Nontrivial Triplon Topology and Triplon Liquid in Kitaev-Heisenberg-type Excitonic Magnets

Abstract: The combination of strong spin-orbit coupling and correlations, e.g. in ruthenates and iridates, has been proposed as a means to realize quantum materials with nontrivial topological properties. We discuss here Mott insulators where onsite spin-orbit coupling favors a local $J_{\textrm{tot}}=0$ singlet ground state. We investigate excitations into a low-lying triplet, triplons, and find them to acquire nontrivial band topology in a magnetic field. We also comment on magnetic states resulting from triplon condensation, where we find, in addition to the same ordered phases known from the $J_{\textrm{tot}}=\tfrac{1}{2}$ Kitaev-Heisenberg model, a triplon liquid taking the parameter space of Kitaev's spin liquid.