Role of coherence in quantum-dot-based nanomachines within the Coulomb blockade regime

TL;DR

This paper investigates how quantum coherence influences the operation and efficiency of quantum-dot-based nanomachines in the Coulomb blockade regime, highlighting the potential for true quantum machines reliant on superpositions.

Contribution

It introduces a configuration where quantum coherence is essential for nanomachine function, advancing the understanding of quantum effects in thermoelectric and quantum motor devices.

Findings

Quantum coherence enables true quantum machines in Coulomb blockade regime.

Efficiency is affected by decoherence and higher-order effects.

Coherent superpositions are crucial for device operation.

Abstract

During the last decades, quantum dots within the Coulomb blockade regime of transport have been proposed as essential building blocks for a wide variety of nanomachines. This includes thermoelectric devices, quantum shuttles, quantum pumps, and even quantum motors. However, in this regime, the role of quantum mechanics is commonly limited to provide energy quantization while the working principle of the devices is ultimately the same as their classic counterparts. Here, we study quantum-dot-based nanomachines in the Coulomb blockade regime, but in a configuration where the coherent superpositions of the dots' states plays a crucial role. We show that the studied system can be used as the basis for different forms of "true" quantum machines that should only work in the presence of these coherent superpositions. We analyze the efficiency of these machines against different nonequilibrium sources (bias voltage, temperature gradient, and external driving) and the factors that limit it, including decoherence and the role of the different orders appearing in the adiabatic expansion of the charge/heat currents.