Highly directional and carrier density-independent plasmons in quasi-one-dimensional electron gas systems

Abstract Recent advancements in developing metahyperbolic surfaces through substrate patterning have enabled the realization of highly-directional hyperbolic surface plasmons, but the feasibility of reproducing the same properties in natural hyperbolic two-dimensional (2D) materials is still unexplored. In this study, we expand the possibility of natural 2D materials in achieving electromagnetic scenarios akin to those observed in metahyperbolic surfaces. Natural hyperbolic 2D materials provide inherent advantages for simplicity, predictability, and lower losses compared to meta-surfaces. By employing first-principles calculations, we find that realistic 2D material, specifically the RuOCl2 monolayer, are suitable alternatives to metahyperbolic surfaces. Indeed, RuOCl2 monolayer sustains carrier-density-independent and broadband low-loss hyperbolic responses across the terahertz to ultraviolet spectral range, owning to the highly-anisotropic electronic band structures characterized by quasi-one-dimensional electron gas. These findings shed light on the integration of hyperbolicity in natural 2D materials, opening new avenues for the design and development of optoelectronic devices and nanoscale imaging systems.