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Many-body excitonic picture of ultrafast photoexcited dynamics in van der Waals heterostructures

ORAL

Abstract

Ultrafast optical dynamics in transition metal dichalcogenide (TMD) heterobilayers is of fundamental scientific interest and importance for potential optoelectronics applications. Despite much progress in experiment measurements, their theoretical interpretations remain basically at an insufficient level. A full understanding of this phenomenon requires accurate descriptions of both nonequilibrium dynamics and many-body excitonic physics. In this work, based on our first-principles time-dependent adiabatic GW approach [1], we propose a new many-body excitonic mechanism for the dynamics of converting photoexcited intralayer to interlayer excitations and the associated ultrafast optical responses in TMD heterobilayers. We find that nonlocal couplings between the intralayer and interlayer exciton states (i.e., two-particle correlated electron-hole pairs) dominate the ultrafast optical response, conceptually different from the previously-believed single-particle picture of independent charge transfer between layers. Strong excitonic effects (electron-hole interactions) are discovered to be the main driving force for real-time evolution of the photo-excitations, and play a crucial role on the ultrafast pump-probe optical responses by enhancing the probed optical signal by over one-order of magnitude with a rising time of about 300 femtoseconds, in good agreement with experiments.

[1] Y.-H. Chan, D. Y. Qiu, F. H. da Jornada, and S. G. Louie, Proc. Natl. Acad. Sci. U.S.A. 118, e1906938118 (2021)

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Presenters

  • CHEN HU

    Lawrence Berkeley National Laboratory

Authors

  • CHEN HU

    Lawrence Berkeley National Laboratory

  • Mit H Naik

    University of California, Berkeley, University of California at Berkeley and Lawrence Berkeley National Lab, University of California at Berkeley; Lawrence Berkeley National Lab

  • Yang-hao Chan

    Academia Sinica, Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan, Institute of Atomic and Molecular Sciences, Academia Sinica, Lawrence Berkeley National Laboratory

  • Steven G Louie

    University of California at Berkeley, University of California, Berkeley, University Of California, Berkeley, University of California at Berkeley and Lawrence Berkeley National Lab, University of California at Berkeley; Lawrence Berkeley National Lab, UC Berkeley, University of California at Berkeley, and Lawrence Berkeley National Laboratory, UC berkeley, Lawrence Berkeley National Laboratory, Physics Department, UC Berkeley and Lawrence Berkeley National Lab, Department of Physics, University of California at Berkeley and Materials Sciences Division, Lawrence Berkeley National Laboratory, LBNL & UC Berkeley