Evidence of s-wave superconductivity in ternary intermetallic La3Pd4Si4

TL;DR

This study provides evidence that La3Pd4Si4 is a conventional s-wave superconductor with a nodeless, isotropic energy gap, based on magnetic penetration depth measurements indicating temperature-independent behavior below 0.25 Tc.

Contribution

First direct measurement of the magnetic penetration depth in La3Pd4Si4 confirming its s-wave, nodeless superconducting gap and describing the superfluid density with a two-phase model.

Findings

Superconducting gap is isotropic and nodeless.

Behavior consistent with conventional BCS superconductivity.

Minor anomaly suggests possible impurity phase presence.

Abstract

We measured the temperature dependence of the magnetic penetration depth of La3Pd4Si4 down to 0.02 Tc. We observe a temperature-independent behaviour below 0.25 Tc, which is firm evidence for a nodeless superconducting gap in this material. The data display a very small anomaly around 1 K which we attribute to the possible presence of a superconducting impurity phase. The superfluid density is well described by a two-phase model, considering La3Pd4Si4 and the impurity phase. The present analysis suggests that the superconducting energy gap of La3Pd4Si4 is isotropic, as expected for conventional BCS superconductors.