Generalized method of image and the tunneling spectroscopy in high-Tc superconductors

A generalized method of image is developed to investigate the tunneling spectrum from the metal into a class of states, with the tight-binding dispersion fully included. The broken reflection symmetry is shown to be the necessary condition for the appearance of the zero-bias conductance peak (ZBCP). Applying this method to the d-wave superconductor yields results in agreement with experiments regarding the splitting of ZBCPs in magnetic field. Furthermore, a ZBCP is predicted for tunneling into the (110) direction of the d-density wave state, providing a signature to look for in experiments.