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The interlayer coupling is emerging as a new parameter for tuning the physical properties of two- dimensional (2D) van der Waals materials. When two identical semiconductor monolayers are stacked with a twist angle, the periodic interlayer coupling modulation due to the moire ́ superlattice may endow exotic physical phenomena, such as moire ́ excitons and correlated electronic phases. To gain insight into these new phenomena, it is crucial to unveil the underlying coupling between atomic layers. Recently, the rhombohedral-stacked transition metal dichalcogenide (TMD) bilayer has attracted significant interest because of the emergence of an out-of-plane polarization from nonferroelectric monolayer constituents. However, as a key parameter responsible for the physical properties, the interlayer coupling and its relationship with ferroelectricity remain elusive. Here, we probe the asymmetric interlayer coupling between the conduction band of one layer and the valence band from the other layer in a 3R-MoS2 bilayer, which can be understood as a result of a layer-dependent Berry phase winding. By performing optical spectroscopy in a dual-gated device, we show an effective type-II band alignment exists at K points in the 3R-MoS2 bilayer. Furthermore, by unraveling various contributions to the band offset, we quantitatively determine the asymmetric interlayer coupling and spontaneous polarization in 3R-MoS2. Our results unveil the physical nature of stacking-induced ferroelectricity in TMD homostructures and have important implications for moire ́ physics in 2D semiconductors.

Rights:

• Creative Commons BY Attribution 4.0 International
  

Keyword: Interlayer coupling, ferroelectricity, 3R-MoS2

Date published: 2022-10-14

Publisher: American Physical Society (APS)

Journal:

• Physical Review X (ISSN: 21603308) vol. 12 issue. 4 041005

Funding:

• Natural Sciences and Engineering Research Council of Canada
• Canada Foundation for Innovation
• Canada First Research Excellence Fund
• Canada Research Chairs
• New Frontiers in Research Fund
• Max Planck–UBC–UTokyo Centre for Quantum Materials

Manuscript type: Publisher's version (Version of record)

MDR DOI:

First published URL: https://doi.org/10.1103/physrevx.12.041005

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Updated at: 2025-02-28 16:30:26 +0900

Published on MDR: 2025-02-28 16:30:27 +0900