Thermoelectric power of metallic Rb3C60: phonon-drag and carrier diffusion contributions

Thermoelectric power (S) of Rb(3)C(60) fullerides in the metallic phase is theoretically estimated. We first develop aHamiltonian model that incorporates the scattering rates within the relaxation time approximation to estimatethe phonon-drag thermoelectric power (S(ph)(drag)) incorporating the scattering of phonons with defects, electrons ascarriers, grain boundaries, and phonon-phonon interactions. As a next step, Mott expression within parabolicband approximation is used to analyze the electron diffusive thermoelectric power (S(diff(c)) using Fermi energy aselectron parameter, and S(c)(diff)) shows a linear temperature dependence. The S(ph)(drag)) is nonzero in both normal andsuperconducting states. Its behavior is determined by competition among the several operating scattering rates forheat carriers and a balance between diffusive carrier and phonon-drag contributions. Acoustic phonons areeffectively scattered by various scatterers for the thermoelectric power. S infers a change in slope above transitiontemperature and becomes almost linear above 70 K.

Keywords:

Rb3C60 , Thermoelectric power , Phonon drag , Carrier diffusion , Intermolecular phonon