Fig. 4

k _c is the crossing point of VBM and CBM. The band structures in a and b show that a larger strain can induce a larger Γ point inversed band gap (GPIBG). The magnitude of k _c will be increased as GPIBG becomes larger. Since the strength of SOC |A| increases as k does, thus, the magnitude of SOC gap increases as k _c does. Therefore, the SOC gap can be enhanced by strain. c The band structures of strained antimonene with the other high symmetry points. Due to the anisotropic property of α-phase antimonene, the x direction crossing point locates at a higher energy level than that of in y direction and causes an indirect bulk band gap. While the strain increases, the SOC gap is increased, but the energy difference between x direction crossing point and y direction crossing point is increased too. Consequently, the bulk band gap will close again when the strain becomes too large. d The magnitude of the SOC gap in k _y direction and the indirect bulk band gap of antimonene against different values of y direction strain (x direction strain is +14 %); negative indirect bulk band gaps indicate that the indirect bulk band gap of antimonene is closed and the system turns into a metal