Single-particle spectral function formulated and calculated by variational Monte Carlo method*

A method to calculate the one-body Green's function for ground states of correlated electron materials is formulated by extending the variational Monte Carlo method. We benchmark against the exact diagonalization (ED) for the one- and two-dimensional Hubbard models of 16 site lattices, which proves high accuracy of the method. The application of the method to larger-sized Hubbard model on the square lattice correctly reproduces the Mott insulating behavior at half filling and gap structures of $d$-wave superconducting state in the hole doped Hubbard model, evidencing a wide applicability to strongly correlated electron systems.