Active Tuning of Hyperbolic Polaritons in van der Waals Materials by Integrating a Gated Graphene Layer

Although in-plane anisotropic PhPs can be steered and even canalized by twisting individual crystal layers in a van der Waals (vdW) stack, active control of their propagation via external stimuli presents a significant challenge. In this chapter, we report on a technology in which anisotropic PhPs supported by biaxial vdW layers are actively tuned by simply gating a graphene layer. Excitingly, we predict active tuning of optical topological transitions, which enable controlling the canalization of PhPs along different in-plane directions in twisted heterostructures. Apart from their fundamental interest, these findings hold promises for the development of optoelectronic devices, such as sensors or photodetectors, based on PhPs with dynamically controllable properties. Some of the calculations in this chapter were performed in collaboration with Arturo González-Morán, Nathaniel Capote-Robayna and Kirill Voronin (Donostia International Physics Center, Spain). The results were published in “Active Tuning of Highly Anisotropic Phonon Polaritons in Van der Waals Crystal Slabs by Gated Graphene” by Gonzalo Álvarez-Pérez, Arturo González-Morén et al. ACS Photonics 9 (2), 383–390 (2022).