Abstract
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.
Highlights
Topological photonics is a new and exciting area of optical science that deals with and employs the robust characteristics of periodic structures, known as topological indices, to produce scattering-free, localized optical excitations. Such excitations exist at the edges or domain walls of photonic topological insulators (PTIs) [1] and are spectrally located inside PTIs’ bandgaps
While most emphasis in topological photonics has been on two- and three-dimensional PTIs supporting either edge or surface states [1, 4,5,6,7,8,9,10,11,12,13,14], it is well known that even one-dimensional photonic crystals (PhCs) can have topological properties
The metal metasurface provides an interface for active and effective spatial modulation of local carrier densities, which mediates the hybridization of Bloch plasmonic modes and interacts directly with the graphene surface plasmon polaritons (GSPPs) modes in the infrared regime
Summary
It was found to be connected to experimentally measurable surface impedance or reflection coefficients from the PhC interface [20, 27], thereby establishing a connection between physical observables and the Zak phase Because, by their very definition, PhCs enable the creation of bandgaps due to Bragg scattering, both the lattice period and the confinement length of the interface states must be comparable to the wavelength of light for conventional photonic structures constructed out of metals and dielectrics. We demonstrate how a special class of electromagnetic excitation – graphene surface plasmon polaritons (GSPPs) – can be utilized to produce strongly localized (sub-wavelength) interface states at the domain wall between two metallic electrically biased 1D Bragg gratings described below. The latter takes into account nonlocal effects [67]
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