Unconventional electronic ground states and novel physical properties due to strong spin-orbit couplings and correlation effects in 5d oxides

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One of the most important consequences of relativistic effects in molecules and solids is the coupling of spin and orbital degrees of freedom. In 3d-metal oxides, the spin-orbit coupling is relatively weak and most of the intriguing physics rests on the presence of strong electron correlations. Electron-electron interactions turn nevertheless progressively weaker when going to heavier transition-metal elements, i.e., 4d and 5d systems, as the d orbitals become more and more extended. The relativistic spin-orbit coupling, on the other hand, follows the opposite trend: it increases progressively. In 5d-metal compounds, e.g., iridates and osmates, the interesting situation arises where these interactions meet on the same energy scale. The interplay between crystal-field effects, local multiplet physics, spin-orbit couplings, and intersite hopping that subsequently emerges has opened up a new window of interest in correlated electronic materials, offering novel types of correlated ground states and excitations. The more exotic examples are possible topological states in iridates, such as the topological Mott insulator, and the possible realization of the long-sought Kitaev model with bond-dependent spin-spin interactions.The goal of this project is providing deeper theoretical insight into the basic electronic structure and magnetic properties of intriguing 5d oxide compounds such as the iridates and osmates. For this purpose, we will build on concepts and computational tools from wavefunction electronic-structure theory, in particular, correlated multireference methods from modern quantum chemistry and recently developed solid-state embedding techniques. Our work shall foster new perspectives over the interplay of correlation effects and spin-orbit interactions in solids.