Monolayer NaW₂O₂Br₆: a gate tunable near-infrared hyperbolic plasmonic surface

Electrically tunable hyperbolic polaritons in two dimensional (2D) materials can offer unexplored opportunities in integrating photonics and nano-optoelectronics into a single chip. Here, we suggest that monolayer NaW₂O₂Br₆ can host electrically tunable hyperbolic plasmon polaritons for infrared light via first-principles calculations. 2D monolayer NaW₂O₂Br₆ exhibits an extremely anisotropic metallic property: conducting for one direction but almost insulating for the other direction, which could be considered as a 2D analogue of metal/dielectric multilayers, a typical structure for hyperbolic metamaterials. More interestingly, we also demonstrate that the hyperbolic properties in the near-infrared range, including the hyperbolic windows, figure of merit, and propagation directions of plasmon beams, can be effectively modulated by carrier doping at the order of 10¹³ cm^-2, which even can be accessed by solid-gated field effect transistors. Thus, it is anticipated that monolayer NaW₂O₂Br₆ has a great potential in constructing field programmable polariton nanodevices for emerging and diverse photonic applications.