Adiabatic theory of off-center vibronic polarons: Local dynamics and itinerant features along a linear chain

The vibronic mixing by an odd-parity vibrational mode of two opposite-parity nearly-degenerate electronic states at a molecular site may drive the small polaron off-center. An associated electric dipole may occur due to broken inversion symmetry which will exert an effect on the electric, optical and transport properties of the host crystal. We first investigate the polaron field in the non-interacting limit and then include Coulomb and dispersive interactions leading to the formation of polaron pairs.