SUPERCONDUCTING STATE IN THE 3-BAND HUBBARD-MODEL - A VARIATIONAL MONTE-CARLO STUDY

We study the superconducting (SC) states with d(x)2(-y)2 and extended s symmetry in the three-band Hubbard model on a CuO2 plane using the v ariational Monte Carlo method in the limit U-d --> infinity, where U-d is the Coulomb repulsion between holes on a Cu site. By comparing the energy among the SC, paramagnetic (PM), and antiferromagnetic (AFM) s tates, we obtain a phase diagram and find that the d(x)2(-y)2-wave SC state becomes the lowest energy state near the phase boundary between the PM and AFM phases. In contrast to the d(x)2(-y)2-wave SC state, th e energy of the extended s-wave SC state is always higher than that of the AFM state.