Interlayer decoupling in twisted bilayers of $β$-phosphorus and arsenic: a computational study
We investigate magnetism and band structure engineering in Moiré superlattice of blue phosphorus ($β$-P) and grey arsenene ($β$-As) bilayers, using \textit{ab initio} calculations. The electronic states near the valence and conduction band edges have significant $p_z$ character in both the bilayers. Thus, twisting the layers significantly reduce the interlayer orbital overlap, leading to a decrease in the binding energy (up to $\sim33\%$) and an increase in interlayer distance (up to $\sim10\%$), compared to the most stable AA-stacking. This interlayer decoupling also results in a notable increase (up to $\sim$25-50\%) of the bandgap of twisted bilayers, with the valance band edge becoming relatively flat with van-Hove singularities in the density of states. Thus, hole doping induces a Stoner instability, leading to ferromagnetic ground state, which is more robust in Moiré superlattices, than that of AA-stacked $β$-P and $β$-As.