Moiré superlattices formed from transition metal dichalcogenides support a variety of quantum electronic phases that are highly tunable using applied electromagnetic fields. While the valley degree of freedom affects optoelectronic properties in the constituent transition metal dichalcogenides, it has yet to be fully explored in moiré systems. Here we establish twisted double-bilayer WSe2 as an experimental platform to study electronic correlations within Γ-valley moiré bands. Through local and global electronic compressibility measurements, we identify charge-ordered phases at multiple integer and fractional moiré fillings. By measuring the magnetic field dependence of their energy gaps and the chemical potential upon doping, we reveal spin-polarized ground states with spin-polaron quasiparticle excitations. In addition, an applied displacement field induces a metal–insulator transition driven by tuning between Γ- and K-valley moiré bands. Our results demonstrate control over the spin and valley character of the correlated ground and excited states in this system.
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Source data are provided with this paper. Additional data that support the findings of this study are available from the corresponding author upon reasonable request.
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We acknowledge helpful conversations with A.H. MacDonald. We thank T. Heinz, A. O’Beirne and H.B. Ribeiro for their assistance with second-harmonic generation measurements. Experimental work was primarily supported by the National Science Foundation (Grant no. NSF-DMR-2103910). B.E.F. acknowledges an Alfred P. Sloan Foundation Fellowship and a Cottrell Scholar Award. The work at the Massachusetts Institute of Technology is supported by a Simons Investigator Award from the Simons Foundation. L.F. is partly supported by the David and Lucile Packard Foundation. K.W. and T.T. acknowledge support from the Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research (JSPS KAKENHI, Grant nos. 19H05790, 20H00354 and 21H05233). B.A.F. acknowledges a Stanford Graduate Fellowship. Part of this work was performed at the Stanford Nano Shared Facilities, supported by the National Science Foundation (Award no. ECCS-2026822).
The authors declare no competing interests.
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Foutty, B.A., Yu, J., Devakul, T. et al. Tunable spin and valley excitations of correlated insulators in Γ-valley moiré bands. Nat. Mater. 22, 731–736 (2023). https://doi.org/10.1038/s41563-023-01534-z