A. K. Yadav, C. T. Nelson, S. L. Hsu, Z. Hong, J. D. Clarkson, C. M. Schlepüetz, A. R. Damodaran, P. Shafer, E. Arenholz, L. R. Dedon, A. Vishwanath, A. M. Minor, L. Q. Chen, J. F. Scott, L. W. Martin, and R. Ramesh, University of California, Berkeley, Pennsylvania State University, Lawrence Berkeley Laboratory, Argonne National Laboratory, University of St. Andrews.
National Science Foundation under the MRSEC program (DMR-142062, DMR-1451219 and DMR-1210588, Department of Energy (DE-AC02-05CH11231, DE-SC0012375 & DE-AC02- 06CH11357), Army Research Office (W911NF-14-1-0104),
The complex interplay of spin, charge, orbital and lattice degrees of freedom supports exotic physical phenomena. In recent years, complex spin topologies have emerged as a consequence of the electronic band structure and the interplay between spin and spin–orbit coupling. Here we produce complex topologies of electrical polarization—nanometre-scale vortex–antivortex arrays that are reminiscent of rotational spin topologies—by making use of the competition between charge, orbital and lattice degrees of freedom in superlattices of alternating lead titanate and strontium titanate. Atomic-scale mapping of the polar atomic displacements by scanning transmission electron microscopy reveals the presence of long-range ordered vortex–antivortex arrays that exhibit nearly continuous polarization rotation. Phase-field modelling confirms that the vortex array is the low-energy state for a range of superlattice periods. These observations have implications for the creation of new states of matter (such as dipolar skyrmions, hedgehog states) and associated phenomena in ferroic materials, such as electrically controllable chirality.
Yadav, A. K.; Nelson, C. T.; Hsu, S. L.; Hong, Z.; Clarkson, J. D.; Schlepütz, C. M.; Damodaran, A. R.; Shafer, P.; Arenholz, E.; Dedon, L. R.; Chen, D.; Vishwanath, A.; Minor, A. M.; Chen, L. Q.; Scott, J. F.; Martin, L. W.; Ramesh, R. Observation of Polar Vortices in Oxide Superlattices. Nature 2016, 530 (7589), 198–201. DOI: 10.1038/nature16463