Atomic Mapping of Polar Topologies in Oxide Superlattices

Since the discovery of full flux-closure domains in PbTiO3/SrTiO3 multilayers grown on GdScO3 substrates[1], various polar topological domain structures such as vortices, skyrmions, merons and polar waves etc. were subsequently discovered in the ferroelectric films and superlattices. These polar topological structures are nanoscale objects and have potential applications in high-density non-volatile memory devices. The topological protection makes them very stable under small external stimuli and the cross-talk can be effectively avoided. Besides the industrial potential, they also possess rich emerging physical properties, such as negative capacitance, enhanced conductivity, electrocaloric effect, and so on. We choose and introduce some recent observations of polar topologies in ferroelectric films. It is pointed out that the PbTiO3/SrTiO3 system is becoming hot in modulating polar topologies these days. Both misfit strains and insulating layers play important roles in tuning the topologies. We expect more investigations to be carried out for unveiling the mask of complex structures in oxide films, multilayers and superlattices with perovskite structure.<br/> <br/><u>References</u><br/>[1] Y. L. Tang, Y.L. Zhu et al., Science 348(2015)547-551.<br/>[2] The financial support from the National Natural Science Foundation of China with No. 51971223 is acknowledged.