HOPPING THERMOPOWER IN THE REGIME OF BALLISTIC PHONONS

It is argued that at low temperatures, under the conditions when the p honon mean free path exceeds the system size (regime of ballistic phon ons); the thermopower cannot be calculated using the standard approach based on the local equilibrium approximation fcr the electron distrib ution function. Under these conditions, the hopping thermopower is sho wn to vanish.