Atomic reconstruction and flat bands in strain engineered transition metal dichalcogenide bilayer moiré systems*

Strain-induced lattice mismatch leads to moiré patterns in homobilayer transition metal dichalcogenides (TMDs). We investigate the structural and electronic properties of such strained moiré patterns in TMD homobilayers. The moiré patterns in strained TMDs consist of several stacking domains which are separated by tensile solitons. The order parameter distribution shows the formation of aster topological defects at the highest energy stackings. In contrast, twisted TMDs host shear solitons at the domain walls, and the order parameter distribution shows the formation of vortex defects. The strained moiré systems also host several well-separated flat bands at both the valence and conduction band edges. The flat bands in these strained moiré superlattices provide platforms for studying the Hubbard model on a triangular lattice as well as the ionic Hubbard model on a honeycomb lattice. The wavefunction localization, which is different from twisted TMDs, is in excellent agreement with recent spectroscopic experiments [1].

1. D. Edelberg et al., Nature Physics 16, 1097-1102 (2020)