Srivatsa N S, Moessner Roderich, Nielsen Anne E B
Max-Planck-Institut für Physik komplexer Systeme, Nöthnitzer Strasse 38, D-01187 Dresden, Germany.
Phys Rev Lett. 2020 Dec 11;125(24):240401. doi: 10.1103/PhysRevLett.125.240401.
Many-body localization (MBL) provides a mechanism to avoid thermalization in many-body quantum systems. Here, we show that an emergent symmetry can protect a state from MBL. Specifically, we propose a Z_{2} symmetric model with nonlocal interactions, which has an analytically known, SU(2) invariant, critical ground state. At large disorder strength, all states at finite energy density are in a glassy MBL phase, while the lowest energy states are not. These do, however, localize when a perturbation destroys the emergent SU(2) symmetry. The model also provides an example of MBL in the presence of nonlocal, disordered interactions that are more structured than a power law. Finally, we show how the protected state can be moved into the bulk of the spectrum.
多体局域化（MBL）为避免多体量子系统中的热化提供了一种机制。在此，我们表明一种涌现对称性可以保护一个态免受MBL影响。具体而言，我们提出了一个具有非局域相互作用的(Z_{2})对称模型，其具有一个解析可知的、(SU(2))不变的临界基态。在大无序强度下，有限能量密度的所有态都处于玻璃态MBL相，而最低能量态则不然。然而，当一个微扰破坏涌现的(SU(2))对称性时，这些态会发生局域化。该模型还提供了一个存在比幂律更具结构的非局域无序相互作用时的MBL示例。最后，我们展示了受保护态如何能移动到能谱的主体部分。
