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

Kin Fai Mak, Jie Shan, Tony F. Heinz

Research output: Contribution to journalArticle

285 Scopus citations

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.

Original languageEnglish (US)
Article number046401
JournalPhysical Review Letters
Volume106
Issue number4
DOIs
StatePublished - Jan 25 2011

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)

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