论文标题
在缓慢的非绝热量子动力学下的新兴拓扑
Emergent topology under slow non-adiabatic quantum dynamics
论文作者
论文摘要
通过非平衡淬灭动力学对平衡拓扑量子相的表征为检测平衡定义的拓扑不变性提供了一种新颖而有效的方案。然而,以前的大多数研究都集中在理想的突然淬火状态上。在这里,我们提供了一种通用的非绝热协议,以缓慢淬灭哈密顿量,并研究拓扑阶段的非绝热动力学特征方案。 {\ it慢}的淬灭协议是通过引入类似库仑的Landau-Zener问题来实现的,它可以以统一的方式描述从突然的淬灭状态(深度绝热极限)到绝热制度的交叉。通过在非绝热演化后分析获得最终状态载体,我们可以计算时间平均的自旋极化和相应的拓扑自旋纹理。我们发现,Quech后哈密顿量的拓扑不变性直接以频带反转表面上的自旋纹理值的值进行特征。与突然的淬灭状态相比,必须采取额外的步骤来计算自旋极化的{\ it梯度},这种非绝热表征为检测拓扑不变性提供了一种{\ it最小}方案。我们的发现不仅限于类似库仑的淬灭协议下的1D和2D拓扑阶段,但也适用于更高维系统或不同的淬灭协议。
Characterization of equilibrium topological quantum phases by non-equilibrium quench dynamics provides a novel and efficient scheme in detecting topological invariants defined in equilibrium. Nevertheless, most of the previous studies have focused on the ideal sudden quench regime. Here we provide a generic non-adiabatic protocol of slowly quenching the system Hamiltonian, and investigate the non-adiabatic dynamical characterization scheme of topological phase. The {\it slow} quench protocol is realized by introducing a Coulomb-like Landau-Zener problem, and it can describe, in a unified way, the crossover from sudden quench regime (deep non-adiabatic limit) to adiabatic regime. By analytically obtaining the final state vector after non-adiabatic evolution, we can calculate the time-averaged spin polarization and the corresponding topological spin texture. We find that the topological invariants of the post-quench Hamiltonian are characterized directly by the values of spin texture on the band inversion surfaces. Compared to the sudden quench regime, where one has to take an additional step to calculate the {\it gradients} of spin polarization, this non-adiabatic characterization provides a {\it minimal} scheme in detecting the topological invariants. Our findings are not restricted to 1D and 2D topological phases under Coulomb-like quench protocol, but are also valid for higher dimensional system or different quench protocol.