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Time-resolved ARPES Signatures and Visualization of Exciton Formation in Monolayer MoS<sub>2</sub>

ORAL

Abstract

In the study of correlations in solids, angle-resolved photoemission spectroscopy (ARPES) represents a powerful tool to capture and quantify quasi-particles and interactions throughout momentum space. Coulomb-bound electron-hole pairs (excitons) are typically studied via optical spectroscopies which, however, lack momentum resolution. We will present time-resolved ARPES (trARPES) studies of monolayer MoS2, evidencing the formation of 2D excitons in transient photoemission signatures. We studied ML MoS2 on HOPG cooled to 80 K. The sample was optically excited below the gap, followed by femtosecond ARPES probing with 22.3 eV extreme-UV pulses. Transient ARPES maps exhibit a downward dispersing band below the conduction band at K valley, in agreement with theoretically-predicted exciton spectral function. Importantly, we reveal a crossover that occurs in time from an upward to the downward dispersion, evidencing tr-ARPES visualization of exciton formation. We will discuss these dynamics along with co-existing time-dependent band dynamics and theoretical modeling. The results highlight the novel application for tr-ARPES to access excitonic quasi-particles and correlations, forging new paths to exploring many-body interactions in low-dimensional quantum materials.

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Presenters

  • Yi Lin

    Materials Sciences Division, Lawrence Berkeley National Laboratory, Lawrence Berkeley National Laboratory, Materials Science Division, Lawrence Berkeley National Laboratory

Authors

  • Yi Lin

    Materials Sciences Division, Lawrence Berkeley National Laboratory, Lawrence Berkeley National Laboratory, Materials Science Division, Lawrence Berkeley National Laboratory

  • Yang-hao Chan

    Lawrence Berkeley National Laboratory, University of California at Berkeley and Lawrence Berkeley National Laboratory, University of California, Berkeley, Department of physics, University of California at Berkeley, Berkeley, California

  • Woojoo Lee

    Physics, University of Texas at Austin, Department of Physics, The University of Texas at Austin

  • Li-Syuan Lu

    Department of Electrophysics, National Chiao Tung University

  • Zhenglu Li

    Department of Physics, University of California, Berkeley, UC Berkeley & Lawrence Berkeley National Laboratory, University of California at Berkeley, and Lawrence Berkeley National Laboratory, University of California at Berkeley and Lawrence Berkeley National Laboratory, Lawrence Berkeley National Laboratory, University of California, Berkeley, Lawrence Berkeley National Laboratory and University of California at Berkeley, Department of physics, University of California at Berkeley, Berkeley, California

  • Sung-Kwan Mo

    Lawrence Berkeley National Laboratory, Advanced Light Source, Lawrence Berkeley National Laboratory, Advanced Light Source

  • Wen-Hao Chang

    Department of Electrophysics, National Chiao Tung University, Electrophysics, National Chiao Tung University, Natl Chiao Tung Univ

  • Chih-Kang Shih

    Physics, University of Texas at Austin, University of Texas at Austin, Department of Physics, The University of Texas at Austin

  • Steven G Louie

    University of California, Berkeley, Department of Physics, University of California, Berkeley, University of California at Berkeley and Lawrence Berkeley National Laboratory, UC Berkeley & Lawrence Berkeley National Laboratory, University of California at Berkeley, and Lawrence Berkeley National Laboratory, Lawrence Berkeley National Laboratory, Department of physics, University of California at Berkeley, Berkeley, California

  • Alessandra Lanzara

    University of California, Berkeley, Department of Physics, University of California, Physics, University of California, Berkeley, Lawrence Berkeley National Laboratory, Department of Physics, University of California Berkeley, Physics, University of California Berkeley, Physics, UC Berkeley

  • Robert A Kaindl

    Materials Sciences Division, Lawrence Berkeley National Laboratory, Lawrence Berkeley National Laboratory, Department of Physics, Arizona State University, Physics, Arizona State University