Tunable and enhanced Faraday rotation induced by the epsilon-near-zero response of a Weyl semimetal

Abstract

In this paper, we theoretically study the Faraday (FR) rotation effect excited by a transverse-magnetic (TM)-polarized wave passing through a bulk Weyl semimetal (WSM). Results show that the FR angle maintains a large value $(\ensuremath{\sim}\text{--}{21}^{\ensuremath{\circ}})$ with high transmission $(|{t}_{pp}|\ensuremath{\sim}87%)$, which is caused by the close transmission coefficient of $|{t}_{ps}|$ $|{t}_{ps}|$ and $|{t}_{pp}|$. What is more important, the FR angle can be further enhanced at the epsilon-near-zero (ENZ) frequency, where a maximum FR rotation angle (absolute value) of 45\ifmmode^\circ\else\textdegree\fi{} has been obtained due to the sharp decreases of $|{t}_{pp}|$. Remarkably, the ENZ frequency of the WSM can be regulated by varying the Fermi energy and tilt degree, resulting in the tunable and enhanced FR angle at the different ENZ frequencies. Particularly, it is demonstrated that the incident angle should be declined with the increase of WSM thickness for enhancing the FR angle at the ENZ frequency. We also examine the effect of Weyl node separation on the FR angle. Our studies provide a simple and effective method to enhance and control the FR effect with a WSM or other topological semimetals.