Multigap Superconductivity in a charge density wave superconductor LaPt2Si2

TL;DR

This study reveals that LaPt2Si2 exhibits multigap superconductivity with two distinct isotropic s-wave gaps, while maintaining time-reversal symmetry, as evidenced by muon spin rotation measurements.

Contribution

The paper provides the first detailed muon spin rotation analysis demonstrating multigap superconductivity in LaPt2Si2, a charge density wave superconductor with a quasi-2D structure.

Findings

Fits to an s+s-wave model indicate two gaps of different sizes.

Time-reversal symmetry remains intact across the superconducting transition.

Superconducting gap structure is isotropic despite the charge density wave state.

Abstract

The superconducting gap structure of a charge density wave (CDW) superconductor LaPt$_2$Si$_2$ ($T_c$ = 1.6~K) having a quasi two dimensional crystal structure has been investigated using muon spin rotation/relaxation ($\mu$SR) measurements carried out 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 an isotropic $s+s-$wave model 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 indicating the fact that time-reversal symmetry is preserved in the system.