Mixing between J(eff)=1/2 and 3/2 orbitals in Na2IrO3: A spectroscopic and density functional calculation study

Abstract

We investigated the electronic structure of Na2IrO3 using optical spectroscopy, first-principles calculation, and x-ray absorption spectroscopy. We found that the electronic structure of Na2IrO3 is mainly determined by anisotropic hopping interactions and spin-orbit coupling. Due to the hopping interaction, the orbital character of the bands near the Fermi level deviates from the spin-orbit coupling-induced J(eff) = 1/2 states. Polarization-dependent O 1s x-ray absorption spectroscopy showed that the J(eff) = 1/2 state of an Ir atom can be mixed with the J(eff) = 3/2 state of the neighboring Ir atom. This result implies that mixing between the J(eff) = 1/2 and 3/2 states in the valence state should be carefully considered in proposed exotic states of Na2IrO3, such as topological insulator and quantum spin liquid states.