Ultrafast Extreme-UV ARPES Studies of Electron and Exciton Dynamics in the Transition-Metal Dichalcogenide MoSe$_{\mathrm{\mathbf{2}}}$

ORAL

Abstract

Semiconducting transition-metal dichalcogenides exhibit intriguing physical properties, including a large spin-orbit splitting, strong Coulomb interactions, and optical access to the valley degree of freedom. Important insight into the fundamental microscopic interactions can be obtained via studies of the momentum-resolved non-equilibrium carrier dynamics. Here, we present time-resolved ARPES investigations of MoSe$_{\mathrm{2}}$ crystals using high-repetition-rate extreme-UV femtosecond pulses, enabling us to track the electron dynamics within the full Brillouin zone with high sensitivity. After resonantly driving excitons at the K-point, the transient ARPES signals reveal a rapid time evolution governed by inter-valley scattering to the conduction band minimum on a 70-fs time scale. We will discuss the momentum-space dynamics as well as distinct temporal and spectral features that provide evidence for the first observation of excitons via angle-resolved photoemission spectroscopy.

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Authors

  • Jan H. Buss

    MSD, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA

  • Frederic Joucken

    MSD, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA

  • Yiming Xu

    MSD, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA

  • Julian Maklar

    MSD, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA

  • He Wang

    MSD, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA

  • Changhyun Ko

    Dept. of Materials Science and Engineering, University of California, Berkeley, CA, 94720, USA

  • Sefaattin Tongay

    School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe, AZ, 85287, USA, Arizona State University

  • Jinqiao Wu

    Dept. of Materials Science and Engineering, University of California, Berkeley, CA, 94720, USA

  • Robert A. Kaindl

    MSD, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA