Phonon-assisted Oscillatory Enhancement of Exciton Dynamics in Monolayer MoSe<sub>2</sub>

ORAL

Abstract

Exciton-phonon interaction plays a major role in the relaxation dynamics of photocarriers in monolayer semiconducting transition metal dichalcogenides (TMDs). Despite a few experimental studies on phonon-limited excitonic relaxation, details behind which phonon modes and how they affect the formation and relaxation of excitons are still lacking. We observe an oscillatory enhancement of neutral exciton signal in monolayer MoSe2 in photoluminescence excitation (PLE), with a period matching the M-point longitudinal acoustic phonon, LA(M). Numerical fit to the emission lineshapes also reveals the oscillatory behavior, suggesting that the presence of LA(M) phonons significantly modifies the relaxation dynamics. This is verified by our observation of oscillatory exciton lifetime in time-resolved PLE. What is unusual here is the dominating role of acoustic phonons, rather than optical phonons as commonly expected. Our theory suggests the importance of Q valleys in the dynamics of excitons, although photocarriers are predominantly localized in K valleys. Reference: Chow et al., npj 2D Mater. Appl. 1, 33 (2017).

*Supported by DoE (Basic Energy Sciences), RGC of Hong Kong, Croucher Foundation, NSF (MRSEC) and WA Clean Energy Institute.

–

Presenters

  • Colin Chow

    • Department of Physics, University of Washington - Seattle

Authors

  • Colin Chow

    • Department of Physics, University of Washington - Seattle

  • Hongyi Yu

    • Department of Physics and Center of Theoretical and Computational Physics, University of Hong Kong

  • Aaron Jones

    • Department of Physics, University of Washington - Seattle

  • John Schaibley

    • Department of Physics, University of Washington - Seattle
    • University of Arizona

  • Michael Koehler

    • Department of Materials Science and Engineering, The University of Tennessee
    • Materials Science and Engineering, The University of Tennessee
    • Department of Materials Science and Engineering, University of Tennessee

  • David Mandrus

    • Department of Materials Science and Engineering, The University of Tennessee
    • Oak Ridge National Lab
    • Oak Ridge National Laboratory
    • Department of Materials Science and Engineering, University of Tennessee
    • University of Tennessee
    • Materials Science and Technology, Oak Ridge National Laboratory
    • Materials Science and Engineering, The University of Tennessee
    • Materials Science and Engineering, University of Tennessee
    • Material Science and Technology Division, Oak Ridge National Laboratory
    • Oakridge National Laboratory
    • University of Tennessee, Knoxville
    • Univ of Tennessee, Knoxville

  • Roberto Merlin

    • Physics Department, Univ of Michigan - Ann Arbor
    • Univ of Michigan - Ann Arbor
    • Department of Physics, University of Michigan - Ann Arbor

  • Wang Yao

    • Department of Physics, University of Hong Kong
    • Hong Kong University
    • University of Hong Kong
    • The University of Hong Kong
    • Department of Physics and Center of Theoretical and Computational Physics, University of Hong Kong

  • Xiaodong Xu

    • University of Washington
    • Univ of Washington
    • Physics, Univ of Washington
    • Department of Physics, University of Washington
    • Physics, University of Washington
    • Physics, and Materials Science and Engineering, Univ of Washington
    • Department of Physics, University of Washington - Seattle