Phonon anomaly and anisotropic superconducting gap in non-centrosymmetric Li2(Pd1-xPtx)3B

TL;DR

This study investigates how the specific heat and superconducting gap structure in non-centrosymmetric Li2(Pd1-xPtx)3B vary with composition, revealing phonon anomalies and a transition from fully-gapped to nodal superconductivity as Pt content increases.

Contribution

It provides the first systematic analysis of the specific heat across different compositions, uncovering phonon anomalies and the evolution of the superconducting gap structure in Li2(Pd1-xPtx)3B.

Findings

Phononic specific heat deviates from Debye model in Pt-rich samples.

Superconducting gap transitions from fully gapped to nodal with increasing Pt.

Nodal superconductivity observed at x ≥ 0.9.

Abstract

We report the systematic investigation of the specific heat of the noncentrosymmetric supercon- ductor Li2(Pd1-xPtx)3B as a function of x. There is a large deviation of the phononic specific heat from the conventional Debye specific heat for Pt-rich samples. In contrast with the fully-gapped con- ventional behavior for small x, a power-law temperature dependence of the electronic specific heat is observed even at x = 0.5. This results manifest a strongly-anisotropic or nodal superconducting gap even at x = 0.5 and a nodal superconducting gap for x >~ 0.9.