Anomalously large Seebeck coefficient of CuFeS2 derives from large asymmetry in the energy dependence of carrier relaxation time

The Seebeck effect in a material originates from the distribution of asymmetry in the electron transport under a temperature gradient, which has contributions from the energy-dependent electronic density-of-states, and carrier mobility. However, because the energy dependence of the common electron scattering mechanisms is weak, the mobility-driven Seebeck coefficient has long been ignored in most thermoelectric materials, and the energy asymmetry of the density-of-states has been considered the dominant contribution. In this work, we describe a hopping transport behavior observed in CuFeS2, and a large carrier Hall mobility gradient of dμH/dT that creates an unusually large energy-dependent mobility contribution to the Seebeck coefficient. The work offers several ideas regarding the mobility-driven Seebeck effect and its potential utilization in the design of thermoelectric materials.