Quantitative Theory of Triplet Pairing in the Unconventional Superconductor LaNiGa$_2$

TL;DR

This paper develops a quantitative theory for triplet pairing in LaNiGa$_2$, predicting a distinctive double-peak DOS signature and matching experimental specific heat data, advancing understanding of unconventional superconductivity.

Contribution

It introduces a detailed, ab initio model of LaNiGa$_2$ that predicts unique DOS features and aligns with experimental observations without adjustable parameters.

Findings

Predicted a double-peak structure in the DOS for LaNiGa$_2$

Achieved excellent agreement with experimental specific heat data

Suggested the spin-splitting is detectable with current technology

Abstract

The exceptionally low-symmetry crystal structures of the time-reversal symmetry breaking superconductors LaNiC$_2$ and LaNiGa$_2$ lead to an internally-antisymmetric non-unitary triplet (INT) state as the only possibility compatible with experiments. We argue that this state has a distinct signature: a double-peak structure in the Density of States (DOS) which resolves in the spin channel in a particular way. We construct a detailed model of LaNiGa$_2$ capturing its electronic band structure and magnetic properties ab initio. The pairing mechanism is described via a single adjustable parameter. The latter is fixed by the critical temperature $T_c$ allowing parameter-free predictions. We compute the electronic specific heat and find excellent agreement with experiment. The size of the ordered moment in the superconducting state is compatible with zero-field muon spin relaxation experiments and the predicted spin-resolved DOS suggests the spin-splitting is within the reach of present experimental technology.