Cooling limit of a quantum thermocouple*

A quantum thermocouple is investigated beyond linear response using the method of nonequilibrium Green's functions (NEGF). Insights on the maximum cooling power and coldest temperature achievable are calculated through an effective field theory of the interacting pi-electrons which characterize molecular junctions' transport properties. The limits on cooling are determined by the interplay of the Peltier effect and Joule heating. Different junction couplings (such as sequential exchange and super-exchange) in a quantum thermocouple are tested to determine the possibility of achieving the thermodynamic limit of Carnot efficiency.