Data archive of "Imperfect Many-Body Localization in Exchange-Disordered Isotropic Spin Chains"

abstract of the article:
We investigate many-body localization in isotropic Heisenberg spin chains with the local exchange parameters being subject to quenched disorder. Such systems incorporate a nonabelian symmetry in their Hamiltonian by an invariance under global SU(2)-rotations. Nonabelian symmetries are predicted to hinder the emergence of a many-body localized phase even in presence of strong disorder. We report on numerical studies using exact diagonalization for chains of common spin length 1/2 and 1. The averaged consecutive-gap ratios display a transition compatible with a crossover from an ergodic phase at small disorder strength to an incompletely localized phase at stronger disorder. The sample-to-sample variance of the averaged consecutive-gap ratio displays a maximum at the transition and distinguishes the incompletely localized phase from a fully many-body localized phase by its scaling behavior.

论文摘要：我们研究了局域交换参数受淬火无序（quenched disorder）调控的各向同性海森堡自旋链中的多体局域化（many-body localization）现象。此类系统的哈密顿量（Hamiltonian）具有全局SU(2)旋转不变性，因而蕴含非阿贝尔对称性（nonabelian symmetry）。理论预测，即便存在强淬火无序，非阿贝尔对称性也会阻碍多体局域化相的形成。我们针对自旋量子数为1/2和1的典型自旋链，开展了基于精确对角化（exact diagonalization）的数值模拟研究。平均相邻能隙比所展现的转变特征，与弱无序强度下的遍历相（ergodic phase）到强无序下的不完全局域化相之间的跨接（crossover）相吻合。平均相邻能隙比的样本间方差在该跨接点处呈现峰值，且可通过其标度行为（scaling behavior）将不完全局域化相与完全多体局域化相区分开来。