QUANTUM VIBRATIONAL IMPURITY EMBEDDED IN A ONE-DIMENSIONAL CHAIN

We perform a fully quantum mechanical numerical calculation for the pr oblem of a single electron (or excitation) propagating in an N-site on e-dimensional chain in the presence of a single Holstein impurity. We compute the long-time averaged probability for finding the electron on the impurity site as a function of the nonlinearity parameter, define d in terms of the electron-phonon coupling strength and the oscillator frequency, The results, in the intermediate nonlinearity parameter ra nge, differ substantially from the ones obtained through the use of th e discrete nonlinear Schrodinger equation, even in the high-frequency regime. (C) 1997 Published by Elsevier Science B.V.