Multifaceted moiré superlattice physics in twisted WSe 2 bilayers

Lattice reconstruction in twisted transition-metal dichalcogenide (TMD) bilayers gives rise to piezo- and ferroelectric moire potentials for electrons and holes, as well as a modulation of the hybridization across the bilayer. Here, we develop hybrid k⋅p tight-binding models to describe electrons and holes in the relevant valleys of twisted TMD homobilayers with parallel (P) and antiparallel (AP) orientations of the monolayer unit cells. We apply these models to describe moire superlattice effects in twisted WSe2 bilayers, in conjunction with microscopic ab initio calculations, and considering the influence of encapsulation, pressure, and an electric displacement field. Our analysis takes into account mesoscale lattice relaxation, interlayer hybridization, piezopotentials, and a weak ferroelectric charge transfer between the layers, and it describes a multitude of possibilities offered by this system, depending on the choices of P or AP orientation, twist angle magnitude, and electron/hole valley.