Spin correlations in the two-leg antiferromagnetic ladder in a magnetic field
Spin correlations in the two-leg antiferromagnetic ladder in a magnetic field
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磁场中两腿反铁磁梯的自旋相关性
DOI：
10.1103/physrevb.63.134438
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发表时间：
2001
影响因子：
3.7
通讯作者：
A. Furusaki
中科院分区：
文献类型：
--
作者：
T. Hikihara;A. Furusaki
本文研究了磁场作用下S=1/2 XXZ链和两腿反铁磁阶梯的无间隙不相称区中基态自旋相关，其中无间隙激发形成了Tomonaga-Luttinger （TL）液体。我们用密度-矩阵重整化-群方法数值计算了两种模型的自旋相关函数和局部磁化强度。通过将100个自旋的开放XXZ链的数值结果拟合到高斯模型的相关函数上，确定了TL-liquid参数K和相关函数的幅值。从拟合中估计的K值与从Bethe ansatz中得到的确切值非常吻合。我们将同样的方法应用于由200个自旋组成的开放阶梯，并确定了K对磁化强度m的依赖关系。K- m关系随着腿和横条方向上耦合常数的比值而急剧变化。我们还讨论了这些结果对核自旋弛豫速率1/T_1和动态自旋结构因素的实验意义。
We study the ground-state spin correlations in the gapless incommensurate regime of a S=1/2 XXZ chain and a two-leg antiferromagnetic ladder under a magnetic field, in which the gapless excitations form a Tomonaga-Luttinger (TL) liquid. We calculate numerically the two-spin correlation functions and the local magnetization in the two models using the density-matrix renormalization-group method. By fitting the numerical results for an open XXZ chain of 100 spins to correlation functions of a Gaussian model, we determine the TL-liquid parameter K and the amplitudes of the correlation functions. The value of K estimated from the fits is in excellent agreement with the exact value obtained from the Bethe ansatz. We apply the same method to the open ladder consisting of 200 spins and determine the dependence of K on the magnetization M. The K-M relation changes drastically depending on the ratio of the coupling constants in the leg and rung directions. We also discuss implications of these results to experiments on the nuclear spin relaxation rate 1/T_1 and dynamical spin structure factors.