论文标题
在二维随机量子磁体中极端抑制抗磁磁性和临界缩放
Extreme Suppression of Antiferromagnetic Order and Critical Scaling in a Two-Dimensional Random Quantum Magnet
论文作者
论文摘要
Sr $ _2 $ cuteo $ _6 $是一个方形的néelantiferromagnet，在第一邻居$ s = 1/2 $ cu之间，由plaquette中心介导。通过W代替TE，受影响的杂质plaquettes主要具有第二邻二邻，从而导致局部磁性挫败感。在这里，我们报告了SR $ _2 $可爱$ _ {1-x} $ W $ _x $ o $ $ _6 $的研究，使用中子衍射和$μ$ SR技术，表明Néel订单已经在$ x = 0.025 \ pm 0.005 $中消失了。我们使用二维Heisenberg自旋模型来解释这种极端的抑制作用，表明W型杂质在温度下降低距离为$ 1/r^2 $的订单参数的变形，$ t = 0 $。相关的对数奇点会导致任何$ x> 0 $的订单损失。小$ x> 0 $和$ t> 0 $的订单是由弱平面耦合引起的。在SR $ _2 $可爱$ _ {1-x} $ w $ _x $ o $ $ _6 $的非磁性阶段中，$μ$ $ $ SR放松速率显示出具有较大动态指数的量子关键缩放，$ z \ 3 $，一致，与随机的singlet状态一致。
Sr$_2$CuTeO$_6$ is a square-lattice Néel antiferromagnet with superexchange between first-neighbor $S=1/2$ Cu spins mediated by plaquette centered Te ions. Substituting Te by W, the affected impurity plaquettes have predominantly second-neighbor interactions, thus causing local magnetic frustration. Here we report a study of Sr$_2$CuTe$_{1-x}$W$_x$O$_6$ using neutron diffraction and $μ$SR techniques, showing that the Néel order vanishes already at $x = 0.025 \pm 0.005$. We explain this extreme order suppression using a two-dimensional Heisenberg spin model, demonstrating that a W-type impurity induces a deformation of the order parameter that decays with distance as $1/r^2$ at temperature $T=0$. The associated logarithmic singularity leads to loss of order for any $x>0$. Order for small $x>0$ and $T>0$ is induced by weak interplane couplings. In the nonmagnetic phase of Sr$_2$CuTe$_{1-x}$W$_x$O$_6$, the $μ$SR relaxation rate exhibits quantum critical scaling with a large dynamic exponent, $z \approx 3$, consistent with a random-singlet state.
