Localization dynamics in a centrally coupled system
Localization dynamics in a centrally coupled system
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DOI：
10.1103/physrevb.103.134201
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发表时间：
2020-03
影响因子：
3.7
通讯作者：
Nathan Ng;Sebastian Wenderoth;Rajagopala Reddy Seelam;E. Rabani;H. Meyer;M. Thoss;M. Kolodrubetz
中科院分区：
文献类型：
--
作者：
Nathan Ng;Sebastian Wenderoth;Rajagopala Reddy Seelam;E. Rabani;H. Meyer;M. Thoss;M. Kolodrubetz
在相互作用将中心自由度和浴缸耦合的系统中，人们会期望浴缸相的信号反映在中心自由度的动力学中。这一点最近在与中心量子比特或单腔模式耦合的多体局域浴场中进行了探索--这些系统在各种平台上具有越来越多的实验相关性。这类模型还通过量化外部驱动器与Floquet多体定位有一个有趣的联系，尽管这一点相对来说还没有被探索过。在这里，我们采用多层多组态时变Hartree(ML-MCTDH)方法，这是一种著名的树张量网络算法，用于数值模拟中心自由度的动力学，该中心自由度由一个$d$能级系统(QUDIT)表示，耦合到一个无序相互作用的一维自旋浴。ML-MCTDH允许我们达到大约10^2$格点，比精确对角化或核多项式方法所能实现的系统规模大得多。从中间时间动力学出发，对系统-浴场耦合进行适当的重新标度，我们发现了一个明确定义的量子动力学热力学极限。在相对较短的时间内，自旋系统在Edward-Anderson自旋玻璃序参数或纠缠熵中显示出类似的标度崩塌。在较长的时间尺度上，我们看到纠缠增长缓慢，这可能是由于局域系统中的退相机制或中心自由度介导的远程相互作用引起的。类似的局部化迹象也出现在未定标的系统-浴场耦合中。
In systems where interactions couple a central degree of freedom and a bath, one would expect signatures of the bath's phase to be reflected in the dynamics of the central degree of freedom. This has been recently explored in connection with many-body localized baths coupled with a central qubit or a single cavity mode -- systems with growing experimental relevance in various platforms. Such models also have an interesting connection with Floquet many-body localization via quantizing the external drive, although this has been relatively unexplored. Here we adapt the multilayer multiconfigurational time-dependent Hartree (ML-MCTDH) method, a well-known tree tensor network algorithm, to numerically simulate the dynamics of a central degree of freedom, represented by a $d$-level system (qudit), coupled to a disordered interacting 1D spin bath. ML-MCTDH allows us to reach $\approx 10^2$ lattice sites, a far larger system size than what is feasible with exact diagonalization or kernel polynomial methods. From the intermediate time dynamics, we find a well-defined thermodynamic limit for the qudit dynamics upon appropriate rescaling of the system-bath coupling. The spin system shows similar scaling collapse in the Edward-Anderson spin glass order parameter or entanglement entropy at relatively short times. At longer time scales, we see slow growth of the entanglement, which may arise from dephasing mechanisms in the localized system or long-range interactions mediated by the central degree of freedom. Similar signs of localization are shown to appear as well with unscaled system-bath coupling.