Phase Coexistence and Metal-Insulator Transition in Few-Layer Phosphorene: A Computational Study

Based on ab initio density functional calculations, we propose $\ensuremath{\gamma}\text{\ensuremath{-}}\mathrm{P}$ and $\ensuremath{\delta}\text{\ensuremath{-}}\mathrm{P}$ as two additional stable structural phases of layered phosphorus besides the layered $\ensuremath{\alpha}\text{\ensuremath{-}}\mathrm{P}$ (black) and $\ensuremath{\beta}\text{\ensuremath{-}}\mathrm{P}$ (blue) phosphorus allotropes. Monolayers of some of these allotropes have a wide band gap, whereas others, including $\ensuremath{\gamma}\text{\ensuremath{-}}\mathrm{P}$, show a metal-insulator transition caused by in-layer strain or changing the number of layers. An unforeseen benefit is the possibility to connect different structural phases…