Metallicity and Topology in Iridate Domain Walls

Cooperation and competition between strong electron correlations and spin-orbit couplings have attracted much attention. Iridium oxides offer playgrounds for such an interplay and indeed exhibit intriguing phenomena. Especially, theoretical predictions on realization of topological Weyl semimetals had inspired extensive studies of pyrochlore iridates R₂Ir₂O₇ (R: rare-earth elements). However, direct observation of Weyl electrons has hardly been realized in R₂Ir₂O₇, yet.
To find routes to realize the topological quantum states in iridates, we studied low-energy effective hamiltonians of R₂Ir₂O₇ and pyrochlore osmium oxides. By focusing on magnetic domain walls and employing a symmetry adapted effective hamiltonian of R₂Ir₂O_7, we have proposed that, after pair-annihilation of Weyl electrons, magnetic domain walls in R₂Ir₂O₇ host two-dimensional metallic states, which show metal-insulator transitions, optical Hall effects, and circular dichroism. We also examined properties of magnetic domain walls in pyrochlore osmium oxides in comparison with those in iridates.