Hidden Crossover and Relaxor-Like Response from Emerging Polar Skyrmion Correlations in Ferroelectric Superlattices

TL;DR

This study reveals a hidden thermal crossover in ferroelectric superlattices where polar skyrmions transition from uncorrelated to interlayer-correlated states, causing a relaxor-like dielectric response without disorder.

Contribution

Using large-scale phase-field simulations, we identify a disorder-free mechanism for relaxor behavior driven by topological defect correlations in ferroelectric superlattices.

Findings

Polar skyrmions evolve from uncorrelated to correlated states with temperature.

A broad dielectric susceptibility peak indicates a hidden crossover.

The peak shifts with frequency, mimicking relaxor ferroelectrics.

Abstract

Polar skyrmions in ferroelectric superlattices are nanoscale topological polarization textures typically regarded as weakly coupled objects confined to individual layers, with a role secondary to that of the underlying symmetry-breaking order parameter. Here using large-scale phase-field simulations of ferroelectric superlattices, we uncover a hidden thermal crossover deep inside the ferroelectric phase, where polar skyrmions evolve from an uncorrelated, layer-resolved state into an interlayer-correlated ensemble. This crossover occurs without additional symmetry breaking or a new order parameter, but produces a pronounced broad peak in the dielectric susceptibility. The anomaly originates from the competition between correlation-enhanced response, associated with the growth of interlayer skyrmion correlations, and polarization-induced stiffness, which suppresses dielectric fluctuations at low temperature. Under AC driving, the peak shifts with frequency, resembling relaxor ferroelectrics despite the absence of quenched disorder or polar nanoregions. Our results establish a disorder-free route to relaxor-like dielectric response and identify topological defect correlations as an organizing principle for thermodynamic anomalies, providing a mechanism distinct from conventional critical behavior associated with symmetry breaking and divergent order-parameter fluctuations.