Atomic-Scale Defects Might Determine the Second Harmonic Generation from Plasmonic Graphene Nanostructures.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanophotonics

Background:

• Graphene nanoflakes exhibit unique plasmonic properties.
• Lattice imperfections can significantly influence material characteristics.
• Nonlinear optical responses are crucial for advanced photonic devices.

Purpose of the Study:

• To theoretically investigate the effect of atomic-scale lattice defects in graphene nanoflakes on their nonlinear optical response.
• To understand how defects influence second harmonic generation in graphene plasmonic nanoantennas.
• To explore the impact of single carbon atom vacancies on nonlinear hyperpolarizability.

Main Methods:

• Theoretical investigation using the many-body time-dependent density matrix approach.
• Simulation of second harmonic generation in graphene plasmonic nanoantennas with varying symmetries.
• Analysis of the influence of missing carbon atom vacancy defects.

Main Results:

• A single defect in a large graphene nanoflake can strongly impact nonlinear hyperpolarizability.
• Lattice imperfections can override inherent symmetry constraints in graphene nanoantennas.
• The observed defect-induced effects cannot be replicated using the relaxation time approximation.

Conclusions:

• Atomic scale defects play a critical role in tuning the nonlinear optical properties of graphene nanoflakes.
• Understanding defect impacts is essential for designing high-performance nonlinear graphene-based photonic devices.
• The findings necessitate advanced theoretical frameworks beyond the relaxation time approximation for accurate predictions.