Quantum Monte Carlo Optimization in Many Fermion Systems

摘要

We have developed a Quantum Monte Carlo optimization (QMCO) method for many fermion systems. The ground state wave function is written as a linear combination of the basis states generated using the auxiliary field method The bases are chosen with weights that are determined by diagonalizing the Hamiltonian to lower the ground state energy. The QMCO method is free from a difficulty originating from the negative sign problem. We apply the QMCO method to the two-leg ladder and two-dimensional Hubbard model. We can reproduce the exact results for the Hubbard model on small clusters. The pair correlation function is indeed enhanced compared to that for U(velence)0 as the strength of the repulsive Coulomb interaction increases.