Edge Currents in Superconductors with a Broken Time-Reversal Symmetry

We analyze edge currents and edge bands at the surface of a time-reversal symmetry breaking d_x²-y²+id_xy superconductor. We show that the currents have large Friedel oscillations with two interfering frequencies: √2k_F from subgap states, and 2k_F from the continuum. The results are based independently on a self-consistent slave-boson mean-field theory for the t-J model on a triangular lattice, and on a T-matrix scattering theory calculation. The shape of the edge-state band, as well as the particular frequency √2k_F of the Friedel oscillations, are attributes unique for the d_x²-y²+id_xy case, and may be used as a fingerprint for its identification. Extensions to different time-reversal symmetry breaking superconductors can be achieved within the same approach.