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arXiv 2009.11286cond-mat.dis-nn
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具有长程反铁磁相互作用的无序量子自旋链的纠缠特性

Entanglement Properties of Disordered Quantum Spin Chains with Long-Range Antiferromagnetic Interactions

Youcef Mohdeb, Javad Vahedi, N. Moure, A. Roshani, Hyun-Yong Lee, Ravindra N. Bhatt, Stefan Kettemann, Stephan Haas

摘要:

本文研究了具有随机长程耦合的量子自旋链中的纠缠熵和纠缠度,量子自旋链在空间上以幂律指数$α$衰减。使用强无序重整化群(SDRG)技术,我们找到了主方程的解析解的强无序不动点,其特征在于一个不动点分布的耦合与有限的动力学指数,它描述了系统一致的制度$α> 1/2$。SDRG方法的数值实现产生的平均并发的幂律空间衰减,这也证实了精确的数值对角化。然而,我们发现,最低阶的SDRG方法是不足以获得典型值的并发。因此,我们实现了一个校正方案,使我们能够获得的领导阶校正的随机单重态。这种方法产生一个幂律空间衰减的典型值的并发,我们得到的数值实现的校正和分析。其次,使用数值SDRG,纠缠熵(EE)被发现是在数值上增强的所有$α$,对应于一个临界行为与一个有效的中心荷$c = {\rm ln} 2$,独立于$α$。这是由一个分析推导证实。使用数值精确对角化(ED),我们确认的EE和弱依赖于$α$的对数增强。对于广泛的距离$l$,EE符合一个关键的行为与接近$c=1$的中心荷,这是相同的清洁Haldane-Shastry模型与$α=2$的功率衰减相互作用。与此观察一致,我们发现使用ED的并发显示幂律衰减,虽然较小的功率指数比SDRG获得。

英文摘要:

We examine the concurrence and entanglement entropy in quantum spin chains with random long-range couplings, spatially decaying with a power-law exponent $α$. Using the strong disorder renormalization group (SDRG) technique, we find by analytical solution of the master equation a strong disorder fixed point, characterized by a fixed point distribution of the couplings with a finite dynamical exponent, which describes the system consistently in the regime $α> 1/2$. A numerical implementation of the SDRG method yields a power law spatial decay of the average concurrence, which is also confirmed by exact numerical diagonalization. However, we find that the lowest-order SDRG approach is not sufficient to obtain the typical value of the concurrence. We therefore implement a correction scheme which allows us to obtain the leading order corrections to the random singlet state. This approach yields a power-law spatial decay of the typical value of the concurrence, which we derive both by a numerical implementation of the corrections and by analytics. Next, using numerical SDRG, the entanglement entropy (EE) is found to be logarithmically enhanced for all $α$, corresponding to a critical behavior with an effective central charge $c = {\rm ln} 2$, independent of $α$. This is confirmed by an analytical derivation. Using numerical exact diagonalization (ED), we confirm the logarithmic enhancement of the EE and a weak dependence on $α$. For a wide range of distances $l$, the EE fits a critical behavior with a central charge close to $c=1$, which is the same as for the clean Haldane-Shastry model with a power-la-decaying interaction with $α=2$. Consistent with this observation, we find using ED that the concurrence shows power law decay, albeit with smaller power exponents than obtained by SDRG.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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