Tuning quantum nonlocal effects in graphene plasmonics.

Area of Science:

• Condensed Matter Physics
• Quantum Mechanics
• Materials Science

Background:

• Electron systems exhibit unique responses to rapidly changing electrodynamic fields, characterized by spatial nonlocality.
• Standard probes using gradually varying fields often miss subtle electronic structure details.
• Graphene plasmons offer a unique platform due to their extremely slow propagation velocities.

Purpose of the Study:

• To probe the nonlocal response of the graphene electron liquid using graphene plasmons.
• To investigate quantum effects in electron systems that are not observable with conventional methods.
• To provide a new experimental approach for determining the full spatiotemporal response of electron systems.

Main Methods:

• Utilizing near-field imaging experiments.
• Employing graphene plasmons propagating at velocities near the electron Fermi velocity.
• Comparing experimental results with the quantum description of massless Dirac electrons.

Main Results:

• Experimental results showed a parameter-free match with the theoretical quantum description.
• Identified three key nonlocal quantum effects: single-particle velocity matching, interaction-enhanced Fermi velocity, and interaction-reduced compressibility.
• Demonstrated the capability of the experimental approach to capture complex electronic behaviors.

Conclusions:

• The study successfully probes nonlocal quantum effects in graphene's electron liquid.
• The findings validate the quantum mechanical description of massless Dirac electrons.
• The developed experimental method offers a powerful tool for characterizing electron system dynamics.