Strength of effective Coulomb interactions in graphene and graphite

TL;DR

This paper calculates the effective Coulomb interactions in graphene and graphite from first principles, revealing the strength of on-site and nearest-neighbor interactions and their implications for electronic phases.

Contribution

It provides first-principles calculations of frequency-dependent Coulomb interactions in graphene and graphite, highlighting the significance of non-local terms and dielectric properties.

Findings

On-site Coulomb interaction U_00 = 9.3 eV in graphene.

Nearest-neighbor Coulomb interaction U_01 = 5.5 eV.

Graphite's dielectric constant b = 2.5 matches experiments.

Abstract

To obtain an effective many-body model of graphene and related materials from first principles we calculate the partially screened frequency dependent Coulomb interaction. In graphene, the effective on-site (Hubbard) interaction is U_00 = 9.3 eV in close vicinity to the critical value separating conducting graphene from an insulating phase emphasizing the importance of non-local Coulomb terms. The nearest-neighbor Coulomb interaction strength is computed to U_01 = 5.5 eV. In the long wavelength limit, we find the effective background dielectric constant of graphite to be \epsilon = 2.5 in very good agreement with experiment.