Topological nodal quasiparticles from the vortex lattice of s-wave superconductors

A type-II superconductor (SC) will respond to an external magnetic field by forming Abrikosov vortices. While the Majorana physics of a single quantum vortex has been extensively discussed, the topological consequence of a spatially periodic vortex lattice is much less understood. In this work, we focus on electronic properties of the vortex lattice for three-dimensional (3D) fullly gapped superconductors with an isotropic s-wave pairing. By turning on a vortex lattice, 1D low-energy Caroli-Matricon-de Gennes (CdGM) states will be trapped around each vortex core, whose inter-vortex hoppings will generate an emergent 3D band structure for CdGM quasiparticles. Our main finding is that when the normal state is a Dirac semimetal, the 3D vortex-lattice spectrum features nodal Bogoliubov-de Gennes (BdG) Fermi surfaces, whose gapless nature is topology-enforced. Surprisingly, these topological nodal quasiparticles persist even when the normal state is deformed to a trivial metal with no electronic band inversion. Being directly applicable to real-world superconductors such as LiFeAs, our work establishes vortex-lattice engineering as a novel experimentally feasible pathway towards topological superconductivity.