Radiative heat transfer in low-symmetry Bravais crystal

TL;DR

This paper demonstrates that low-symmetry Bravais crystals, specifically {eta}-Ga2O3, can significantly enhance near-field thermal radiation and enable twist-induced thermal control surpassing traditional materials, with potential applications in thermal photonics.

Contribution

The study introduces a twist-induced near-field thermal control system using low-symmetry Bravais crystals, highlighting the shear effect's role in enhancing thermal radiation modulation.

Findings

NFTR exceeds blackbody limit by nearly four orders of magnitude.

Twist-induced modulation is stronger in low-symmetry crystals than in high-symmetry ones.

Shear effect significantly enhances thermal control via elliptical polaritons.

Abstract

Over the last few years, broken symmetry within crystals has attracted extensive attention since it can improve the control of light propagation. In particular, low-symmetry Bravais crystal can support shear polaritons which has great potential in thermal photonics. In this work, we report a twist-induced near-field thermal control system based on the low-symmetry Bravais crystal medium (\b{eta}-Ga2O3). The near-field thermal radiation (NFTR) between such crystal slabs is nearly four orders of magnitude larger than the blackbody limit, exceeding the NFTR from other traditional dielectric materials. Moreover, we show that this crystal can serve as an excellent platform for twist-induced near-field thermal control. Due to the intrinsic shear effect, the twist-induced modulation supported by low-symmetry Bravais crystal exceeds that by high-symmetry crystal. We further clarify how the shear effect affects the twist-induced thermal-radiation modulation supported by hyperbolic and elliptical polaritons and show that the shear effect significantly enhances the twist-induced thermal control induced by the elliptical polariton mode. These results open new directions for thermal-radiation control in low-symmetry materials, including geological minerals, common oxides, and organic crystals.