Ultrafast non-radiative dynamics of atomically thin MoSe<sub>2</sub> [electronic resource].
- Washington, D.C. : United States. Dept. of Energy. Office of Basic Energy Sciences, 2017. and Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy
- Physical Description:
- Article numbers 1,745 : digital, PDF file
- Additional Creators:
- SLAC National Accelerator Laboratory, United States. Department of Energy. Office of Basic Energy Sciences, National Science Foundation (U.S.), and United States. Department of Energy. Office of Scientific and Technical Information
- Restrictions on Access:
- Free-to-read Unrestricted online access
- Non-radiative energy dissipation in photoexcited materials and resulting atomic dynamics provide a promising pathway to induce structural phase transitions in two-dimensional materials. However, these dynamics have not been explored in detail thus far because of incomplete understanding of interaction between the electronic and atomic degrees of freedom, and a lack of direct experimental methods to quantify real-time atomic motion and lattice temperature. Here, we explore the ultrafast conversion of photoenergy to lattice vibrations in a model bi-layered semiconductor, molybdenum diselenide, MoSe<sub>2</sub>. Specifically, we characterize sub-picosecond lattice dynamics initiated by the optical excitation of electronic charge carriers in the high electron-hole plasma density regime. Our results focuses on the first ten picosecond dynamics subsequent to photoexcitation before the onset of heat transfer to the substrate, which occurs on a ~100 picosecond time scale. Photoinduced atomic motion is probed by measuring the time dependent Bragg diffraction of a delayed mega-electronvolt femtosecond electron beam. Transient lattice temperatures are characterized through measurement of Bragg peak intensities and calculation of the Debye-Waller factor (DWF). These measurements show a sub-picosecond decay of Bragg diffraction and a correspondingly rapid rise in lattice temperatures. We estimate a high quantum yield for the conversion of excited charge carrier energy to lattice motion under our experimental conditions, indicative of a strong electron-phonon interaction. First principles nonadiabatic quantum molecular dynamics simulations (NAQMD) on electronically excited MoSe<sub>2</sub> bilayers reproduce the observed picosecond-scale increase in lattice temperature and ultrafast conversion of photoenergy to lattice vibrations. Calculation of excited-state phonon dispersion curves suggests that softened vibrational modes in the excited state are involved in efficient and rapid energy transfer between the electronic system and the lattice.
- Published through SciTech Connect., 10/17/2017., Nature Communications 8 1 ISSN 2041-1723 AM, and Ming -Fu Lin; Vidya Kochat; Aravind Krishnamoorthy; Lindsay Bassman; Clemens Weninger; Qiang Zheng; Xiang Zhang; Amey Apte; Chandra Sekhar Tiwary; Xiaozhe Shen; Renkai Li; Rajiv Kalia; Pulickel Ajayan; Aiichiro Nakano; Priya Vashishta; Fyuki Shimojo; Xijie Wang; David M. Fritz; Uwe Bergmann.
- Funding Information:
- AC02-76SF00515, SC00014607, AC02-05CH11231, and ACI-1548562
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