Electrically defined topological interface states of graphene surface plasmons based on a gate-tunable quantum Bragg grating

Abstract

A periodic metagate is designed on top of a boron nitride-graphene heterostructure to modulate the local carrier density distribution on the monolayer graphene. This causes the bandgaps of graphene surface plasmon polaritons to emerge because of either the interaction between the plasmon modes, which are mediated by the varying local carrier densities, or their interaction with the metal gates. Using the example of a double-gate graphene device, we discuss the tunable band properties of graphene plasmons due to the competition between these two mechanisms. Because of this, a bandgap inversion, which results in a Zak phase switching, can be realized through electrostatic gating. Here we also show that an anisotropic plasmonic topological edge state exists at the interface between two graphene gratings of different Zak phases. While the orientation of the dipole moments can differentiate the band topologies of each graphene grating, the angle of radiation remains a tunable property. This may serve as a stepping stone toward active control of the band structures of surface plasmons for potential applications in optical communication, wave steering, or sensing.

Nanopolaritonic second-order topological insulator based on graphene plasmons

“…48 Also, by adding the second gate (a top metagate or a simple backgate beneath the existing metagate), the electric control over topological plasmons can be greatly enhanced to enable switching between distinct low-dimensional topological phases. 49 This would constitute a major advance over the single-gate geometry analyzed here, e.g., switching between two domain wall configurations in Fig. 5(a).…”

Photonic crystal for graphene plasmons

“…Our gate-imprinted platform paves the way to the design of more elaborate infrared circuits that host valley plasmons 27,35–39 , topological edge states 40–43 and adds to the toolkit of photonic-crystal-controlled light-matter interactions 44,45 . The top–down fabrication technique for the photonic crystal presented here is fully compatible with the state-of-the-art MOSFET devices, making our system a viable candidate for future electrostatically-reconfigurable plasmonic integrated circuits 46 .…”

Interface States in the Acoustic Quasiperiodic System Based on Non‐Bragg Resonances

“…[ 18 ] This phenomenon was initially and extensively studied in periodic structures. [ 19–21 ] By connecting two different periodic structures [ 22 ] or two nonidentical materials, [ 23 ] the interface states can be introduced. With the development and abundance of artificial periodic materials, interface states are implemented in various structures and materials, for example, photonics, [ 24 ] elastic waves, [ 25 ] metamaterials, [ 26 ] surface plasmons, [ 27 ] and phononics.…”