  Ferroelectrics are characterized by domain structures as are other ferroics.
At the nanoscale though, ferroelectrics may exhibit non-trivial or exotic
polarization configurations under proper electrostatic and elastic conditions.
These polar states may possess emerging properties not present in the bulk
compounds and are promising for technological applications. Here, the
observation of rotational polarization topologies at the nanoscale by means of
aberration-corrected scanning transmission electron microscopy is reported in
BaTiO3/SrTiO3 superlattices grown on cubic SrTiO3(001). The transition from a
highly homogeneous polarization state to the formation of rotational
nanodomains has been achieved by controlling the superlattice period while
maintaining compressive clamping of the superlattice to the cubic SrTiO3
substrate. The nanodomains revealed in BaTiO3 prove that its nominal tetragonal
structure also allows rotational polar textures.
