Fractionally Charged Vortices at Superconductor-Chern Insulator Interfaces

Abstract

We investigate the interfacial vortex physics of a heterostructure composed of a type-II $s$-wave superconductor (SC) and a $C=1$ Chern insulator (CI). By deriving an effective $(2+1)$-dimensional theory, we show that the interfacial Cooper-pair degrees of freedom are described by two coupled Abelian-Higgs fields interacting via a Chern-Simons term inherited from the CI. This interaction endows the photon field with a topological mass and induces a \emph{fractional} electric charge of $e/2$ on the vortices. The topological mass fundamentally reshapes the interfacial vortex lattice, while the fractional charge leads to the formation of unique four-vortex bound clusters. We thus predict a \emph{topological Abrikosov lattice}, establishing a novel phase of matter at the SC-CI interface.