Superconducting State in Electron-doped High-Temperature Superconductors

Magnetic and superconducting properties of electron-doped high-temperature superconductors are studied with fluctuation exchange approximation applied to the Hubbard model on a square lattice. In contrast to hole-doped cases, the hot spots, the intersections of the magnetic Brillouin zone boundary and the Fermi surface, are located near the diagonals of the Brillouin zone. This is found to result in (1) a weaker coupling between the antiferromagnetic spin fluctuations and quasiparticles and (2) a peculiar deviation of the angular dependence of the order parameter from a simple form of cos k x a -cos k y a . The latter is consistent with the implication from Raman scattering experiments, and can be direct evidence of superconductivity caused by antiferromagnetic spin fluctuations.