title: Radiatively Limited Dephasing and Exciton Dynamics in MoSe2 Monolayers Revealed with Four-Wave Mixing Microscopy.
abstract: By implementing four-wave mixing (FWM) microspectroscopy, we measure coherence and population dynamics of the exciton transitions in monolayers of MoSe2. We reveal their dephasing times T2 and radiative lifetime T1 in a subpicosecond (ps) range, approaching T2 = 2T1 and thus indicating radiatively limited dephasing at a temperature of 6 K. We elucidate the dephasing mechanisms by varying the temperature and by probing various locations on the flake exhibiting a different local disorder. At the nanosecond range, we observe the residual FWM produced by the incoherent excitons, which initially disperse toward the dark states but then relax back to the optically active states within the light cone. By introducing polarization-resolved excitation, we infer intervalley exciton dynamics, revealing an initial polarization degree of around 30%, constant during the initial subpicosecond decay, followed by the depolarization on a picosecond time scale. The FWM hyperspectral imaging reveals the doped and undoped areas of the sample, allowing us to investigate the neutral exciton, the charged one, or both transitions at the same time. In the latter, we observe the exciton-trion beating in the coherence evolution indicating their coherent coupling.
authors: Univ. Grenoble Alpes , F-38000 Grenoble, France.|CNRS, Institut Néel , "Nanophysique et Semiconducteurs" group, F-38000 Grenoble, France.
authors: Tomasz
authors: T
authors: Jakubczyk
authors: Univ. Grenoble Alpes , F-38000 Grenoble, France.|CNRS, Institut Néel , "Nanophysique et Semiconducteurs" group, F-38000 Grenoble, France.
authors: Valentin
authors: V
authors: Delmonte
authors: Laboratoire National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA-EMFL , 25 Av. des Martyrs, 38042 Grenoble, France.|Institute of Experimental Physics, Faculty of Physics, University of Warsaw , ul. Pasteura 5, 02-093 Warsaw, Poland.
authors: Maciej
authors: M
authors: Koperski
authors: Laboratoire National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA-EMFL , 25 Av. des Martyrs, 38042 Grenoble, France.
authors: Karol
authors: K
authors: Nogajewski
authors: Laboratoire National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA-EMFL , 25 Av. des Martyrs, 38042 Grenoble, France.
authors: Clément
authors: C
authors: Faugeras
authors: Cardiff University School of Physics and Astronomy , The Parade, Cardiff CF24 3AA, United Kingdom.
authors: Wolfgang
authors: W
authors: Langbein
authors: Laboratoire National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA-EMFL , 25 Av. des Martyrs, 38042 Grenoble, France.
authors: Marek
authors: M
authors: Potemski
authors: Univ. Grenoble Alpes , F-38000 Grenoble, France.|CNRS, Institut Néel , "Nanophysique et Semiconducteurs" group, F-38000 Grenoble, France.
authors: Jacek
authors: J
authors: Kasprzak