Topological aspects and transport properties of edge states in the multi-band superconductor Sr2RuO4

Abstract

Motivated by the spin-triplet superconductor Sr2RuO4, we investigate the edge states by using a two-band tight-binding model with interorbital hybridization and spin-orbit coupling. In particular we focus on the topological aspects and the transport properties in the chiral spin-triplet superconducting phase. The Fermi surfaces correspond to the ones of Sr2RuO4 where the α and the β bands have hole- and electron-like characters, respectively. Although a full quasiparticle excitation gap is present in the bulk system, gapless edge states appear and affect both the spin and the charge currents. We study the interplay between electron- and hole-like particles in the formation of these edge states and edge currents. Topologically the two bands compensate for each other such that the edge state is not topologically protected. The repulsive interaction yields a spin polarization near the edges and lifts the degeneracy of the subgap edge states. The net spontaneous magnetization generated through both the edge charge current and the spin polarization may be small due to canceling effects. The lifting of the spin degeneracy could likely be detected by quasiparticle tunneling for the surface density of states.