arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1902.06995cond-mat.mes-hallcond-mat.str-el
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周期驱动Kitaev模型的拓扑与局部化

Topology and localization of a periodically driven Kitaev model

I. C. Fulga, M. Maksymenko, M. T. Rieder, N. H. Lindner, E. Berg

摘要:

周期驱动的量子多体系统支持物质的反常拓扑相,这是静态系统无法实现的。在许多情况下,这些异常相可以是多体局部化的,这意味着它们是稳定的,并且不会由于驱动而升温。在驱动系统中,什么类型的反常拓扑现象可以被稳定化,特别是,表现出非阿贝尔任意子的反常相位可以被稳定化?我们解决这个问题,使用一个完全可解的,频闪驱动的2D Kitaev自旋模型,其中各向异性交换耦合在连续的时间间隔提高。该模型显示了丰富的相图,其中包含异常的拓扑相。我们使用弱和强散射矩阵不变量定义的费米自由度的特点,这些阶段。特别重要的是一个异常的阶段,其零通量部门表现出费米子带与零陈数,而一个漩涡绑定一对马约拉纳模式,我们支持非阿贝尔编织统计。我们进一步表明,在添加无序,零通量部门的模型成为本地化。然而,该模型不保持局部的有限密度的旋涡。结合到涡旋的Majorana模式的杂交形成“涡旋带”,其通过形成陈带或热金属相而离域。我们的结论是,虽然该模型不能多体本地化,它仍然可能表现出较长的热化时间,由于需要创建一个有限密度的旋涡离域发生。

英文摘要:

Periodically driven quantum many-body systems support anomalous topological phases of matter, which cannot be realized by static systems. In many cases, these anomalous phases can be many-body localized, which implies that they are stable and do not heat up as a result of the driving. What types of anomalous topological phenomena can be stabilized in driven systems, and in particular, can an anomalous phase exhibiting non-Abelian anyons be stabilized? We address this question using an exactly solvable, stroboscopically driven 2D Kitaev spin model, in which anisotropic exchange couplings are boosted at consecutive time intervals. The model shows a rich phase diagram which contains anomalous topological phases. We characterize these phases using weak and strong scattering-matrix invariants defined for the fermionic degrees of freedom. Of particular importance is an anomalous phase whose zero flux sector exhibits fermionic bands with zero Chern numbers, while a vortex binds a pair of Majorana modes, which as we show support non-Abelian braiding statistics. We further show that upon adding disorder, the zero flux sector of the model becomes localized. However, the model does not remain localized for a finite density of vortices. Hybridization of Majorana modes bound to vortices form "vortex bands", which delocalize by either forming Chern bands or a thermal metal phase. We conclude that while the model cannot be many-body localized, it may still exhibit long thermalization times, owing to the necessity to create a finite density of vortices for delocalization to occur.

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