The polaron: Ground state, excited states, and far from equilibrium

We describe a variational approach for solving the Holstein polaron model w ith dynamical quantum phonons on an infinite lattice. The method is simple, fast, extremely accurate, and gives ground and excited state energies and wavefunctions at any momentum k. The method can also be used to calculate c oherent quantum dynamics fdr inelastic tunneling and for strongly driven po larons far from equilibrium.