First-principles simulations on the structural and energetic properties of domains in PbTiO$_3$/SrTiO$_3$ superlattices

TL;DR

This study uses first-principles density functional theory to analyze the structural and energetic properties of stripe domains in PbTiO3/SrTiO3 superlattices, revealing competition between polydomain and monodomain phases and a transition in electrostatic coupling with increasing periodicity.

Contribution

It provides the first detailed first-principles analysis of stripe domain structures and their energetics in PbTiO3/SrTiO3 superlattices, highlighting the transition in electrostatic coupling regimes.

Findings

Polydomain and monodomain phases have comparable energies.

Transition from strong to weak electrostatic coupling with increasing periodicity.

Domain walls exhibit continuous polarization rotation and are highly isotropic.

Abstract

We report first-principles calculations, within the density functional theory, on the structural and energetic properties of 180$^\circ$ stripe domains in (PbTiO$_{3}$)$_{n}$/(SrTiO$_{3}$)$_{n}$ superlattices. For the explored periodicities ($n$=3 and 6) we find that the polydomain structures compete in energy with the monodomain phases. Our results suggest the progressive transition, as a function of $n$, from a strong to a weak electrostatic coupling regime between the SrTiO$_{3}$ and PbTiO$_{3}$ layers. Structurally, they display continuous rotation of polarization connecting 180$^\circ$ domains. A large offset between [100] atomic rows across the domain wall and huge strain gradients are observed. The domain wall energy is very isotropic, depending very weakly on the stripe orientation.