Topological Aspect and Magnetic Property of a Chiral p-Wave Superconductor

Abstract

Motivated by spin-triplet superconductor Sr2RuO4, the topological aspect and the magnetic property of edge states in the chiral p-wave phase are investigated by means of a ribbon-shaped model. The Fermi surfaces consisting of three sheets correspond to the α-β-bands and the γ-band of Sr2RuO4. While there exists a full quasiparticle excitation gap in the bulk system, two types of low-energy gapless edge states appear inside the superconducting gap in the ribbon system, which consist of almost flat dispersions from the α-β-bands and the linear ones at the Γ point from the γ-band. The effect of the repulsive interaction readily leads to the spin magnetism near the edges, due to a Stoner-like spin splitting in the superconducting phase. This gives rise to a spontaneous magnetization near the edges. Since there is the edge current due to time reversal symmetry breaking in the superconducting phase, the net spontaneous magnetic field near the edges can be suppressed strongly, which may explain the negative results in the experimental search for chiral edge currents. The Chern number obtained from the α-β-bands cancels due to the electronand hole-like Fermi surface characters. In contrast, the edge states with linear dispersions from the γ-band are protected topologically. We also show that Sr2RuO4 is close to a Lifshitz transition, which may render the chiral edge states rather fragile.