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 $H_{C}$ 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/$v_{Fy}$). 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 $v_{Fy}$ originating from peculiar shape of the Fermi surface.