基于Kagome结构阻挫磁体新材料探索

Our main focus of this project is to search for new Kagome structure’s materials with frustrated magnet. Some new materials with Kagome structure will be firstly synthesized based on the known materials such as Barlowite ( Cu4(OH)6FBr ), and some unknown system will be explored. Based on the structure and physical properties measurement, some exotic phenomenon may be discovered. Combined with the theoretical investigation, we try to explain the properties and reasonable theoretical description of the physical mechanism..Frustrated magnets are materials in which localized magnetic moments, or spins, interact through competing exchange interactions that cannot be simultaneously satisfied. Quantum Spin Liquid (QSL) is a novel state which may be achieved in the frustrated magnets. QSL shows a lot of exotic behaviors such as emergent gauge fields and fractional particle excitations. QSL is related to the mechanism of high temperature superconductors and fractional quantum Hall effect. .The sample preparation is the most important thing in this project. The hydrothermal method, vapor transport method and some other chemical way will be performed to prepare the new materials and high quality single crystals. The exploration can be performed by replacing the inter-Kagome Cu with some non-magnetic element and synthesizing some new system materials, such as Cu3Zn(OH)6FBr. A series of materials will be synthesized and performed for systematic study..Our laboratory provide sufficient measuring instruments for structural determination and physical properties characterization. These instruments includes high sensitive Spring-8, X-ray diffractometer, TEM, Quantum Design PPMS, MPMS and so on. We are skillful to perform the measurement and analyze the data. We will determine the crystal structure and study the detailed physical properties including magnetic properties, specific heat, and so on. We will try our best to find the exotic phenomenon. Neutron scatter measurement and nuclear magnetic resonance will be carried out to study the magnetic structure and characters of collective phenomena. With the cooperation of the theoretical computation, we will give reasonable explanations for the exotic behaviors..Frustrated magnets as strong correlated system has attracted a lot of attention in condensed matter physics. Many novel phenomenon has been uncovered such as fractionalized spinon excitations, quantum critical behavior and topological degeneracy. We hope to synthesize a series of new Kagome structure materials based on this project and study the physical mechanism experimentally and theoretically as well as try to discovery some topological and superconducting phases.

本项目以探索基于Kagome结构阻挫磁体的新材料为研究对象。几何阻挫磁体中的量子自旋系统，可能进入被称为量子自旋液体的顺磁基态。关于量子自旋液体的研究，对理解高温超导机制、实现拓扑量子计算，拓展朗道对称性破缺范式有重要的推动作用。Kagome 结构的阻挫磁体是一种非常有希望实现量子自旋液体的体系。我们希望通过对Kagome结构阻挫磁体新材料的探索，发现新奇物性，探究其背后的物理机制，对量子自旋液体形成系统性研究。新材料的探索与合成，高质量的单晶样品的生长对研究阻挫系统中复杂的自旋结构、自旋激发以及相关的物理机制有着重要的价值。本项目将对新材料进行准确、系统的结构分析以及物性研究，针对具有可能出现量子自旋液体、新奇磁结构、量子临界现象等新奇物性的材料，开展更加细致的研究，促进强关联系统的自旋关联、长程量子纠缠、拓扑序等等凝聚态前沿领域的研究进展。

本项目以探索基于Kagome结构阻挫磁体的新材料为研究对象。几何阻挫磁体中的量子自旋系统，可能进入被称为量子自旋液体的顺磁基态。Kagome结构的阻挫磁体是一种非常有希望实现量子自旋液体的体系，关于量子自旋液体的研究，对理解高温超导机制、实现拓扑量子计算，拓展朗道对称性破缺范式有重要的推动作用。在本基金支持下，我们在Kagome结构阻挫磁体及其他新材料领域取得了一系列重要的科研成果，包括新的量子自旋液体候选材料的发现，Kagome结构磁体材料的发现，同时我们也在拓扑量子材料领域进行了探索和研究，得到了一系列研究成果。.主要进展有以下几个方面：.（1）在Kagome结构阻挫体系研究方向，我们首次合成了新的量子自旋液体候选材料Cu3Zn(OH)6FCl，该材料体系的成功合成，为人们研究量子自旋液体行为提供了新的素材。该工作发表在Chinese Physical Letter Express上【Chin. Phys. Lett. 36, 017502 (2019)】并得到了著名物理学家Y. S. Lee的高度评价；我们首次合成了具有Kagome结构的反铁磁体α-Cu3Mg(OH)6Br2，并通过磁化率，比热和中子衍射等物性测量手段对其磁结构进行了研究【Phys. Rev. B 100 (2019) 155129】；我们也利用中子衍射和μ子自旋旋转和弛豫（SR）技术系统地研究了Cu4-xZnx(OH)6FBr的磁性，绘制出其磁性相图【Chin. Phys. Lett. 37, 10, 107503, 2020】。.（2）在拓扑量子材料研究方向，我们在NbSixTe2材料中发现一维无质量Dirac费米子，该研究首次报道了具有四重简并度的一维无质量狄拉克费米子型准粒子，并为范德瓦尔斯异质结的设计提供了一个新的具有一维电子态的构成单元NbSi0.45Te2【Nat. Mater. (2020): 1-7】；我们研究了磁性外尔半金属Co3Sn2S2的电子关联和平带性质，该研究为外尔半金属中的平带物理带来一个新的机会【Nat. Commun. (2020):11.3985】；我们研究了本征磁性拓朴绝缘体EuSn2As2及MnBi2nTe3n+1的狄拉克表面态，观察到反铁磁TI材料 MnBi2nTe3n+1中无能隙的Dirac表面态，为磁性拓扑绝缘体的非平庸拓扑提供了清晰的证据