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Title: Exciton–exciton annihilation and biexciton stimulated emission in graphene nanoribbons

Graphene nanoribbons display extraordinary optical properties due to one-dimensional quantum-confinement, such as width-dependent bandgap and strong electron–hole interactions, responsible for the formation of excitons with extremely high binding energies. Here we use femtosecond transient absorption spectroscopy to explore the ultrafast optical properties of ultranarrow, structurally well-defined graphene nanoribbons as a function of the excitation fluence, and the impact of enhanced Coulomb interaction on their excited states dynamics. We show that in the high-excitation regime biexcitons are formed by nonlinear exciton–exciton annihilation, and that they radiatively recombine via stimulated emission. We obtain a biexciton binding energy of ≈250meV, in very good agreement with theoretical results from quantum Monte Carlo simulations. As a result, these observations pave the way for the application of graphene nanoribbons in photonics and optoelectronics.
Authors:
 [1] ;  [2] ;  [2] ;  [3] ;  [4] ;  [4] ;  [4] ;  [5] ;  [6] ;  [7] ;  [4] ;  [8]
  1. Politecnico di Milano, Milano (Italy); Univ. of Cambridge, Cambridge (United Kingdom)
  2. Istituto di Fotonica e Nanotecnologie, Milano (Italy)
  3. Politecnico di Milano, Milano (Italy)
  4. Max Planck Institute for Polymer Research, Mainz (Germany)
  5. Univ. of Graz, Graz (Austria)
  6. Univ. di Modena e Reggio Emilia, Modena (Italy); Istituto Nanoscience, Modena (Italy)
  7. Istituto Nanoscience, Modena (Italy)
  8. Politecnico di Milano, Milano (Italy); Istituto di Fotonica e Nanotecnologie, Milano (Italy)
Publication Date:
OSTI Identifier:
1255251
Grant/Contract Number:
SC0012704
Type:
Accepted Manuscript
Journal Name:
Nature Communications
Additional Journal Information:
Journal Volume: 7; Journal ID: ISSN 2041-1723
Publisher:
Nature Publishing Group
Research Org:
Brookhaven Science Associates, LLC, Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 77 NANOSCIENCE AND NANOTECHNOLOGY