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arXiv 2201.10384cond-mat.str-elquant-ph
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$K$层Ising复曲面码的量子相变

Quantum phase transitions in the $K$-layer Ising toric code

L. Schamriss, L. Lenke, M. Mühlhauser, K. P. Schmidt

摘要:

我们研究了$K$层Ising复曲面码与$K$层二维复曲面码通过Ising相互作用耦合的量子相图。而对于小的伊辛相互作用,系统显示源自每层中的复曲面代码的$\mathbb{Z}_2^K$拓扑顺序,系统显示高伊辛极限中的$\mathbb{Z}_2$拓扑顺序。后者证明了一般$K$通过推导一个有效的低能量模型在$K^{\rm th}$阶简并微扰理论,这是一个有效的各向异性单层环面代码的集体伪自旋1/2的孤立伊辛链段的两个基态。对于特定的情况下,$K=3$和$K=4$,我们应用高阶级数展开,以确定在低和高伊辛极限的间隙系列。外推的基本能隙给出了令人信服的证据表明,基态相图由一个单一的量子临界点在三维伊辛 * 普适性类的两个$K$分离两种类型的拓扑秩序,这是一致的双层伊辛复曲面代码与以前的研究结果。

英文摘要:

We investigate the quantum phase diagram of the $K$-layer Ising toric code corresponding to $K$ layers of two-dimensional toric codes coupled by Ising interactions. While for small Ising interactions the system displays $\mathbb{Z}_2^K$ topological order originating from the toric codes in each layer, the system shows $\mathbb{Z}_2$ topological order in the high-Ising limit. The latter is demonstrated for general $K$ by deriving an effective low-energy model in $K^{\rm th}$-order degenerate perturbation theory, which is given as an effective anisotropic single-layer toric code in terms of collective pseudo-spins 1/2 refering to the two ground states of isolated Ising chain segments. For the specific cases $K=3$ and $K=4$ we apply high-order series expansions to determine the gap series in the low- and high-Ising limit. Extrapolation of the elementary energy gaps gives convincing evidence that the ground-state phase diagram consists of a single quantum critical point in the 3d Ising* universality class for both $K$ separating both types of topological order, which is consistent with former findings for the bilayer Ising toric code.

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