  Novel interplay of spin-orbit coupling and electron correlations in complex
Ir oxides recently emerged as a new paradigm for correlated electron physics.
Because of a large spin-orbit coupling of ~0.5 eV, which is comparable to the
transfer energy t and the crystal field splitting $\Delta$ and Coulomb U, a
variety of ground states including magnetic insulator, band insulator,
semimetal and metal, shows up in a narrow materials phase space. Utilizing such
subtle competition of the ground states, we successfully tailor a spin-orbital
magnetic insulator out of a semimetal SrIrO$_3$ by controlling dimensionality
using superlattice of [(SrIrO$_3$)$_m$, SrTiO$_3$] and show that a magnetic
ordering triggers the transition to magnetic insulator. Those results can be
described well by a first-principles calculation. This study is an important
step towards the design and the realization of topological phases in complex Ir
oxides with very strong spin-orbit coupling.
