Quantitative theory of triplet pairing in the unconventional superconductor <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi mathvariant="normal">LaNiGa</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math>
S. K. Ghosh, Gábor Csire, Philip Whittlesea, James F. Annett, Martin Gradhand, B. Újfalussy, Jorge Quintanilla
Abstract
The exceptionally low-symmetry crystal structures of the time-reversal symmetry-breaking superconductors ${\mathrm{LaNiC}}_{2}$ and ${\mathrm{LaNiGa}}_{2}$ lead to an internally antisymmetric nonunitary triplet 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 ${\mathrm{LaNiGa}}_{2}$ 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.