Emergence of Transverse Dielectric Response in Ferroelectric Dielectric Heterostructures

We report the emergence of a transverse dielectric response in PbTiO$_{3}$/SrTiO$_{3}$ superlattices hosting polar vortex structures. Using second-principles simulations, we find that an electric field applied along one direction induces significant local polarization responses along orthogonal directions, with magnitudes approaching half that of the diagonal susceptibility components. These off-diagonal responses are strongly dependent on the topology of the vortex structure and can be deterministically tuned or even reversed via homogeneous electric fields or epitaxial strain. Notably, the transverse susceptibilities become comparable to the diagonal components during a field- or strain-induced transition to a polarization wave state. This discovery opens avenues for engineering reconfigurable nanoscale dielectric responses in topologically textured ferroelectric systems.