Application of the shift-invert Lanczos algorithm to a nonequilibrium Green's function for transport problems

Nonequilibrium Green's function theory and related methods are widely used to describe transport phenomena in many-body systems, but they often require a costly inversion of a large matrix. We show here that the shift-invert Lanczos method can dramatically reduce the computational effort. We apply the method to two test problems, namely a simple model Hamiltonian and to a more realistic Hamiltonian for nuclear fission. For a Hamiltonian of dimension 66 103 we find that the computation time is reduced by a factor of 33 compared to the direct calculation of the Green's function.