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arXiv 2007.10357cond-mat.dis-nncond-mat.stat-mechquant-ph
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一类强关联无序图的局部化

Localisation on certain graphs with strongly correlated disorder

Sthitadhi Roy, David E. Logan

摘要:

相互作用量子系统中的多体局域化可以被视为底层福克空间图上的无序跳跃问题。有效的Fock空间无序的一个重要特征是,Fock空间站点能量是强相关的-最大限度地使网站上的图形上的有限距离分开。出于这一点,并了解这种相关性的影响更根本,我们研究安德森本地化凯莱树和随机规则图,最大相关的障碍。由于这种相关性抑制了无序势的短距离波动,人们可能会天真地认为它们不利于局域化。然而,我们发现,存在一个安德森过渡,事实上,本地化是更强大的意义上说,关键的障碍规模与图形连接$K$为$\sqrt{K}$,在显着的对比$K\ln K$在不相关的情况下。这种缩放被认为是密切相关的稳定性的多体本地化。我们的分析集中在局部传播子的精确递归公式以及自洽平均场论上;结果使用精确对角化得到证实。

英文摘要:

Many-body localisation in interacting quantum systems can be cast as a disordered hopping problem on the underlying Fock-space graph. A crucial feature of the effective Fock-space disorder is that the Fock-space site energies are strongly correlated -- maximally so for sites separated by a finite distance on the graph. Motivated by this, and to understand the effect of such correlations more fundamentally, we study Anderson localisation on Cayley trees and random regular graphs, with maximally correlated disorder. Since such correlations suppress short distance fluctuations in the disorder potential, one might naively suppose they disfavour localisation. We find however that there exists an Anderson transition, and indeed that localisation is more robust in the sense that the critical disorder scales with graph connectivity $K$ as $\sqrt{K}$, in marked contrast to $K\ln K$ in the uncorrelated case. This scaling is argued to be intimately connected to the stability of many-body localisation. Our analysis centres on an exact recursive formulation for the local propagators as well as a self-consistent mean-field theory; with results corroborated using exact diagonalisation.

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