Crystallographic and superconducting properties of the fully-gapped noncentrosymmetric 5d-electron superconductors CaMSi3 (M=Ir, Pt)

TL;DR

This study investigates the crystallographic and superconducting properties of noncentrosymmetric 5d-electron superconductors CaIrSi3 and CaPtSi3, revealing fully gapped superconductivity with conventional orbital depairing limitations and no evidence of noncentrosymmetric physics in critical fields.

Contribution

It provides detailed experimental characterization of CaIrSi3 and CaPtSi3, showing their fully gapped superconductivity and clarifying the absence of high, non-Pauli-limited critical fields.

Findings

Superconductors are fully gapped as indicated by specific heat.

Upper critical fields are below 1 T, limited by orbital depairing.

High carrier masses necessary for noncentrosymmetric effects are not present.

Abstract

We report crystallographic, specific heat, transport, and magnetic properties of the recently discovered noncentrosymmetric 5d-electron superconductors CaIrSi3 (Tc = 3.6 K) and CaPtSi3 (Tc = 2.3 K). The specific heat suggests that these superconductors are fully gapped. The upper critical fields are less than 1 T, consistent with limitation by conventional orbital depairing. High, non-Pauli-limited {\mu}0 Hc2 values, often taken as a key signature of novel noncentrosymmetric physics, are not observed in these materials because the high carrier masses required to suppress orbital depairing and reveal the violated Pauli limit are not present.