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説明:

We identify an optical excitation mechanism that can transfer a valley polarization from photo-excited electron-hole pairs to free charge carriers in twisted WSe2/MoSe2 heterobilayers. For small twist angles, the valley lifetimes of these charge carriers are surprisingly short, despite the occurrence of interlayer excitons with their presumably long recombination and polarization lifetimes. For large twist angles, we measure an increase in both the valley polarization and its respective lifetime by more than two orders of magnitude. Interestingly, in such devices we observe an interlayer transfer of valley polarization from the WSe2 layer into the MoSe2 layer. This mechanism enables the creation of a photo-induced valley polarization of free charge carriers in MoSe2, which amplitude scales with the gate-induced charge carrier density. This is in contrast to monolayer MoSe2, where such a gate-tunable valley polarization cannot be achieved. By combining time-resolved Kerr rotation, photoluminesence and angle-resolved photoemission spectroscopy measurements with first principles calcula- tions, we show that these findings can be explained by twist angle dependent interlayer scattering mechanisms involving the Q- and Γ-valleys.

権利情報:

• Creative Commons BY Attribution 4.0 International
  

キーワード: Valley-polarized excitons, interlayer transfer, WSe2/MoSe2 heterobilayers

刊行年月日: 2023-08-22

出版者: Springer Science and Business Media LLC

掲載誌:

• npj 2D Materials and Applications (ISSN: 23977132) vol. 7 issue. 1 58

研究助成金:

原稿種別: 出版者版 (Version of record)

MDR DOI:

公開URL: https://doi.org/10.1038/s41699-023-00420-1

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更新時刻: 2025-02-23 22:48:06 +0900

MDRでの公開時刻: 2025-02-23 22:48:06 +0900