Emergence of metal–semiconductor phase transition in <i>MX</i> ₂ (<i>M</i> = Ni, Pd, Pt; <i>X</i> = S, Se, Te) moiré superlattices

Abstract Two-dimensional (2D) moiré superlattices with a small twist in orientation exhibit a broad range of physical properties due to the complicated intralayer and interlayer interactions modulated by the twist angle. Here, we report a metal–semiconductor phase transition in homojunction moiré superlattices of NiS 2 and PtTe 2 with large twist angles based on high-throughput screening of 2D materials MX 2 ( M = Ni, Pd, Pt; X = S, Se, Te) via density functional theory (DFT) calculations. Firstly, the calculations for different stacking configurations (AA, AB and AC) reveal that AA stacking ones are stable for all the bilayer MX 2 . The metallic or semiconducting properties of these 2D materials remain invariable for different stacking without twisting except for NiS 2 and PtTe 2 . For the twisted configurations, NiS 2 transfers from metal to semiconductor when the twist angles are 21.79°, 27.79°, 32.20° and 60°. PtTe 2 exhibits a similar transition at 60°. The phase transition is due to the weakened d–p orbital hybridization around the Fermi level as the interlayer distance increases in the twisted configurations. Further calculations of untwisted bilayers with increasing interlayer distance demonstrate that all the materials undergo metal–semiconductor phase transition with the increased interlayer distance because of the weakened d–p orbital hybridization. These findings provide fundamental insights into tuning the electronic properties of moiré superlattices with large twist angles.