Direct evidence for efficient ultrafast charge separation in epitaxial WS2
/graphene heterostructures

Aeschlimann, S.; Rossi, A.; Chavez Cervantes, M.; Krause, R.; Arnoldi, B.; Stadtmüller, B.; Aeschlimann, M.; Forti, S.; Fabbri, F.; Coletti, C.; Gierz, I.

doi:10.1126/sciadv.aay0761

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Direct evidence for efficient ultrafast charge separation in epitaxial WS₂/graphene heterostructures

MPG-Autoren

Aeschlimann, S.
Ultrafast Electron Dynamics, Condensed Matter Dynamics Department, Max Planck Institute for the Structure and Dynamics of Matter, Max Planck Society;
Center for Free Electron Laser Science;
University of Regensburg, Institute for Experimental and Applied Physics;

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Chavez Cervantes, M.
Center for Free Electron Laser Science;
International Max Planck Research School for Ultrafast Imaging & Structural Dynamics (IMPRS-UFAST), Max Planck Institute for the Structure and Dynamics of Matter, Max Planck Society;

Krause, R.
Ultrafast Electron Dynamics, Condensed Matter Dynamics Department, Max Planck Institute for the Structure and Dynamics of Matter, Max Planck Society;
Center for Free Electron Laser Science;
University of Regensburg, Institute for Experimental and Applied Physics;

Fabbri, F.
NEST, Istituto Nanoscienze, CNR and Scuola Normale Superiore;
International Max Planck Research School for Ultrafast Imaging & Structural Dynamics (IMPRS-UFAST), Max Planck Institute for the Structure and Dynamics of Matter, Max Planck Society;
University of Kaiserslautern, Department of Physics and Research Center OPTIMAS;

Gierz, I.
Ultrafast Electron Dynamics, Condensed Matter Dynamics Department, Max Planck Institute for the Structure and Dynamics of Matter, Max Planck Society;
Center for Free Electron Laser Science;
University of Regensburg, Institute for Experimental and Applied Physics;

Externe Ressourcen

https://arxiv.org/abs/1904.01379
(Preprint)

https://dx.doi.org/10.1126/sciadv.aay0761
(Verlagsversion)

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eaay0761.full.pdf
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Zitation

Aeschlimann, S., Rossi, A., Chavez Cervantes, M., Krause, R., Arnoldi, B., Stadtmüller, B., et al. (2020). Direct evidence for efficient ultrafast charge separation in epitaxial WS₂/graphene heterostructures. Science Advances, 6(20): eaay0761. doi:10.1126/sciadv.aay0761.

Zitierlink: https://hdl.handle.net/21.11116/0000-0006-6604-3

Zusammenfassung

We use time- and angle-resolved photoemission spectroscopy (tr-ARPES) to investigate ultrafast charge transfer in an epitaxial heterostructure made of monolayer WS₂ and graphene. This heterostructure combines the benefits of a direct-gap semiconductor with strong spin-orbit coupling and strong light-matter interaction with those of a semimetal hosting massless carriers with extremely high mobility and long spin lifetimes. We find that, after photoexcitation at resonance to the A-exciton in WS₂, the photoexcited holes rapidly transfer into the graphene layer while the photoexcited electrons remain in the WS₂ layer. The resulting charge-separated transient state is found to have a lifetime of ∼1 ps. We attribute our findings to differences in scattering phase space caused by the relative alignment of WS₂ and graphene bands as revealed by high-resolution ARPES. In combination with spin-selective optical excitation, the investigated WS₂/graphene heterostructure might provide a platform for efficient optical spin injection into graphene.