Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Article
  • Published:

Realization of the Haldane Chern insulator in a moiré lattice

Abstract

The Chern insulator displays a quantized Hall effect without Landau levels. Theoretically, this state can be realized by engineering complex next-nearest-neighbour hopping in a honeycomb lattice—the so-called Haldane model. Despite its profound effect on the field of topological physics and recent implementation in cold-atom experiments, the Haldane model has not yet been realized in solid-state materials. Here we report the experimental realization of a Haldane Chern insulator in AB-stacked MoTe2/WSe2 moiré bilayers, which form a honeycomb moiré lattice with two sublattices residing in different layers. We show that the moiré bilayer filled with two holes per unit cell is a quantum spin Hall insulator with a tunable charge gap. Under a small out-of-plane magnetic field, it becomes a Chern insulator with a finite Chern number because the Zeeman field splits the quantum spin Hall insulator into two halves with opposite valleys: one with a positive and the other with a negative moiré band gap. We also demonstrate experimental evidence of the Haldane model at zero external magnetic field by proximity coupling the moiré bilayer to a ferromagnetic insulator.

This is a preview of subscription content, access via your institution

Access options

Buy this article

Prices may be subject to local taxes which are calculated during checkout

Fig. 1: AB-stacked MoTe2/WSe2 moiré bilayer.
Fig. 2: QSH insulator at ν= 2.
Fig. 3: Magnetic-field-induced Haldane Chern insulator.
Fig. 4: Temperature dependence of the Chern insulator.
Fig. 5: Proximity-coupled CrBr3–MoTe2/WSe2 device.

Similar content being viewed by others

Data availability

All other data are available from the corresponding authors on reasonable request. Source data are provided with this paper.

References

  1. Klitzing, K. V., Dorda, G. & Pepper, M. New method for high-accuracy determination of the fine-structure constant based on quantized Hall resistance. Phys. Rev. Lett. 45, 494–497 (1980).

    Article  ADS  Google Scholar 

  2. Haldane, F. D. M. Model for a quantum Hall effect without Landau levels: condensed-matter realization of the ‘parity anomaly’. Phys. Rev. Lett. 61, 2015–2018 (1988).

    Article  MathSciNet  CAS  PubMed  ADS  Google Scholar 

  3. Chang, C.-Z. et al. Experimental observation of the quantum anomalous Hall effect in a magnetic topological insulator. Science 340, 167–170 (2013).

    Article  CAS  PubMed  ADS  Google Scholar 

  4. Sharpe, A. L. et al. Emergent ferromagnetism near three-quarters filling in twisted bilayer graphene. Science 365, 605–608 (2019).

    Article  CAS  PubMed  ADS  Google Scholar 

  5. Deng, Y. et al. Quantum anomalous Hall effect in intrinsic magnetic topological insulator MnBi2Te4. Science 367, 895–900 (2020).

    Article  CAS  PubMed  ADS  Google Scholar 

  6. Serlin, M. et al. Intrinsic quantized anomalous Hall effect in a moiré heterostructure. Science 367, 900–903 (2020).

    Article  CAS  PubMed  ADS  Google Scholar 

  7. Chen, G. et al. Tunable correlated Chern insulator and ferromagnetism in a moiré superlattice. Nature 579, 56–61 (2020).

    Article  CAS  PubMed  ADS  Google Scholar 

  8. Li, T. et al. Quantum anomalous Hall effect from intertwined moiré bands. Nature 600, 641–646 (2021).

    Article  CAS  PubMed  ADS  Google Scholar 

  9. Jotzu, G. et al. Experimental realization of the topological Haldane model with ultracold fermions. Nature 515, 237–240 (2014).

    Article  CAS  PubMed  ADS  Google Scholar 

  10. Kane, C. L. & Mele, E. J. Quantum spin Hall effect in graphene. Phys. Rev. Lett. 95, 226801 (2005).

    Article  CAS  PubMed  ADS  Google Scholar 

  11. Kane, C. L. & Mele, E. J. Z2 topological order and the quantum spin Hall effect. Phys. Rev. Lett. 95, 146802 (2005).

    Article  CAS  PubMed  ADS  Google Scholar 

  12. Hasan, M. Z. & Kane, C. L. Colloquium: topological insulators. Rev. Mod. Phys. 82, 3045–3067 (2010).

    Article  CAS  ADS  Google Scholar 

  13. Qi, X. & Zhang, S. Topological insulators and superconductors. Rev. Mod. Phys. 83, 1057–1110 (2011).

    Article  CAS  ADS  Google Scholar 

  14. Liu, C.-X., Qi, X.-L., Dai, X., Fang, Z. & Zhang, S.-C. Quantum anomalous Hall effect in Hg1-yMnyTe quantum wells. Phys. Rev. Lett. 101, 146802 (2008).

    Article  PubMed  ADS  Google Scholar 

  15. König, M. et al. Quantum spin Hall insulator state in HgTe quantum wells. Science 318, 766–770 (2007).

    Article  PubMed  ADS  Google Scholar 

  16. Knez, I., Du, R.-R. & Sullivan, G. Evidence for helical edge modes in inverted InAs/GaSb quantum wells. Phys. Rev. Lett. 107, 136603 (2011).

    Article  PubMed  ADS  Google Scholar 

  17. Fei, Z. et al. Edge conduction in monolayer WTe2. Nat. Phys. 13, 677–682 (2017).

    Article  CAS  Google Scholar 

  18. Wu, S. et al. Observation of the quantum spin Hall effect up to 100 kelvin in a monolayer crystal. Science 359, 76–79 (2018).

    Article  MathSciNet  CAS  PubMed  ADS  Google Scholar 

  19. Zhang, Y., Devakul, T. & Fu, L. Spin-textured Chern bands in AB-stacked transition metal dichalcogenide bilayers. Proc. Natl Acad. Sci. USA 118, e2112673118 (2021).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  20. Pan, H., Xie, M., Wu, F. & Das Sarma, S. Topological phases in AB-stacked MoTe2/WSe2: Z2 topological insulators, Chern insulators, and topological charge density waves. Phys. Rev. Lett. 129, 056804 (2022).

    Article  CAS  PubMed  ADS  Google Scholar 

  21. Xie, Y.-M., Zhang, C.-P., Hu, J.-X., Mak, K. F. & Law, K. T. Valley-polarized quantum anomalous Hall state in moiré MoTe2/WSe2 heterobilayers. Phys. Rev. Lett. 128, 026402 (2022).

    Article  CAS  PubMed  ADS  Google Scholar 

  22. Rademaker, L. Spin-orbit coupling in transition metal dichalcogenide heterobilayer flat bands. Phys. Rev. B 105, 195428 (2022).

    Article  CAS  ADS  Google Scholar 

  23. Devakul, T. & Fu, L. Quantum anomalous Hall effect from inverted charge transfer gap. Phys. Rev. X 12, 021031 (2022).

    CAS  Google Scholar 

  24. Katmis, F. et al. A high-temperature ferromagnetic topological insulating phase by proximity coupling. Nature 533, 513–516 (2016).

    Article  CAS  PubMed  ADS  Google Scholar 

  25. Zhao, W. et al. Magnetic proximity and nonreciprocal current switching in a monolayer WTe2 helical edge. Nat. Mater. 19, 503–507 (2020).

    Article  CAS  PubMed  ADS  Google Scholar 

  26. Wu, F., Lovorn, T., Tutuc, E. & Macdonald, A. H. Hubbard model physics in transition metal dichalcogenide moiré bands. Phys. Rev. Lett. 121, 026402 (2018).

    Article  CAS  PubMed  ADS  Google Scholar 

  27. Wu, F., Lovorn, T., Tutuc, E., Martin, I. & MacDonald, A. H. Topological insulators in twisted transition metal dichalcogenide homobilayers. Phys. Rev. Lett. 122, 086402 (2019).

    Article  CAS  PubMed  ADS  Google Scholar 

  28. Li, T. et al. Continuous Mott transition in semiconductor moiré superlattices. Nature 597, 350–354 (2021).

    Article  CAS  PubMed  ADS  Google Scholar 

  29. Andrei, E. Y. & MacDonald, A. H. Graphene bilayers with a twist. Nat. Mater. 19, 1265–1275 (2020).

    Article  CAS  PubMed  ADS  Google Scholar 

  30. Balents, L., Dean, C. R., Efetov, D. K. & Young, A. F. Superconductivity and strong correlations in moiré flat bands. Nat. Phys. 16, 725–733 (2020).

    Article  CAS  Google Scholar 

  31. Liu, J. & Dai, X. Orbital magnetic states in moiré graphene systems. Nat. Rev. Phys. 3, 367–382 (2021).

    Article  CAS  Google Scholar 

  32. Andrei, E. Y. et al. The marvels of moiré materials. Nat. Rev. Mater. 6, 201–206 (2021).

    Article  CAS  ADS  Google Scholar 

  33. Wang, L. et al. Correlated electronic phases in twisted bilayer transition metal dichalcogenides. Nat. Mater. 19, 861–866 (2020).

    Article  CAS  PubMed  ADS  Google Scholar 

  34. Ghiotto, A. et al. Quantum criticality in twisted transition metal dichalcogenides. Nature 597, 345–349 (2021).

    Article  CAS  PubMed  ADS  Google Scholar 

  35. MacDonald, A. H. Introduction to the physics of the quantum Hall regime. Preprint at arXiv.org/cond-mat/9410047 (1994).

  36. Lau, C. N., Bockrath, M. W., Mak, K. F. & Zhang, F. Reproducibility in the fabrication and physics of moiré materials. Nature 602, 41–50 (2022).

    Article  CAS  PubMed  ADS  Google Scholar 

  37. MacNeill, D. et al. Breaking of valley degeneracy by magnetic field in monolayer MoSe2. Phys. Rev. Lett. 114, 037401 (2015).

    Article  CAS  PubMed  ADS  Google Scholar 

  38. Wang, Z., Shan, J. & Mak, K. F. Valley- and spin-polarized Landau levels in monolayer WSe2. Nat. Nanotechnol. 12, 144–149 (2017).

    Article  CAS  PubMed  ADS  Google Scholar 

  39. Tao, Z. et al. Valley-coherent quantum anomalous Hall state in AB-stacked MoTe2/WSe2 bilayers. Preprint at arXiv.org/2208.07452 (2022).

  40. Kennes, D. M. et al. Moiré heterostructures as a condensed-matter quantum simulator. Nat. Phys. 17, 155–163 (2021).

    Article  CAS  Google Scholar 

  41. Wang, L. et al. One-dimensional electrical contact to a two-dimensional material. Science 342, 614–617 (2013).

    Article  CAS  PubMed  ADS  Google Scholar 

  42. Tang, Y. et al. Simulation of Hubbard model physics in WSe2/WS2 moiré superlattices. Nature 579, 353–358 (2020).

    Article  CAS  PubMed  ADS  Google Scholar 

  43. Regan, E. C. et al. Mott and generalized Wigner crystal states in WSe2/WS2 moiré superlattices. Nature 579, 359–363 (2020).

    Article  CAS  PubMed  ADS  Google Scholar 

  44. Hohenadler, M., Parisen Toldin, F., Herbut, I. F. & Assaad, F. F. Phase diagram of the Kane–Mele–Coulomb model. Phys. Rev. B 90, 085146 (2014).

    Article  ADS  Google Scholar 

  45. Liu, G. B., Shan, W. Y., Yao, Y., Yao, W. & Xiao, D. Three-band tight-binding model for monolayers of group-VIB transition metal dichalcogenides. Phys. Rev. B 88, 085433 (2013).

    Article  ADS  Google Scholar 

  46. Zhao, W. et al. Gate-tunable heavy fermions in a moiré Kondo lattice. Nature 616, 61–65 (2023).

    Article  CAS  PubMed  ADS  Google Scholar 

  47. Movva, H. C. P. et al. Density-dependent quantum Hall states and Zeeman splitting in monolayer and bilayer WSe2. Phys. Rev. Lett. 118, 247701 (2017).

    Article  PubMed  ADS  Google Scholar 

  48. Li, Y. et al. Measurement of the optical dielectric function of monolayer transition-metal dichalcogenides: MoS2, MoSe2, WS2, and WSe2. Phys. Rev. B 90, 205422 (2014).

    Article  ADS  Google Scholar 

  49. Frank, T., Högl, P., Gmitra, M., Kochan, D. & Fabian, J. Protected pseudohelical edge states in Z2-trivial proximitized graphene. Phys. Rev. Lett. 120, 156402 (2018).

    Article  CAS  PubMed  ADS  Google Scholar 

  50. Gustafsson, M. V. et al. Ambipolar Landau levels and strong band-selective carrier interactions in monolayer WSe2. Nat. Mater. 17, 411–415 (2018).

    Article  CAS  PubMed  ADS  Google Scholar 

  51. Han, Z., Li, T., Zhang, L., Sullivan, G. & Du, R.-R. Anomalous conductance oscillations in the hybridization gap of InAs/GaSb quantum wells. Phys. Rev. Lett. 123, 126803 (2019).

    Article  CAS  PubMed  ADS  Google Scholar 

  52. König, M. et al. The quantum spin Hall effect: theory and experiment. J. Phys. Soc. Jpn 77, 031007 (2008).

    Article  ADS  Google Scholar 

Download references

Acknowledgements

We thank L. Fu, Y. Zhang and A. H. MacDonald for fruitful discussions. The work at Cornell was supported by the US Department of Energy, Office of Science, Basic Energy Sciences, under award no. DE-SC0019481 (transport studies); the Air Force Office of Scientific Research under award nos. FA9550-19-1-0390 (development of moiré superlattices proximity coupled to a 2D magnet) and FA9550-20-1-0219 (magneto-optical studies); and the National Science Foundation (NSF) under award no. DMR-1807810 (analysis). The work at Cornell was also funded in part by the Gordon and Betty Moore Foundation (grant https://doi.org/10.37807/GBMF11563). The work at the University of California at Santa Barbara was primarily supported by the Army Research Office under award no. W911NF-20-2-0166 and by the Gordon and Betty Moore Foundation EPIQS programme under award no. GBMF9471. The growth of the hBN crystals was supported by the Elemental Strategy Initiative of MEXT, Japan and CREST (JPMJCR15F3), JST. We used the Cornell NanoScale Facility, an NNCI member supported by NSF grant no. NNCI-2025233. We also acknowledge support from the David and Lucille Packard Fellowship (K.F.M.), the Kavli Postdoctoral Fellowship (W.Z.) and the Swiss National Science Foundation (P.K.).

Author information

Authors and Affiliations

Authors

Contributions

W.Z., Y.Z. and L.L. fabricated the devices. W.Z., K.K., Y.Z., L.L., C.L.T. and E.R. performed the electrical measurements and analysed the data. P.K., W.Z. and Z.T. carried out the optical measurements. K.K. performed the tight-binding model calculations. K.W. and T.T. grew the bulk hBN crystals. W.Z., K.K., J.S. and K.F.M. designed the scientific objectives and oversaw the project. All authors discussed the results and commented on the manuscript.

Corresponding authors

Correspondence to Wenjin Zhao, Jie Shan or Kin Fai Mak.

Ethics declarations

Competing interests

The authors declare no competing interests.

Peer review

Peer review information

Nature Physics thanks the anonymous reviewers for their contribution to the peer review of this work.

Additional information

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Extended data

Extended Data Fig. 1 Nonlocal transport supporting the QSH insulator.

a, Nonlocal resistance \({R}_{{\rm{nl}}}\) as a function of top and bottom gate voltages at \(B=0\) and \(T=\)330 mK. The green and orange dashed lines denote, respectively, the electric field direction at fixed \(\nu =2\) and the filling factor direction at fixed \(E={E}_{c}\). b, Optical micrograph of Device 1. The top gate (TG) and bottom gate (BG) are outlined by a black and red dashed line, respectively. The scale bar is 5 \({\rm{\mu }}{\rm{m}}\). c, Schematics of the measurement geometry. The device is current (I) biased along the arrow direction. The voltage drop \({V}_{{\rm{nl}}}\) is measured at the other end of the device. \({R}_{{\rm{nl}}}\) is negligible except at \(\nu =2\). Before band inversion, \({R}_{{\rm{nl}}}\) cannot be probed appropriately because the current is practically zero; after band inversion, it grows with increasing electric field. This is consistent with the helical edge transport in a QSH insulator.

Extended Data Fig. 2 QSH effect in devices of different twist angles.

a, b, Longitudinal resistance as a function of top and bottom gate voltages of Device 3 (2-degree twisted) at T = 300 mK (a) and Device 2 (near 0-degree twisted) at T = 10 mK (b). c, Two-terminal resistance measured by adjacent contacts as a function of top and bottom gate voltages of a bilayer MoTe2/monolayer WSe2 Device 4 (near 0-degree twisted) at T = 1.6 K. d-f, Line-cuts of a-c at varying top gate voltages. The grey dashed lines mark the quantized resistance \(\frac{h}{{2e}^{2}}(\)≈12.9 kΩ). For Device 3, \({R}_{{\rm{xx}}}\) at \(\nu =2\) is the smallest right after band inversion and plateaus with further increase of the electric field. \({R}_{{\rm{xx}}}\) and \({R}_{2{\rm{p}}}\) increase continuously with electric field after band inversion for Device 2 and 4, respectively.

Extended Data Fig. 3 Magneto-transport in Device 1 at 1.6 K.

a, b, Hall resistance as a function of the top and bottom gate voltages at B = 3 T (a) and of the magnetic field and filling factor at \(E={E}_{c}\) (b). The orange dashed line in a corresponds to \(E={E}_{c}\). The green dashed line in b marks the \({R}_{{\rm{xy}}}\) maximum. We determine the slope of the dashed lines to be \({n}_{{\rm{M}}}\frac{dv}{dB}=c\frac{e}{h}\) with c = 1.1 ± 0.1. Right inset shows the magnetic-field dependence of \({R}_{{\rm{xy}}}\) along the green dashed line.

Extended Data Fig. 4 Transport under different magnetic fields for Device 2.

a-e, Hall resistance (left) and longitudinal resistance (right) at 10 mK (lattice temperature) as a function of the top and bottom gate voltages. The magnetic field is 0.5 T (a), 1 T (b), 2 T (c, same as Fig. 3a of the main text), 3 T (d), 4 T (e).

Extended Data Fig. 5 High-magnetic-field transport.

a, \({R}_{{\rm{xy}}}\) (top) and \({R}_{{\rm{xx}}}\) (bottom) of Device 2 as a function of top and bottom gate voltages at B = 11.8 T and T = 10 \({\rm{m}}\)K (lattice temperature). The Landau levels (identified by the resistance minimum) are indexed. b, c, \({R}_{{\rm{xy}}}\) (top) and \({R}_{{\rm{xx}}}\) (bottom) as a function of filling factor and magnetic field at E = 0.435 V/nm (before band inversion, b) and at E = 0.463 V/nm (near band inversion, c). The dashed lines show the Landau fan. The white oval shows the Landau level that disperses with a negative slope.

Extended Data Fig. 6 The electric-field span of the Chern state as a function of magnetic field.

a, \({R}_{{\rm{xy}}}\) and \({R}_{{\rm{xx}}}\) of Device 2 at \(\nu =2\) and T = 10 mK (lattice temperature) as a function of electric field. The data are extracted from Extended Data Fig. 4. b, The electric-field span, \(\Delta E\), of the Chern state as a function of magnetic field. For each magnetic field, the electric-field dependence of \({R}_{{\rm{xy}}}\) is fit with a Gaussian function and \(\Delta E\) is determined as half of the variance. The error bars are one-sigma uncertainty of \(\Delta E\) in the Gaussian function fitting. The red dashed line is the best fit to \(\Delta E=\sqrt{{a}^{2}+{({bB})}^{2}}\) with fitting parameters a = 2.2 ± 0.1 mV/nm and b = 2.0 ± 0.1 mV/nmT.

Extended Data Fig. 7 Tight-binding model calculations.

a-c, Band structure simulated using the tight-binding Hamiltonian described in Methods. Red and blue curves denote the spin-up and spin-down bands, respectively. Under zero magnetic field (a), the bands are inverted at both the \({\rm{K}}\) and \({{\rm{K}}}^{{\prime} }\) valleys. This is a QSH insulator (QSHI). Under a small magnetic field (b), the bands in the \({{\rm{K}}}^{{\prime} }\) valley cross at one momentum. Under a sufficiently high magnetic field (c), the gap changes sign for the \({{\rm{K}}}^{{\prime} }\) valley; this is a Chern insulator. d, The direct band gap near the \({\rm{K}}/{{\rm{K}}}^{{\prime} }\) valleys as a function of the Zeeman energy and the sublattice/interlayer potential difference. The three symbols mark the phase space for which the electronic band structure is represented in a-c, respectively.

Extended Data Fig. 8 RC and MCD spectrum in AB-stacked MoTe2/WSe2 proximity-coupled to bilayer CrBr3.

a, Schematic side view of a dual-gated device of AB-stacked MoTe2/WSe2 moiré bilayer proximity-coupled to bilayer CrBr3. b, Bottom gate voltage dependence of the RC spectrum near the WSe2 intralayer exciton resonance for Vtg = −3.6 V. The strong feature near 1.67 eV is the neutral exciton resonance. It evolves into much weaker charged exciton resonances for \({V}_{{\rm{bg}}} < -1{\rm{V}}\). c, Bottom gate voltage dependence of the spontaneous MCD spectrum near the WSe2 exciton resonance at Vtg = −3.9 V. At this value of \({V}_{{\rm{tg}}}\), the WSe2 layer is doped for the entire range of bottom gate voltage. The MCD reported in the main text is spectrally integrated over the spectral window given by the black dashed lines (1.661–1.666 eV), which covers the attractive polaron resonance of WSe2.

Source data

Source Data Fig. 2

Statistical source data for Fig. 2.

Source Data Fig. 3

Statistical source data for Fig. 3.

Source Data Fig. 4

Statistical source data for Fig. 4.

Source Data Fig. 5

Statistical source data for Fig. 5.

Rights and permissions

Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Zhao, W., Kang, K., Zhang, Y. et al. Realization of the Haldane Chern insulator in a moiré lattice. Nat. Phys. 20, 275–280 (2024). https://doi.org/10.1038/s41567-023-02284-0

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/s41567-023-02284-0

This article is cited by

Search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing