| Summary: | The ability to synthesize high-quality, complex-oxide heterostructures has created a
veritable playground in which to explore emergent phenomena and exotic phases which arise
from the interplay of spin, charge, orbital, and lattice degrees of freedom. Of particular
interest is the creation of artificial heterostructures and superlattices built from two
or more materials. Through such approaches, it is possible to observe new phases and
phenomena that are not present in the parent materials alone. This is especially true in
ferroelectric materials where the appropriate choice of superlattice constituents can lead
to structures with complex phase diagrams and rich physics. In this article, we review and
explore future directions in such ferroic superlattices wherein recent studies have
revealed complex emergent polarization topologies, novel states of matter, and intriguing
properties that arise from our ability to manipulate materials with epitaxial strain,
interfacial coupling and interactions, size effects, and more. We focus our attention on
recent work in (PbTiO3)n/(SrTiO3)n
superlattices wherein exotic polar-vortex structures have been observed. We review the
history of these observations and highlights of recent studies and conclude with an
overview and prospectus of how the field may evolve in the coming years.
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