Strong coherent coupling between graphene surface plasmons and anisotropic black phosphorus localized surface plasmons

Abstract

The anisotropic plasmons properties of black phosphorus allow for realizing direction-dependent plasmonics devices. Here, we theoretically investigated the hybridization between graphene surface plasmons (GSP) and anisotropic black phosphorus localized surface plasmons (BPLSP) in the strong coupling regime. By dynamically adjusting the Fermi level of graphene, we show that the strong coherent GSP-BPLSP coupling can be achieved in both armchair and zigzag directions, which is attributed to the anisotropic black phosphorus with different in-plane effective electron masses along the two crystal axes. The strong coupling is quantitatively described by calculating the dispersion of the hybrid modes using a coupled oscillator model. Mode splitting energy of 26.5 meV and 19 meV are determined for the GSP-BPLSP hybridization along armchair and zigzag direction, respectively. We also find that the coupling strength can be strongly affected by the distance between graphene sheet and black phosphorus nanoribbons. Our work may provide the building blocks to construct future highly compact anisotropic plasmonics devices based on two-dimensional materials at infrared and terahertz frequencies.

The Optical Properties and Plasmonics of Anisotropic 2D Materials

“…Therefore, BP films are treated as a model system to host the anisotropic and hyperbolic 2D plasmons . Great theoretical and experimental efforts have been devoted to investigating the plasmons in this natural anisotropic material. Below, we discuss the theoretical studies on the plasmon dynamics of BP films and the experimental progress in detecting BP plasmons, as well as the potential applications of plasmons in anisotropic 2D materials.…”

“…Such anisotropy is affected by the thickness of the insulating layer between the G–BP bilayer. Nong et al theoretically investigated the plasmon hybridization in the graphene–BP nanoribbon heterostructure. The coupled oscillator model reveals that the coupling strength is anisotropic and is significantly influenced by the spacer thickness between the graphene and BP nanoribbons.…”

“…In the past few years, tremendous attention has been given to graphene plasmons, with a remarkable manifestation of high tunability and low loss . Recently, a number of theoretical efforts have been devoted to studying the plasmonic properties of BP, where anisotropic plasmon dispersions occur due to its band anisotropy . Fascinatingly, the hyperbolic plasmon polaritons, whose iso‐frequency contour is a hyperbola, are predicted to naturally exist in BP films, which originate from the coupling between the intraband and interband optical conductivity .…”

Functional Mid‐Infrared Polaritonics in van der Waals Crystals

“…Furthermore, in graphene nanorings, bonding and antibonding hybridized plasmons have been demonstrated, and resonant extinction close to near‐infrared was achieved with the antibonding modes . In addition to the graphene nanoresonators, some theoretical works have reported that far‐infrared to THz light modulation could be achievable with nanostructured monolayer black phosphorus, which also supports highly confined localized plasmons modes …”

Wideband tunable perfect absorption of graphene plasmons via attenuated total reflection in Otto prism configuration

“…Graphene, the truly two-dimensional crystal consisting of carbon atoms in a honeycomb lattice, has received extensive research interest due to its excellent optoelectronic properties and potential applications [1,2]. Its unique electronic features, characterized by massless Dirac fermions and unconventional transport properties, render it to possess the most distinct electromagnetic confinement behavior: the capability of supporting intrinsic plasmon modes with extremely tight confinement, relatively long lifetime, and very low losses at infrared and terahertz frequencies [3][4][5][6][7][8][9][10][11]. Especially, such plasmonic responses can be actively modulated under electrostatic gate control [12][13][14][15][16][17], a feature that is not available in traditional metallic surface plasmons.…”