We investigate the effect of impurities on the thermal entanglement in a spin-1/2 Ising–Heisenberg butterfly-shaped chain, where four interstitial Heisenberg spins are localized on the vertices of a rectangular plaquette in a unit block. By using the transfer-matrix approach, we numerically calculate the partition function and the reduced density matrix of this model. The bipartite thermal entanglement between different Heisenberg spin pairs is quantified by the concurrence. We also discuss the fluctuations caused by the impurities through the uniform distribution and the Gaussian distribution. Considering the effects of the external magnetic field, temperature, Heisenberg and Ising interactions as well as the parameter of anisotropy on the thermal entanglement, our results show that comparing with the case of the clean model, in both the two-impurity model and the impurity fluctuation model the entanglement is more robust within a certain range of anisotropic parameters and the...

中文翻译：

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自旋1/2 Ising–Heisenberg蝴蝶形链与杂质的热缠结

我们研究了自旋1/2 Ising–Heisenberg蝴蝶形链中杂质对热缠结的影响，在该链中，四个间质Heisenberg自旋位于一个单元块中的矩形拼块的顶点上。通过使用传递矩阵方法，我们用数值方法计算了该模型的分配函数和降密度矩阵。不同的海森堡自旋对之间的二分热纠缠通过并发来量化。我们还讨论了通过均匀分布和高斯分布由杂质引起的波动。考虑到外部磁场，温度，海森堡和伊辛相互作用以及各向异性参数对热缠结的影响，我们的结果表明，与纯模型的情况相比，