Strong terahertz plasmonic resonances in thin-film Cd3As2: a three-dimensional Dirac semimetal

Linear energy band dispersion in Dirac semimetals has been associated with strong plasmon coupling in terahertz regime. Graphene, in this regard, has been projected to play crucial role in terahertz optoelectronics due to high carrier mobility and conductivity. However, in the realm of quantum materials, a three-dimension analogue of graphene, Cd
₃
As
₂
, so called 3D semimetal, has been shown to have carrier mobility and fermi-velocity well exceeding that in graphene. We experimentally demonstrate synthesis of high-quality large-area Cd
₃
As
₂
thin-films and realization of THz plasmonic structures. The structures exhibit quality factor ~5, at frequency of ~0.7 THz, the highest reported to-date at room temperature in any semiconductor or semimetal. Our results evidence that the 3D nature of Cd
₃
As
₂
provides for a more robust platform for terahertz applications than what is otherwise possible in graphene.