Veselago lens and Klein collimator in disordered graphene

Area of Science:

• Condensed matter physics
• Materials science
• Nanotechnology

Background:

• Graphene nanoribbons exhibit unique electronic properties due to quantum confinement and relativistic effects.
• The phenomenon of Klein tunneling allows relativistic charge carriers to traverse potential barriers without reflection.
• Electrostatic gating enables the creation of tunable p-n junctions in graphene nanoribbons.

Purpose of the Study:

• To investigate electron transport through graphene nanoribbons with electrostatic gates defining p-n junctions.
• To explore the formation of Veselago lenses and Klein collimators based on the p-n interface sharpness.
• To analyze the impact of interface roughness and bulk disorder on the guiding properties of these nanoribbons.

Main Methods:

• Numerical simulations of electron transport using a third nearest neighbor tight-binding model.
• Modeling of realistic graphene nanoribbon sizes and p-n junction geometries.
• Analysis of electron beam focusing and collimation effects under varying disorder conditions.

Main Results:

• Sharp p-n interfaces facilitate Klein tunneling, leading to the formation of a Veselago lens that refocuses electron beams.
• Wider transition regions at the p-n junction act as Klein collimators, guiding electrons with near-perpendicular incidence.
• Interface roughness and bulk disorder significantly influence the guiding properties, with specific bounds identified for observing focusing effects.

Conclusions:

• The study provides critical insights into the design and experimental realization of electronic lenses and collimators in graphene nanoribbons.
• Understanding the role of disorder is essential for achieving controlled electron beam manipulation in these devices.
• The findings offer practical guidelines for fabricating graphene-based electronic optics with potential applications in future nanoelectronic devices.