Khuntia P, Bert F, Mendels P, Koteswararao B, Mahajan A V, Baenitz M, Chou F C, Baines C, Amato A, Furukawa Y
Ames Laboratory, U.S. Department of Energy, Ames, Iowa 50011, USA.
Laboratoire de Physique des Solides, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91405 Orsay Cedex, France.
Phys Rev Lett. 2016 Mar 11;116(10):107203. doi: 10.1103/PhysRevLett.116.107203.
PbCuTe_{2}O_{6} is a rare example of a spin liquid candidate featuring a three-dimensional magnetic lattice. Strong geometric frustration arises from the dominant antiferromagnetic interaction that generates a hyperkagome network of Cu^{2+} ions although additional interactions enhance the magnetic lattice connectivity. Through a combination of magnetization measurements and local probe investigations by NMR and muon spin relaxation down to 20 mK, we provide robust evidence for the absence of magnetic freezing in the ground state. The local spin susceptibility probed by the NMR shift hardly deviates from the macroscopic one down to 1 K pointing to a homogeneous magnetic system with a low defect concentration. The saturation of the NMR shift and the sublinear power law temperature (T) evolution of the 1/T_{1} NMR relaxation rate at low T point to a nonsinglet ground state favoring a gapless fermionic description of the magnetic excitations. Below 1 K a pronounced slowing down of the spin dynamics is witnessed, which may signal a reconstruction of spinon Fermi surface. Nonetheless, the compound remains in a fluctuating spin liquid state down to the lowest temperature of the present investigation.
PbCuTe₂O₆是具有三维磁晶格的自旋液体候选物的一个罕见例子。强烈的几何阻挫源于占主导地位的反铁磁相互作用，这种相互作用产生了一个由Cu²⁺离子构成的超 Kagome 网络，尽管其他相互作用增强了磁晶格的连通性。通过结合磁化测量以及利用核磁共振（NMR）和μ子自旋弛豫进行的局部探针研究，直至温度低至20 mK，我们提供了确凿证据，证明基态不存在磁冻结。通过NMR位移探测的局部自旋磁化率在低至1 K时几乎与宏观磁化率没有偏差，这表明该磁系统均匀且缺陷浓度低。NMR位移的饱和以及低温度下1/T₁ NMR弛豫率的亚线性幂律温度（T）演化表明，基态为非单重态，有利于对磁激发进行无隙费米子描述。在1 K以下，自旋动力学明显减慢，这可能预示着自旋子费米面的重构。尽管如此，在本研究的最低温度下，该化合物仍处于波动的自旋液体状态。
