Phonon Drag Thermoelectric Power in Graphite

Abstract

According to Takezawa et al., the thermoelectric power (Remark: Graphics omitted.) along the basal plane in a synthetic single crystal graphite exhibits a sharp negative dip at T=35°K and a positive peak centered at 120°K. Subtracting the diffusion component (Remark: Graphics omitted.) by use of an appropriate assumption, they have separated the phonon drag contribution (Remark: Graphics omitted.) from (Remark: Graphics omitted.). To get a theoretical explanation for (Remark: Graphics omitted.), coupled Boltzmann equations for carriers and phonons are solved on the basis of a simplified ellipsoidal band model. The calculated (Remark: Graphics omitted.) is proportional to T⁻³ above the dip temperature T_d(35°K) and at T<T_d it tends to zero as T^2∼4 with decreasing temperature. These behaviors are in qualitative agreement with the observed result.