Abstract:
Topological superconductors are often believed to be the best venue for non-Abelian Majorana zero modes (MZMs), while their experimental realizations are generally challenging for various reasons. In the first part of my talk, I will discuss two concrete examples to illustrate an alternative strategy for MZMs, which only involves a topologically trivial s-wave superconductor and a field-induced vortex. I will first describe how normal-state electronic topologies account for multiple vortex-line topologies in several high-Tc iron-based superconductors. Our theory explains the missing and recovery of vortex Majorana signals observed in LiFeAs. I will further establish 3D Luttinger semimetals as a new paradigm for vortex topological physics. For the second part, I will discuss the physical consequences of a spatially periodic vortex lattice. Remarkably, the vortex-bound states are found to form a set of emergent zero-energy Fermi surfaces with nontrivial topological properties, even though the underlying bulk superconductor is trivial and fully gapped.