Interface chiral engineering via cation implementation in transition-metal dichalcogenide materials

The charge-density-wave (CDW) phases in many transition-metal dichalcogenide (TMDC) materials host commensurate Star-of-David (SoD) domains with left- and right-handed chirality. Stacking between chiral domains reflects the overall energy of the bilayer systems, determines the interlayer electronic coupling, and leads to a range of emergent phenomena. Using density functional theory calculations, we systematically investigate the effect of Nb substitutes at representative SoD sites in 1T-TaS₂ or 1T-TaSe₂ bilayers. We find that cation substitutes residing at SoD centers can facilitate the formation of heterochiral stacking. The ensuing CDW moiré superstructures possess novel electronic structures such as flat bands and concentric CDW patterns. Our works suggest that precision cation implementation can be an effective tool for engineering interface CDW chirality in TMDC materials.