Tunneling Conductance in Normal Metal-High-T_c Cuprate Junctions in the Presence of Magnetic Field

The magnetic field responses of the zero-bias conductance peak (ZBCP) in tunneling spectra of high-T_c cuprate junctions are studied theoretically. Our calculation is based on the lattice Green's function method and takes the realistic electronic structure of the high-T_c cuprate into account. In marked contrast to previous works, it is shown that the critical magnetic field strength Hc exists for the splittings of the ZBCP's to be discernible. H_C is almost proportional to the product of the magnitude of pair potential, transmissivity of the junction, and the inverse of the Fermi velocity parallel to the interface (1/υ_Fy). The calculated H_c's for the hole-doped superconductors are higher than those for electron-doped ones because of relatively large magnitude of pair potential and the small magnitude of υ_Fy originating from peculiar shape of the Fermi surface.