Nodeless superconductivity in the charge density wave superconductor LaPt$_2$Si$_2$

TL;DR

This study reveals that LaPt$_2$Si$_2$ exhibits fully gapped s-wave superconductivity with moderate electron-phonon coupling, based on measurements of penetration depth and point contact spectroscopy.

Contribution

It provides the first detailed experimental evidence of nodeless s-wave superconductivity in LaPt$_2$Si$_2$, a charge density wave superconductor.

Findings

Exponential temperature dependence of penetration depth indicates fully gapped superconductivity.

Point contact spectra fit well with an s-wave BCS model.

Superconducting gap shows typical BCS temperature and magnetic field dependence.

Abstract

We have studied the superconducting gap structure of LaPt$_2$Si$_2$ by measuring the temperature dependence of the London penetration depth shift $\Delta\lambda(T)$ and point contact spectroscopy of single crystals. $\Delta\lambda(T)$ shows an exponential temperature dependence at low temperatures, and the derived normalized superfluid density $\rho_{s}(T)$ can be well described by a single-gap s-wave model. The point-contact conductance spectra can also be well fitted by an s-wave Blonder-Tinkham-Klapwijk model, where the gap value shows a typical BCS temperature and magnetic field dependence consistent with type-II superconductivity. These results suggest fully gapped superconductivity in LaPt$_2$Si$_2$, with moderately strong electron-phonon coupling.