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arXiv 1702.03581cond-mat.stat-mechmath-phmath.MPquant-ph
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熵、能隙与Fredkin自旋链的多参数形变

Entropy, gap and a multi-parameter deformation of the Fredkin spin chain

Department of Physics, University of Virginia(弗吉尼亚大学物理系)

Zhao Zhang, Israel Klich

AI总结:

本研究提出Fredkin自旋1/2链的多参数无挫形变模型,构建了含面积律-体积律相变的相图,推导了不同参数下谱隙的上下界,给出了纠缠有界但谱隙消失的系统实例。

摘要:

我们提出了Fredkin自旋1/2链的一种多参数形变,其基态是Dyck路径的加权叠加态,权重依赖于沿链分布的一组参数$t_i$。引入这些参数的方式可使系统保持无挫特性,同时允许我们探索一系列可能的相。在参数均匀且添加颜色自由度的情况下,我们构建了相图,其中存在面积律与体积律之间的相变。半链的体积熵为$n \log s$,其中$n$为半链长度,$s$为颜色数。接下来,我们证明了$t>1, s>1$相的谱隙上界,其标度为$\Delta=O((4s)^nt^{-n^2/2})$,这与近期关于形变Motzkin模型的结果类似,但推导方式不同。最后,利用额外的变分论证,我们证明了$t>1, s=1$时模型能隙的指数下界,这提供了一个纠缠熵有界但谱隙趋于零的系统示例。

英文摘要:

We introduce a multi-parameter deformation of the Fredkin spin $1/2$ chain whose ground state is a weighted superposition of Dyck paths, depending on a set of parameters $t_i$ along the chain. The parameters are introduced in such a way to maintain the system frustration-free while allowing to explore a range of possible phases. In the case where the parameters are uniform, and a color degree of freedom is added we establish a phase diagram with a transition between an area law and a volume low. The volume entropy obtained for half a chain is $n \log s$ where $n$ is the half-chain length and $s$ is the number of colors. Next, we prove an upper bound on the spectral gap of the $t>1, s>1$ phase, scaling as $Δ=O((4s)^nt^{-n^2/2})$, similar to a recent a result about the deformed Motzkin model, albeit derived in a different way. Finally, using an additional variational argument we prove an exponential lower bound on the gap of the model for $t>1, s=1$, which provides an example of a system with bounded entanglement entropy and a vanishing spectral gap.

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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