Superstructures arising from V trimers with orbital ordering in BaV_{10}O_{15}

In BaV_{10}O_{15} with quasitriangular V lattices, we found unique superstructures characterized by (qq0)-type peaks in the momentum space, where q varies continuously with temperature between q=0 and 1/3 and locks at 1/3. Such a threefold superstructure is likely caused by the dense arrangement of the V trimers associated with the orbital ordering of V. The results indicate that the superstructure of the V trimers, each of which is also a superstructure, gives rise to the ordered phases with peculiar characteristics.