Topological and edge state properties of a three-band model for Sr2RuO4

Abstract

Modeling the spin-triplet superconductor Sr2RuO4 through a three-orbital tight-binding model, we investigate topological properties and edge states assuming chiral p-wave pairing. In concordance with experiments, the three Fermi surfaces consist of two electronlike and one holelike surface, corresponding to the α, β, and γ band on the level of a two-dimensional system. The quasiparticle spectra and other physical quantities of the superconducting phase are calculated by means of a self-consistent Bogoliubov-de Gennes approach for a ribbon-shaped system. While a full quasiparticle excitation gap is realized in the bulk system, at the edges gapless states appear, some of which have linear and others of which have a nearly flat dispersion around zero energy. This study shows the interplay between spin-orbit-coupling-induced spin currents, chiral edge currents, and correlation-driven surface magnetism. The topological nature of the chiral p-wave state manifests itself in the γ band characterized by an integer Chern number. As the γ band is close to a Lifshitz transition in Sr 2RuO4, changing the sign of the Chern number, the topological nature may be rather fragile. © 2013 American Physical Society.