Ultrafast non-excitonic valley Hall effect in MoS2/WTe2 heterobilayers

Jekwan Lee, Wonhyeok Heo, Myungjun Cha, Kenji Watanabe, Takashi Taniguchi, Jehyun Kim, Soonyoung Cha, Dohun Kim, Moon-Ho Jo and Hyunyong Choi ()
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Jekwan Lee: Seoul National University
Wonhyeok Heo: Seoul National University
Myungjun Cha: Seoul National University
Kenji Watanabe: National Institute for Materials Science
Takashi Taniguchi: National Institute for Materials Science
Jehyun Kim: Seoul National University
Soonyoung Cha: Institute for Basic Science
Dohun Kim: Seoul National University
Moon-Ho Jo: Institute for Basic Science
Hyunyong Choi: Seoul National University

Nature Communications, 2021, vol. 12, issue 1, 1-6

Abstract: Abstract The valley Hall effect (VHE) in two-dimensional (2D) van der Waals (vdW) crystals is a promising approach to study the valley pseudospin. Most experiments so far have used bound electron-hole pairs (excitons) through local photoexcitation. However, the valley depolarization of such excitons is fast, so that several challenges remain to be resolved. We address this issue by exploiting a unipolar VHE using a heterobilayer made of monolayer MoS2/WTe2 to exhibit a long valley-polarized lifetime due to the absence of electron-hole exchange interaction. The unipolar VHE is manifested by reduced photoluminescence at the MoS2 A exciton energy. Furthermore, we provide quantitative information on the time-dependent valley Hall dynamics by performing the spatially-resolved ultrafast Kerr-rotation microscopy; we find that the valley-polarized electrons persist for more than 4 nanoseconds and the valley Hall mobility exceeds 4.49 × 103 cm2/Vs, which is orders of magnitude larger than previous reports.

Date: 2021
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DOI: 10.1038/s41467-021-21013-w

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