Multigap superconductivity in the charge density wave superconductor LaPt2Si2

The superconducting gap structure of a charge density wave (CDW) superconductor LaPt2Si2 (T-c = 1.6 K) having a quasi-two-dimensional crystal structure has been investigated using muon spin rotation/relaxation (mu SR) measurements in transverse field (TF), zero field (ZF), and longitudinal field (LF) geometries. Rigorous analysis of TF-mu 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 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.