Ab initio studies on the interplay between spin-orbit interaction and Coulomb correlation in Sr2IrO4 and Ba2IrO4.

Ab initio analyses of A(2)IrO(4) (A=Sr,Ba) are presented. Effective Hubbard-type models for Ir 5d t(2g) manifolds downfolded from the global band structure are solved based on the dynamical mean-field theory. The results for A=Sr and Ba correctly reproduce paramagnetic metals undergoing continuous transitions to insulators below the Néel temperature T(N). These compounds are classified not into Mott insulators but into Slater insulators. However, the insulating gap opens by a synergy of the Néel order and significant band renormalization, which is also manifested by a 2D bad metallic behavior in the paramagnetic phase near the quantum criticality.