A heat engine made of quantum dot molecules with high figure of merits

TL;DR

This paper theoretically investigates a quantum dot molecule heat engine that converts heat into electrical power, demonstrating high efficiency, bipolar current behavior, and potential diode applications based on quantum effects.

Contribution

It introduces a novel quantum dot molecule heat engine with high figure of merit and explores its efficiency, bipolar behavior, and diode functionality under various conditions.

Findings

Charge current shows bipolar oscillations with gate voltage.

Efficiency is higher in orbital depletion state due to many-body effects.

Direction-dependent charge currents suggest diode applications.

Abstract

The transport of electrons through serially coupled quantum dot molecules (SCQDM) is investigated theoretically for application as an energy harvesting engine (EHE), which converts thermal heat to electrical power. We demonstrate that the charge current driven by a temperature bias shows bipolar oscillatory behavior with respect to gate voltage due to the unbalance between electrons and holes, which is different from the charge current driven by an applied bias. In addition, we reveal a Lenz's law between the charge current and the thermal induced voltage. The efficiency of EHE is higher for SCQDM in the orbital depletion situation rather than the orbital filling situation, owing to the many-body effect. The EHE efficiency is enhanced with increasing temperature bias, but suppressed as the electron hopping strength reduces. The fluctuation of QD energy levels at different sites also leads to a reduction of EHE efficiency. Finally, we demonstrate direction-dependent charge currents driven by the temperature bias for application as a novel charge diode.