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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Journal Article

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

MPS-Authors

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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;

/persons/resource/persons180733

Chavez Cervantes, M.
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;

/persons/resource/persons202145

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;

/persons/resource/persons133795

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;

External Resource

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

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

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eaay0761.full.pdf
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aay0761_SM.pdf
(Supplementary material), 4MB

Citation

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.

Cite as: https://hdl.handle.net/21.11116/0000-0005-EE0E-1

Abstract

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.