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 presence of surface states and band gap 0.3 eV in the bulk. We study effect hydrostatic pressure $P$ doping with rare earth elements on aspect this material bulk from first principles perspective. Our shows that under moderate P$>$7.9 GPa, electronic show transition an Weyl semi-metal state inversion. This may be correlated structural change van der Waals 3D system observed at $P$=7.9 GPa. At large density have significant value Fermi-energy. Intercalating Gd small fraction between Bi$_2$Se$_3$ layers drives metallic anti-ferromagnetic state, nodes below time reversal symmetry is broken finite local field induced by magnetic moments atoms. However, substituting Bi induces order increased direct gap. provides novel approaches tune transitions, particularly capturing elusive semimetal states, materials.