Friction force on slow charges moving over supported graphene

Area of Science:

• Condensed Matter Physics
• Materials Science
• Surface Science

Background:

• Graphene's unique electronic properties make it a promising material for advanced electronic devices.
• Understanding the dielectric interactions between graphene and substrates is essential for device performance.
• Previous models often simplified substrate dynamics, limiting predictive accuracy.

Purpose of the Study:

• To develop a theoretical model for the dielectric coupling between a 2D graphene layer and a 3D substrate.
• To investigate the role of substrate's dynamic response on low-frequency excitations and stopping force on charges above graphene.
• To analyze experimental data to validate the model and understand damping effects.

Main Methods:

• Theoretical modeling using polarization function in random phase approximation for graphene.
• Employing a non-local surface response function for the semi-infinite substrate.
• Comparing theoretical dielectric loss with experimental High-Resolution Electron Energy Loss Spectroscopy (HREELS) data.
• Calculating friction coefficient for charges moving over graphene on metallic substrates.

Main Results:

• The dynamic response of the substrate significantly influences the stopping force on charges.
• Hybridization between graphene's pi plasmon and substrate's phonon excitations was observed.
• The model revealed the importance of phonon excitations in insulating substrates.
• Local field corrections and specific damping rates in graphene had minimal impact compared to substrate effects.

Conclusions:

• The theoretical model accurately describes graphene-substrate dielectric coupling and charge stopping force.
• Substrate phonon excitations play a critical role in the energy loss mechanisms.
• The study highlights the importance of considering substrate dynamics for predicting graphene-based device behavior.