t-J model Studied by the New Lanczos-Power Method

The initial trial wave function used in a simple ground-state projection method, the power method, is systematically improved by using Lanczos algorithm. Much faster convergence to the ground state achieved by using these wave functions significantly reduces the effect of the fermion sign problem. The energy, spin and charge correlation functions are calculated for the ground states of the two-dimensional $t-J$ model. Results for an $8\times8$ cluster with 42 and 26 electrons are presented. The density correlation function for the $t-J$ model at small J shows a surprisingly good agreement with that of a system of non-interacting hard-core bosons.