Intrinsic Plasmon–Phonon Interactions in Highly Doped Graphene: A Near-Field Imaging Study

Abstract

As a two-dimensional semimetal, graphene offers clear advantages for plasmonic applications over conventional metals, such as stronger optical field confinement, in situ tunability, and relatively low intrinsic losses. However, the operational frequencies at which plasmons can be excited in graphene are limited by the Fermi energy E, which in practice can be controlled electrostatically only up to a few tenths of an electronvolt. Higher Fermi energies open the door to novel plasmonic devices with unprecedented capabilities, particularly at mid-infrared and shorter-wave infrared frequencies. In addition, this grants us a better understanding of the interaction physics of intrinsic graphene phonons with graphene plasmons. Here, we present FeCl-intercalated graphene as a new plasmonic material with high stability under environmental conditions and carrier concentrations corresponding to E > 1 eV. Near-field imaging of this highly doped form of graphene allows us to characterize plasmons, including their corresponding lifetimes, over a broad frequency range. For bilayer graphene, in contrast to the monolayer system, a phonon-induced dipole moment results in increased plasmon damping around the intrinsic phonon frequency. Strong coupling between intrinsic graphene phonons and plasmons is found, supported by ab initio calculations of the coupling strength, which are in good agreement with the experimental data.

Graphene-Based Light Sensing: Fabrication, Characterisation, Physical Properties and Performance

“…Contrary to bulk graphite, the intercalation of FLG takes place at relatively low temperatures using a three-zones furnace, it does not require a carrier gas and the time-scale is reduced from tens of days to only 8 hrs. This, together with its environmental stability [ 65 ] and its peculiar plasmonic properties [ 66 ], make FeCl -FLG the ideal candidate for novel opto-electronics devices [ 67 ].…”

Edge modes and Fabry-Perot plasmonic resonances in anomalous-Hall thin films

“…Here ±k 0 are the positions of the poles on the real axis, with k 2 0 (ω) = q 2 p (ω) − q 2 y , and I(x, q y , ω) is the same integral as defined in Eq. (15). The poles of its integrand are now on the real axis at ±k 0 , rather than at ±iq 0 as previously.…”

Polariton panorama

“…One such example ( Figure 5B and C) is graphene surrounded by insulating layers of hexagonal boron nitride hBN or silicon dioxide. Plasmons associated with graphene layers hybridize with phonon polaritons in proximal SiO 2 or hBN layers to form plasmon-phonon polaritons [63,64,212,213]. Hybrid polaritons at the interface of graphene with high-T c superconductors were proposed as a tool to probe Anderson-Higgs electrodynamics [214].…”

“…Panel C: calculated dispersion of the hyperbolic phonon polaritons in h-BN coupled to plasmon polaritons in the graphene layer and forming hyperbolic plasmon-phonon polaritons (HP3) and surface plasmon-phonon polaritons (SP3). Adapted from a study by Bezares et al [212]. Panel D: concept of image polaritons at the interface of hBN and a metal.…”