The observation of unexpected polarization textures such as vortices, skyrmions, and merons in various oxide heterostructures has challenged the widely accepted picture of ferroelectric domain walls as being Ising-like. Bloch components in the 180° domain walls of PbTiO3 have recently been reported in PbTiO3/SrTiO3 superlattices and linked to domain wall chirality. While this opens exciting perspectives, the ubiquity of this Bloch component remains to be further explored. In this work, we present a comprehensive investigation of domain walls in PbTiO3/SrTiO3 superlattices, involving a combination of first- and second-principles calculations, phase-field simulations, diffuse scattering calculations, and synchrotron-based diffuse x-ray scattering. Our theoretical calculations highlight that the previously predicted Bloch polarization in the 180° domain walls in PbTiO3/SrTiO3 superlattices might be more sensitive to the boundary conditions than initially thought and is not always expected to appear. Employing diffuse scattering calculations for larger systems, we develop a method to probe the complex structure of domain walls in these superlattices via diffuse x-ray scattering measurements. Through this approach, we investigate depolarization-driven ferroelectric polarization rotation at the domain walls. Our experimental findings, consistent with our theoretical predictions for realistic domain periods, do not reveal any signatures of a Bloch component in the centers of the 180° domain walls of PbTiO3/SrTiO3 superlattices, suggesting that the precise nature of domain walls in the ultrathin PbTiO3 layers is more intricate than previously thought and deserves further attention. Published by the American Physical Society 2024

中文翻译：

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评估铁电钛酸铅超晶格中 Bloch 畴壁的普遍性


在各种氧化物异质结构中观察到意想不到的极化纹理，例如漩涡、斯格明子和梅隆子，这挑战了广泛接受的铁电畴壁是 Ising 状的形象。最近在 PbTiO3/SrTiO3 超晶格中报道了 PbTiO3/SrTiO3 超晶格中 Bloch 成分，并与畴壁手性有关。虽然这开辟了令人兴奋的前景，但这个 Bloch 组件的普遍性仍有待进一步探索。在这项工作中，我们对 PbTiO3/SrTiO3 超晶格中的畴壁进行了全面研究，涉及第一和第二原理计算、相场模拟、漫散射计算和基于同步加速器的漫散射 X 射线散射的组合。我们的理论计算强调，先前预测的 PbTiO3/SrTiO3 超晶格中 180° 畴壁中的 Bloch 极化可能比最初认为的对边界条件更敏感，并且并不总是预期会出现。对大型系统采用漫散射计算，我们开发了一种方法，通过漫散射 X 射线散射测量来探测这些超晶格中畴壁的复杂结构。通过这种方法，我们研究了畴壁上去极化驱动的铁电极化旋转。我们的实验结果与我们对实际畴周期的理论预测一致，没有揭示 PbTiO3/SrTiO3 超晶格的 180° 畴壁中心存在 Bloch 分量的任何特征，这表明超薄 PbTiO3 层中畴壁的精确性质比以前认为的要复杂得多，值得进一步关注。 美国物理学会 2024 年出版