Tailoring topological transition of anisotropic polaritons by interface engineering in biaxial crystals

TL;DR

This paper introduces a novel interface engineering strategy to dynamically control topological transitions of anisotropic polaritons in biaxial crystals, demonstrated through heterostructures of graphene and { extalpha}-MoO3, with implications for programmable nano-optics.

Contribution

The study presents a momentum-directed approach to tailor topological transitions of anisotropic polaritons via interface coupling, enabling electrical and thickness-based modulation.

Findings

Demonstrated topological transition of polaritons at heterostructure interfaces.

Achieved electrical modulation of topological states by Fermi level tuning in graphene.

Observed thickness-dependent topological transition at constant Fermi level.

Abstract

Polaritons in polar biaxial crystals with extreme anisotropy offer a promising route to manipulate nanoscale light-matter interactions. The dynamical modulation of their dispersion is great significance for future integrated nano-optics but remains challenging. Here, we report a momentum-directed strategy, a coupling between the modes with extra momentum supported by the interface and in-plane hyperbolic polaritons, to tailor topological transitions of anisotropic polaritons in biaxial crystals. We experimentally demonstrate such tailored polaritons at the interface of heterostructures between graphene and {\alpha}-phase molybdenum trioxide ({\alpha}-MoO3). The interlayer coupling can be electrically modulated by changing the Fermi level in graphene, enabling a dynamic topological transition. More interestingly, we found that the topological transition occurs at a constant Fermi level when tuning the thickness of {\alpha}-MoO3. The momentum-directed strategy implemented by interface engineering offers new insights for optical topological transitions, which may shed new light for programmable polaritonics, energy transfer and neuromorphic photonics.