Tunneling into current-carrying surface states of high-T-c superconductors

Theoretical results for the ab-plane tunneling conductance in the d-wave model for high-T-c superconductors are presented. The d-wave model predicts surface bound states below the maximum gap. A subdominant order parameter, stabilized by the surface, leads to a splitting of the zero-bias conductance peak (ZBCP) in zero external field and to spontaneous surface currents. In a magnetic field, screening currents shift the bound state spectrum, leading to a splitting of the ZBCP that is linear in H at low fields and saturates at a pair breaking critical field of order H-c(*) similar or equal to 3 T.