Moiré superlattices formed in ${\mathrm{WS}}_2/{\mathrm{WSe}}_2$ heterobilayers have emerged as an exciting platform to explore the quantum many-body physics. The key mechanism is the introduction of moiré potentials for the band-edge carriers induced by the lateral modulation of interlayer interactions. This trapping potential results in the formation of flat bands, which enhances the strong correlation effect. However, a full understanding of the origin of this intriguing potential remains elusive. In this paper, we present a comprehensive investigation of the origin of moiré potentials in both R-type and H-type moiré patterns formed in ${\mathrm{WS}}_2/{\mathrm{WSe}}_2$ heterobilayers. We show that both lattice reconstruction and interlayer charge transfer contribute significantly to the formation of moiré potentials. In particular, the lattice reconstruction induces a nonuniform local strain, which creates an energy modulation of $\sim 200\mathrm{meV}$ for the conduction band-edge state located at ${\mathrm{WS}}_2$ layer and $\sim 20\mathrm{meV}$ for the valence band-edge state located at ${\mathrm{WSe}}_2$ layer. In addition, the lattice reconstruction also introduces a piezopotential energy, whose amplitude ranges from $\sim 40$ to $\sim 90\mathrm{meV}$ depending on the stacking and band-edge carrier. The interlayer charge transfer induces a built-in electric field, resulting in an energy modulation of $\sim 80\mathrm{meV}$ for an R-type moiré and $\sim 40\mathrm{meV}$ for an H-type moiré. Taking into account both effects from lattice reconstruction and interlayer charge transfer, the formation of moiré potential is well understood for both R-type and H-type moirés. This trapping potential localizes the wavefunctions of conduction and valence bands around the same moiré site for an R-type moiré, while around different moiré site for an H-type one. Our work not only provides an efficient method to study lattice-mismatch-induced moiré patterns, but also gives help in understanding the intriguing moiré physics in ${\mathrm{WS}}_2/{\mathrm{WSe}}_2$ heterobilayers.

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• Twistronics
• Valleytronics
• Electronic structure
• Transition metal dichalcogenides
• Twisted heterostructures