Spontaneous edge current in a small chiral superconductor with a rough surface

Abstract: We study theoretically the spontaneous edge current in a small chiral superconductor with surface roughness. We obtained self-consistent solutions of the pair potential and the vector potential by solving the quasiclassical Eilenberger equation and the Maxwell equation simultaneously. We then employed them to calculate numerically the spatial distribution of the chiral edge current in a small superconductor. The characteristic behavior of the spontaneous edge current depends strongly on the symmetries of the order parameters such as chiral $p$-, chiral $d$- and chiral $f$-wave pairing. The edge current is robust under the surface roughness in the chiral $p$- and chiral $d$-wave superconductors. In the chiral $d$-wave case, the surface roughness tends to flip the direction of the chiral current. On the other hand, the edge current in a chiral $f$-wave superconductor is fragile when there is surface roughness. We also discuss the temperature dependence of a spontaneous magnetization, which is a measurable value in standard experiments.