Broadband circularly polarized thermal radiation from magnetic Weyl semimetals

TL;DR

This paper demonstrates that magnetic Weyl semimetals can emit broadband, high-purity circularly polarized thermal radiation due to their strong gyrotropy, with potential applications in thermal radiation engineering.

Contribution

It reveals the ability of magnetic Weyl semimetals to produce broadband circularly polarized thermal emission and analyzes how this depends on physical parameters like Weyl node separation.

Findings

Planar slabs emit high-purity CP thermal radiation over broad IR range.

Spectral bandwidth increases with Weyl node separation.

Finite-sized bodies emit spectrally broadband CP thermal light, but over smaller angles.

Abstract

We numerically demonstrate that a planar slab made of magnetic Weyl semimetal (a class of topological materials) can emit high-purity circularly polarized (CP) thermal radiation over a broad mid- and long-wave infrared wavelength range for a significant portion of its emission solid angle. This effect fundamentally arises from the strong infrared gyrotropy or nonreciprocity of these materials which primarily depends on the momentum separation between Weyl nodes in the band structure. We clarify the dependence of this effect on the underlying physical parameters and highlight that the spectral bandwidth of CP thermal emission increases with increasing momentum separation between the Weyl nodes. We also demonstrate using recently developed thermal discrete dipole approximation (TDDA) computational method that finite-size bodies of magnetic Weyl semimetals can emit spectrally broadband CP thermal light, albeit over smaller portion of the emission solid angle compared to the planar slabs. Our work identifies unique fundamental and technological prospects of magnetic Weyl semimetals for engineering thermal radiation and designing efficient CP light sources.