Abstract
Electron correlation plays an essential role in the macroscopic quantum phenomena in the moiré heterostructure, such as antiferromagnetism and correlated insulating phases. Unlike the phenomena where the interaction involves only electrons in one layer, the interaction of distinct phases in two or more layers represents a new horizon forward, such as the one in the Kondo lattice model. Here, using interlayer excitons as a probe, we show that the interlayer interactions in heterobilayers of tungsten diselenide and molybdenum disulfide (WSe2/MoS2) can be electrically switched on and off, resulting in a layer-dependent correlated phase diagram, including single-layer, layer-selective, excitonic-insulator and layer-hybridized regions. We demonstrate that these correlated phases affect the interlayer exciton non-radiative decay pathways. These results reveal the role of strong correlation on interlayer exciton dynamics and pave the way for studying the layer-resolved strong correlation behaviour in moiré heterostructures.
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The data that support the findings of this study are available from the corresponding authors upon reasonable request.
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Acknowledgements
This work is supported by the Singapore National Research Foundation and A*STAR through their Competitive Research Program (award no. NRF-CRP22-2019-0004, award no. NRF-CRP23-2019-0002 and the Quantum Engineering Programme) and by the Singapore Ministry of Education (MOE2016-T3-1-006 (S)).
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Q.T. fabricated the devices and performed the optical measurement with the help of Z.Z. and H.C.; X.C. performed the electron diffraction and STEM measurement; K.W. and T.T. provided the high-quality BN; A.R. performed the theoretical analysis with the help of X.D. and A.H.M.; and A.R. and Q.T. analysed the data. A.R., Q.T., A.H.M. and W.G. wrote the manuscript with input from all authors. A.H.M. and W.G. supervised the project. All authors contributed to the discussion of the results.
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Extended data
Extended Data Fig. 1 Gate dependence of IX PL spectra.
Here the colour bar is the intensity. (a) PL spectra as a function of VG. The spectral jump at integer filling factors indicates the gap opening due to electron-electron correlation. (b) PL spectra as a function of . The IX energy experience Stark shift due to the out-of-plane electric field. The estimated interlayer distance is ~0.69 nm, agreeable with the previous reports8,43,47.
Extended Data Fig. 2 Steady-state interlayer exciton PL intensity vs bottom and top gate voltage from two positions in a 1L-WSe2/1L-MoS2 sample at temperature 5 K.
The distance between (a) Location 1 and (b) Location 2 is more than 1 μm.VE.
Extended Data Fig. 3 Gate dependence of IX integrated PL intensity in 1 L/1 L heterostructure.
The intensity is obtained by integrating the time-resolved PL.
Extended Data Fig. 4 Gate dependence of IX PL intensity and lifetime in 1 L/2 L heterostructure.
(a) Steady-state PL intensity vs bottom and top gate voltage at temperature 5 K. PL intensity value peaks at insulating phases with integer filling factor. The peak intensity paths do not follow straight lines. (b) Gate-dependent time-resolved PL. The label shows the VG values. Here, VE = 0V is used. (c) Lifetime vs bottom and top gate voltage. Compared to (a), there is a strong correspondence between PL lifetime and intensity. (d) VG and (e) VE dependent lifetime and integrated PL intensity. The strong correspondence between lifetime and intensity is also observed when the intensity is obtained by integrating the time-resolved PL. Peaks are observed at integer filling factors (labelled in (d)). The gate dependence of the 1 L/2 L heterostructure IX PL spectrum is given in Supplementary Fig. 7.
Extended Data Fig. 5 Gate dependence of IX PL intensity and lifetime in 1 L/3 L heterostructure.
(a) Steady-state PL intensity vs bottom and top gate voltage at temperature 5 K. PL intensity value peaks at insulating phases with integer filling factor. The peak intensity paths do not follow straight lines. (b) Gate-dependent time-resolved PL. The label shows the VG values. Here, VE = 0V is used. (c) Lifetime vs bottom and top gate voltage. Compared to (a), there is a strong correspondence between PL lifetime and intensity. (d) VG and (e) VE dependent lifetime and integrated PL intensity. The strong correspondence between lifetime and intensity is also observed when the intensity is obtained by integrating the time-resolved PL. Peaks are observed at integer filling factors (labelled in (d)). The gate dependence of the 1 L/3 L heterostructure IX PL spectrum is given in Supplementary Fig. 8.
Extended Data Fig. 6 Gate dependence of IX PL intensity and lifetime in another 1 L/1 L sample (Device 2).
(a) Gate-dependent time-resolved PL. The label shows the VG values. Here, VE = 0V is used. (b) VG and (c) VE dependent lifetime and integrated PL intensity. The strong correspondence between lifetime and intensity is also observed when the intensity is obtained by integrating the time-resolved PL.
Supplementary information
Supplementary Information
Supplementary Figs. 1–16 and Notes 1–6.
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Tan, Q., Rasmita, A., Zhang, Z. et al. Layer-dependent correlated phases in WSe2/MoS2 moiré superlattice. Nat. Mater. 22, 605–611 (2023). https://doi.org/10.1038/s41563-023-01521-4
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DOI: https://doi.org/10.1038/s41563-023-01521-4
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