A quantum-dot heat engine operated close to thermodynamic efficiency limits.

Particle-exchange heat engines extract work by using an energy filter to control a thermally driven particle flow between two or more heat reservoirs. These engines have been predicted to reach the same ideal thermodynamic efficiency limits as those accessible to classic cyclical engines, but this prediction has never been verified experimentally. In this work we realize a particle-exchange heat engine based on a quantum dot embedded in an InAs/InP nanowire. We demonstrate an efficiency at maximum power close to the Curzon-Ahlborn efficiency and at the maximum efficiency (~70% of Carnot efficiency) the QD still produces finite power output roughly equal to half of the maximal amount. These results are obtained by measuring the engine’s steady state output power and combining it with the calculated electronic heat flow. This procedure is made possible by an excellent agreement between the modelled and measured generated current, which allows for a quantitative estimate of the heat flow.