Thermal Motors with Enhanced Performance due to Engineered Exceptional Points

TL;DR

This paper demonstrates that thermal motors operating near exceptional points in non-Hermitian systems can achieve enhanced power and efficiency, enabling applications like self-powered microrobots and micro-pumps.

Contribution

It introduces a design principle for thermal motors that exploits exceptional point degeneracies to maximize performance in photonic and electromechanical circuits.

Findings

Maximized power and efficiency near exceptional points.

Thermal motors can be used as autonomous microrobots or micro-pumps.

Designs applicable to photonic and electromechanical systems.

Abstract

A thermal current, generated by a temperature gradient between two reservoirs coupled to a carefully designed photonic or (micro-) electromechanical circuit, might induce non-conservative forces that impulse a mechanical degree of freedom to move along a closed trajectory. We show that in the limit of long - but finite - modulation periods, the extracted power and the efficiency of such autonomous motors can be maximized when an appropriately designed spatio-temporal symmetry violation is induced and when the motor operates in the vicinity of exceptional point (EP) degeneracies. These singularities appear in the spectrum of the effective non-Hermitian Hamiltonian that describes the combined circuit-reservoirs system when we judiciously tailor the coupling between them. In the photonic framework, these motors can be propelled by thermal radiation and can be utilized as autonomous self-powered microrobots, or as micro-pumps for microfluidics in biological environments. The same designs can be also implemented with electromechanical elements for harvesting ambient mechanical (or electrical) noise for powering a variety of auxiliary systems.