Collective modes of doped graphene and a standard 2DEG in a strong magnetic field: linear magneto-plasmons versus magneto-excitons

TL;DR

This paper compares the collective excitations in doped graphene and a standard 2DEG under strong magnetic fields, revealing unique linear magneto-plasmons in graphene that differ from traditional magneto-excitons.

Contribution

It provides a theoretical analysis of the particle-hole excitation spectrum in doped graphene, highlighting the presence of linear magneto-plasmons distinct from those in a standard 2DEG.

Findings

Graphene exhibits linear magneto-plasmons dispersing parallel to ω=v_F q.

Standard 2DEG shows horizontal, dispersionless magneto-excitons.

Potential detection of these modes via inelastic light scattering.

Abstract

A doped graphene layer in the integer quantum Hall regime reveals a highly unusual particle-hole excitation spectrum, which is calculated from the dynamical polarizability in the random phase approximation. We find that the elementary neutral excitations in graphene in a magnetic field are unlike those of a standard two-dimensional electron gas (2DEG): in addition to the upper-hybrid mode, the particle-hole spectrum is reorganized in linear magneto-plasmons that disperse roughly parallel to $\omega=v_F q$, instead of the usual horizontal (almost dispersionless) magneto-excitons. These modes could be detected in an inelastic light scattering experiment.