Phase coexistence and electric-field control of toroidal order in oxide superlattices.

摘要: Systems that exhibit phase competition, order parameter coexistence, and emergent topologies constitute a major part of modern condensed-matter physics. Here, by applying range characterization techniques, simulations, we observe in PbTiO3/SrTiO3 superlattices all these effects can be found. By exploring superlattice period-, temperature- field-dependent evolution structures, several new features. First, it is possible to engineer coexistence mediated first-order transition between an emergent, low-temperature vortex with electric toroidal high-temperature ferroelectric a1/a2 phase. At room temperature, the coexisting phases form mesoscale, fibre-textured hierarchical superstructure. The possesses axial polarization, set net polarization surrounding domains, such multi-order-parameter state belongs class gyrotropic electrotoroidal compounds. Finally, application fields this mixed-phase system permits interconversion concomitant order-of-magnitude changes piezoelectric nonlinear optical responses. Our findings suggest cross-coupled functionalities.