Magnetic Field-Insensitive Anapole State in Gyromagnetic Media

Abstract

In this paper, a metasurface consisting of periodic ferrite disks that shows insensitive responses to external biased magnetic field has been designed and numerically investigated. Microwave ferrite materials with high permittivity support anapole mode arising from destructive interference between electric and toroidal dipole moments. When a low external magnetic field is applied, the magnetic resonant mode splits into two chiral resonances. The transmission spectra of the anapole mode and magnetic resonant mode exhibit different trends as the external bias magnetic field is increased, but the anapole state does not change. The bias magnetic field only impacts the magnetic dipole resonance peak, according to the multipole decomposition theory, hence the anapole possesses features that are insensitive to the magnetic field. We anticipate that our study will pave the way for a variety of applications in some strong magnetic environments thanks to the magnetic field-insensitive property of the suggested metamaterial.