Abstract
We discuss the renormalization of the polarizability of a nanoparticle in the presence of either: (1) a continuous graphene sheet; or (2) a plasmonic graphene grating, taking into account retardation effects. Our analysis demonstrates that the excitation of surface plasmon polaritons in graphene produces a large enhancement of the real and imaginary parts of the renormalized polarizability. We show that the imaginary part can be changed by a factor of up to 100 relative to its value in the absence of graphene. We also show that the resonance in the case of the grating is narrower than in the continuous sheet. In the case of the grating it is shown that the resonance can be tuned by changing the grating geometric parameters.
Highlights
The polarizability of a nanoparticle is a response function which relates the electric dipole moment produced in it to an externally applied electric field
The denominator is close to unity in both cases, so in the case of a metal nanoparticle, we have a stronger renormalization of the polarizability in the presence of a graphene sheet
In this paper we have studied the influence of two plasmonic structures on the effective polarizability of a nanoparticle made of either a metal or a polar dielectric or semiconductor
Summary
The polarizability of a nanoparticle is a response function which relates the electric dipole moment produced in it to an externally applied electric field. The imaginary part of the polarizability controls the extinction and absorption cross-sections of a nanoparticle subjected to an impinging electromagnetic field [7,8] These quantities are essential for the understanding of scattering experiments of electromagnetic radiation involving nanoparticles, either isolated or forming clusters. It is of major importance to understand how the imaginary part of the polarizability is renormalized relative to its value in a vacuum when it is near an interface, the most common setup in experiments It would be of particular relevance (from the device engineering viewpoint), if the dielectric properties of the interface, near which the nanoparticle is located, could be tuned. This would provide a route for controlling the value of the nanoparticle polarizability in real time.
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