Stability of Staggered Flux State in d-p Model Studied Using Variational Monte Carlo Method

The stability of a staggered flux (SF) or d-density wave state is studied in a d-p model using a variational Monte Carlo (VMC) method. This state possesses a local circular current and possibly causes the pseudogap phase in high-Tc cuprate superconductors. We introduce into the trial function a configuration dependent phase factor, which was recently shown to be indispensable to stabilize current-carrying states. We pay attention to the energy gain as a function of adjacent O-O hopping and Cu-site coulomb repulsion U. It is found the SF state becomes stable for hole doping rates of and , owing to the reduction in kinetic energy, but seems fragile because the energy gain rapidly decays on doping holes for any . The loop current tends to increase as increases.