Observation of polar vortices in oxide superlattices

摘要: The complex interplay of spin, charge, orbital and lattice degrees freedom provides a plethora exotic phases physical phenomena. In recent years, spin topologies have emerged as consequence the electronic band structure between spin-orbit coupling in materials. Here we produce electrical polarization--namely, nanometre-scale vortex-antivortex (that is, clockwise-anticlockwise) arrays that are reminiscent rotational topologies--by making use competition superlattices alternating lead titanate strontium layers. Atomic-scale mapping polar atomic displacements by scanning transmission electron microscopy reveals presence long-range ordered exhibit nearly continuous polarization rotation. Phase-field modelling confirms vortex array is low-energy state for range superlattice periods. Within this range, large gradient energy from counterbalanced corresponding reduction overall electrostatic (which would otherwise arise discontinuities at titanate/strontium interfaces) elastic associated with epitaxial constraints domain formation. These observations implications creation new states matter (such dipolar skyrmions, hedgehog states) phenomena ferroic materials, such electrically controllable chirality.