Polarization of graphene in a strong magnetic field beyond the Dirac cone approximation

TL;DR

This paper investigates the excitation spectrum of graphene under strong magnetic fields using a full tight-binding model, revealing complex behaviors beyond traditional approximations, including effects of interactions, disorder, and temperature.

Contribution

It extends the analysis of graphene's polarization spectrum beyond the Dirac cone approximation by incorporating a full π-band model and electron-electron interactions.

Findings

Landau level quantization validity range studied

Non-trivial spectrum quantization near Van Hove singularity

Disorder and temperature effects on absorption peaks analyzed

Abstract

In this paper we study the excitation spectrum of graphene in a strong magnetic field, beyond the Dirac cone approximation. The dynamical polarizability is obtained using a full $\pi$-band tight-binding model where the effect of the magnetic field is accounted for by means of the Peierls substitution. The effect of electron-electron interaction is considered within the random phase approximation, from which we obtain the dressed polarization function and the dielectric function. The range of validity of the Landau level quantization within the continuum approximation is studied, as well as the non-trivial quantization of the spectrum around the Van Hove singularity. We further discuss the effect of disorder, which leads to a smearing of the absorption peaks, and temperature, which activates additional inter-Landau level transitions induced by the Fermi distribution function.