Figure 1
From: Topological insulator metamaterials with tunable negative refractive index in the optical region
Schematic of the proposed structure. (a) Schematic of the MDM structure consisting of a 60-nm-thick Bi2Se3 dielectric layer between two 30-nm-thick Au films perforated with a square array of elliptical holes suspended in air. The lattice constant is L = 400 nm, and hole diameters are d1 = 240 nm and d2 = 120 nm. (b) Illustration of the square lattice of ENA.