Anomalous transverse transport in antiferromagnetic iridate thin films

Fundamental interests arise in systems where both electronic correlation and electronic topology play significant roles. Their interplay could provide opportunities for realizing novel topological magnetic materials and developing a unified picture of topological correlated electrons. However, a key challenge in this extensive and largely unexplored regime is the fact that topological properties, such as Berry phase, concern extended electronic wavefunctions described in momentum space while electrons are localized in real space in correlated systems. This dilemma calls for representative correlated materials where topological properties can be reliably measured and controlled. In this talk, I will discuss our recent work on magnetic iridates that simulate the single-orbital Hubbard Hamiltonian by engineering the complex hopping via epitaxy to implement nontrivial topology. While the correlated pseudospin-half electrons have an antiferromagnetic Mott insulating ground state, they were found to exhibit nontrivial anomalous Hall effect and anomalous Nernst effect that are characteristic of the underlying topology. In particular, the anomalous Nernst effect was found to be at least one order larger than what was previously reported for magnetic oxides and similar to many reported Weyl semimetals. But the asymmetry of the anomalous Nernst conductivity suggests the underlying origin is distinct from the usual Berry curvature mechanism of electron band structure. These unusual phenomena highlight the rich interplay of electronic topology and electronic correlation in the magnetic oxides.