# Interacting Electrons in Graphene: Fermi Velocity Renormalization and Optical Response

## TL;DR

This paper presents a parameter-free Hartree-Fock model for electrons in graphene that accurately predicts Fermi velocity renormalization and optical response, validated by quantum Monte Carlo simulations.

## Contribution

The authors develop a novel Hartree-Fock theory for graphene that uses a topological invariant, enabling parameter-free predictions of electronic properties.

## Key findings

- Agreement with experimental Fermi velocity data
- Derived explicit optical conductivity expression
- Quantum Monte Carlo results agree with mean-field predictions

## Abstract

We have developed a Hartree-Fock theory for electrons on a honeycomb lattice aiming to solve a long-standing problem of the Fermi velocity renormalization in graphene. Our model employs no fitting parameters (like an unknown band cutoff) but relies on a topological invariant (crystal structure function) that makes the Hartree-Fock sublattice spinor independent of the electron-electron interaction. Agreement with the experimental data is obtained assuming static self-screening including local field effects. As an application of the model, we derive an explicit expression for the optical conductivity and discuss the renormalization of the Drude weight. The optical conductivity is also obtained via precise quantum Monte Carlo calculations which compares well to our mean-field approach.