Dirac charge dynamics in graphene by infrared spectroscopy

TL;DR

This study uses infrared spectromicroscopy to investigate charge dynamics in graphene, confirming key Dirac fermion properties and revealing many-body interaction effects that cause deviations from idealized models.

Contribution

It provides detailed IR spectroscopic evidence of Dirac charge dynamics in graphene and uncovers many-body interactions affecting quasiparticle behavior.

Findings

Verification of Dirac fermion characteristics in graphene

Observation of deviations from linear energy dispersion

Evidence of many-body interactions influencing electronic response

Abstract

A remarkable manifestation of the quantum character of electrons in matter is offered by graphene, a single atomic layer of graphite. Unlike conventional solids where electrons are described with the Schrodinger equation, electronic excitations in graphene are governed by the Dirac Hamiltonian. Some of the intriguing electronic properties of graphene, such as massless Dirac quasiparticles with linear energy-momentum dispersion, have been confirmed by recent observations. Here we report an infrared (IR) spectromicroscopy study of charge dynamics in graphene integrated in gated devices. Our measurements verify the expected characteristics of graphene and, owing to the previously unattainable accuracy of IR experiments, also uncover significant departures of the quasiparticle dynamics from predictions made for Dirac fermions in idealized, free standing graphene. Several observations, including a marked deviation of the energy bands from the simple linear dispersion, point to the relevance of many body interactions to the rather exotic electromagnetic response in graphene.