Ultrafast Spectroscopy of Exciton and Exciton Dynamics in Few and Monolayer Flakes of WS$_{\mathrm{2}}$.

ORAL

Abstract

Single layer of Transitional metal dichalcogenides (MX$_{\mathrm{2}})$ are 2D semiconductor that has a direct band gap in visible spectrum and possesses a strong spin-orbit interaction along with broken inversion symmetry in crystal structure. Thus they have possible application in optoelectronic devices, photovoltaics and photodetection, molecular sensing, 'valleytronics', and flexible transparent electronics. Tungsten Disulphide (WS$_{\mathrm{2}})$, one of the member of MX$_{\mathrm{2}}$ family, has a direct band gap of 2.2 eV and a large valley splitting of about 0.4 eV. This leads to the existence of two distinct and direct excitons A and B. Here, we present a detailed study of exciton states and their decay mechanisms in mono and few layer WS$_{\mathrm{2}}$ using femto-second transient absorption spectroscopy. We report a new peak in its differential absorption spectra at 3.01\textpm 0.1 eV whose origin in k space is under further investigation. The exponential fitting of decay curve of the exciton A reveals three time components as 1.7\textpm 0.3 ps, 33.5\textpm 10 ps and 670\textpm 15 ps, most likely corresponding to carrier-carrier scattering, carrier-phonon scattering, and radiative relaxation respectively.

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Authors

  • Sudiksha Khadka

    Ohio University

  • Scott Cushing

    National Radio Astronomy Observatory, Jodrell Bank Centre for Astrophysics, New York University Abu Dhabi, Naval Research Laboratory, CSIRO Astronomy and Space Sciences, George Mason University, ASTRON, NASA Goddard Space Flight Center, University of Wisconsin-Milwaukee,, Station de radioastronomie de Nancay, Columbia Astrophysics Laboratory, Max-Planck-Institut fur Physik, West Virginia Univ, West Virginia University, Lehigh University, Fraunhofer Institute for Physical Measurement Techniques, Department of Microsystems Engineering (IMTEK), Pennsylvania State University, Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506, USA, Massachusetts Institute of Technology, University of Minnesota, Pennsylvania State Univ, University of Maryland, Towson University, Department of Physics, Villanova University, University of Virginia, Boston University, Univ of Maryland-College Park, Harvard University, The Pennsylvania State Unversity, University of Wisconsin-Madison, McMaster University, California State University - Long Beach, National Chiao Tung University, National Chiao Tung University, Taiwan, Ohio University, University of Rennes, UMR CNRS 6251, Rennes, France, University of Bordeaux, UMR 5804, Floirac, France, University of Bordeaux, UMR 5255, Talence, France, Sandia National laboratories, Livermore, CA, Department of Chemistry, West Virginia University, Morgantwon, WV, The Pennsylvania State University, University of Toronto, Departamento de F\'isica, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago, Chile, Cinvestav-Unidad Queretaro, Queretaro-76230, Mexico, Department of Physics and Astronomy, West Virginia University, Morgantown, WV-26505-6315, USA, The University of Arizona, TU Dortmund, Dortmund, Naval Air Warfare Center - Aircraft Division

  • Scott Cushing

    National Radio Astronomy Observatory, Jodrell Bank Centre for Astrophysics, New York University Abu Dhabi, Naval Research Laboratory, CSIRO Astronomy and Space Sciences, George Mason University, ASTRON, NASA Goddard Space Flight Center, University of Wisconsin-Milwaukee,, Station de radioastronomie de Nancay, Columbia Astrophysics Laboratory, Max-Planck-Institut fur Physik, West Virginia Univ, West Virginia University, Lehigh University, Fraunhofer Institute for Physical Measurement Techniques, Department of Microsystems Engineering (IMTEK), Pennsylvania State University, Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506, USA, Massachusetts Institute of Technology, University of Minnesota, Pennsylvania State Univ, University of Maryland, Towson University, Department of Physics, Villanova University, University of Virginia, Boston University, Univ of Maryland-College Park, Harvard University, The Pennsylvania State Unversity, University of Wisconsin-Madison, McMaster University, California State University - Long Beach, National Chiao Tung University, National Chiao Tung University, Taiwan, Ohio University, University of Rennes, UMR CNRS 6251, Rennes, France, University of Bordeaux, UMR 5804, Floirac, France, University of Bordeaux, UMR 5255, Talence, France, Sandia National laboratories, Livermore, CA, Department of Chemistry, West Virginia University, Morgantwon, WV, The Pennsylvania State University, University of Toronto, Departamento de F\'isica, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago, Chile, Cinvestav-Unidad Queretaro, Queretaro-76230, Mexico, Department of Physics and Astronomy, West Virginia University, Morgantown, WV-26505-6315, USA, The University of Arizona, TU Dortmund, Dortmund, Naval Air Warfare Center - Aircraft Division

  • Scott Cushing

    National Radio Astronomy Observatory, Jodrell Bank Centre for Astrophysics, New York University Abu Dhabi, Naval Research Laboratory, CSIRO Astronomy and Space Sciences, George Mason University, ASTRON, NASA Goddard Space Flight Center, University of Wisconsin-Milwaukee,, Station de radioastronomie de Nancay, Columbia Astrophysics Laboratory, Max-Planck-Institut fur Physik, West Virginia Univ, West Virginia University, Lehigh University, Fraunhofer Institute for Physical Measurement Techniques, Department of Microsystems Engineering (IMTEK), Pennsylvania State University, Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506, USA, Massachusetts Institute of Technology, University of Minnesota, Pennsylvania State Univ, University of Maryland, Towson University, Department of Physics, Villanova University, University of Virginia, Boston University, Univ of Maryland-College Park, Harvard University, The Pennsylvania State Unversity, University of Wisconsin-Madison, McMaster University, California State University - Long Beach, National Chiao Tung University, National Chiao Tung University, Taiwan, Ohio University, University of Rennes, UMR CNRS 6251, Rennes, France, University of Bordeaux, UMR 5804, Floirac, France, University of Bordeaux, UMR 5255, Talence, France, Sandia National laboratories, Livermore, CA, Department of Chemistry, West Virginia University, Morgantwon, WV, The Pennsylvania State University, University of Toronto, Departamento de F\'isica, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago, Chile, Cinvestav-Unidad Queretaro, Queretaro-76230, Mexico, Department of Physics and Astronomy, West Virginia University, Morgantown, WV-26505-6315, USA, The University of Arizona, TU Dortmund, Dortmund, Naval Air Warfare Center - Aircraft Division

  • Scott Cushing

    National Radio Astronomy Observatory, Jodrell Bank Centre for Astrophysics, New York University Abu Dhabi, Naval Research Laboratory, CSIRO Astronomy and Space Sciences, George Mason University, ASTRON, NASA Goddard Space Flight Center, University of Wisconsin-Milwaukee,, Station de radioastronomie de Nancay, Columbia Astrophysics Laboratory, Max-Planck-Institut fur Physik, West Virginia Univ, West Virginia University, Lehigh University, Fraunhofer Institute for Physical Measurement Techniques, Department of Microsystems Engineering (IMTEK), Pennsylvania State University, Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506, USA, Massachusetts Institute of Technology, University of Minnesota, Pennsylvania State Univ, University of Maryland, Towson University, Department of Physics, Villanova University, University of Virginia, Boston University, Univ of Maryland-College Park, Harvard University, The Pennsylvania State Unversity, University of Wisconsin-Madison, McMaster University, California State University - Long Beach, National Chiao Tung University, National Chiao Tung University, Taiwan, Ohio University, University of Rennes, UMR CNRS 6251, Rennes, France, University of Bordeaux, UMR 5804, Floirac, France, University of Bordeaux, UMR 5255, Talence, France, Sandia National laboratories, Livermore, CA, Department of Chemistry, West Virginia University, Morgantwon, WV, The Pennsylvania State University, University of Toronto, Departamento de F\'isica, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago, Chile, Cinvestav-Unidad Queretaro, Queretaro-76230, Mexico, Department of Physics and Astronomy, West Virginia University, Morgantown, WV-26505-6315, USA, The University of Arizona, TU Dortmund, Dortmund, Naval Air Warfare Center - Aircraft Division

  • Scott Cushing

    National Radio Astronomy Observatory, Jodrell Bank Centre for Astrophysics, New York University Abu Dhabi, Naval Research Laboratory, CSIRO Astronomy and Space Sciences, George Mason University, ASTRON, NASA Goddard Space Flight Center, University of Wisconsin-Milwaukee,, Station de radioastronomie de Nancay, Columbia Astrophysics Laboratory, Max-Planck-Institut fur Physik, West Virginia Univ, West Virginia University, Lehigh University, Fraunhofer Institute for Physical Measurement Techniques, Department of Microsystems Engineering (IMTEK), Pennsylvania State University, Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506, USA, Massachusetts Institute of Technology, University of Minnesota, Pennsylvania State Univ, University of Maryland, Towson University, Department of Physics, Villanova University, University of Virginia, Boston University, Univ of Maryland-College Park, Harvard University, The Pennsylvania State Unversity, University of Wisconsin-Madison, McMaster University, California State University - Long Beach, National Chiao Tung University, National Chiao Tung University, Taiwan, Ohio University, University of Rennes, UMR CNRS 6251, Rennes, France, University of Bordeaux, UMR 5804, Floirac, France, University of Bordeaux, UMR 5255, Talence, France, Sandia National laboratories, Livermore, CA, Department of Chemistry, West Virginia University, Morgantwon, WV, The Pennsylvania State University, University of Toronto, Departamento de F\'isica, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago, Chile, Cinvestav-Unidad Queretaro, Queretaro-76230, Mexico, Department of Physics and Astronomy, West Virginia University, Morgantown, WV-26505-6315, USA, The University of Arizona, TU Dortmund, Dortmund, Naval Air Warfare Center - Aircraft Division