AVS 61st International Symposium & Exhibition
    2D Materials Focus Topic Wednesday Sessions
       Session 2D+AS+EM+MI+MN+NS+TF-WeA

Paper 2D+AS+EM+MI+MN+NS+TF-WeA3
Electron-Phonon Coupling and Photoluminescence in Single Layer Transition Metal Dichalcogenides

Wednesday, November 12, 2014, 3:00 pm, Room 310

Session: Properties of 2D Materials 
Presenter: Neha Nayyar, University of Central Florida
Authors: N. Nayyar, University of Central Florida
V. Turkowski, University of Central Florida
D.T. Le, University of Central Florida
T.S. Rahman, University of Central Florida
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Single layer MoS2 and other transition metal dichalcogenides have been the subject of numerous investigations because of their unusual optical, electronic and transport properties. To understand and thereby tune their photoluminescent properties, we have analyzed the role of electron-phonon interactions. Density functional perturbation theory is used to calculate the dispersion of system phonons, while electron-phonon coupling is obtained using the Eliashberg approach. Time-dependent density-functional theory based calculations using the density-matrix approach is employed to study the exciton and trion excitations which are found to appear as peaks in the absorption spectrum in the visible range with binding energy ~0.5 – 1 eV and ~0.02-0.03 eV, correspondingly. The emission peak is found to also lie in the visible spectrum and is sensitive to the value of the electron-phonon coupling, which depends on the nature and extent of doping. The position of the spectral peaks may thus be manipulated by doping. Calculations of the self-energy and spectral functions of doped systems show excitations to have 10-100 fs lifetime, which makes the system interesting for ultrafast applications. Comparison will be made of these optical properties of several single layer dichalcogenides and contact will be made with available experimental data. Work supported in part by DOE Grant No. DOE-DE-FG02-07ER46354