Menu Raphaël, Roscilde Tommaso
Univ Lyon, Ens de Lyon, Univ Claude Bernard, CNRS, Laboratoire de Physique, F-69342 Lyon, France.
Phys Rev Lett. 2020 Apr 3;124(13):130604. doi: 10.1103/PhysRevLett.124.130604.
Disorder in quantum systems can lead to the disruption of long-range order in the ground state and to the localization of the elementary excitations. Here we exhibit an alternative paradigm, by which disorder preserves long-range order in the ground state, while it localizes the elementary excitations above it, introducing a stark dichotomy between static properties-mostly sensitive to the density of states of excitations-and nonequilibrium dynamical properties-sensitive to the spatial structure of excitations. We exemplify this paradigm with a positionally disordered 2d quantum Ising model with r^{-6} interactions, capturing the internal-state physics of Rydberg-atom arrays. Disorder is found to lead to multifractality and localization of the spin-wave excitations above a ferromagnetic ground state; as a result, the spreading of entanglement and correlations starting from a factorized state exhibits anomalous diffusion with a continuously varying dynamical exponent, interpolating between ballistic and arrested transport. Our findings are directly relevant for the low-energy dynamics in quantum simulators of quantum Ising models with power-law decaying interactions.
量子系统中的无序会导致基态长程序的破坏以及元激发的局域化。在此，我们展示了一种替代范式，通过这种范式，无序在基态中保持长程序，而在其之上使元激发局域化，在静态性质（主要对激发态密度敏感）和非平衡动力学性质（对激发的空间结构敏感）之间引入了鲜明的二分法。我们以具有(r^{-6})相互作用的位置无序二维量子伊辛模型为例来说明这种范式，该模型捕捉了里德堡原子阵列的内态物理。发现无序会导致铁磁基态之上自旋波激发的多重分形性和局域化；结果，从因子化态开始的纠缠和关联的传播表现出具有连续变化动力学指数的反常扩散，在弹道输运和停滞输运之间插值。我们的发现与具有幂律衰减相互作用的量子伊辛模型的量子模拟器中的低能动力学直接相关。
