Polaronic Impurity Hopping Conduction

Impurity hopping conduction in polar lattices and amorphous substances is investigated by application of the canonical transformation of the small polaron theory. In the case of acoustic coupling only, the results of Miller and Abrahams and Gosar for one‐phonon processes are recovered and compared with the contributions of multi‐phonon processes. In the polar case the assisting roles of acoustic and polar phonons are discussed seperately at temperatures T > θ/2 and T <θ/2 (θ being the Debye temperature). The type of the temperature dependence of the conductivity is determined.