title: Optical Coherence in Atomic-Monolayer Transition-Metal Dichalcogenides Limited by Electron-Phonon Interactions.
abstract: We systematically investigate the excitonic dephasing of three representative transition-metal dichalcogenides, namely, MoS_{2}, MoSe_{2}, and WSe_{2} atomic monolayer thick and bulk crystals, in order to gain a proper understanding of the factors that determine the optical coherence in these materials. Coherent nonlinear optical spectroscopy and temperature dependent absorption, combined with theoretical calculations of the phonon spectra, indicate electron-phonon interactions, to be the limiting factor. Surprisingly, the excitonic dephasing, differs only slightly between atomic monolayers and high quality bulk crystals, which indicates that material imperfections are not the limiting factor in atomically thin monolayer samples. The temperature dependence of the electronic band gap and the excitonic linewidth combined with "ab initio" calculations of the phonon energies and the phonon density of states reveal a strong interaction with the E' and E" phonon modes.
authors.affiliation: Department of Physics, University of South Florida, 4202 East Fowler Ave., Tampa, Florida 33620 USA.
authors.forename: P
authors.initials: P
authors.lastname: Dey
authors.affiliation: Department of Physics, University of South Florida, 4202 East Fowler Ave., Tampa, Florida 33620 USA.
authors.forename: J
authors.initials: J
authors.lastname: Paul
authors.affiliation: Department of Physics, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
authors.forename: Z
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Department of Physics, University of South Florida, 4202 East Fowler Ave., Tampa, Florida 33620 USA.
authors.forename: C E
authors.initials: CE
authors.lastname: Stevens
authors.affiliation: Department of Physics, University of South Florida, 4202 East Fowler Ave., Tampa, Florida 33620 USA.
authors.forename: C
authors.initials: C
authors.lastname: Liu
authors.affiliation: Physics Department, West Virginia University, Morgantown West Virginia, 26506-6315, USA.
authors.forename: A H
authors.initials: AH
authors.lastname: Romero
authors.affiliation: Department of Physics, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
authors.forename: J
authors.initials: J
authors.lastname: Shan
authors.affiliation: Department of Physics, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA.
authors.forename: D J
authors.initials: DJ
authors.lastname: Hilton
authors.affiliation: Department of Physics, University of South Florida, 4202 East Fowler Ave., Tampa, Florida 33620 USA.
authors.forename: D
authors.initials: D
authors.lastname: Karaiskaj