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

Jiyuan Yang; Shi Liu

doi:10.1103/PhysRevB.110.214112

paper

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

arXiv:2408.09808 · doi:10.1103/PhysRevB.110.214112

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.

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