天博克罗地亚入口

Professor Luo Nengneng of the School of Resources, Environment and Materials at Guangxi University (GXU), in collaboration with researchers from The Hong Kong Polytechnic University and other institutions, has made an important breakthrough in the study of topological polar crystals. Their findings, entitled “Intrinsic polar vortex crystals in A-site layer-ordered perovskites,” have been published in Nature. Professor Luo is the paper’s second author, and GXU is the second affiliated institution. The GXU research team was responsible for synthesizing the experimental samples.

Topological phases are generally characterized by topological invariants and are regarded as a special class of material states distinct from conventional phases. They may serve as small and stable information carriers in the era of artificial intelligence. However, nontrivial topological states typically emerge only under nonequilibrium conditions or require external constraints—such as applied electric fields or mechanical boundary conditions—for stabilization, which significantly limits their practical applications.

In ferroelectric materials, the formation of atomic-scale electric-dipole vortex structures generally requires a maximized depolarization field generated by interfacial bound charges to offset the substantial elastic and gradient energies. As a result, it is difficult to form highly ordered topological polar crystals in bulk materials.

To address this challenge, the research team designed and synthesized A-site layer-ordered rare-earth perovskite oxides, NaLnMgWO? ceramics, where Ln represents a lanthanide element. Using scanning transmission electron microscopy (STEM), the researchers directly observed in real space, for the first time, a two-dimensional polar hedgehog-like vortex lattice with a periodicity of approximately 4 nanometers, without the need for any external boundary conditions.

The structure can also undergo continuous evolution through systematic substitution of different lanthanide ions. In combination with first-principles calculations, the team revealed the mechanism underlying its stability: exchange interactions between phonon modes associated with in-phase and antiphase octahedral rotations.

This study not only clarifies a long-standing debate over the origin of layered-ordered perovskite superstructures, but also provides a general framework for designing nontrivial topological structures and functionalities in bulk materials that go beyond those found in conventional systems.

The research marks a breakthrough for GXU in the field of critical metals, advanced functional materials and devices. As a key development area of Guangxi’s Materials and Chemical Engineering Peak Discipline, this field focuses closely on Guangxi’s advantageous critical-metal resources and seeks to translate fundamental advances at the scientific frontier into technological strengths. It aims to provide materials foundations and device prototypes for next-generation information storage and processing technologies.

Going forward, the research team will continue to explore novel topological states in rare-earth perovskite systems and advance the practical development of high-density, low-power topological electronic devices.

图：NaNdMgWO₆的极性位移场和八面体旋转映射

Figure: Polar displacement field and octahedral rotation mapping of NaNdMgWO?