Magnetic penetration depth and gap symmetry of the noncentrosymmetric superconductors CePt3Si and LaPt3Si

TL;DR

This study compares the magnetic penetration depth and gap symmetry of noncentrosymmetric superconductors LaPt3Si and CePt3Si, revealing isotropic gaps in LaPt3Si and line nodes in CePt3Si, highlighting the role of magnetic order.

Contribution

It provides new experimental insights into the gap symmetry of LaPt3Si and its comparison with CePt3Si, emphasizing the influence of magnetic order on unconventional superconductivity.

Findings

LaPt3Si exhibits an isotropic energy gap consistent with BCS theory.

CePt3Si shows line nodes, indicating unconventional pairing.

Parity mixing alone does not cause unconventional superconductivity without magnetic order.

Abstract

We report on measurements of the temperature dependence of the magnetic penetration depth of a very high quality single crystal of nonmagnetic superconductor LaPt3Si without inversion symmetry. The results are compared with those previously reported for the isostructural antiferromagnetic superconductor CePt3Si. At low temperatures, the penetration depth follows a BCS exponential behavior that implies an isotropic energy gap in LaPt3Si, in contrast to a linear response that indicates line nodes in CePt3Si. These line nodes have been argued to be protected by symmetry or accidentally generated by parity mixing. The present results provide support for the viewpoint that parity mixing alone does not seem to lead to unconventionality in CePt3Si and that it requires the antiferromagnetic order to be included.