Direct imaging of valley-polarized excitons in 2D semiconductors

ORAL

Abstract

The monolayer transition-metal dichalcogenides (TMDCs) have been attractive for the applications of valleytronics since excitonic states with valley degree of freedom can be manipulated through circularly polarized light. However, with the complex landscape of exciton species in TMDCs involving spin- or momentum- forbidden dark excitons, the valley depolarization dynamics still lack clear understanding. Such measurements require direct access to the momentum and energy coordinate of constituent electrons and holes, but few experimental techniques provide such information. Meanwhile, time- and angle- resolved photoemission spectroscopy (TR-ARPES) has become a powerful tool to study excitons of 2D semiconductors directly in energy-momentum space [1–4]. In this talk, we will discuss our latest momentum-resolved study on the valley-polarized excitons in monolayer WS2 using TR-ARPES.

[1] J. Madéo et al., Directly Visualizing the Momentum-Forbidden Dark Excitons and Their Dynamics in Atomically Thin Semiconductors, Science 370, 1199 (2020).

[2] M. K. L. Man et al., Experimental Measurement of the Intrinsic Excitonic Wave Function, Science Advances 7, eabg0192 (2021).

[3] O. Karni et al., Structure of the Moiré Exciton Captured by Imaging Its Electron and Hole, Nature 603, 247 (2022).

[4] D. Schmitt et al., Formation of Moiré Interlayer Excitons in Space and Time, Nature 608, 499 (2022).

* *This work was supported in part by JSPS Kakenhi grant number 21H01020. Funding was also provided in part by the Femtosecond Spectroscopy Unit of the Okinawa Institute of Science and Technology Graduate University. We thank the OIST engineering support section for their support.

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Presenters

  • Xing Zhu

    Okinawa Institute of Science and Technology

Authors

  • Xing Zhu

    Okinawa Institute of Science and Technology

  • David R Bacon

    Okinawa Institute of Science and Technology

  • Vivek Pareek

    Okinawa Institute of Science and Technology, Okinawa Institute of Science & Technology

  • Kenji Watanabe

    National Institute for Materials Science, NIMS, Research Center for Electronic and Optical Materials, National Institute for Materials Science, Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan, National Institute for Material Science

  • Takashi Taniguchi

    Kyoto Univ, National Institute for Materials Science, Research Center for Materials Nanoarchitectonics, Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, National Institute for Materials Sciences, NIMS, International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan, National Institute for Material Science, International Center for Materials Nanoarchitectonics, NIMS, Japan, International Center for Materials Nanoarchitectonics, Tsukuba, National Institue for Materials Science, Kyoto University, National Institute of Materials Science, International Center for Materials Nanoarchitectonics and National Institute for Materials Science

  • Michael. K. L. Man

    Okinawa Institute of Science and Technology

  • Julien Madéo

    Okinawa Institute of Science and Technology

  • Keshav M Dani

    Okinawa Institute of Science and Technology, Okinawa Institute of Science & Technology