Properties of edge states in spin-triplet two-band superconductor

TL;DR

This paper investigates the properties of edge states in a two-band spin-triplet superconductor, revealing gapless edge states, spontaneous currents, and edge magnetism influenced by spin-orbit coupling, with implications for experimental observations.

Contribution

It provides a detailed theoretical analysis of edge states in a two-band chiral p-wave superconductor, including effects of hybridization, spin-orbit coupling, and Coulomb interactions, highlighting their impact on edge magnetism and currents.

Findings

Gapless edge states produce spontaneous spin and charge currents.

Edge states are unstable against spin polarization due to Coulomb interactions.

Spin-orbit coupling links current-induced and correlation-induced magnetism.

Abstract

Motivated by Sr2RuO4 the magnetic properties of edge states in a two-band spin-triplet superconductor with electron- and hole-like Fermi surfaces are investigated assuming chiral p-wave pairing symmetry. The two bands correspond to the alpha-beta-bands of Sr2RuO4 and are modeled within a tight-binding model including inter-orbital hybridization and spin-orbit coupling effects. Including superconductivity the quasiparticle spectrum is determined by means of a self-consistent Bogolyubov-de Gennes calculation. While a full quasiparticle excitation gap appears in the bulk, gapless states form at the edges which produce spontaneous spin and/or charge currents. The spin current is the result of the specific band structure while the charge current originates from the superconducting condensate. Together they induce a small spin polarization at the edge. Furthermore onsite Coulomb repulsion is included to show that the edge states are unstable against the formation of a Stoner-like spin polarization of the edge states. Through spin-orbit coupling the current- and the correlation-induced magnetism are coupled to the orientation of the chirality of the superconducting condensate. We speculate that this type of phenomenon could yield a compensation of the magnetic fields induced by currents and also explain the negative result in the recent experimental search for chiral edge currents.