"Light-Cone" Dynamics After Quantum Quenches in Spin Chains
"Light-Cone" Dynamics After Quantum Quenches in Spin Chains
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DOI：
10.1103/physrevlett.113.187203
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发表时间：
2014-10-30
影响因子：
8.6
通讯作者：
Lauchli, Andreas M.
中科院分区：
文献类型：
--
作者：
Bonnes, Lars;Essler, Fabian H. L.;Lauchli, Andreas M.
近年来，量子猝灭后非平衡演化中的信号传播引起了实验和理论的广泛关注。在这种情况下出现的一个关键问题是，什么原理以及淬火的哪些特性决定了特征传播速度。在这里，我们研究了在相互作用的多粒子量子系统的中心范式之一，自旋1/2海森堡XXZ链中的一类猝灭协议的问题。我们用矩阵积态方法考虑从不同初始热密度矩阵到相同最终哈密顿量的淬火。观察到扩散速度随初始密度矩阵变化很大。然而，当将传播速度视为多余能量的函数时，我们实现了惊人的数据崩溃。利用XXZ链可积的事实，我们给出了在适当定义的广义吉布斯系综中用“激发”来解释观测到的速度。
Signal propagation in the nonequilibrium evolution after quantum quenches has recently attracted much experimental and theoretical interest. A key question arising in this context is what principles, and which of the properties of the quench, determine the characteristic propagation velocity. Here we investigate such issues for a class of quench protocols in one of the central paradigms of interacting many-particle quantum systems, the spin-1/2 Heisenberg XXZ chain. We consider quenches from a variety of initial thermal density matrices to the same final Hamiltonian using matrix product state methods. The spreading velocities are observed to vary substantially with the initial density matrix. However, we achieve a striking data collapse when the spreading velocity is considered to be a function of the excess energy. Using the fact that the XXZ chain is integrable, we present an explanation of the observed velocities in terms of "excitations" in an appropriately defined generalized Gibbs ensemble.