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Mahan excitons in room-temperature methylammonium lead bromide perovskites.

  • Palmieri T Laboratory of Ultrafast Spectroscopy, Lausanne Centre for Ultrafast Science (LACUS), Institute of Chemistry and Chemical Engineering (ISIC), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015, Lausanne, Switzerland.
  • Baldini E Laboratory of Ultrafast Spectroscopy, Lausanne Centre for Ultrafast Science (LACUS), Institute of Chemistry and Chemical Engineering (ISIC), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015, Lausanne, Switzerland. ebaldini@mit.edu.
  • Steinhoff A Semiconductor Theory Group, Institute for Theoretical Physics, University of Bremen, Otto-Hahn-Alle 1, P.O. Box 330440, Bremen, Germany.
  • Akrap A Group of Light Fermion Spectroscopy, Department of Physics, Université de Fribourg, 3 Chemin du Musée, 1700, Fribourg, Switzerland.
  • Kollár M Laboratory of Physics of Condensed Matter, Institute of Physics (IPHYS), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015, Lausanne, Switzerland.
  • Horváth E Laboratory of Physics of Condensed Matter, Institute of Physics (IPHYS), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015, Lausanne, Switzerland.
  • Forró L Laboratory of Physics of Condensed Matter, Institute of Physics (IPHYS), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015, Lausanne, Switzerland.
  • Jahnke F Semiconductor Theory Group, Institute for Theoretical Physics, University of Bremen, Otto-Hahn-Alle 1, P.O. Box 330440, Bremen, Germany.
  • Chergui M Laboratory of Ultrafast Spectroscopy, Lausanne Centre for Ultrafast Science (LACUS), Institute of Chemistry and Chemical Engineering (ISIC), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015, Lausanne, Switzerland. majed.chergui@epfl.ch.
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  • 2020-02-14
Published in:
  • Nature communications. - 2020
General Biochemistry, Genetics and Molecular Biology
General Physics and Astronomy
General Chemistry
English In a seminal paper, Mahan predicted that excitonic bound states can still exist in a semiconductor at electron-hole densities above the insulator-to-metal Mott transition. However, no clear evidence for this exotic quasiparticle, dubbed Mahan exciton, exists to date at room temperature. In this work, we combine ultrafast broadband optical spectroscopy and advanced many-body calculations to reveal that organic-inorganic lead-bromide perovskites host Mahan excitons at room temperature. Persistence of the Wannier exciton peak and the enhancement of the above-bandgap absorption are observed at all achievable photoexcitation densities, well above the Mott density. This is supported by the solution of the semiconductor Bloch equations, which confirms that no sharp transition between the insulating and conductive phase occurs. Our results demonstrate the robustness of the bound states in a regime where exciton dissociation is otherwise expected, and offer promising perspectives in fundamental physics and in room-temperature applications involving high densities of charge carriers.
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  • English
Open access status
gold
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https://folia.unifr.ch/global/documents/189839
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