ARPES Studies of Low-energy electronic structure of the strong spin-orbit semimetal SrIrO$_{3}$

The similar energy scales of spin-orbit coupling and electron-electron correlation strength lead to exotic J$_{eff}=$ 1/2 Mott insulating ground states for layered Ruddlesden-Popper 5d iridates, Sr$_{n+1}$Ir$_{n}$O$_{3n+1}$. A metal-insulator transition occurs upon increasing dimensionality from the two-dimensional layered Sr$_{2}$IrO$_{4}$ to the three-dimensional perovskite SrIrO$_{3}$. However, little is known about the electronic structure and nature of the metallic states in SrIrO$_{3}$. We synthesized epitaxial SrIrO$_{3}$ films on (001) LSAT substrates by molecular beam epitaxy and investigated their electronic structure using angle-resolved photoemission spectroscopy. We find an exotic semi-metallic state comprised of massive hole-like bands, whose extrema are pinned very close to the chemical potential, and rapidly dispersive electron bands which dominate the transport. Intriguingly, the bandwidths of SrIrO$_{3}$ are smaller than in its Mott insulating counterpart Sr$_{2}$IrO$_{4}$, indicating that metal-insulator transitions in Ruddlesden-Popper iridates are not simply driven by band narrowing resulting from reduced dimensionality.