Topological transitions to Weyl states in bulk Bi2Se3: Effect of hydrostatic pressure and doping

Bi 2 Se 3, a layered three-dimensional (3D) material, exhibits topological insulating properties due to the presence of surface states and a bandgap of 0.3 eV in the bulk. We study the effect of hydrostatic pressure P and doping with rare earth elements on the topological aspect of this material in bulk from a first principles perspective. Our study shows that under a moderate pressure of P > 7.9 GPa, the bulk electronic properties show a transition from an insulating to a Weyl semi-metal state due to band inversion. This electronic topological transition may be correlated to a structural change from a layered van der Waals material to a 3D system observed at P = 7.9 GPa. At large P, the density of states have a significant value at the Fermi energy. Intercalating Gd with a small doping fraction between Bi 2 Se 3 layers drives the system to a metallic anti-ferromagnetic state, with Weyl nodes below the Fermi energy. At the Weyl nodes, time reversal symmetry is broken due to the finite local field induced by large magnetic moments on Gd atoms. However, substituting Bi with Gd induces anti-ferromagnetic order with an increased direct bandgap. Our study provides novel approaches to tune topological transitions, particularly in capturing the elusive Weyl semimetal states, in 3D topological materials.