Widely Tunable Optical and Thermal Properties of Dirac Semimetal Cd_3As_2

In this paper, a detailed analysis of the temperature‐dependent optical properties of epitaxially grown cadmium arsenide (Cd3As2), a newly discovered 3D Dirac semimetal is reported. Fermi level tuning—instigated from Pauli‐blocking in the linear Dirac cone—and varying Drude response, generate large variations in the mid‐ and far‐infrared optical properties. Thermo‐optic shifts larger than those of traditional III–V semiconductors are demonstrated. Electron scattering rate, plasma frequency edge, Fermi level shift, optical conductivity, and electron effective mass analysis of Cd3As2 thin‐films are quantified and discussed in detail. The ab initio density functional study and experimental analysis of epitaxially grown Cd3As2 promise applications for nanophotonic and nanoelectronic devices, such as reconfigurable metamaterials and metasurfaces, nanoscale thermal emitters, and on‐chip directional antennas.