Realistic nonlocal refrigeration engine based on Coulomb-coupled systems

We investigate, in detail, a triple quantum dot system that exploits Coulomb coupling to achieve nonlocal refrigeration. The system under investigation is a derivative of the nonlocal thermodynamic engine, originally proposed by Sanchez and Buttiker [Phys. Rev. B 83, 085428 (2011)], that employs quadruple quantum dots to attain efficient nonlocal heat harvesting. Investigating the cooling performance and operating regime using the quantum master equation approach, we point out some crucial aspects of the refrigeration engine. In particular, we demonstrate that the maximum cooling power for the setup is limited to about 70% of the optimal design. Proceeding further, we point out that to achieve a target reservoir temperature lower than the average temperature of the current path, the applied voltage must be greater than a given threshold voltage V-TH that increases with the decrease in the target reservoir temperature. In addition, we demonstrate that the maximum cooling power, as well as the coefficient of performance, deteriorates as one approaches a lower target reservoir temperature. The triple quantum dot system, investigated in this paper, combines fabrication simplicity along with descent cooling power and may pave the way towards the practical realization of efficient nonlocal cryogenic refrigeration systems.

Automated summary

A triple quantum dot system utilizing Coulomb coupling for nonlocal refrigeration is investigated, derived from the nonlocal thermodynamic engine proposed by Sanchez and Buttiker. Using the quantum master equation approach, it is shown that the maximum cooling power is limited and achieving a target reservoir temperature requires a voltage greater than a threshold voltage. As the target reservoir temperature decreases, the maximum cooling power and coefficient of performance deteriorate. This system combines fabrication simplicity with efficient cooling power for potential practical application in nonlocal cryogenic refrigeration systems.