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Moiré enhanced charge density wave state in twisted 1T-TiTe2/1T-TiSe2 heterostructures

Abstract

Nanoscale periodic moiré patterns, for example those formed at the interface of a twisted bilayer of two-dimensional materials, provide opportunities for engineering the electronic properties of van der Waals heterostructures1,2,3,4,5,6,7,8,9,10,11. In this work, we synthesized the epitaxial heterostructure of 1T-TiTe2/1T-TiSe2 with various twist angles using molecular beam epitaxy and investigated the moiré pattern induced/enhanced charge density wave (CDW) states with scanning tunnelling microscopy. When the twist angle is near zero degrees, 2 × 2 CDW domains are formed in 1T-TiTe2, separated by 1 × 1 normal state domains, and trapped in the moiré pattern. The formation of the moiré-trapped CDW state is ascribed to the local strain variation due to atomic reconstruction. Furthermore, this CDW state persists at room temperature, suggesting its potential for future CDW-based applications. Such moiré-trapped CDW patterns were not observed at larger twist angles. Our study paves the way for constructing metallic twist van der Waals bilayers and tuning many-body effects via moiré engineering.

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Fig. 1: Evolution of the moiré pattern with twist angle for 1T-TiTe2/1T-TiSe2.
Fig. 2: Strong CDW state confined in moiré pattern at twisted angle near 0°.
Fig. 3: Distribution of the strain field in the moiré pattern near a 0° twist angle.
Fig. 4: DFT calculation of the distribution of the height and strain field near a 0° twist angle.

Data availability

The data supporting the findings of this study are available from the corresponding authors upon reasonable request.

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Acknowledgements

This work was financially supported by the National Natural Science Foundation of China. W.-M.Z., L.Z., Q.-Y.L., Q.-W.W., L.-G.D., J.-G.H. and S.-C.L. acknowledge the National Natural Science Foundation of China (grant nos 11774149 and 11790311). Z.N. and S.M. acknowledge the National Natural Science Foundation of China (grant nos 91850120, 11774328 and 11934003) and the Chinese Academy of Sciences (XDB330301).

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Contributions

S.-C.L. conceived the project and designed the experiments. W.-M.Z. and L.Z. grew the epitaxial TiTe2/TiSe2 heterostructures and performed STM characterizations with the assistance of Q.-Y.L., Q.-W.W., L.-G.D. and J.-G.H.; S.-C.L. supervised the MBE growth and STM characterization. Z.N. performed the DFT calculations under the supervision of L.X. and S.M.; W.-M.Z., L.Z. and S.-C.L. wrote the manuscript with input and comments from all the authors.

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Correspondence to Sheng Meng or Shao-Chun Li.

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Peer review information Nature Materials thanks Jonas Bekaert and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Information

Supplementary Figs. 1–16, Notes 1–4 and refs. 1–3.

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Zhao, WM., Zhu, L., Nie, Z. et al. Moiré enhanced charge density wave state in twisted 1T-TiTe2/1T-TiSe2 heterostructures. Nat. Mater. 21, 284–289 (2022). https://doi.org/10.1038/s41563-021-01167-0

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  • DOI: https://doi.org/10.1038/s41563-021-01167-0

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