Interaction effects and thermoelectric power in low-temperature hopping

The effect of electron-electron interactions on the thermoelectric power for hopping transport in two and three dimensions is calculated in the low-temperature limit. While the conductivity requires a very precise measurement to extract a temperature exponent with enough precision to determine the role of the interactions, it is shown that the thermopower behaviour will reflect the presence of interactions in an unambiguous manner. In contrast to a Mott variable-range hopping model where the thermopower decreases to zero as the temperature decreases (S=0 at T=0), the thermopower in an Efros interaction mode, should approach a non-zero constant as T to 0.