非赝立方结构磁性化合物拓扑磁电物理研究

Correlated electronic systems with topological characters are the cutting-edge frontier of modern condensed matter physics, which own nontrivial physics and broad potential applications. In this project, we propose to study the topological magnetoelectric states and magnetoelectricity in correlated electronic systems of selected transition metal compounds (d/f valence electrons) with non-pseudocubic crystal structures . In particular, we will construct proper theoretical framework for the forming of vortex-antivortex ferroelectric domains and understand the dynamics of ferroelectric vortex. We will also investigate the ground states and excited states in noncoplanar magnetic systems, as well as their magnetic dynamics. The observation and manipulation of topological magnetoelectric states will be realized. For these systems, multiply factors, e.g. element valence, magnetic ions’ concentration, interfacial/surface states, microstructures, lattice mismatch, strain, and external electric/magnetic/optical fields, will be systematically studied to reveal their quantum-level physical effects to the spin-orbital-charge ordering/disordering and topological magnetic states. This project will not only pursuit the understanding of the basic physics of topological magnetoelectricity, but also find several new correlated electronic materials with real space topological states and develop prototype devices based on the topological magnetoelectricity. Our project will enrich the magnetoelectric physics in correlated electronic systems, extend the field of topology in condensed matter physics, and push forward the application of topologically protected robustness of magnetoelectricity.

具有拓扑特性的关联电子体系是当前凝聚态物理领域前沿热点，有深刻的物理内涵和广阔的应用前景。本项目通过理论结合实验，研究几类典型的非赝立方结构过渡金属关联电子(d、f电子)体系中拓扑磁电性及其相互耦合行为。具体而言，本项目将从构建出合理的描述拓扑铁电涡旋畴形成条件的理论并掌握其动力学特征；揭示非共面磁性化合物体系的基态、激发态，以及磁动力学的机制；实现对拓扑磁电态的观测和操控；关注元素价态和磁性离子密度、界面态、微结构、晶格失配、应变及外场（电、磁、光等）等因素对量子层面上自旋、轨道、电荷有序-无序、磁电拓扑电子态的影响。目标是寻求多重磁电拓扑共存和耦合的物理根源，找到几类具有实空间拓扑磁电拓扑态的关联电子材料体系，发展与磁电拓扑特性相关的原型器件。本项目的研究将丰富关联电子体系的磁电物理，并拓展凝聚态物理中拓扑性范畴，且推进拓扑磁电鲁棒性的功能利用。

具有拓扑特性的关联电子体系是当前凝聚态物理领域前沿热点，有深刻的物理内涵和广阔的应用前景。本项目通过理论结合实验，研究几类典型的非赝立方结构过渡金属关联电子(d、f电子)体系中拓扑磁电性及其相互耦合行为。本项目完成了如下几个主要原创性研究内容：1）理论预测了二维亚铁电体系WO2Cl2和MoO2Cl2，揭示了其特殊的非共线亚铁电极性序，以及由此产生的Z2xZ2拓扑畴与极性涡旋。2) 理论预测了具有120度非共线手性磁结构的二维三角格子体系Hf2VC2F2，以及其磁性导致的电极化。3) 理论结合实验研究了了多种4d/5d强自旋轨道耦合的体系的独特磁性，如Jeff=1/2的Sr2IrO4和Jeff=3/2的K2NbCl6。4)成功合成了几类新型亚铁电、铁电、磁电耦合体系并对其性质进行了系统的表征，获得了不可约亚铁电和负压电的实验证据并做了理论解释。这些研究推动了磁电耦合物理与材料的前沿进展，加深了相关领域的物理理解，在低维极性、拓扑磁电结构方面取得了较大的进展。在本项目的支持下，共发表论文54篇，其中SCI收录51篇，中文期刊综述4篇，其中绝大多数为(共同)通讯作者论文（包括Phys. Rev. Lett. 1篇，J. Am. Chem. Soc. 2篇, Nat. Commun. 1篇，Sci. Adv. 1篇)。负责人受邀在国际会议做邀请报告17次，包括2017年APS March Meeting邀请报告，2017年与2019年MRS Fall Meeting邀请报告。依托本项目，培养毕业博士生毕7名，其中一人获中国硅酸盐学会优秀博士论文提名奖；培养毕业硕士生8名，其中一人获江苏省优秀硕士论文。