Seeing Many-Body Effects in Single- and Few-Layer Graphene: Observation of Two-Dimensional Saddle-Point Excitons

Abstract

Significant excitonic effects were observed in graphene by measuring its optical conductivity in a broad spectral range including the two-dimensional pi-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 red-shifted 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.

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Document Details

Document Type
Technical Report
Publication Date
Jan 01, 2010
Accession Number
ADA534735

Entities

People

  • Jie Shan
  • Kin Fai Mak
  • Tony Heinz

Organizations

  • Columbia University

Tags

Communities of Interest

  • Advanced Electronics

DTIC Thesaurus Topics

  • Band Structures
  • Carbon Nanotubes
  • Conductivity
  • Density Functional Theory
  • Electrical Engineering
  • Electron Holes
  • Energy Bands
  • Excitons
  • Experimental Data
  • First Principles Calculations
  • Graphene
  • Graphitic Materials
  • Materials
  • Materials Laboratories
  • Physical Properties
  • Quasiparticles
  • Two Dimensional

Fields of Study

  • Physics

Readers

  • Quantum Dot Semiconductor Device Photonics and Graphene Optoelectronic Materials and THz Physics.

Technology Areas

  • Microelectronics
  • Microelectronics - Graphene