Topological quantum phase transition in 5d transition metal oxide Na2IrO3.

We predict a quantum phase transition from normal to topological insulators in the $5d$ transition metal oxide ${\mathrm{Na}}_{2}{\mathrm{IrO}}_{3}$, where the transition can be driven by the change of the long-range hopping and trigonal crystal field terms. From the first-principles-derived tight-binding Hamiltonian, we determine the phase boundary through the parity analysis. In addition, our first-principles calculations for ${\mathrm{Na}}_{2}{\mathrm{IrO}}_{3}$ model structures show that the interlayer distance can be an important parameter for the existence of a three-dimensional strong topological insulator phase. ${\mathrm{Na}}_{2}{\mathrm{IrO}}_{3}$ is suggested to be a candidate material which can have both a nontrivial topology of bands and strong electron correlations.