Coherent Electronic Band Structure of TiTe₂/TiSe₂ Moiré Bilayer

Bilayers created by stacking single layers from different van-der-Waals materials provide a promising platform for creating novel properties, despite a weak interlayer interaction expected from the van-der-Waals bonding. The interlayer interaction is expected to be even weaker when the two single layers are incommensurate, giving rise a moire modulation. Here, we report a detailed study of such a bilayer system made of a single layer of TiTe₂ atop a single layer of TiSe₂, both prepared by molecular beam epitaxy. The two layers assume the same crystallographic orientation, but he lattice mismatch creates a hexagonal moire superlattice with a large lattice constant of 56.6 Å. Angle-resolved photoemission measurements reveal sharp emergent bands that are distinct from the bands of the single layers alone. First-principles calculations demonstrate that the emergent bands arise from the coherent coupling of the wave functions over the different parts of the stacking variations in the moiré unit cell. This work illustrates a new route for engineering the band structure of van-der-Waals materials through layer stacking and demonstrates an effective methodology for theoretical analysis of the electronic structure of such systems.