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arXiv 1808.07884cond-mat.mes-hallquant-ph
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准周期驱动量子系统的拓扑分类

Topological classification of quasi-periodically driven quantum systems

Philip J. D. Crowley, Ivar Martin, Anushya Chandran

摘要:

由$n_\mathrm{f}$无公度基频驱动的几个能级量子系统在$n_\mathrm{f}$空间维度上表现出非相互作用现象的时间模拟,这是Floquet理论在频率空间中推广的结果。我们将$n_\mathrm{f}=2$的频率晶格模型的基本解组织成一个准能量能带结构,并表明每个带被归类为一个整数陈数。在平凡类中,所有带的Chern数为零,准周期动力学性质类似于Floquet动力学。具有非零Chern带的拓扑类具有戏剧性的动力学特征,包括从一个驱动器到另一个驱动器的能量泵送、对初始条件的混沌对初始条件的敏感性以及期望值的非周期时间动力学。然而,拓扑类是不稳定的通用扰动,由于准确的准能谱中的水平交叉。然而,使用的情况下,在一个准周期性变化的磁场的自旋研究,我们表明,拓扑类可以实现在低频率作为一个预热阶段,并在有限的频率使用反非绝热工具。

英文摘要:

Few level quantum systems driven by $n_\mathrm{f}$ incommensurate fundamental frequencies exhibit temporal analogues of non-interacting phenomena in $n_\mathrm{f}$ spatial dimensions, a consequence of the generalisation of Floquet theory in frequency space. We organise the fundamental solutions of the frequency lattice model for $n_\mathrm{f}=2$ into a quasi-energy band structure and show that every band is classified by an integer Chern number. In the trivial class, all bands have zero Chern number and the quasi-periodic dynamics is qualitatively similar to Floquet dynamics. The topological class with non-zero Chern bands has dramatic dynamical signatures, including the pumping of energy from one drive to the other, chaotic sensitivity to initial conditions, and aperiodic time dynamics of expectation values. The topological class is however unstable to generic perturbations due to exact level crossings in the quasi-energy spectrum. Nevertheless, using the case study of a spin in a quasi-periodically varying magnetic field, we show that topological class can be realised at low frequencies as a pre-thermal phase, and at finite frequencies using counter-diabatic tools.

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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