Self-trapping line of the Holstein molecular crystal model in one dimension

The ground state of the Holstein molecular crystal model of a single electron in one dimension is studied using the Global-Local variational method, analyzing in particular the total energy, kinetic energy, phonon energy, and interaction energy over a broad region of the polaron parameter space. Through the application of objective criteria, a curve is identified that simply, accurately, and robustly locates the self-trapping transition separating small polaron and large polaron behavior. Particular attention is given to the kinetic energy, which is compared quantitatively with other perturbative and nonperturbative methods. copyright 1999 The American Physical Society