Influence of Temperature-Dependent Thomson Coefficient on Thermal Transport in a Low-Dimensional Nanostructure

The Thomson effect heats or cools a material when a current passes along its length in the presence of a temperature gradient ∇T. It is typically neglected in analyses of thermoelectric cooling because the Thomson coefficient Γ(T), which is related to the temperature dependence of the Seebeck coefficient S(T), is ignored. We investigated the influence of (1) and on an intrinsic Si nanowire cooler and found that the temperature dependence of both parameters became more significant at lower temperatures and (2) Γ(T) on the cooling temperature also increased as the current density is raised. These effects caused more heat to be pumped away from the cold side than when Γ was neglected or assumed constant. Cooling was also compared for two systems, one in which phonons and electrons existed in thermal equilibrium, and the other when there was nonequilibrium between them. A nanomaterial with a smaller carrier cooling length induces a relative decrease in the energy transfer between electrons and phonons, which provides better thermoelectric cooling.