A quantum-dot heat engine operating close to the thermodynamic efficiency limits

TL;DR

This paper experimentally demonstrates a quantum-dot particle-exchange heat engine that operates near thermodynamic efficiency limits, showing potential for highly efficient energy conversion in miniaturized solid-state devices.

Contribution

First experimental realization of a quantum-dot based particle-exchange heat engine achieving efficiencies close to thermodynamic limits.

Findings

Efficiency exceeds 70% of Carnot efficiency at maximum power

Engine's efficiency aligns with Curzon-Ahlborn predictions

Demonstrates potential for near-thermodynamic-limit thermoelectric devices

Abstract

Cyclical heat engines are a paradigm of classical thermodynamics, but are impractical for miniaturization because they rely on moving parts. A more recent concept is particle-exchange (PE) heat engines, which uses energy filtering to control a thermally driven particle flow between two heat reservoirs. As they do not require moving parts and can be realized in solid-state materials, they are suitable for low-power applications and miniaturization. It was predicted that PE engines could reach the same thermodynamically ideal efficiency limits as those accessible to cyclical engines, but this prediction has not been verified experimentally. Here, we demonstrate a PE heat engine based on a quantum dot (QD) embedded into a semiconductor nanowire. We directly measure the engine's steady-state electric power output and combine it with the calculated electronic heat flow to determine the electronic efficiency $\eta$. We find that at the maximum power conditions, $\eta$ is in agreement with the Curzon-Ahlborn efficiency and that the overall maximum $\eta$ is in excess of 70$\%$ of the Carnot efficiency while maintaining a finite power output. Our results demonstrate that thermoelectric power conversion can, in principle, be achieved close to the thermodynamic limits, with direct relevance for future hot-carrier photovoltaics, on-chip coolers or energy harvesters for quantum technologies.