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arXiv 2101.11240quant-phcond-mat.stat-mechcond-mat.str-el
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一维复杂跳跃格点上单粒子扩展量子行走的长时间动力学:广义流体力学描述

Long time dynamics of a single particle extended quantum walk on a one dimensional lattice with complex hoppings: a generalized hydrodynamic description

Hemlata Bhandari, P. Durganandini

摘要:

我们研究了一维空间晶格上单个粒子(初始定位在单个位置)的连续时间量子行走,该空间晶格具有复杂的最近邻和次最近邻跳跃幅度。复杂的耦合导致手征传播和因果锥结构不对称的起源。给出了大时空极限下量子行走动力学的流体力学描述。我们发现一个全球性的“准稳态”,它可以描述的局部准粒子密度满足欧拉型流体动力学方程,其特征在于由一组无限的守恒律满足缩放的累积位置矩。此外,我们发现,有异常的亚扩散标度附近的极值前,这可以描述高阶流体动力学方程。具有非零实分量的任何复次近邻跳变的长时间行为类似于纯实跳变(除了不对称分布之外)。有一个临界耦合强度,在那里有一个Lifshitz过渡的因果结构的拓扑结构的变化,从一个政权与一个因果锥的政权与两个嵌套的因果锥。另一方面,对于纯虚的次近邻跳跃,由于存在退化的最大前沿(以相同的最大速度移动),存在从一个因果锥到具有两个部分重叠的锥的制度的过渡。在这两种情况下,在临界耦合强度的Lifshitz转变和标度行为(两者)的性质是不同的。

英文摘要:

We study the continuous time quantum walk of a single particle (initially localized at a single site) on a one-dimensional spatial lattice with complex nearest neighbour and next-nearest neighbour hopping amplitudes. Complex couplings lead to chiral propagation and a causal cone structure asymmetric about the origin. We provide a hydrodynamic description for quantum walk dynamics in large space time limit. We find a global "quasi-stationary state" which can be described in terms of the local quasi-particle densities satisfying Euler type of hydrodynamic equation and is characterized by an infinite set of conservation laws satisfied by scaled cumulative position moments. Further, we show that there is anomalous sub-diffusive scaling near the extremal fronts, which can be described by higher order hydrodynamic equations. The long time behaviour for any complex next-nearest neighbour hopping with a non-zero real component is similar to that of purely real hopping (apart from asymmetric distribution). There is a critical coupling strength at which there is a Lifshitz transition where the topology of the causal structure changes from a regime with one causal cone to a regime with two nested causal cones. On the other hand, for purely imaginary next-nearest neighbour hopping, there is a transition from one causal cone to a regime with two partially overlapping cones due to the existence of degenerate maximal fronts (moving with the same maximal velocity). The nature of the Lifshitz transition and the scaling behaviour (both) at the critical coupling strength is different in the two cases.

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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