Light-induced topological phases in oxide superlattices

The curling dipolar texture of skyrmions and vortices in PbTiO₃/SrTiO₃ superlattices is not limited by the symmetry that is prescribed by the bulk crystal structure. I will present ultrafast snapshots of the vortex dynamics recorded with X-ray free electron lasers (XFEL) that reveal how polarization rotations evolve at the fundamental timescale of electronic and lattice excitations. Following intense terahertz excitation, collective modes emerge in the form of nanoscale circular patterns of atomic displacements, which reverse their vorticity on picosecond timescales [1]. I will also discuss the single-shot photoinduced formation of polar vortex supercrystals [2], which are created via coherent and incoherent topological defect transformation pathways as observed by XFEL experiments. These results demonstrate that nanoscale polarization rotation is a promising avenue toward high frequency applications, circumventing slow domain wall motion in classic ferroelectrics.