Prediction of quantum spin Hall and Rashba effects in two-dimensional ilmenite oxides


Using first-principles calculations, we investigate the structural, electronic, and topological properties of two-dimensional (2D) pristine ilmenite oxides ABO₃ (A = Au, Ag, or Cu; and B = Bi, Sb, or As) and their corresponding Janus structures. Phonon dispersions reveal the dynamic stability of these compounds. Interestingly, pristine CuBiO₃ and AuBiO₃, and Janus Cu₀.₅Ag₀.₅BiO₃, Au₀.₅Cu₀.₅BiO₃, Au₀.₅Ag₀.₅BiO₃, and CuBi₀.₅As₀.₅O₃ are topological insulators, while AuBi₀.₅As₀.₅O₃, CuBi₀.₅Sb₀.₅O₃, and AuBi₀.₅Sb₀.₅O₃ are topological semimetals, as confirmed by their Z2 invariance and conducting edge states under the hybrid functional approach. Moreover, we found van Hove singularities in Au₀.₅Ag₀.₅BiO₃ and Cu₀.₅Ag₀.₅BiO₃ near the Fermi level, suggesting the coexistence of superconductivity and nontrivial topology. Finally, isotropic Rashba spin-splitting is studied in detail for Au₀.₅Ag₀.₅BiO₃. Our findings demonstrate that 2D ilmenite oxides can be a new material playground for potential spintronic applications.