Strong nonreciprocal thermal radiation of transverse electric wave in Weyl semimetal

Abstract

Nonreciprocal thermal radiation offers significant opportunities for realizing photonic energy conversion at the thermodynamic limit and controlling radiative heat transfer at the nanoscale. Numerous methods have been proposed to achieve nonreciprocal thermal radiation. However, these studies have mainly focused on transverse magnetic (TM) wave, while the case of the transverse electric (TE) wave incidence has rarely been explored. In this work, a nonreciprocal emitter for TE wave is designed. The emitter consists of a Weyl semimetal film and an Ag substrate, which can achieve strong nonreciprocity at the wavelength of 10.02 μm. By tailoring the angle of the plane of incidence with respect to the Weyl nodes of WS, the nonreciprocity can be effectively enhanced. We show the reflectivity for the co-polarization and cross-polarization to further reveal the physical mechanism of the strong nonreciprocal thermal radiation of TE incidence. The enhanced nonreciprocity is attributed to the polarization conversion and the Fabry-Perot (FP) resonances. Besides, the variation of the absorptivity spectrum and emissivity spectrum with the thicknesses of Weyl semimetal film and angles are also shown. We believe that this work will provide new approaches for the application of nonreciprocal thermal radiation.