Hu Ying, Zoller Peter, Budich Jan Carl
Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences, 6020 Innsbruck, Austria.
Institute for Theoretical Physics, University of Innsbruck, 6020 Innsbruck, Austria.
Phys Rev Lett. 2016 Sep 16;117(12):126803. doi: 10.1103/PhysRevLett.117.126803.
We consider a two-dimensional system initialized in a topologically trivial state before its Hamiltonian is ramped through a phase transition into a Chern insulator regime. This scenario is motivated by current experiments with ultracold atomic gases aimed at realizing time-dependent dynamics in topological insulators. Our main findings are twofold. First, considering coherent dynamics, the nonequilibrium Hall response is found to approach a topologically quantized time-averaged value in the limit of slow but nonadiabatic parameter ramps, even though the Chern number of the state remains trivial. Second, adding dephasing, the destruction of quantum coherence is found to stabilize this Hall response, while the Chern number generically becomes undefined. We provide a geometric picture of this phenomenology in terms of the time-dependent Berry curvature.
我们考虑一个二维系统，在其哈密顿量通过相变进入陈绝缘体区域之前，初始处于拓扑平凡态。这种情况是受当前超冷原子气体实验的启发，这些实验旨在实现拓扑绝缘体中的时间相关动力学。我们的主要发现有两个方面。首先，考虑相干动力学，发现在缓慢但非绝热的参数斜坡极限下，非平衡霍尔响应趋近于一个拓扑量子化的时间平均值，尽管该状态的陈数仍然是平凡的。其次，加入退相后，发现量子相干的破坏使这种霍尔响应稳定，而陈数通常变得未定义。我们根据随时间变化的贝里曲率给出了这种现象学的几何图像。
