Moving Media as Photonic Heat Engine and Pump

TL;DR

This paper explores a novel photonic heat engine and pump based on non-reciprocal materials and fluctuational electrodynamics, demonstrating thermodynamic limits, efficiency bounds, and the physical mechanisms involved.

Contribution

It introduces a theoretical framework for photonic heat engines and pumps utilizing non-reciprocal materials, including efficiency bounds and relativistic thermodynamics analysis.

Findings

The propulsion force is due to non-reciprocity and Doppler drag.

Nonreciprocal materials can reduce the velocity needed for heat pumping.

The thermodynamic efficiency is bounded by the Carnot limit, independent of reference frame.

Abstract

A system consisting of two slabs with different temperatures can exhibit a non-equilibrium lateral Casimir force on either one of the slabs when Lorentz reciprocity is broken in at least one of the slabs. This system constitutes a photonic heat engine that converts radiative heat into work done by the non-equilibrium lateral Casimir force. Reversely, by sliding two slabs at a sufficiently high relative velocity, heat is pumped from the slab at a lower temperature to the other one at a higher temperature. Hence the system operates as a photonic heat pump. In this work, we study the thermodynamic performance of such a photonic heat engine and pump via the fluctuational electrodynamics formalism. The propulsion force due to the non-reciprocity and the drag force due to the Doppler effect was revealed as the physical mechanism behind the heat engine. We also show that in the case of the heat pump, the use of nonreciprocal materials can help reduce the required velocity. We present an ideal material dispersion to reach the Carnot efficiency limit. Furthermore, we derive a relativistic version of the thermodynamic efficiency for our heat engine and prove that it is bounded by the Carnot efficiency that is independent of the frame of reference. Our work serves as a conceptual guide for the realization of photonic heat engines based on fluctuating electromagnetic fields and relativistic thermodynamics and shows the important role of electromagnetic non-reciprocity in operating them.