Abstract:
This licentiate thesis is made up of two parts, the first part is concerned with quantum spin
liquids and the second part is about RIXS interferometry on cluster Mott insulators. Quantum
spin liquids are fascinating phases of matter, which lack long-range magnetic order at zero
temperature due to magnetic frustration. They are known to exhibit long-range entanglement
and have fractionalized excitations. In this thesis we study spin-orbital liquids. They belong to
a family of generalized Kitaev spin liquids, which are exactly solvable models of quantum
spin liquids. We generalize the spin-orbital model to a three- and a four-coordinated threedimensional
lattice and study the impact of symmetries and exactly solvable perturbations on
the low-energy physics. The second part of the thesis is concerned with cluster Mott
insulators, and how they can be probed using resonant inelastic X-ray scattering (RIXS).
Cluster Mott insulators are materials in which strong electron-electron interactions force the
electrons to localize on clusters of atoms. They thus form “molecules” within the solid, which
give rise to interference patterns in the RIXS intensity. These interference patterns do not only
inform us about the existence of quasimolecular states, but also about their character. We
discuss RIXS interferometry on the trimer iridate Ba4NbIr3O12.