Trapping of lattice polarons by impurities

We consider the effects of impurities on polarons in three dimensions using a continuous time quantum Monte Carlo algorithm. An exact treatment of the phonon degrees of freedom leads to a very efficient algorithm, and we are able to compute the polaron dynamics on an infinite lattice by developing an auxiliary weighting scheme. The magnitude of the impurity potential, the electron-phonon coupling, and the phonon frequency are varied. We determine the magnitude of the impurity potential required for polaron trapping. For small electron-phonon coupling the number of phonons increases dramatically on trapping combined with a sharp decrease in kinetic energy. The polaron binding diagram is computed, showing that intermediatecoupling low-phonon-frequency polarons are localized by exceptionally small impurities.