Fermiology with nodal structures in nonsymmorphic superconductor LaNiGa$_2$: A de Haas-van Alphen study

TL;DR

This study uses quantum oscillation measurements and first-principles calculations to explore the electronic structure of LaNiGa$_2$, revealing nodal band crossings and topological features that influence its unconventional superconductivity.

Contribution

It provides the first detailed experimental and theoretical investigation of LaNiGa$_2$'s fermiology and confirms the presence of symmetry-protected nodal structures linked to its topological crystalline superconductivity.

Findings

Nonsymmorphic $Cmcm$ lattice symmetry verified.

Nodal band crossings pinned at the Fermi level identified.

Evidence of low-energy nodal quasiparticles contributing to superconductivity.

Abstract

Topological metals possess various types of symmetry-protected degenerate band crossings. When a topological metal becomes superconducting, the low-energy electronic excitations stemming from the band crossings located close to the Fermi level may contribute to highly unusual pairing symmetry and superconducting states. In this work, we study the electronic band structure of the time-reversal symmetry breaking superconductor LaNiGa$_2$ by means of quantum oscillation measurements. A comprehensive investigation combining angle-resolved high-field de Haas-van Alphen (dHvA) spectroscopy and first-principles calculations reveals the fermiology of LaNiGa$_2$ and verifies its nonsymmorphic $Cmcm$ lattice symmetry, which promises nodal band crossings pinned at the Fermi level with fourfold degeneracies. Moreover, such nodal structures, proposed to play a crucial role giving rise to the interorbital triplet pairing, are indeed captured by our dHvA analysis. Our results identify LaNiGa$_2$ as a prototypical topological crystalline superconductor and highlight the putative contribution of low-energy nodal quasiparticles to unconventional superconducting pairing.