Correlated Dirac semimetal states in nonsymmorphic MIrO₃ (M=Sr, Ba and Ca)

Nonsymmorphic symmetries can give rise to Dirac semimetal (DSM) states. However, few studies have been conducted on DSMs in interacting systems. Here, we induce interacting DSM states in nonsymmorphic iridium oxides SrIrO₃, BaIrO₃ and CaIrO₃, and contend that the interaction of electron-electron correlations, strong spin-orbital coupling, and symmetry protection can drive robust and exotic DSM states. Based on the density functional theory combined with dynamical mean-field theory (DFT + DMFT), with the Coulomb interaction parameters computed through doubly screened Coulomb correction approach, we discover that the Dirac fermions are constituted by the Jeff = 1/2 state of iridium, which is reorganized from the t2g orbitals of iridium under the combined effect of strong spin-orbit coupling and crystal field effects, and the Jeff = 1/2 state exhibits a significantly mass enhancement, with the calculated value showing agreement with the experimental results reported in the literature. Moreover, the nonsymmorphic symmetries induce topological surface bands and Fermi arcs on the (001) surface, which are well separated from bulk states. Our findings establish nonsymmorphic iridium oxides as correlated DSMs under strong electron-electron and spin-orbital interactions.