Widely Tunable Optical and Thermal Properties of Dirac Semimetal Cd₃As₂

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.