RIXS and XMCD on vanadium lacunar spinels AV4X8

The large family of lacunar spinels AM4X8 is a versatile host of quantum magnetic phases such as a skyrmion-lattice phase. The structure shows M4 tetrahedra. For 5d GaTa4Se8, a tetrahedral cluster Mott character has been established by Ta L-edge RIXS. Cluster physics is also discussed for 3d AV4X8 but direct experimental evidence for a cluster character of the electronic structure – in contrast to a magnetic cluster behaviour – is still missing. Using XMCD and RIXS at the V L edge, we aim to unravel the electronic structure of GaV4Se8, GaV4S8, and GeV4S8, focusing on a possible cluster Mott character and the role of hybridisation with the ligands.