Two dimensional honeycomb-kagome Be3Pb2: a mechanically flexible topological insulator with high intrinsic carrier mobilities

Abstract

We theoretically predict a stable 2D nanosheet consisting of Pb and Be atoms sited at the honeycomb and kagome sites, respectively, forming a mixed honeycomb-kagome phase of Be₃Pb₂. Without the spin–orbit interaction, its band structure resembles that of honeycomb-structured graphene, namely, the valence and conduction bands touch at isolated points, whose energies linearly depend on the momentum. The presence of spin–orbit coupling (SOC), however, would result in a small bandgap opening, ∼116 meV. So, the SOC induces an electronic phase transition from a semimetal to a semiconductor. A coarse estimation based on the deformation potential method gives rise to very high carrier mobilities which are at least comparable to those of black phosphorene. Most interestingly, the 2D Be₃Pb₂ shows a non-trivial topology in the electronic structure accompanying the SOC induced band gap opening. Hence, 2D Be₃Pb₂ would be a versatile candidate for many applications, e.g., nanoelectronic devices.