McCarter Margaret R, Kim Kook Tae, Stoica Vladimir A, Das Sujit, Klewe Christoph, Donoway Elizabeth P, Burn David M, Shafer Padraic, Rodolakis Fanny, Gonçalves Mauro A P, Gómez-Ortiz Fernando, Íñiguez Jorge, García-Fernández Pablo, Junquera Javier, Lovesey Stephen W, van der Laan Gerrit, Park Se Young, Freeland John W, Martin Lane W, Lee Dong Ryeol, Ramesh Ramamoorthy
Department of Physics, University of California, Berkeley, California 94720, USA.
Department of Physics, Soongsil University, Seoul 06978, Korea.
Phys Rev Lett. 2022 Dec 9;129(24):247601. doi: 10.1103/PhysRevLett.129.247601.
An escalating challenge in condensed-matter research is the characterization of emergent order-parameter nanostructures such as ferroelectric and ferromagnetic skyrmions. Their small length scales coupled with complex, three-dimensional polarization or spin structures makes them demanding to trace out fully. Resonant elastic x-ray scattering (REXS) has emerged as a technique to study chirality in spin textures such as skyrmions and domain walls. It has, however, been used to a considerably lesser extent to study analogous features in ferroelectrics. Here, we present a framework for modeling REXS from an arbitrary arrangement of charge quadrupole moments, which can be applied to nanostructures in materials such as ferroelectrics. With this, we demonstrate how extended reciprocal space scans using REXS with circularly polarized x rays can probe the three-dimensional structure and chirality of polar skyrmions. Measurements, bolstered by quantitative scattering calculations, show that polar skyrmions of mixed chirality coexist, and that REXS allows valuation of relative fractions of right- and left-handed skyrmions. Our quantitative analysis of the structure and chirality of polar skyrmions highlights the capability of REXS for establishing complex topological structures toward future application exploits.
凝聚态物质研究中一个日益严峻的挑战是对诸如铁电和铁磁斯格明子等新兴序参量纳米结构的表征。它们的小尺度长度以及复杂的三维极化或自旋结构使得对其进行全面追踪颇具难度。共振弹性X射线散射（REXS）已成为一种研究斯格明子和畴壁等自旋纹理中手性的技术。然而，它在研究铁电体中的类似特征方面的应用程度要低得多。在此，我们提出了一个用于对由电荷四极矩的任意排列产生的REXS进行建模的框架，该框架可应用于铁电体等材料中的纳米结构。借此，我们展示了如何使用圆偏振X射线通过REXS进行扩展的倒易空间扫描来探测极性斯格明子的三维结构和手性。由定量散射计算支持的测量结果表明，混合手性的极性斯格明子共存，并且REXS能够评估右旋和左旋斯格明子的相对比例。我们对极性斯格明子的结构和手性的定量分析突出了REXS在建立复杂拓扑结构以用于未来应用开发方面的能力。
