Trimer quantum spin liquid candidate Ba4Ir3O10: magnetic excitations of a cluster Mott insulator

The iridate Ba4Ir3O10 hosts a quasi-2D network of trimers and has been discussed as an unusual quantum spin liquid. RIXS data have been explained in terms of a quasi-1D spinon continuum based on frustrated intra-trimer exchange. We acquired some RIXS data of Ba4Ir3O10 with 60 meV resolution upon commissioning at ID20, establishing the trimer nature of the electronic states above 0.3 eV. The picture of intra-trimer exchange proposed in the litearture is not applicable. We will determine the character of the magnetic excitations and a possible quantum spin-liquid nature with a careful high-resolution RIXS study.