title: Intrinsic homogeneous linewidth and broadening mechanisms of excitons in monolayer transition metal dichalcogenides.
abstract: The band-edge optical response of transition metal dichalcogenides, an emerging class of atomically thin semiconductors, is dominated by tightly bound excitons localized at the corners of the Brillouin zone (valley excitons). A fundamental yet unknown property of valley excitons in these materials is the intrinsic homogeneous linewidth, which reflects irreversible quantum dissipation arising from system (exciton) and bath (vacuum and other quasiparticles) interactions and determines the timescale during which excitons can be coherently manipulated. Here we use optical two-dimensional Fourier transform spectroscopy to measure the exciton homogeneous linewidth in monolayer tungsten diselenide (WSe2). The homogeneous linewidth is found to be nearly two orders of magnitude narrower than the inhomogeneous width at low temperatures. We evaluate quantitatively the role of exciton-exciton and exciton-phonon interactions and population relaxation as linewidth broadening mechanisms. The key insights reported here—strong many-body effects and intrinsically rapid radiative recombination—are expected to be ubiquitous in atomically thin semiconductors.
authors.affiliation: Department of Physics and Center for Complex Quantum Systems, University of Texas at Austin, Austin, Texas 78712, USA.
authors.forename: Galan
authors.initials: G
authors.lastname: Moody
authors.affiliation: Department of Physics and Center for Complex Quantum Systems, University of Texas at Austin, Austin, Texas 78712, USA.
authors.forename: Chandriker
authors.initials: C
authors.lastname: Kavir Dass
authors.affiliation: Department of Physics and Center for Complex Quantum Systems, University of Texas at Austin, Austin, Texas 78712, USA.
authors.forename: Kai
authors.initials: K
authors.lastname: Hao
authors.affiliation: Department of Automatic Control Engineering, Feng Chia University, Taichung 40724, Taiwan.
authors.forename: Chang-Hsiao
authors.initials: CH
authors.lastname: Chen
authors.affiliation: Physical Science and Engineering Division, King Abdullah University of Science &Technology (KAUST), Thuwal 23955, Saudi Arabia.
authors.forename: Lain-Jong
authors.initials: LJ
authors.lastname: Li
authors.affiliation: Department of Physics and Center for Complex Quantum Systems, University of Texas at Austin, Austin, Texas 78712, USA.
authors.forename: Akshay
authors.initials: A
authors.lastname: Singh
authors.affiliation: Department of Physics and Center for Complex Quantum Systems, University of Texas at Austin, Austin, Texas 78712, USA.
authors.forename: Kha
authors.initials: K
authors.lastname: Tran
authors.affiliation: Department of Physics, University of Washington, Seattle, Washington 98195, USA.|Department of Materials Science and Engineering, University of Washington, Seattle, Washington 98195, USA.
authors.forename: Genevieve
authors.initials: G
authors.lastname: Clark
authors.affiliation: Department of Physics, University of Washington, Seattle, Washington 98195, USA.|Department of Materials Science and Engineering, University of Washington, Seattle, Washington 98195, USA.
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Xu
authors.affiliation: Institut f. Theoretische Physik, Nitchlineare Optik und Quantenelektronik, Technische Universität Berlin, 10623 Berlin, Germany.
authors.forename: Gunnar
authors.initials: G
authors.lastname: Berghäuser
authors.affiliation: Department of Applied Physics, Chalmers University of Technology, Gothenburg, Sweden.
authors.forename: Ermin
authors.initials: E
authors.lastname: Malic
authors.affiliation: Institut f. Theoretische Physik, Nitchlineare Optik und Quantenelektronik, Technische Universität Berlin, 10623 Berlin, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Knorr
authors.affiliation: Department of Physics and Center for Complex Quantum Systems, University of Texas at Austin, Austin, Texas 78712, USA.
authors.forename: Xiaoqin
authors.initials: X
authors.lastname: Li