Plasmon dynamics in graphene

TL;DR

This study investigates plasmon dynamics in mono- and bi-layer graphene using terahertz metrology, revealing that electron interactions and wave function structure significantly influence collective oscillations, with deviations from non-interacting models.

Contribution

It demonstrates that the pseudospin structure of Dirac fermions affects plasmon behavior, highlighting the role of interactions in collective excitations in graphene.

Findings

Measured Drude weight exceeds non-interacting predictions

Enhancement of Drude weight increases at lower carrier densities

Interactions and wave function structure influence plasmon dynamics

Abstract

Plasmon are collective oscillations of mobile electrons with dynamics controlled by their charge stiffness("Drude weight"). Using terahertz spacetime metrology, we probe Plasmon dynamics of mono- and bi-layer graphene. In both systems, the experimentally measured Drude weight systematically exceeds the prediction based on non-interacting electronic system. The relative enhancement increases as the carrier density decreases. We attribute the observed deviation to the interplay of interactions and wave function structure of the Dirac fermions in multi-layer graphene. Our results establish that pseudospin structure of the single-particle electronic wave function can directly influence collective excitations, with implications that extend beyond graphene to a broad class of quantum materials.