The reverse flow and amplification of heat in quantum-dot systems

For classical systems, heat is impossible to be transferred from a cool bath to a hot bath without the existence of any external agency. Here, we show that such a phenomenon can occur in quantum systems through a simple device that a quantum dot is embedded between the two reservoirs described by different statistical distribution functions. The reverse flow and amplification of heat in the device can be realized by regulating the energy levels of the quantum dot and the chemical potentials of reservoirs. It is of particular interest to discover that because of the existence of the quantum tunneling effect in the device, this new quantum phenomenon can be observed even when the chemical potential gradient and the temperature gradient are in the same direction. Moreover, the reverse heat flow and amplification coefficient of the quantum device are calculated. The novelty of this device is that the reverse flow of heat does not need externally driving force and this seemingly paradoxical phenomenon does not violate the laws of thermodynamics. It is further expounded that the quantum device has some practical applications. For example, the device can work as a micro/nano cooler. The performance characteristics of the cooler are revealed for different distribution functions. The coefficients of performance of the cooler operated at different conditions are calculated and the optimum selection criteria of key parameters are supplied.