The superconducting gap structure of a charge density wave (CDW) superconductor ${\mathrm{LaPt}}_2{\mathrm{Si}}_2(T_c=1.6$ K) having a quasi-two-dimensional crystal structure has been investigated using muon spin rotation/relaxation $\left(\mu \mathrm{SR}\right)$ measurements in transverse field (TF), zero field (ZF), and longitudinal field (LF) geometries. Rigorous analysis of TF-$\mu \mathrm{SR}$ spectra in the superconducting state corroborates that the temperature dependence of the effective penetration depth, ${\lambda }_L$, derived from muon spin depolarization, fits to a two gap $s$ wave model (i.e., $s+s$ wave) suggesting that the Fermi surface contains two gaps of different magnitude rather than an isotropic gap expected for a conventional $s$ wave superconductor. On the other hand, ZF $\mu \mathrm{SR}$ data do not show any significant change in muon spin relaxation rate above and below the superconducting transition temperature indicating the fact that time-reversal symmetry is preserved in the superconducting state of this material.

• Received 28 February 2018
• Revised 1 May 2018

DOI:https://doi.org/10.1103/PhysRevB.97.184509