Helical scattering signatures of strain and electronic textures in YbFe 2 O 4 from three-dimensional reciprocal-space imaging

The insulating ternary oxide YbFe${}_{2}$O${}_{4}$ displays an unusual frustration-driven incommensurate charge-ordering (CO) transition, linked to possible ferroelectricity. Based on high-resolution synchrotron data, we report a detailed structural model showing that the CO phase is an incommensurate charge-density wave and cannot be ferroelectric, since the electrical dipole moments are also incommensurately modulated. The change between continuous and ``spotty'' helices of scattering at the CO transition is attributed to three-dimensional fluctuations of the direction of the ordering wave vector.