Interplay of strong correlations and covalency in ionic band insulators

We have addressed the role of electronic correlations in different kind of band insulators by using two orbital Hubbard model within dynamical mean-field theory (DMFT). We have derived exact results for a single-particle spectral function at Fermi level within DMFT. Our numerical results calculated using impurity solvers namely, hybridization expansion continuous-time quantum Monte-Carlo (HY-CTQMC) and multi-orbital iterative perturbation theory (MO-IPT) corroborated with our predicted analytical results.