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arXiv 1601.01637cond-mat.stat-mech
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量子Ising链中的慢猝灭;动力学相变和拓扑

Slow quenches in a quantum Ising chain; dynamical phase transitions and topology

Shraddha Sharma, Uma Divakaran, Anatoli Polkovnikov, Amit Dutta

摘要:

我们研究了具有最近邻铁磁相互作用的一维横向伊辛链在量子临界点(QCP)上的慢猝灭动力学(以逆速率$τ^{-1}$为特征),并分析了Loschlavian重叠(使用最终波函数(在猝灭结束时达到)与最终与时间无关的哈密顿量的后续时间演化测量)。研究相应的广义“配分函数“的Fisher零点,我们探测了被称为动态相变(DPTs)的返回概率的速率函数中表现出的非解析性。在突然淬火的情况下,我们表明,DPTs生存{在随后的时间演化的淬火后,在两个临界点的模型足够慢的速度;此外,一个有趣的“叶”结构的Fisher零点出现。我们还将动力学拓扑序参量($ν_D(t)$)作为时间($t$)的函数(从猝灭完成的瞬间开始测量)与拓扑学方面联系起来。值得注意的是,$ν_D(t)$的时间演化在单个QCP和两个QCP的猝灭后表现出显著不同的行为。} {在前一种情况下,$ν_D (t)$在每个DPT逐步增加1(即,$Δν_D =1$)。另一方面,在后一种情况下,$ν_D(t)$基本上在0和1之间振荡(即,连续DPT分别与$Δν_D =1$和$Δν_D =-1$一起出现),除了当两个连续的DPT携带相同符号的拓扑电荷时它显示出单位因子的突然跳跃的时刻。

英文摘要:

We study the slow quenching dynamics (characterized by an inverse rate, $τ^{-1}$) of a one-dimensional transverse Ising chain with nearest neighbor ferromagentic interactions across the quantum critical point (QCP) and analyze the Loschmidt overlap {measured using the subsequent temporal evolution of the final wave function (reached at the end of the quenching) with the final time-independent Hamiltonian}. Studying the Fisher zeros of the corresponding generalized "partition function", we probe non-analyticities manifested in the rate function of the return probability known as dynamical phase transitions (DPTs). In contrast to the sudden quenching case, we show that DPTs survive {in the subsequent temporal evolution following the quenching across two critical points of the model for a sufficiently slow rate; furthermore, an interesting "lobe" structure of Fisher zeros emerge.} We have also made a connection to topological aspects studying the dynamical topological order parameter ($ν_D(t)$), as a function of time ($t$) {measured from the instant when the quenching is complete. Remarkably, the time evolution of $ν_D(t)$ exhibits drastically different behavior following quenches across a single QCP and two QCPs. } {In the former case, $ν_D (t)$ increases step-wise by unity at every DPT (i.e., $Δν_D =1$). In the latter case, on the other hand, $ν_D(t)$ essentially oscillates between 0 and 1 (i.e., successive DPTs occur with $Δν_D =1$ and $Δν_D =-1$, respectively), except for instants where it shows a sudden jump by a factor of unity when two successive DPTs carry a topological charge of same sign.

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