Loop-Magnetic Structure of Geometrically Frustrated CsW2O6

The triad of geometric frustration, competing electronic interactions, and strong spin-orbit coupling provides a uniquely fertile basis for the emergence of unconventional and intriguing quantum phases. While frustration leads to a highly degenerate physical state which is often unstable against external perturbation, the tuneability of electronic interactions as well as the intermixing of charge, spin, and orbital degrees of freedom provide an exceptionally rich toolset to experimentalist. In this regard, the pyrochlore system CsW2O6 recently emerged as a particularly promising candidate. At ambient conditions, CsW2O6 shows no sign of electronic order, but displays signatures of charge frustration on the W sublattice. Towards lower temperatures, the frustration is (partially) lifted across a bad metal-to-insulator transition, and the system displays a weak diamagnetic response. A previous structural study suggested the formation of charge order on regular trimers, whilst a recent theoretical study proposed the formation of large orbital molecules consisting of up to 10 W atoms each, including a peculiar chiral magnetic loop structure, due to strong spin-orbit coupling. This proposal builds upon a previous Neutron powder diffraction experiment which discovered first evidence of the predicted magnetic loop structure. The aim of this proposal is to elucidate this unique magnetic ordering using single crystal Neutron diffraction, e.g. to identify non-collinear magnetic order.