题 目：Collective Thermoelectric Effect in Three-Terminal Thermoelectric Systems and Beyond
Collective effects in thermoelectric efficiency and power are revealed by studying three-terminal thermoelectric systems where there are two heat currents (forces) coupled with a single electric current (force). Collective effects here refer to the phenomena that when both heat forces (i.e., temperature gradients) are exploited to generate electric power the maximal efficiency is larger than that for the case when only one of the heat forces is used. The figure of merit and the power factor for the collective thermoelectric effect are derived for three-terminal thermoelectric systems which differ significantly from the conventional ones that are valid for two-terminal thermoelectric systems. The collective phenomena are supposed to be valuable for applications as it can improve the performance of the device considerably. It is found that the improvement by the collective effect is robust to parasitic heat conductance which prevails in realistic devices. Finally we discuss possible realization and how to scale the nano-device to macroscopic one. We also talk about some general results beyond three- terminal systems.