Thermoelectric Effect in Mott Variable-Range Hopping

On the basis of the Kubo-Luttinger linear response theory combined with the scaling theory of Anderson localization predicting the energy dependence of localization length near the mobility edge, we have studied the thermoelectric response of a disordered system exhibiting Mon variable-range hopping (VRH). We found that the low-temperature Seebeck coefficient for VRH conduction in a d-dimensional system varies as S proportional to Td/(d+1), which is different from the widely used expression, S proportional to T(d-1)/(d+1), based on the energy-independent localization length. It is seen that the low-T behavior of S(T) of the thiospinel CuCrTiS4 is in full agreement with the new scheme.