Topological phase transitions in perovskite superlattices driven by temperature, electric field, and doping

TL;DR

This study uses deep potential molecular dynamics to explore topological phase transitions in (PbTiO3)$_{10}$/(SrTiO3)$_{10}$ superlattices driven by temperature, electric field, and doping, revealing complex polarization behaviors and structural configurations.

Contribution

It provides atomistic insights into topological phase transitions and polarization dynamics in superlattices under various external stimuli, including doping effects.

Findings

Identified a phase transition sequence from ferroelectric-like to antiferroelectric-like to paraelectric with increasing temperature.

Demonstrated reversible polarization switching and vortex core movements under electric fields.

Showed that Pb doping alters dipolar configurations, enlarging skyrmion bubbles and affecting thermal and electrical responses.

Abstract

Many dipolar topological structures have been experimentally demonstrated in (PbTiO$_3$)$_n$/(SrTiO$_3$)$_n$ superlattices, such as flux-closure, vortice, and skyrmion. In this work, we employ deep potential molecular dynamics (MD) to investigate the dynamical response of the (PbTiO$_3$)$_{10}$/(SrTiO$_3$)$_{10}$ superlattice, supporting polar vortex arrays, to temperature and electric field at the atomic level. Our simulations reveal a unique phase transition sequence from ferroelectric-like to antiferroelectric-like to paraelectric in the in-plane direction as temperature increases. In the ferroelectric-like state, we observe field-driven reversible switching of in-plane polarization coupled with out-of-plane movements of vortex cores during MD simulations. In the antiferroelectric-like region, the polarization-electric field hysteresis loop exhibits a superparaelectric feature, showing nearly no loss. This behavior is attributed to a strong recovering force to form polar vortex arrays, dictated by the electrical and mechanical boundary conditions within the superlattice. The (PbTiO$_3$)$_{10}$/(SrTiO$_3$)$_{10}$ superlattice in the antiferroelectric-like state also demonstrates large in-plane susceptibility and tunability. The effect of Pb doping in the SrTiO$_3$ layer on the topological structural transition in the superlattice is investigated. The weakened depolarization field in the PbTiO$_3$ layers leads to new dipolar configurations, such as enlarged skyrmion bubble within $c$ domains in (PbTiO$_3$)$_{10}$/(Pb$_{0.4}$Sr$_{0.6}$TiO$_3$)$_{10}$, and we quantify their thermal and electrical responses through MD simulations. These quantitative atomistic insights will be useful for the controlled optimization of perovskite superlattices for various device applications.