Abstract
We predict that in a twisted homobilayer of transition-metal dichalcogenide MoS$_2$, spin-orbit coupling in the conduction band states from $\pm K$ valleys can give rise to moir\'{e} flat bands with nonzero Chern numbers in each valley. The nontrivial band topology originates from a unique combination of angular twist and local mirror symmetry breaking in each individual layer, which results in unusual skyrmionic spin textures in momentum space with skyrmion number $\mathcal{S} = \pm 2$. Our Hartree-Fock analysis further suggests that density-density interactions generically drive the system at $1/2$-filling into a valley-polarized state, which realizes a correlated quantum anomalous Hall state with Chern number $\mathcal{C} = \pm 2$. Effects of displacement fields are discussed with comparison to nontrivial topology from layer-pseudospin magnetic fields.
Highlights
The discovery of possible correlated insulating states [1] and superconductivity [2] in magic-angle twisted bilayer graphene has paved a new avenue toward engineering electronic structures where interactions play a decisive role [3–19]
Focusing on the specific case of a twisted homobilayer MoS2 we predict that an interplay among angular twist, local symmetry breaking, and spin-orbit coupling in the conduction band (CB) states creates moiré flat bands with nonzero Chern numbers C = ±2, and density-density interactions generically drive the system at 1/2-filling into a valley-polarized correlated quantum anomalous Hall (QAH) state
While on-going activities in twisted transition-metal dichalcogenides (TMDs) have focused mainly on valence band (VB) moiré bands [29–35], our proposal of moiré Chern bands generated by spin-orbit coupling (SOC) opens a new pathway into the largely unknown territory of CB moiré physics
Summary
The discovery of possible correlated insulating states [1] and superconductivity [2] in magic-angle twisted bilayer graphene has paved a new avenue toward engineering electronic structures where interactions play a decisive role [3–19]. Under appropriate symmetry breaking conditions, flat bands in twisted graphene acquire nonzero Chern numbers [22–25], which manifest experimentally as quantum anomalous Hall (QAH) states when spin or valley degeneracies are lifted spontaneously through electronic correlations [26–28]. Recent works on untwisted TMDs, on the other hand, revealed that the small spin-orbit splitting in CB states, when combined with Rashba SOC introduced by mirror symmetry breaking, can lead to nontrivial Berry phase effects [41–43]. Focusing on the specific case of a twisted homobilayer MoS2 we predict that an interplay among angular twist, local symmetry breaking, and spin-orbit coupling in the CB states creates moiré flat bands with nonzero Chern numbers C = ±2, and density-density interactions generically drive the system at 1/2-filling into a valley-polarized correlated QAH state.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
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 callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
