Abstract
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 ZBCP's in magnetic fields. 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.