• DOI:10.1103/PHYSREVB.103.024203
• Corpus ID: 222090360

Absence of true localization in many-body localized phases

@article{KieferEmmanouilidis2020AbsenceOT,
  title={Absence of true localization in many-body localized phases},
  author={Maximilian Kiefer-Emmanouilidis and Razmik G. Unanyan and Michael Fleischhauer and Jesko Sirker},
  journal={arXiv: Disordered Systems and Neural Networks},
  year={2020}
}

• M. Kiefer-Emmanouilidis, R. Unanyan, +1 author J. Sirker
• Published 1 October 2020
• Physics
• arXiv: Disordered Systems and Neural Networks

We have recently shown that the logarithmic growth of the entanglement entropy following a quantum quench in a many-body localized (MBL) phase is accompanied by a slow growth of the number entropy, $S_N\sim\ln\ln t$. This violates the standard scenario of MBL and raises the question whether the observed behavior is transient or continues to hold at strong disorder in the thermodynamic limit. Here we provide an in-depth numerical study of $S_N(t)$ for the disordered Heisenberg chain and find strong evidence that the system is not fully localized even at strong disorder. Calculating the Renyi number entropy $S_N^{(\alpha)}(t)$ for $\alpha\ll 1$---which is sensitive to large number fluctuations occurring with low probability---we demonstrate that the particle number distribution $p(n)$ in one half of the system has a small but continuously growing tail. This indicates a steady increase of the number of particles crossing between the partitions in the interacting case, and is in sharp contrast to Anderson localization, where $S_N^{(\alpha)}(t)$ saturates.