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arXiv 2108.10329cond-mat.str-elcond-mat.stat-mech
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自旋为2的链中SU $(3)$临界性的情况

The case of SU$(3)$ criticality in spin-2 chains

Chengshu Li, Victor Luiz Quito, Eduardo Miranda, Rodrigo Pereira, Ian Affleck, Pedro L. S. Lopes

摘要:

在[(https://doi.org/10.1103/PhysRevLett.114.145301){Chen等人,物理修订信函$\mathbf{114}$,145301(2015)}],自旋-2链显示具有增强的SU $(3)$对称性的扩展临界相。这一假设是非常出乎意料的自旋2系统,正如我们所说,将意味着一个非传统的机制对称性的出现。然而,缺乏方便的临界点的重整化群微扰展开,与通常的困难,在临界或小间隙阶段的数值方法的收敛结盟,使验证这个假设的SU $(3)$对称相一个非平凡的事情。通过追踪与自旋1链的相图的相似之处,并寻找对有限尺寸效应鲁棒的签名,我们对这一阶段的存在提出了批评。我们进行非阿贝尔密度矩阵重整化群研究多极静态关联函数,能谱标度,单模近似,和纠缠谱来阐明这个问题。我们确定,假设的SU $(3)$自旋-2相,事实上,占主导地位的铁八极相关性,并观察到缺乏Luttinger液体样的行为在关联函数,这表明,也许是不关键的。我们进一步构建了一个无限家庭的自旋$S$系统与类似的铁八极占主导地位的准SU $(3)$的现象,奇怪的是,我们注意到,自旋3版本的问题是位于一个子空间的精确G $_2$对称性,使这一点的兴趣在磁性系统中的斐波那契拓扑性质的搜索。

英文摘要:

It was proposed in [(https://doi.org/10.1103/PhysRevLett.114.145301){Chen et al., Phys. Rev. Lett. $\mathbf{114}$, 145301 (2015)}] that spin-2 chains display an extended critical phase with enhanced SU$(3)$ symmetry. This hypothesis is highly unexpected for a spin-2 system and, as we argue, would imply an unconventional mechanism for symmetry emergence. Yet, the absence of convenient critical points for renormalization group perturbative expansions, allied with the usual difficulty in the convergence of numerical methods in critical or small-gapped phases, renders the verification of this hypothetical SU$(3)$-symmetric phase a non-trivial matter. By tracing parallels with the well-understood phase diagram of spin-1 chains and searching for signatures robust against finite-size effects, we draw criticism on the existence of this phase. We perform non-Abelian density matrix renormalization group studies of multipolar static correlation function, energy spectrum scaling, single-mode approximation, and entanglement spectrum to shed light on the problem. We determine that the hypothetical SU$(3)$ spin-2 phase is, in fact, dominated by ferro-octupolar correlations and also observe a lack of Luttinger-liquid-like behavior in correlation functions that suggests that is perhaps not critical. We further construct an infinite family of spin-$S$ systems with similar ferro-octupolar-dominated quasi-SU$(3)$-like phenomenology; curiously, we note that the spin-3 version of the problem is located in a subspace of exact G$_2$ symmetry, making this a point of interest for search of Fibonacci topological properties in magnetic systems.

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