Tunable terahertz plasmonic response in three-dimensional Dirac semimetal cadmium arsenide

Linearly dispersing band structure profoundly impacts the terahertz properties of materials, particularly in enhancing harmonic generation due to large nonlinear susceptibilities. While efficient terahertz harmonic generation has been demonstrated in 2D and 3D Dirac semimetals including, respectively, graphene and cadmium arsenide (Cd₃As₂), methods to control and tune their terahertz nonlinear response remain largely unexplored.

Cd₃As₂, with an intrinsic carrier concentration of 10¹⁷-10¹⁸ cm^-3, exhibits a screened plasma frequency in the terahertz range. This important characteristic presents an opportunity to create a plasmonic response with a terahertz nonlinear susceptibility. This study demonstrates how Cd₃As₂ plasmonic arrays serve as a platform to enhance the nonlinear response. Furthermore, we present a systematic approach to isolate nonlinear effects from the linear response, providing deeper insight into the role of the carriers in determining the overall electrodynamics. Our findings pave the way for novel applications in terahertz optics and optoelectronics, offering a promising avenue for the development of tunable terahertz devices.