Fermiology with nodal structures in nonsymmorphic superconductor LaNiGa2: A de Haas-van Alphen study

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 LaNiGa₂ 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 LaNiGa₂ 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 LaNiGa₂ as a prototypical topological crystalline superconductor and highlight the putative contribution of low-energy nodal quasiparticles to unconventional superconducting pairing.