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中国物理学会期刊

由超辐射引起的迁移率边和重返局域化

CSTR: 32037.14.aps.71.20212246

Mobility edges and reentrant localization induced by superradiance

CSTR: 32037.14.aps.71.20212246
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  • 研究了束缚在梯子形光晶格中的中性原子与高精度腔耦合的系统, 发现由超辐射引起的准周期调制可以导致迁移率边和重返局域化现象的出现. 在平均场近似下, 超辐射现象可以引起两种不同频率的准周期调制, 它们可以由腔场和泵浦场有效调节. 在本文的观测范围内, 当高频调制强度小于某一临界值时, 系统随着低频调制强度的增加经历一次局域转变. 通过数值求解分形维度、密度分布、平均参与率、平均逆参与率以及标度分析, 证明了局域转变历经的临界相区存在迁移率边; 当高频调制强度大于临界值时, 随着低频调制强度的增强, 系统依次经历完全扩展相-临界相-完全局域相-临界相-完全局域相, 这是一个典型的重返局域化现象. 最后给出了局域化相图. 该研究结果为超辐射相变和重返局域化现象的研究建立了联系, 也为重返局域化的研究搭建了新的平台.

     

    We study a Bose-Einstein condensate trapped by a ladder lattice in a high-fitness cavity. The ladder lattice is loaded in the x\text-y plane and the cavity is along the x direction. A pump laser shines on atoms from the z direction. Under the mean-field approximation, we consider the emergence of the quasi-periodic potentials induced by superradiance in the ladder lattice, which is described by \hatH_\textMF=\hatH_\textLad+\hatV_\texteff with the effective potential \hatV_\texteff(\alpha)=\displaystyle \sum\nolimits_i = 1^N\displaystyle \sum\nolimits_\sigma = 1,2\left\lambda_\rmD\cos(2\pi\beta i)+U_\rmD\cos^2(2\pi\beta i)\right\hatc^†_i,\sigma\hatc_i,\sigma. We find that the quasi-periodic potential can induce the reentrant localization transition and the regime with mobility edges. In the smaller U_\rmD case, the system exhibits a localization transition. The transition is associated with an intermediate regime with mobility edges. When U_\rmD goes beyond a critical value U_\rmD^(\rm c), with the increase of \lambda_\rmD, the system undergoes a reentrant localization transition. This indicates that after the first transition, some of the localized eigenstates change back to the extended ones for a range of \lambda_\rmD. For a larger \lambda_\rmD, the system experiences the second localization transition, then all states become localized again. Finally, the local phase diagram of the system is also discussed. This work builds a bridge between the reentrant localization and the superradiance, and it provides a new perspective for the reentrant localization.

     

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