Topologically protected Dirac plasmons in a graphene superlattice.

Area of Science:

• Condensed Matter Physics
• Photonics
• Materials Science

Background:

• Topological optical states offer defect immunity crucial for advanced photonic applications.
• Current methods for achieving these states are often complex, bulky, or limited to microwave frequencies.
• Time-reversal symmetry breaking is a key mechanism for realizing topological optical states.

Purpose of the Study:

• To theoretically demonstrate a simple and robust method for realizing topologically protected optical states at infrared frequencies.
• To explore the potential of two-dimensional (2D) materials, specifically patterned graphene, for hosting such states.
• To investigate the role of magnetic fields in inducing nonreciprocal plasmon behavior for topological state emergence.

Main Methods:

• Theoretical modeling of a periodically patterned graphene monolayer in a magnetic field.
• Analysis of plasmon behavior and nonreciprocity at superlattice junctions in the graphene structure.
• Investigation of the emergence of topologically protected edge states and localized bulk modes.

Main Results:

• Demonstration of highly confined topologically protected optical states in infrared frequencies.
• Realization of these states in a simple 2D graphene honeycomb superlattice structure.
• Observation of substantial plasmon nonreciprocity under a moderate 2 tesla magnetic field.

Conclusions:

• A simple and robust approach for creating topologically nontrivial optical states in 2D atomic layers.
• Potential for developing fast, nanoscale, and defect-immune photonic devices.
• Graphene-based structures offer a promising platform for next-generation topological photonics.