Description
Two-dimensional (2D) tetragonal group-V materials have attracted considerable interest, while their topological properties remain largely unexplored. Using density functional theory, topological quantum chemistry theory, and a tight-binding model, we show that monolayer tetragonal antimonene (T-Sb) realizes a higher-order topological insulator (HOTI). A layer-dependent analysis reveals an even-odd oscillation between HOTI and trivial phases with varying layer numbers. Upon stacking these 2D layers into a three-dimensional structure, successive phase transitions from a metal to a strong topological insulator and eventually to a weak HOTI are driven by tuning the interlayer van der Waals (vdW) coupling. Tight-binding (TB) model analysis shows that these transitions are closely related to the vdW-modulated vertical hopping strength and onsite energy of Sb pz orbitals. Moreover, the TB model predicts a weak topological insulator phase within an appropriate parameter regime of interlayer vdW interaction and spin-orbit coupling, as verified in T-Sb materials. These results highlight vdW engineering as an experimentally accessible strategy for designing diverse topological phases based on 2D HOTIs.
