Figure 5.

Comparison of repulsive force from isotropic and anisotropic ε-near-zero materials. Spectra of the force per unit radiated power acting on a vertical dipole situated at a height h=0.01λ above different ε-near-zero materials, including natural isotropic materials silver⁵⁶ and silicon carbide⁶² and three anisotropic metamaterial realisations shown in Figures 3 and 4. Silicon carbide is represented only in labels (the related spectrum at around 10 µm is not shown in order not to obscure other spectra). The fractional bandwidth Δf/f₀ is indicated, where Δf is the repulsion force bandwidth and f₀ is the centre frequency of the repulsion force spectrum.