Coefficient of performance at maximum cooling power of a simplified quantum dot refrigerator model with resistance

A simplified analytical model of single-level quantum dot (QD) refrigerator was studied without considering the electron spin and Coulomb interaction. Based on the ballistic transport of electrons between two reservoirs across the QD, the Joule heat of the system was assumed to be generated from the Ohmic contacts between the QD and reservoirs. By using the transition rate equation, the performance of the QD refrigerator was studied with respect to the electron transmission probability and the partition ratio (i.e. the fraction of Joule heat generated in the system that releases into the cold reservoir). The analytical expression of the maximum coefficient of performance (COP) was obtained under the exoreversible working condition. The Carnot-bound-dependent COP at maximum cooling power of the QD system was also demonstrated numerically. The results of this work may provide some guidance for the design of mesoscopic refrigerators.