Deep moire potentials in twisted transition metal dichalcogenide bilayers

In twisted bilayers of semiconducting transition metal dichalcogenides, a combination of structural rippling and electronic coupling gives rise to periodic moire potentials that can confine charged and neutral excitations(1-5). Here we show that the moire potential in these bilayers at small angles is unexpectedly large, reaching values above 300 meV for the valence band and 150 meV for the conduction band-an order of magnitude larger than theoretical estimates based on interlayer coupling alone. We further demonstrate that the moire potential is a non-monotonic function of moire wavelength, reaching a maximum at a moire period of similar to 13 nm . This non-monotonicity coincides with a change in the structure of the moire pattern from a continuous variation of stacking order at small moire wavelengths to a one-dimensional soliton-dominated structure at large moire wavelengths. We show that the in-plane structure of the moire pattern is captured by a continuous mechanical relaxation model, and find that the moire structure and internal strain, rather than the interlayer coupling, are the dominant factors in determining the moire potential. Our results demonstrate the potential of using precision moire structures to create deeply trapped carriers or excitations for quantum electronics and opto-electronics.

Automated summary

In twisted bilayers of semiconducting transition metal dichalcogenides, the moire potential is unexpectedly large, reaching values above 300 meV and is a non-monotonic function of moire wavelength.