André Souto; Rui M. S. Pereira; Jaime E. Santos; Nuno Peres; Mikhail Vasilevskiy
https://www.spiedigitallibrary.org/conference-proceedings-of-spie/10453/104530V/Electromagnetic-properties-of-a-monolayer-of-polarisable-particles-deposited-on/10.1117/12.2271960.pdf?SSO=1
Interesting plasmonic effects can arise from the
combination of small polarisable particles with graphene, related to surface
plasmon-polaritons (SPPs) supported by the latter in the terahertz (THz)
spectral range. The electromagnetic coupling between graphene SPPs and dipole
moments of nanoparticles (NPs) deposited on top of it gives rise to optical
properties that aren’t present in the individual components of this system. The
NPs’ polarisability is renormalized due to the electromagnetic back action of the
SPPs which are excited in graphene when an external propagating electromagnetic
wave impinges on the particle. Moreover, beyond the usual dipole-dipole
interaction, an indirect particle-particle coupling arises via polarisation
charges induced on the graphene-covered interface by each particle – this
indirect coupling oscillates with the interparticle distance. We derived
coupled-dipole equations taking into account all these effects, allowing us to
calculate an effective optical conductivity of the particles’ monolayer. One of
the G+NPs system’s unique properties is a collective polariton mode, causing a
considerable enhancement of the THz radiation absorption in graphene, while the
reflection drops to nearly zero for a broad range of angles of incidence. The
frequency of this resonant mode can be adjusted by changing the Fermi energy in
graphene via electrostatic gating and therefore it can be used for electrically
controlled reflection and transmission of THz radiation
