Theoretical proposal of a method to identify the symmetry of the order parameter in high-T_c superconductivity

A new experimental method to judge the symmetry of the order parameter in high-T_c superconductivity is proposed. The interference of reflected holes from different directions due to the Andreev reflection causes quite different phenomena among s-,d_x2-y2- and d_xy-wave superconductivity. It is shown that this interference effect may be observed as a change of the conductance below T_c, which enables us to identify the symmetry of the pairing state in high-T_c superconductivity. Various cases in which the experimental setup deviates from the ideal situation are also studied and experimental condition for this method is clarified.