Smaha Rebecca W, He Wei, Jiang Jack Mingde, Wen Jiajia, Jiang Yi-Fan, Sheckelton John P, Titus Charles J, Wang Suyin Grass, Chen Yu-Sheng, Teat Simon J, Aczel Adam A, Zhao Yang, Xu Guangyong, Lynn Jeffrey W, Jiang Hong-Chen, Lee Young S
Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA.
Department of Chemistry, Stanford University, Stanford, CA 94305, USA.
NPJ Quantum Mater. 2020;5(1). doi: https://doi.org/10.1038/s41535-020-0222-8.
The spin- kagome antiferromagnet is considered an ideal host for a quantum spin liquid (QSL) ground state. We find that when the bonds of the kagome lattice are modulated with a periodic pattern, new quantum ground states emerge. Newly synthesized crystalline barlowite (Cu(OH)FBr) and Zn-substituted barlowite demonstrate the delicate interplay between singlet states and spin order on the spin- kagome lattice. Comprehensive structural measurements demonstrate that our new variant of barlowite maintains hexagonal symmetry at low temperatures with an arrangement of distorted and undistorted kagome triangles, for which numerical simulations predict a pinwheel valence bond crystal (VBC) state instead of a QSL. The presence of interlayer spins eventually leads to an interesting pinwheel = 0 magnetic order. Partially Zn-substituted barlowite (CuZn(OH)FBr) has an ideal kagome lattice and shows QSL behavior, indicating a surprising robustness of the QSL against interlayer impurities. The magnetic susceptibility is similar to that of herbertsmithite, even though the Cu impurities are above the percolation threshold for the interlayer lattice and they couple more strongly to the nearest kagome moment. This system is a unique playground displaying QSL, VBC, and spin order, furthering our understanding of these highly competitive quantum states.
自旋 - Kagome反铁磁体被认为是量子自旋液体（QSL）基态的理想宿主。我们发现，当Kagome晶格的键以周期性模式调制时，会出现新的量子基态。新合成的晶体羟溴铜石（Cu(OH)FBr）和锌取代的羟溴铜石展示了自旋 - Kagome晶格上单重态与自旋序之间的微妙相互作用。综合结构测量表明，我们新的羟溴铜石变体在低温下保持六方对称性，具有扭曲和未扭曲的Kagome三角形排列，数值模拟预测其为风车价键晶体（VBC）态而非QSL态。层间自旋的存在最终导致了有趣的风车(S = 0)磁序。部分锌取代的羟溴铜石（CuZn(OH)FBr）具有理想的Kagome晶格并表现出QSL行为，表明QSL对层间杂质具有惊人的鲁棒性。尽管铜杂质高于层间晶格的渗流阈值且它们与最近的Kagome磁矩耦合更强，但其磁化率与水锌矿相似。这个系统是展示QSL、VBC和自旋序的独特平台，有助于我们进一步理解这些高度竞争的量子态。
