Highly mobile vortex structures inside polar twin boundaries in SrTiO3

We present computer simulations of previously unknown polarization singularities (vortexes) inside polar SrTiO3 twin boundaries. Usually polarity in twin walls is ferri-electric, whereas vortex excitations lead to true ferroelectricity on a very local scale. As a result, in-plane electric fields can selectively stabilize one of the vortex polarization states and enhance the ability of the walls to move. This behavior can explain the well-known and uniquely high, mobility of twin boundaries in SrTiO3. For nanoscale ferroelectric memory devices, we envisage a precisely controllable device, where a desired domain wall pattern is manipulated by shifting the vortex position electrically.