Superconducting State in the Three-Band Hubbard Model: A Variational Monte Carlo Study

Abstract

We study the superconducting (SC) states with d x 2 - y 2 and extended s symmetry in the three-band Hubbard model on a CuO 2 plane using the variational Monte Carlo method in the limit U d →∞, 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) states, 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, the energy of the extended s -wave SC state is always higher than that of the AFM state.