Topological and electronic transitions in a Sb(111) nanofilm: the interplay between quantum confinement and surface effect

When the dimension of a solid structure is reduced, there will be two emerging effects, quantum confinement and surface effect, which dominate at nanoscale. Based on first-principles calculations, we demonstrate that due to an intriguing interplay between these two dominating effects, the topological and electronic (topoelectronic) properties of Sb (111) nanofilms undergo a series of transitions as a function of the reducing film thickness: transforming from a topological semimetal to a topological insulator at 7.8 nm (22 bilayer), then to a quantum spin Hall (QSH) phase at 2.7 nm (8 bilayer), and finally, to a normal (topological trivial) semiconductor at 1.0 nm (3 bilayer). Our theoretical findings identify the existence of the QSH in the Sb (111) nanofilms within a narrow range of thickness and suggest that the Sb (111) nanofilms provide an ideal test bed for experimental study of topoelectronic phase transitions.