Abstract
Lasers, photovoltaics, and thermoelectrically-pumped light emitting diodes are thermodynamic machines which use excitons (electron-hole pairs) as the working medium. The heat transfers in such devices are highly irreversible, leading to low efficiencies. Here we predict that reversible heat transfers between a quantum-dot exciton and its phonon environment can be induced by laser pulses. We calculate the heat transfer when a quantum-dot exciton is driven by a chirped laser pulse. The reversibility of this heat transfer is quantified by the efficiency of a heat engine in which it forms the hot stroke, which we predict to reach 95% of the Carnot limit. This performance is achieved by using the time-dependent laser-dressing of the exciton to control the heat current and exciton temperature. We conclude that reversible heat transfers can be achieved in excitonic thermal machines, allowing substantial improvements in their efficiency.
Highlights
Lasers, photovoltaics, and thermoelectrically-pumped light emitting diodes are thermodynamic machines which use excitons as the working medium
We show that heat can be transferred from the phonon bath to the exciton, and assess the performance of a heat engine in which this forms the hot stroke
Our work shows that the amplitude and frequency profile of a driving laser pulse can be tuned to give complete control of exciton heat flows and exciton temperatures on picosecond timescales
Summary
Photovoltaics, and thermoelectrically-pumped light emitting diodes are thermodynamic machines which use excitons (electron-hole pairs) as the working medium. We calculate the heat transfer when a quantum-dot exciton is driven by a chirped laser pulse The reversibility of this heat transfer is quantified by the efficiency of a heat engine in which it forms the hot stroke, which we predict to reach 95% of the Carnot limit. This performance is achieved by using the time-dependent laser-dressing of the exciton to control the heat current and exciton temperature. Our work shows that the amplitude and frequency profile of a driving laser pulse can be tuned to give complete control of exciton heat flows and exciton temperatures on picosecond timescales This opens up the possibility of reaching thermodynamic efficiency limits in exciton-photon thermal machines
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