Physical properties of noncentrosymmetric superconductor LaIrSi3: A {\mu}SR study

TL;DR

This study investigates the superconducting properties of LaIrSi3, revealing weakly coupled, conventional type-I s-wave superconductivity with preserved time-reversal symmetry, using heat capacity, resistivity, neutron diffraction, and muon spin relaxation measurements.

Contribution

First comprehensive muSR and thermodynamic study confirming conventional type-I superconductivity in LaIrSi3 with detailed analysis of its anisotropic s-wave gap.

Findings

Superconducting transition temperature T_c = 0.72 K.

Weakly coupled electron-phonon superconductivity.

Conventional type-I s-wave pairing with preserved time-reversal symmetry.

Abstract

The results of heat capacity C_p(T, H) and electrical resistivity \rho(T,H) measurements down to 0.35 K as well as muon spin relaxation and rotation (\muSR) measurements on a noncentrosymmetric superconductor LaIrSi3 are presented. Powder neutron diffraction confirmed the reported noncentrosymmetric body-centered tetragonal BaNiSn3-type structure (space group I4\,mm) of LaIrSi3. The bulk superconductivity is observed below T_c = 0.72(1) K. The intrinsic \Delta C_e/\gamma_n T_c = 1.09(3) is significantly smaller than the BCS value of 1.43, and this reduction is accounted by the \alpha-model of BCS superconductivity. The analysis of the superconducting state C_e(T) data by the single-band \alpha-model indicates a moderately anisotropic order parameter with the s-wave gap \Delta(0)/k_B T_c = 1.54(2) which is lower than the BCS value of 1.764. Our estimates of various normal and superconducting state parameters indicate a weakly coupled electron-phonon driven type-I s-wave superconductivity in LaIrSi3. The \muSR results also confirm the conventional type-I superconductivity in LaIrSi3 with a preserved time reversal symmetry and hence a singlet pairing superconducting ground state.