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Inverted valley polarization in optically excited transition metal dichalcogenides

Author

Listed:
  • Gunnar Berghäuser

    (Chalmers University of Technology)

  • Ivan Bernal-Villamil

    (Chalmers University of Technology)

  • Robert Schmidt

    (University of Münster)

  • Robert Schneider

    (University of Münster)

  • Iris Niehues

    (University of Münster)

  • Paul Erhart

    (Chalmers University of Technology)

  • Steffen Michaelis de Vasconcellos

    (University of Münster)

  • Rudolf Bratschitsch

    (University of Münster)

  • Andreas Knorr

    (Technische Universität Berlin)

  • Ermin Malic

    (Chalmers University of Technology)

Abstract

Large spin–orbit coupling in combination with circular dichroism allows access to spin-polarized and valley-polarized states in a controlled way in transition metal dichalcogenides. The promising application in spin-valleytronics devices requires a thorough understanding of intervalley coupling mechanisms, which determine the lifetime of spin and valley polarizations. Here we present a joint theory–experiment study shedding light on the Dexter-like intervalley coupling. We reveal that this mechanism couples A and B excitonic states in different valleys, giving rise to an efficient intervalley transfer of coherent exciton populations. We demonstrate that the valley polarization vanishes and is even inverted for A excitons, when the B exciton is resonantly excited and vice versa. Our theoretical findings are supported by energy-resolved and valley-resolved pump-probe experiments and also provide an explanation for the recently measured up-conversion in photoluminescence. The gained insights might help to develop strategies to overcome the intrinsic limit for spin and valley polarizations.

Suggested Citation

  • Gunnar Berghäuser & Ivan Bernal-Villamil & Robert Schmidt & Robert Schneider & Iris Niehues & Paul Erhart & Steffen Michaelis de Vasconcellos & Rudolf Bratschitsch & Andreas Knorr & Ermin Malic, 2018. "Inverted valley polarization in optically excited transition metal dichalcogenides," Nature Communications, Nature, vol. 9(1), pages 1-8, December.
    • Handle: RePEc:nat:natcom:v:9:y:2018:i:1:d:10.1038_s41467-018-03354-1
    DOI: 10.1038/s41467-018-03354-1
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    Cited by:

    1. Jinjae Kim & Jiwon Park & Hyojin Choi & Taeho Kim & Soonyoung Cha & Yewon Lee & Kenji Watanabe & Takashi Taniguchi & Jonghwan Kim & Moon-Ho Jo & Hyunyong Choi, 2024. "Correlation-driven nonequilibrium exciton site transition in a WSe2/WS2 moiré supercell," Nature Communications, Nature, vol. 15(1), pages 1-9, December.

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