Magnetic structure in the S = 1/2 frustrated pyrochlore slab antiferromagnet Averievite Cu5(VO4)2O2CsCl

The search for quantum spin liquids (QSLs) remains a cornerstone of condensed matter physics. The S = 1/2 kagome Heisenberg magnet (KHM) is considered the most promising model system for the realisation of 2D QSLs. We have synthesised high quality powders of a new S=1/2 KHM averievite and its Zn-doped variants ZnxCu5–x(VO4)2O2CsCl, where x = 0, 1 and 2. We have performed extensive magnetometry, neutron diffraction (exp no. RB1920248) and inelastic neutron scattering (exp no. 4-05-746) measurements on our range of Zn-averievite samples between 0 < x < 2. Our results demonstrate the evolution of magnetic order to disorder with increased Zn doping, towards a potential QSL state in the ideal kagome geometry of x = 2. However, there are three major limitations with the data we have thus far collected due to the fact that the samples are powders: (i) the magnetic structure of x=0 cannot be uniquely refined; (ii) the spin waves of x=0 cannot be modelled using linear spin wave theory to extract exchange parameters; (iii) the powder-averaged Q-dependence of the diffuse excitations for x=2 do not allow confirmation of a QSL state. We will use this experiment to uniquely resolve the magnetic structure for x=0 using single crystal diffraction on WISH. The results will in turn aid the modelling of the spin waves in future inelastic scattering experiments and, ultimately, deepen our understanding of the potential QSL state when x=2.

对量子自旋液体（quantum spin liquids, QSLs）的探索始终是凝聚态物理的基石性研究领域。自旋S=1/2的笼目海森堡磁体（kagome Heisenberg magnet, KHM）被认为是实现二维量子自旋液体最具潜力的模型体系。我们合成了新型自旋S=1/2笼目海森堡磁体——阿韦里耶矿（averievite）及其锌掺杂变体ZnₓCu₅₋ₓ(VO₄)₂O₂CsCl（其中x=0、1、2）的高质量粉体。我们针对系列锌掺杂阿韦里耶矿样品（0<x<2）开展了全面的磁学测量、中子衍射（实验编号RB1920248）及非弹性中子散射（实验编号4-05-746）测试。实验结果表明，随着锌掺杂量提升，磁有序态逐渐向无序态演化，在理想笼目几何结构的x=2样品中有望实现量子自旋液体态。然而，由于样品为粉体形式，我们目前已获取的数据存在三方面主要局限：其一，x=0样品的磁结构无法被唯一精修；其二，无法通过线性自旋波理论对x=0样品的自旋波进行建模以提取交换相互作用参数；其三，x=2样品的弥散激发的粉体平均Q依赖特性无法证实量子自旋液体态的存在。本实验将利用WISH谱仪的单晶体衍射技术，唯一确定x=0样品的磁结构。该结果将助力后续非弹性散射实验中的自旋波建模工作，并最终深化我们对x=2样品中潜在量子自旋液体态的理解。