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Revealing the strong coupling of atomic motion to interlayer excitons through photocurrent imaging at room temperature.

ORAL

Abstract

In atomically thin van der Waals crystals photoexcited excitons are expected to be delocalized over many atomic sites, weakening the electron-phonon coupling strength. Surprisingly, we show that a heterostructure composed of stacked layers exhibits interlayer excitons that are strongly coupled to atomic vibrational motion. To overcome the small oscillator strength of interlayer excitons, we use photocurrent measurements for their high sensitivity and relatively large quantum efficiency. Using Multi-Parameter Dynamic Photoresponse Microscopy on heterostructures made of monolayer MoSe2 and bilayer WSe2 encapsulated with hBN, we isolate the signal from the interlayer exciton under precise charge neutrality conditions. We vary the voltage across the material interface while maintaining charge neutrality, thus tuning the potential energy landscape of the interlayer exciton. This results in photoconductance oscillations with a period of 30 meV, the energy of the dominant phonon mode. Interestingly, even as the interlayer exciton exhibits signatures of localization and strong coupling to atomic motion, the large interlayer photocurrent measured in the heterojunction means that the electrons and holes that make up the interlayer exciton are delocalized and move freely in the MoSe2/WSe2.

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Presenters

  • Trevor Arp

    Department of Physics, University of California, Santa Barbara, University of California, Riverside

Authors

  • Trevor Arp

    Department of Physics, University of California, Santa Barbara, University of California, Riverside

  • Fatemeh Barati

    New York Univ NYU, Center for Quantum Phenomena, Department of Physics, New York University, Department of Physics, New York University, University of California, Riverside

  • Shanshan Su

    Department of Electrical and Computer Engineering, University of California, Riverside, University of California, Riverside

  • Roger Lake

    University of California, Riverside, Department of Electrical and Computer Engineering, University of California, Riverside, CA, USA., Department of Electrical and Computer Engineering, University of California, Riverside

  • Justin Song

    Nanyang Technological University, Division of Physics and Applied Physics, Nanyang Technological University, Division of Physics & Applied Physics, Nanyang Technological University, Singapore, nanyang technological university

  • Mark Rudner

    Niels Bohr International Academy and the Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, Niels Bohr Institute, University of Copenhagen, Niels Bohr Institute, Niels Bohr Institute / University of Copenhagen

  • Vivek M Aji

    University of California, Riverside, Department of Physics and Astronomy, University of California, Riverside

  • Nathaniel Monroe Gabor

    University of California, Riverside, Department of Physics and Astronomy, University of California, Riverside