Spontaneous magnetisation in the superconducting state of LaNiGa2
Abstract
Muon spin relaxation shows spontaneous magnetism in the superconducting state of LaNiGa2. Symmetry analyses imply nonunitary triplet pairing with line nodes and predict a sub-dominant magnetisation consistent with SQUID measurements. In contrast, there is evidence from penetration depth and specific heat for two-gap, nodeless superconductivity. It was proposed to reconcile this by assuming equal-spin inter-orbital pairing. Here we show within a mean-field framework, that this gives rise to a nodeless, two-gap spectrum. We probe the state's stability in the presence of finite inter-orbital energy splitting and derive an analytical expression for the resulting spontaneous magnetisation. Furthermore, we present a detailed calculation combining a realistic first-principles band structure with a pheonmenological pairing interaction. We find that equal-spin pairing between certain Nickel d-orbitals can describe the specific heat quantitatively. We predict the two-gap structure in differential tunnelling conductance and the size of the spontaneous magnetic moment.
We acknowledge support from EPSRC (EP/P007392/1, EP/P00749X/1) and the Hungarian National Research, Development and Innovation Office (contract K115632).- Publication:
-
APS March Meeting Abstracts
- Pub Date:
- 2019
- Bibcode:
- 2019APS..MARH09012C