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

TL;DR

This paper models Sr2RuO4 as a three-band superconductor with chiral p-wave pairing, analyzing topological properties and edge states, revealing gapless edge modes and the influence of spin-orbit coupling and Lifshitz transition.

Contribution

It introduces a detailed three-orbital model for Sr2RuO4, exploring its topological edge states and the effects of spin-orbit coupling and Lifshitz transition on its topological nature.

Findings

Gapless edge states with linear and flat dispersion appear at the edges.

The gamma-band exhibits a topological Chern number, indicating non-trivial topology.

The topological phase is fragile near a Lifshitz transition.

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 electron-like and one hole-like one corresponding to the alpha-, beta- and gamma-band on the level of a two-dimensional system. The quasi-particle 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 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 gamma-band characterized by an integer Chern number. As the gamma-band is close to a Lifshitz transition in Sr2RuO4, changing the sign of the Chern number, the topological nature may be rather fragile.