  Cu2OSeO3 is known as a unique example of insulating multiferroic compounds
with skyrmion spin texture, which is characterized by the chiral cubic crystal
structure at ambient pressure. Recently, it has been reported that this
compound shows pressure-induced structural transition with large enhancement of
magnetic ordering temperature Tc. In the present study, we have investigated
the detailed crystal structure in the high pressure phase, by combining the
synchrotron X-ray diffraction experiment with the diamond anvil cell and the
analysis based on the genetic algorithm. Our results suggest that the original
pyrochlore Cu network is sustained even after the structural transition, while
the orientation of SeO3 molecule as well as the position of oxygen in the
middle of Cu tetrahedra are significantly modified. The latter features may be
the key for the reported enhancement of Tc and associated stabilization of
skyrmion phase at room temperature.
