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Topological Insulators in Twisted Transition Metal Dichalcogenide Homobilayers

TitleTopological Insulators in Twisted Transition Metal Dichalcogenide Homobilayers
Publication TypeJournal Article
Year of Publication2019
AuthorsF. Wu, T. Lovorn, E. Tutuc, I. Martin, and A.. H. MacDonald
JournalPhys. Rev. Lett.
Date PublishedFEB 28
Type of ArticleArticle

We show that moire bands of twisted homobilayers can be topologically nontrivial, and illustrate the tendency by studying valence band states in +/- K valleys of twisted bilayer transition metal dichalcogenides, in particular, bilayer MoTe2. Because of the large spin-orbit splitting at the monolayer valence band maxima, the low energy valence states of the twisted bilayer MoTe2 at the +K (-K) valley can be described using a two-band model with a layer-pseudospin magnetic field Delta(r) that has the moire period. We show that Delta(r) has a topologically nontrivial skyrmion lattice texture in real space, and that the topmost moire valence bands provide a realization of the Kane-Mele quantum spin-Hall model, i. e., the two-dimensional time-reversal-invariant topological insulator. Because the bands narrow at small twist angles, a rich set of broken symmetry insulating states can occur at integer numbers of electrons per moire cell.