The electronic structure of NaIrO₃, Mott insulator or band insulator?

Motivated by the unveiled complexity of nonmagnetic insulating behavior in the pentavalent post-perovskite NaIrO₃, we have studied its electronic structure and phase diagram in the plane of Coulomb repulsive interaction and spin-orbit coupling by using the newly developed local density approximation plus Gutzwiller method. Our theoretical study proposes that the metal-insulator transition can be generated by two different physical pictures: renormalized band insulator or Mott insulator regime. For the realistic material parameters in NaIrO₃, Coulomb interaction U = 2.0 eV (J = U/4) and spin-orbit coupling strength η = 0.33 eV, it tends to favor the renormalized band insulator picture as revealed by our study.