Electric Field Induced Twisted Bilayer Graphene Infrared Plasmon Spectrum

In this work, we investigate the role of an external electric field in modulating the spectrum and electronic structure behavior of twisted bilayer graphene (TBG) and its physical mechanisms. Through theoretical studies, it is found that the external electric field can drive the relative positions of the conduction band and valence band to some extent. The difference of electric field strength and direction can reduce the original conduction band, and through the Fermi energy level, the band is significantly influenced by the tunable electric field and also increases the density of states of the valence band passing through the Fermi level. Under these two effects, the valence and conduction bands can alternately fold, causing drastic changes in spectrum behavior. In turn, the plasmon spectrum of TBG varies from semiconductor to metal. The dielectric function of TBG can exhibit plasmon resonance in a certain range of infrared.

The influence of the electroneutrality of the metal layer on the plasmon spectrum in "dielectric-metal-dielectric" structures

This paper proposes a model that takes into account the discretization of the Fermi wave vector and energy levels, as well as the condition of electroneutrality when investigating the influence of metal thickness on the spectrum of SPPs waves in heterogeneous dielectric-metal-dielectric structures.

Plasmon spectrum of graphene monolayer on substrate

Plasmon modes in monolayer graphene on substrate are analyzed taking into account the thickness of graphene and substrate material layer in the evaluation of Coulomb potential. It is shown that plasmon mode in graphene monolayer has linear dispersion in contrast to multilayer graphene in long-wavelength limit. The slope of plasmon spectrum is determined by the thickness and dielectric constant of substrate. Obtained results are in good agreement with experimental data and other theoretical considerations.

Spectral signatures of charge transfer in assemblies of molecularly-linked plasmonic nanoparticles

Self-assembly of functionalized nanoparticles (NPs) provides a unique class of nanomaterials for exploring and utilizing quantum-plasmonic effects that occur if the interparticle separation between NPs approaches a few nanometers and below. We review recent theoretical and experimental studies of plasmon coupling in self-assembled NP structures that contain molecular linkers between the NPs. Charge transfer through the interparticle gap of an NP dimer results in a significant blue-shift of the bonding dipolar plasmon (BDP) mode relative to classical electromagnetic predictions, and gives rise to new coupled plasmon modes, the so-called charge transfer plasmon (CTP) modes. The blue-shift of the plasmon spectrum is accompanied by a weakening of the electromagnetic field in the gap of the NPs. Due to an optical far-field signature that is sensitive to charge transfer across the gap, plasmonic molecules represent a sensor platform for detecting and characterizing gap conductivity in an optical fashion and for characterizing the role of molecules in facilitating the charge transfer across the gap.

Plasmon dispersions in ultrathin metallic films

We present an eigen-equation for plasmon of ultrathin films based on the self-consistent linear response approximation (SCLRA). The calculations for plasmon dispersion in both single and multilayer systems are reported. There are two types of plasmon in the plasmon spectrum, two-dimensional (2D) and bulk-like (BL) modes. The plasmon energy of the 2D mode is zero in the long wave limit, while the one of BL mode is nonzero in the long-wave limit. Given a surface electron density, with the decrease of the wave vector the dispersions of the 2D plasmon of different layer systems become equal to each other, and approach results of the pure 2D system.