Size Dependence of the Transport Properties of Bismuth in the Phonon-Drag Region

Abstract

The low-temperature size effects in the phonon-drag thermopower and electrical and thermal conductivities of bismuth, measured under identical experimental conditions on a tuningfork sample of arm thicknesses 2.8 and 1.2 mm, are reported. The thin arm has the highest positive thermopower and a plateau is observed for both thicknesses in a different temperature range. It is shown that the size effect in the thermopower and electrical conductivity occurs in the same temperature range, suggesting that the nonequilibrium phonon distribution should be taken into account in discussing the electrical conductivity at low temperatures. The thermal conductivity exhibits a size effect at temperatures higher than expected.