Abstract
The long-wavelength moiré superlattices in twisted 2D structures have emerged as a highly tunable platform for strongly correlated electron physics. We study the moiré bands in twisted transition metal dichalcogenide homobilayers, focusing on WSe2, at small twist angles using a combination of first principles density functional theory, continuum modeling, and Hartree-Fock approximation. We reveal the rich physics at small twist angles θ < 4∘, and identify a particular magic angle at which the top valence moiré band achieves almost perfect flatness. In the vicinity of this magic angle, we predict the realization of a generalized Kane-Mele model with a topological flat band, interaction-driven Haldane insulator, and Mott insulators at the filling of one hole per moiré unit cell. The combination of flat dispersion and uniformity of Berry curvature near the magic angle holds promise for realizing fractional quantum anomalous Hall effect at fractional filling. We also identify twist angles favorable for quantum spin Hall insulators and interaction-induced quantum anomalous Hall insulators at other integer fillings.
Highlights
The long-wavelength moiré superlattices in twisted 2D structures have emerged as a highly tunable platform for strongly correlated electron physics
We predict the realization of generalized Kane −Mele models with topological flat band, interaction-driven Haldane insulator and Mott insulators in twisted transition metal dichalcogenides (TMD) homobilayers at small twist angles
Our phase diagram demonstrates the high experimental tunability of TMD twisted homobilayers, where the applied displacement field can tune between quantum anomalous Hall phase and Mott insulators involving three types of magnetic orders: ferromagnet with spin/valley polarization (FMz), ferromagnetically align in the xy plane (FMxy), and AFMxy
Summary
The long-wavelength moiré superlattices in twisted 2D structures have emerged as a highly tunable platform for strongly correlated electron physics. In this regime of very small twist angles, the character of the top two valence bands can be understood from an effective tight binding model on a moiré honeycomb lattice that takes the form of a Kane−Mele model, as suggested in the insightful work of Wu et al.[14] As we will later show, the original Kane−Mele description with up to second nearest neighbor hopping terms only describes the band structure well for very small angles θ ≲ 1∘.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
