Enhanced and tunable magneto-optical Kerr effects based on epsilon-near-zero response of Weyl semimetal

Abstract

In this paper, we theoretically reveal a 4 × 4 magneto-optical matrix to study the Kerr effects induced by the transverse-magnetic (TM) and transverse-electric (TE) polarized waves illuminating on a bulk Weyl semimetal (WSM). It is shown that the Kerr angles θp and θs maintain large absolute values of nearly 21°, which are mainly caused by the close cross-polarized and co-polarized reflection coefficients. What is more important, the Kerr angles can be further enhanced at two different frequencies close to the epsilon-near-zero (ENZ) frequency, where the maximum Kerr rotation angles (absolute value) of 45° have been obtained due to the sharp increases of the co-polarized reflection coefficients. Remarkably, the ENZ frequency of WSM can be adjusted by altering the Fermi energy and tilt degree, thereby resulting in the enhanced Kerr angles at different frequencies. Additionally, it is demonstrated that the incident angle should be declined with the increase of WSM thickness to enable the further enhancement of the Kerr angle θs. We also examine the effect of Weyl node separation on the Kerr angles. Our studies provide a simple and effective method to enhance and adjust the Kerr angles with a WSM or other topological semimetals.