An important step in understanding the exotic electronic, vibrational, and optical properties of the moiré lattices is the inclusion of the effects of structural relaxation of the unrelaxed moiré lattices. Here, we propose novel structures for twisted bilayer of transition metal dichalcogenides. For $\theta \gtrsim 58.4^{\circ }$, we show a dramatic reconstruction of the moiré lattices, leading to a trimerization of the unfavorable stackings. We show that the development of curved domain walls due to the threefold symmetry of the stacking energy landscape is responsible for such lattice reconstruction. Furthermore, we show that the lattice reconstruction notably changes the electronic band structure. This includes the occurrence of flat bands near the edges of the conduction as well as valence bands, with the valence band maximum, in particular, corresponding to localized states enclosed by the trimer. We also find possibilities for other complicated, entropy stabilized, lattice reconstructed structures.

• Received 23 January 2020
• Accepted 17 February 2021

DOI:https://doi.org/10.1103/PhysRevB.103.L121102