Skip to content Skip to navigation

Seeing many-body effects in single- and few-layer graphene: observation of two-dimensional saddle-point excitons.

TitleSeeing many-body effects in single- and few-layer graphene: observation of two-dimensional saddle-point excitons.
Publication TypeJournal Article
Year of Publication2011
AuthorsMak, KFai, Shan, J, Heinz, TF
JournalPhys Rev Lett
Volume106
Issue4
Pagination046401
Date Published2011 Jan 28
ISSN1079-7114
Abstract

Significant excitonic effects were observed in graphene by measuring its optical conductivity in a broad spectral range including the two-dimensional π-band saddle-point singularities in the electronic structure. The strong electron-hole interactions manifest themselves in an asymmetric resonance peaked at 4.62 eV, which is redshifted by nearly 600 meV from the value predicted by ab initio GW calculations for the band-to-band transitions. The observed excitonic resonance is explained within a phenomenological model as a Fano interference of a strongly coupled excitonic state and a band continuum. Our experiment also showed a weak dependence of the excitonic resonance in few-layer graphene on layer thickness. This result reflects the effective cancellation of the increasingly screened repulsive electron-electron (e-e) and attractive electron-hole (e-h) interactions.

DOI10.1103/PhysRevLett.106.046401
Alternate JournalPhys. Rev. Lett.
PubMed ID21405342