Reconstruction of moiré lattices in twisted transition metal dichalcogenide bilayers

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 un-relaxed moiré lattices.
Here, we propose novel structures for twisted bilayer of transition metal dichalcogenides (TMDs).
For θ > 58.4^o , we show a dramatic reconstruction of the moiré lattices, leading to a trimerization
of the unfavorable stacking. We show that the development of curved domain walls due to the
three-fold symmetry of the stacking energy landscape is responsible for such lattice reconstruction.
Furthermore, we show that the lattice reconstruction notably changes 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.