Quantum ratchets act as heat pumps

Abstract

Ratchets are systems that combine local asymmetry with non-equilibrium processes to generate directed particle flow. Recently it was found that in quantum ratchets, where an asymmetric tunnelling barrier is tilted symmetrically and periodically, the direction of the generated current depends on temperature—that is, on the energy distribution of particles. Here we highlight the fact that ratchets that have this property can be operated as heat pumps. We analyse a specific mesoscopic ratchet for electrons in terms of a heat pump, and discuss limits to the coefficient of performance.