Skin Effect of Electromagnetic Flux in Anisotropic Zero‐Index Metamaterials

Abstract Skin effect in electromagnetism describes the tendency of alternating current to predominantly flow near the surface rather than through the center of a conductor. Here, another skin effect of electromagnetic flux is reported to occur in non‐conductive materials, specifically within 3D anisotropic zero‐index metamaterials, as well as its potential application in subwavelength wave manipulation. It is found that when a medium of near‐zero longitudinal permittivity and permeability is embedded with inclusions whose transverse permittivity and/or permeability approach zero, the electromagnetic flux therein is directed and extremely compressed beneath the surfaces of inclusions within a skin depth less than λ₀/150. This unusual effect empowers arbitrary control of electromagnetic flux at deep subwavelength scale. Customized subwavelength pathways for electromagnetic flux are demonstrated in full‐wave simulations via practical implementations. The study opens a new avenue for extreme confinement and flexible control of electromagnetic flux at deep‐subwavelength scale.