Large Faraday rotation angle with high transmittance in Weyl semimetal assisted by resonant tunneling

Abstract

Over the past decades, a series of nanostructures have been proposed to intensively enhance the Faraday rotation angle. However, the mutual inhibition between the Faraday rotation angle and the transmittance poses a challenge to achieve large Faraday rotation angle with high transmittance. In this paper, a sandwich structure consisting of two Weyl semimetal (WSM) layers of the same thickness and a dielectric layer is designed. Empowered by the resonant tunneling, the enhanced Faraday rotation effect is accompanied by an increase in transmittance. In the presence of realistic level of optical loss, the transmittance can be up to reach 97.4% when the resonant tunneling conditions of left-handed and right-handed polarized light are satisfied simultaneously, and its corresponding Faraday rotation angle can also be as high as −51.1 degrees. By adjusting the axial vector of the WSM layer, we design an optical isolator with a transmittance of up to 97% and a Faraday rotation angle of 45 degrees. This simple triple-layer structure provides some theoretical basis and reference value for future research into non-reciprocal devices.