Study of the exotic quantum magnetic state in paratacamite

Since the discovery of spin-liquid behaviors in herbertsmithite ZnCu3(OH)6Cl2, thousands of papers have been published on this subject. However, it remains an open issue about the intrinsic nature of the ground state in herbertsmithite, because ZnCu3(OH)6Cl2 was obtained by substituting Cu2(OH)3Cl [or exprssed as Cu4(OH)6Cl2] and inevitably contained a lot of defects. Previously we found unconventional magnetic transitions and coexistence of order and spin fluctuations in clinoatacamite, Cu2(OH)3Cl [2005 Phys. Rev. Lett. 95 057201], which was the parent compound of herbertsmithite [ZnCu3(OH)6Cl2, which was obtained by substituting Cu with non-magnetic Zn]. Fortunately, now we succeeded in synthesizing single crystals of paratacamite Cu2(OH)3Cl which is a polymorphous structure to clinoatacamite but with high symmetry like herbertsmithite. It is the optimum compound to study with muSR.

自羟氯铜锌矿（herbertsmithite, ZnCu3(OH)6Cl2）中自旋液体行为被发现以来，已有数千篇相关学术论文问世。然而，由于羟氯铜锌矿（ZnCu3(OH)6Cl2）是通过取代Cu2(OH)3Cl（亦可表示为Cu4(OH)6Cl2）制备得到，且不可避免地存在大量结构缺陷，其基态的本征性质至今仍是一个悬而未决的科学问题。此前我们在2005年《物理评论快报》（Phys. Rev. Lett.）第95卷第057201号文章中报道了斜纤氯铜矿（clinoatacamite, Cu2(OH)3Cl）中存在非常规磁相变以及有序态与自旋涨落共存的现象；而斜纤氯铜矿正是羟氯铜锌矿的母体化合物——羟氯铜锌矿通过将其中的Cu替换为非磁性Zn而制得。值得庆幸的是，我们现已成功合成出副氯铜矿（paratacamite, Cu2(OH)3Cl）的单晶，该物质与斜纤氯铜矿为同质多象结构，但其结构对称性与羟氯铜锌矿一样较高，是开展μ子自旋共振（muSR）研究的最优体系。