Real-space imaging of acoustic plasmons in large-area graphene grown by chemical vapor deposition

An acoustic plasmon mode in a graphene-dielectric-metal structure has recently been spotlighted as a superior platform for strong light-matter interaction. It originates from the coupling of graphene plasmon with its mirror image and exhibits the largest field confinement in the limit of a sub-nm-thick dielectric. Although recently detected in the far-field regime, optical near-fields of this mode are yet to be observed and characterized. Here, we demonstrate a direct optical probing of the plasmonic fields reflected by the edges of graphene via near-field scattering microscope, revealing a relatively small propagation loss of the mid-infrared acoustic plasmons in our devices that allows for their real-space mapping at ambient conditions even with unprotected, large-area graphene grown by chemical vapor deposition. We show an acoustic plasmon mode that is twice as confined and has 1.4 times higher figure of merit in terms of the normalized propagation length compared to the graphene surface plasmon under similar conditions. We also investigate the behavior of the acoustic graphene plasmons in a periodic array of gold nanoribbons. Our results highlight the promise of acoustic plasmons for graphene-based optoelectronics and sensing applications.

Усиление терагерцового излучения высокодобротными резонансными плазмонами в двухслойной периодической структуре на основе графена в режиме антикроссинга плазмонных мод

The spectrum of amplification of terahertz radiation in a structured active graphene bilayer consisting of two identical periodic graphene microribbon arrays separated by a thin dielectric barrier layer is theoretically investigated. The system supports optical and acoustic plasmon modes. The resonant frequencies of the optical and acoustic modes change oppositely with the dielectric-layer thickness, which allows plasmon-mode anticrossing. It is shown that the investigated graphene structure is characterized by a strong plasmon response and giant terahertz-radiation amplification at plasma resonance frequencies in the vicinity of the anticrossing between the optical and acoustic plasmon modes at room temperature.

MAGNETOPLASMONS IN SYMMETRY DRIVEN BILAYER ELECTRON SYSTEM

The effect of space symmetry on magnetoplasmon charge density excitations in a weekly tunnel coupled bilayer electron system is considered. The magnetic field corresponds to the filling factor ν = 4. The energy of optic magnetoplasmon is not affected by space symmetry. Three other collective magnetoplasmon modes are determined by relations between parameters of asymmetry, tunnel parameter and energy of acoustic plasmon.