Enhancing far-field thermal radiation by Floquet engineering

TL;DR

This paper demonstrates that time modulation of a SiC film can significantly enhance far-field thermal radiation by coupling surface phonon polaritons with propagating modes, surpassing equilibrium limits and enabling active control of thermal emission.

Contribution

It introduces a Floquet engineering approach to actively control and enhance far-field thermal radiation beyond static material limitations.

Findings

Time modulation enables radiative transfer beyond equilibrium limits.

Enhanced emission results from coupling evanescent and propagating modes.

Radiative heat flux increases with modulation strength.

Abstract

Time modulation introduces a dynamic degree of freedom for tailoring thermal radiation beyond the limits of static materials. Here we investigate far-field thermal radiation from a periodically time-modulated SiC film under the Floquet nonequilibrium Green's function framework. We show that time modulation enables radiative energy transfer into the far field that surpasses the limit imposed by the equilibrium thermal fluctuations. This enhancement originates from the modulation-induced coupling between evanescent surface phonon polaritons and propagating modes, effectively bridging the energy and momentum mismatch through frequency conversion. Notably, even at zero temperature, the film emits a finite radiative heat flux due to nonequilibrium photon occupation generated by the modulation. The radiative output grows with increasing modulation strength, highlighting the role of external work in driving far-field emission. These results establish time modulation as an effective mechanism for bridging near-field and far-field regimes, opening new pathways for active thermal radiation control.