Theory of interaction-induced renormalization of Drude weight and plasmon frequency in chiral multilayer graphene

TL;DR

This paper develops a quantum kinetic theory to understand how electron-electron interactions in doped multilayer graphene influence optical properties, revealing a chirality-dependent enhancement of Drude weight and plasmon frequency.

Contribution

It introduces a pseudospin Bloch equation framework to describe interaction effects on optical conductivity in multilayer graphene, highlighting the role of chirality.

Findings

Interaction induces a significant increase in Drude weight.

Plasmon frequency is strongly enhanced by electron-electron interactions.

Higher-energy bands contribute notably to renormalization effects.

Abstract

We develop a theory for the optical conductivity of doped multilayer graphene including the effects of electron-electron interactions. Applying the quantum kinetic formalism, we formulate a set of pseudospin Bloch equations that governs the dynamics of the nonequilibrium density matrix driven by an external \emph{a.c.} electric field under the influence of Coulomb interactions. These equations reveal a dynamical mechanism that couples the Drude and interband responses arising from the chirality of pseudospin textures in multilayer graphene systems. We demonstrate that this results in an interaction-induced enhancement of the Drude weight and plasmon frequency strongly dependent on the pseudospin winding number. Using bilayer graphene as an example, we also study the influence of higher-energy bands and find that they contribute considerable renormalization effects not captured by a low-energy two-band description. We argue that this enhancement of Drude weight and plasmon frequency occurs generally in materials characterized by electronic chirality.