Spin dynamics and possible topological magnons in the nonstoichiometric pyrochlore iridate Tb2Ir2 O7 studied by RIXS

We report on a resonant inelastic x-ray scattering study on a single crystal of a nonstoichiometric pyrochlore iridate Tb2+xIr2-xO7-y (x≃0.25) that magnetically orders at TN≃50 K. We observe a propagating gapped magnon mode at low energy and model it using a Hamiltonian consisting of a Heisenberg exchange [J=16.2(9)meV] and Dzyaloshinskii-Moriya interactions [D=5.2(3)meV], which shows the robustness of interactions despite Tb stuffing at the Ir site. Strikingly, the ratio D/J=0.32(3) supports possible nontrivial topological magnon band crossing. This material may thus host coexisting fermionic and bosonic topology, with potential for manipulating electronic and magnonic topological bands thanks to the d-f interaction.