title: Polaron crossover and bipolaronic metal-insulator transition in the half-filled Holstein model.
abstract: The formation of a finite-density polaronic state is analyzed in the context of the Holstein model using the dynamical mean-field theory. The spinless and spinful fermion cases are compared to disentangle the polaron crossover from the bipolaron formation. The exact solution of dynamical mean-field theory is compared with weak-coupling perturbation theory, noncrossing (Migdal), and vertex correction approximations. We show that polaron formation is not associated with a metal-insulator transition, which is instead due to bipolaron formation.
authors: Enrico Fermi Center, Rome, Italy.
authors: M
authors: M
authors: Capone
authors: S
authors: S
authors: Ciuchi