Three-Dimensional Invisibility to Superscattering Induced by Zeeman-Split Modes

We report that the fundamental three-dimensional (3-D) scattering single-channel limit can be overcome in magneto-optical assisted systems by inducing nondegenerate magnetoplasmonic modes. In addition, we propose a 3-D active (magnetically assisted) forward-superscattering to invisibility switch, functioning at the same operational wavelength. Our structure is composed of a high-index dielectric core coated by indium antimonide (InSb), a semiconductor whose permittivity tensorial elements may be actively manipulated by an external magnetic bias $B_0$. In the absence of $B_0$, InSb exhibits isotropic epsilon-near-zero (ENZ) and plasmonic behavior above and below its plasma frequency, respectively, a frequency band which can be utilized for attaining invisibility using cloaks with permittivity less than that of free space. With realistic $B_0$ magnitudes as high as 0.17 T, the gyroelectric properties of InSb enable the lift of mode degeneracy, and the induction of a Zeeman-split type dipolar magnetoplasmonic mode that beats the fundamental single-channel limit. This all-in-one design allows for the implementation of functional and highly tunable optical devices.