Reversible Electron Heat Engines

Abstract

Brownian heat engines use local temperature gradients in asymmetric, periodic potentials to move particles against an external force. The efficiency of such machines is generally limited by irreversible heat flow carried by particles that make contact with different heat baths. Here we show that by using a suitably chosen energy filter, particles can be transferred reversibly between reservoirs that have different temperatures and electrochemical potentials. We use an idealized mesoscopic electron system as our paradigm. Electrons are transferred elastically through an energy filter between two otherwise thermally isolated, identical, two‐dimensional (2D) electron reservoirs. If the transmission energy of the ideal filter is tuned to the energy at which the Fermi occupation functions in the two reservoirs are equal, then no spontaneous energy or particle flow will occur between the reservoirs, even though the reservoirs are not in equilibrium. Operation as a heat engine or refrigerator respectively is obtained for filter energies above and below the energy at which the occupation function of the reservoirs are equal. By choosing the width and position of the energy filter, the machine can operate arbitrarily closely to Carnot efficiency, in full agreement with the Second Law of thermodynamics. It is interesting to note that, to our knowledge, the required ideal energy filters can be achieved only using the quantum wave properties of particles, for instance using resonant tunneling via a 0D quantum dot.Brownian heat engines use local temperature gradients in asymmetric, periodic potentials to move particles against an external force. The efficiency of such machines is generally limited by irreversible heat flow carried by particles that make contact with different heat baths. Here we show that by using a suitably chosen energy filter, particles can be transferred reversibly between reservoirs that have different temperatures and electrochemical potentials. We use an idealized mesoscopic electron system as our paradigm. Electrons are transferred elastically through an energy filter between two otherwise thermally isolated, identical, two‐dimensional (2D) electron reservoirs. If the transmission energy of the ideal filter is tuned to the energy at which the Fermi occupation functions in the two reservoirs are equal, then no spontaneous energy or particle flow will occur between the reservoirs, even though the reservoirs are not in equilibrium. Operation as a heat engine or refrigerator respectively is obt...