Moiré induced topology and flat bands in twisted bilayer WSe${}_2$: A first-principles study

Abstract

We study the influence of strong spin-orbit interaction on the formation of flat bands in relaxed twisted bilayer WSe${}_2$. Flat bands, well separated in energy, emerge at the band edges for twist angles ($\theta$) near 0${}^{\circ }$ and 60${}^{\circ }$. For $\theta$ near 0${}^{\circ }$, the interlayer hybridization together with a moiré potential determines the electronic structure. The bands near the valence band edge have nontrivial topology, with Chern numbers equal to +1 or $-$1. We propose that the nontrivial topology of the first band can be probed experimentally for twist angles less than a critical angle of 3.5${}^{\circ }$. For $\theta$ near 60${}^{\circ }$, the flattening of the bands arising from the K point of the unit cell Brillouin zone is a result of atomic rearrangements in the individual layers. Our findings on the flat bands and the localization of their wavefunctions for both ranges of $\theta$ match well with recent experimental observations.

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• Theory of Topological Superconductivity and Antiferromagnetic Correlated Insulators in Twisted Bilayer WSe${}_2$
• Evolution of flat bands in MoSe${}_2$/WSe${}_2$ moiré lattices: A study combining machine learning and band unfolding methods
• Electrons surf phason waves in moiré bilayers
• Twistronics and moiré superlattice physics in 2D transition metal dichalcogenides
• Atomic relaxation and flat bands in strain-engineered transition metal dichalcogenide bilayer moiré systems
• Designable exciton mixing through layer alignment in WS${}_2$-graphene heterostructures
• In-plane magnetic field-induced orbital FFLO superconductivity in twisted WSe${}_2$ homobilayers
• Review of the tight-binding method applicable to the properties of moiré superlattices
• Strain-induced exciton mobility in layered WS2 from first principles