Phase diagram of the Cu–O model in the oxide superconductors: Variational Monte Carlo study

Abstract

A variational Monte Carlo method is formulated to study the ground state of the model for the Cu–O plane in the oxide superconductors. The possibility of superconductivity is investigated employing the Gutzwiller-projected BCS and SDW wave functions with respect to dependences on electron density ρ and transfer t pp between neighboring oxygen orbitals. Near half-filling the SDW state is most stable for both the hole and electron doping cases. Away from half-filling when hole doping ratio δ∼0.2, the d-wave superconducting state turns out to be more favorable than the SDW state. The superconducting condensation energy is in reasonable agreement with the experimental value obtained from the critical magnetic field H c.