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; Hyunyong Choi

doi:10.1038/s41467-021-21013-w

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, Hyunyong Choi

Department of Electrical and Electronic Engineering

Research output: Contribution to journal › Article › peer-review

1 Citation (Scopus)

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.

Original language	English
Article number	1635
Journal	Nature communications
Volume	12
Issue number	1
DOIs	https://doi.org/10.1038/s41467-021-21013-w
Publication status	Published - 2021 Dec 1

Bibliographical note

Funding Information:
J.L., W.H., M.C., and H.C. were supported by the National Research Foundation of Korea (NRF) through the government of Korea (MSIP) (Grant NRF-2018R1A2A1A05079060, NRF-2020M3F3A2A03082472), Creative Materials Discovery Program (Grant 2017M3D1A1040828), Scalable Quantum Computer Technology Platform Center (Grant 2019R1A5A1027055), and the Institute for Basic Science (IBS), Korea under Project code IBS-R014-G1-2018-A1. Part of this study has been performed using facilities at IBS Center for Correlated Electron Systems, Seoul National University.

Publisher Copyright:
© 2021, The Author(s).

All Science Journal Classification (ASJC) codes

Chemistry(all)
Biochemistry, Genetics and Molecular Biology(all)
Physics and Astronomy(all)

Access to Document

10.1038/s41467-021-21013-w

Cite this

@article{31314ac0dff54ffba93092d6f78483ce,

title = "Ultrafast non-excitonic valley Hall effect in MoS2/WTe2 heterobilayers",

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.",

author = "Jekwan Lee and Wonhyeok Heo and Myungjun Cha and Kenji Watanabe and Takashi Taniguchi and Jehyun Kim and Soonyoung Cha and Dohun Kim and Jo, {Moon Ho} and Hyunyong Choi",

note = "Funding Information: J.L., W.H., M.C., and H.C. were supported by the National Research Foundation of Korea (NRF) through the government of Korea (MSIP) (Grant NRF-2018R1A2A1A05079060, NRF-2020M3F3A2A03082472), Creative Materials Discovery Program (Grant 2017M3D1A1040828), Scalable Quantum Computer Technology Platform Center (Grant 2019R1A5A1027055), and the Institute for Basic Science (IBS), Korea under Project code IBS-R014-G1-2018-A1. Part of this study has been performed using facilities at IBS Center for Correlated Electron Systems, Seoul National University. Publisher Copyright: {\textcopyright} 2021, The Author(s).",

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doi = "10.1038/s41467-021-21013-w",

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T1 - Ultrafast non-excitonic valley Hall effect in MoS2/WTe2 heterobilayers

AU - Lee, Jekwan

AU - Heo, Wonhyeok

AU - Cha, Myungjun

AU - Watanabe, Kenji

AU - Taniguchi, Takashi

AU - Kim, Jehyun

AU - Cha, Soonyoung

AU - Kim, Dohun

AU - Jo, Moon Ho

AU - Choi, Hyunyong

N1 - Funding Information: J.L., W.H., M.C., and H.C. were supported by the National Research Foundation of Korea (NRF) through the government of Korea (MSIP) (Grant NRF-2018R1A2A1A05079060, NRF-2020M3F3A2A03082472), Creative Materials Discovery Program (Grant 2017M3D1A1040828), Scalable Quantum Computer Technology Platform Center (Grant 2019R1A5A1027055), and the Institute for Basic Science (IBS), Korea under Project code IBS-R014-G1-2018-A1. Part of this study has been performed using facilities at IBS Center for Correlated Electron Systems, Seoul National University. Publisher Copyright: © 2021, The Author(s).

PY - 2021/12/1

Y1 - 2021/12/1

N2 - 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.

AB - 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.

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