Topological Quantum Phase Transition in 5$d$ Transition Metal Oxide   Na$_2$IrO$_3$
  We predict a quantum phase transition from normal to topological insulators in the 5$d$ transition metal oxide Na$_2$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 Na$_2$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. Na$_2$IrO$_3$ is suggested to be a candidate material which can have both a nontrivial topology of bands and strong electron correlations. 
Choong H. Kim, Heung Sik Kim, Hogyun Jeong, Hosub Jin, Jaejun Yu
cond-mat.mtrl-sci cond-mat.str-el