Mahan excitons in room-temperature methylammonium lead bromide perovskites

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...

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Published in:Nature communications Vol. 11; no. 1; pp. 850 - 8
Main Authors: Palmieri, Tania, Baldini, Edoardo, Steinhoff, Alexander, Akrap, Ana, Kollár, Márton, Horváth, Endre, Forró, László, Jahnke, Frank, Chergui, Majed
Format: Journal Article
Language:English
Published: London Nature Publishing Group UK 12.02.2020
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Subjects:
639/624/400/584
639/766/119/1000
639/766/119/2795
639/766/119/995
Broadband
Carrier density
Charge density
Current carriers
Energy
Equilibrium
Excitons
Holes (electron deficiencies)
Humanities and Social Sciences
Laboratories
Many body problem
multidisciplinary
Optics
Perovskites
Photoexcitation
Physics
Room temperature
Science
Science (multidisciplinary)
Semiconductors
Single crystals
Spectroscopy
ISSN:2041-1723, 2041-1723
Online Access:Get full text
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Summary: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. The Mahan exciton, exotic quasiparticle predicted in 1967, had never been found in room temperature semiconductors. With ultrafast optics and many-body theory, Palmieri et al. show that methylammonium lead bromide perovskites are ideal platforms to unveil Mahan exciton physics at room temperature.
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ISSN:2041-1723
2041-1723
DOI:10.1038/s41467-020-14683-5