Surface plasmon engineering in graphene functionalized with organic molecules: a multiscale theoretical investigation

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Graphene supports deep subwavelength surface plasmons at terahertz (THz) frequencies, offering low energy loss and strong field localization.
• Graphene's electronic properties are locally tunable via gating or molecular adsorption, enabling gradient index profiles.
• Local tuning of graphene opens possibilities for flexible control and manipulation of surface plasmon propagation.

Purpose of the Study:

• To explore the potential of functionalizing graphene with organic molecules for creating tunable plasmonic metasurfaces.
• To demonstrate the realization of arbitrary gradient effective refractive index profiles on graphene.
• To design and analyze an ultrathin broadband THz plasmonic lens as a proof-of-concept.

Main Methods:

• A multiscale theoretical approach combining first-principles electronic structure calculations and finite-difference time-domain (FDTD) simulations.
• Coupling of simulation methods via graphene's surface conductivity.
• Patterning two types of organic molecules on graphene to engineer specific doping profiles.

Main Results:

• Demonstrated realization of plasmonic metasurfaces with any desired gradient effective refractive index profile by patterning organic molecules on graphene.
• Showcased the ability to manipulate surface plasmon beams according to the engineered index profile.
• Designed and analyzed an ultrathin broadband THz plasmonic lens, validating the concept.

Conclusions:

• Functionalized graphene offers a versatile platform for creating advanced plasmonic devices with tailored properties.
• The proposed method allows for sophisticated control over surface plasmon propagation, surpassing limitations of traditional metamaterials.
• This approach paves the way for diverse plasmonic applications in the terahertz regime.