Tunable charge density wave in a lateral black/blue phosphorene heterostructure: A first-principles calculation

We reveal a one-dimensional (1D) charge density wave (CDW) at the lateral interface of black/blue phosphorene heterostructure (BBPH). This emerging CDW is induced by Fermi surface nesting and characterized by dimerization of unsaturated P atoms at the boundary. Accordingly, lattice distortion and band-gap opening simultaneously occur in the BBPH with prominently lowered total energy from metallic structure (MS) to the CDW phase. Due to the quantum confinement effect, the band gap increases as the heterostructure width reduces. Under an accessible electron doping level of ~1014cm-2, the relative stability between the CDW phase and the MS can be flipped because of their different electron occupation distributions and enhanced electrostatic repulsion at the boundary. In addition, this junction boundary provides a good platform to study the 1D Su-Schrieffer-Heeger (SSH) model. We predict that an SSH-type electron soliton would emerge when there is a dimerization fault, which carries a topologically protected unpaired electron, and can migrate along the boundary with a tunable energy barrier.