arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1705.09804cond-mat.str-el
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时间周期Kitaev链的纠缠性质

Entanglement properties of the time periodic Kitaev Chain

Daniel J. Yates, Aditi Mitra

摘要:

研究了具有最近邻和次最近邻跳变的时间周期Kitaev链的纠缠特性。研究了时间周期哈密顿量的精确本征态(Floquet基态,FGS),以及在时间周期驱动的影响下对初始态进行幺正演化得到的物理态的情况.拓扑相位的特征在于不同数量的马约拉纳零($\mathbb{Z}_0$)和$π$($\mathbb{Z}_π$)模式,其中零模式即使在没有驱动的情况下也存在,而$π$模式由于共振驱动而出现。FGS的纠缠谱和物理态都表现出与准能谱不同数目的拓扑Majorana模。在一个驱动周期内,FGS的ES中的Majorana边缘模式的数量随时间从$|\mathbb{Z}_0-\mathbb{Z}_π|$变化到$\mathbb{Z}_0+\mathbb{Z}_π$,其中最大的$\mathbb{Z}_0+\mathbb{Z}_π$模式出现在周期的特定时间反转对称点处。另一方面,对于物理状态,ES中仅出现从初始波函数继承的模式,即$\mathbb{Z}_0$模式。物理状态中不存在$\mathbb{Z}_π$模式,因为它们与由于共振驱动而同时产生的体激发合并。通过将母波函数映射到布洛赫球上,解释了ES中Majorana零模和$π$模的拓扑性质。

英文摘要:

The entanglement properties of the time periodic Kitaev chain with nearest neighbor and next nearest neighbor hopping, is studied. The cases of the exact eigenstate of the time periodic Hamiltonian, referred to as the Floquet ground state (FGS), as well as a physical state obtained from time-evolving an initial state unitarily under the influence of the time periodic drive are explored. Topological phases are characterized by different numbers of Majorana zero ($\mathbb{Z}_0$) and $π$ ($\mathbb{Z}_π$) modes, where the zero modes are present even in the absence of the drive, while the $π$ modes arise due to resonant driving. The entanglement spectrum (ES) of the FGS as well as the physical state show topological Majorana modes whose number is different from that of the quasi-energy spectrum. The number of Majorana edge modes in the ES of the FGS vary in time from $|\mathbb{Z}_0-\mathbb{Z}_π|$ to $\mathbb{Z}_0+\mathbb{Z}_π$ within one drive cycle, with the maximal $\mathbb{Z}_0+\mathbb{Z}_π$ modes appearing at a special time-reversal symmetric point of the cycle. For the physical state on the other hand, only the modes inherited from the initial wavefunction, namely the $\mathbb{Z}_0$ modes, appear in the ES. The $\mathbb{Z}_π$ modes are absent in the physical state as they merge with the bulk excitations that are simultaneously created due to resonant driving. The topological properties of the Majorana zero and $π$ modes in the ES are also explained by mapping the parent wavefunction to a Bloch sphere.

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