Path Integrals in the Physics of Lattice Polarons

A path-integral approach to lattice polarons is developed. The method is based on exact analytical elimination of phonons and subsequent Monte Carlo simulation of self-interacting fermions. The analytical basis of the method is presented with emphasis on visualization of polaron effects, which path integrals provide. Numerical results on the polaron energy, mass, spectrum and density of states are given for short-range and long-range electron-phonon interactions. It is shown that certain long-range interactions significantly reduce the polaron mass, and anisotropic interactions enhance polaron anisotropy. The isotope effect on the polaron mass and spectrum is discussed. A path-integral approach to the Jahn-Teller polaron is developed. Extensions of the method to lattice bipolarons and to more complex polaron models are outlined.