Monolayer NaW 2 O 2 Br 6 : 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 NaW 2 O 2 Br 6 can host electrically tunable hyperbolic plasmon polaritons for infrared light via first-principles calculations. 2D monolayer NaW 2 O 2 Br 6 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 10 13 cm -2 , which even can be accessed by solid-gated field effect transistors. Thus, it is anticipated that monolayer NaW 2 O 2 Br 6 has a great potential in constructing field programmable polariton nanodevices for emerging and diverse photonic applications.