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中国物理学会期刊

周期驱动非互易Aubry-André模型中的多重分形态和迁移率边

CSTR: 32037.14.aps.74.20241633

Multifractal state and mobility edges in a periodically driven non-reciprocal Aubry-André model

CSTR: 32037.14.aps.74.20241633
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  • 研究了在非互易Aubry-André模型中由方波式周期驱动所诱导的多重分形态和迁移率边. 通过数值计算逆参与率、能谱的实复转变以及平均逆参与率的标度分析等, 发现在以高于临界频率的驱动下系统展现完全的局域相. 同时在Floquet谱的特定区域存在CAT态, 不同于厄米情况, 其波函数分布的两个峰值展现非等权叠加的特性, 这是由非互易物理所决定的. 而以低于临界频率的驱动下, Floquet谱中存在迁移率边和多重分形态. 该研究结果为周期驱动系统中局域化性质的研究提供了新的视角.

     

    In this work, we investigate the delocalization-localization transition of Floquet eigenstates in a driven chain with an incommensurate Aubry-André (AA) on-site potential and a small non-reciprocal hopping term that is driven periodically in time. The driving protocol is chosen such that the Floquet Hamiltonian corresponds to a localized phase in the high-frequency limit and a delocalized phase in the low-frequency limit. By numerically calculating the inverse participation ratio and the fractal dimension D_q, we identify a clear delocalization-localization transition of the Floquet eigenstates at a critical frequency \omega_\rm c\approx0.318\pi. This transition aligns with the real-to-complex spectrum transition of the Floquet Hamiltonian. For the driven frequency \omega>\omega_\mathrmc, the system resides in a localized phase, and we observe the emergence of CAT states—linear superposition of localized single particle states—in the Floquet spectrum. These states exhibit weight distributions concentrated around a few nearby sites of the chain, forming two peaks of unequal weight due to the non-reciprocal effect, distinguishing them from the Hermitic case. In contrast, for \omega<\omega_\mathrmc, we identify the presence of a mobility edge over a range of driving frequencies, separating localized states (above the edge) from multifractal and extended states (below the edge). Notably, multifractal states are observed in the Floquet eigenspectrum across a broad frequency range. Importantly, we highlight that the non-driven, non-reciprocal AA model does not support multifractal states nor a mobility edge in its spectrum. Thus, our findings reveal unique dynamical signatures that do not exist in the non-driven non-Hermitian scenario, providing a fresh perspective on the localization properties of periodically driven systems. Finally, we provide a possible circuit experiment scheme for the periodically driven non-reciprocal AA model. In the following work, we will extend our research to clean systems, such as Stark models, to explore the influence of periodic driving on their localization properties.

     

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