Charge Transfer Plasmons: Optical Frequency Conductances and Tunable Infrared Resonances

Abstract

A charge transfer plasmon (CTP) appears when an optical-frequency conductive pathway between two metallic nanoparticles is established, enabling the transfer of charge between nanoparticles when the plasmon is excited. Here we investigate the properties of the CTP in a nanowire-bridged dimer geometry. Varying the junction geometry controls its conductance, which modifies the resonance energies and scattering intensities of the CTP while also altering the other plasmon modes of the nanostructure. Reducing the junction conductance shifts this resonance to substantially lower energies in the near- and mid-infrared regions of the spectrum. The CTP offers both a high-information probe of optical frequency conductances in nanoscale junctions and a new, unique approach to controllably engineering tunable plasmon modes at infrared wavelengths.

Graphene Optical Switch Based on Charge Transfer Plasmons

“…Consequently, by increasing the length of the pathway, the conductance reduces slightly and delays the shuttle of the photoexcited charges. Nevertheless, it is noteworthy that due to the substantial conductivity of highly doped graphene sheet, we do not expect dramatic shift in the position of CTP peak to the mid‐infrared region (MIR) as it happens in dissipative metallic and lossy junctions . On the other hand, increasing the space between proximal disks causes drastic decay in the amplitude of the dipolar peak at high energies.…”

“…Recently, alternative and affordable methods have been proposed and analyzed theoretically and experimentally to excite CTPs in the near‐infrared (NIR), and terahertz (THz) spectra, via direct transfer of charges between subwavelength plasmonic objects across a conductive bridge. In both tunneling and direct shuttling of electrons, having an active control over CTPs is limited and can be controlled partially by varying the intensity of the incident radiation or morphological variations .…”

“…This can be better understood by analyzing the conductance of the graphene junction. It is shown that increasing the length of the conductive bridge between neighbor nanoparticles causes increase in electron travel time between the nanoparticles as well as dramatic decay of plasmons due to longer travel area . Therefore, for the highly doped n ‐type graphene layer, the frequency‐dependent conductance can be written as: G ( ω ) = σ ( ω ) WT / L a , where W , T , and L a are the width (fixed to 160 nm), thickness (here set and fixed to 0.35 nm), and the length of the graphene layer, respectively.…”

From active plasmonic devices to plasmonic molecular electronics

“…Another interesting model, which presents some similarities with a molecular junction, consists of two nanodisks connected by a metallic bridge . Figure shows two NPs connected by a conducting bridge (Figs (a)) or separated (Figs (a)).…”

“…The CTP resonance blue‐shifts when the conductance of the bridge increases whereas the BDP resonance decreases drastically and practically disappears. (Adapted from reference ; copyright 2015 American Chemical Society). For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.…”