Ring Current In The High-temperature Superconductors, Quantum Monte Carlo Simulation

Since the discovery of the high temperature superconductors, much attention has been paid to the search of the microscopic superconducting mechanism. Especially, the explanation of the anomalous normal-state properties is more challenging.Firstly, the models and theories proposed for the high temperature superconductors are reviewed, including the one-, two-, three-band and the extended Hubbard models as well as the phenomenological marginal-Fermi-Liquid theory. Secondly, the constrained path quantum Monte Carlo method to compute the ground-state properties of interacting fermion systems is described in detail. The validity of the algorithm has been verified through the calculation of the ground-state energy and the various correlation functions of the electronic system in the two-dimensional one-band Hubbard model.The possibility of the existence of the circulating current phases in the two dimensional three-band Hubbard model has been studied numerically by applying the constrained-path quantum Monte Carlo method. In order to characterize the circulating current phases, various operators in the second quantization form are introduced and their correlation functions of different spin configurations are numerically computed in our simulations.The simulation results demonstrate that, within the physical ranges of the model parameters, the correlation functions of hole hoppings giving rise to closed current flow patterns in the circulating current phases are larger by one order of magnitude than those of hole hoppings corresponding to open current flows. This provides the evidence for the existence of the circulating current phases in the three-band Hubbard model.