论文标题
弱开放量子系统中的双重和域墙
Bistabilities and domain walls in weakly open quantum systems
论文作者
论文摘要
如果系统的稳态是唯一的，则可以通过广义吉布斯集团有效地描述具有近似保护定律的弱抽水系统。但是，如果有多种稳态解决方案，例如一种双稳态，则这种描述可能会失败。在这种情况下，可能会形成域和域壁。在一维（1D）系统中，任何类型的噪声（热或非热）通常会导致此类域的扩散。我们在具有两个近似保护定律，能量和总磁化的$ z $组成的1D自旋链中研究这种物理学。磁化强度的双重性是通过耦合到适当选择的lindblad操作员引起的。我们分析了弱耦合强度$ε$对非平衡浴的理论。在此限制中，我们认为可以使用流体动力近似值，这些近似值用空间和时间依赖于时间依赖的拉格朗日参数来描述系统。这里的噪声项会强制执行域的创建，其中域墙的典型宽度为$ \ sim 1/\sqrtε$，而域壁的密度在$ 1/\sqrtε$中成倍小。这是通过在存在噪声的情况下对简化流体动力方程的数值模拟所示的。
Weakly pumped systems with approximate conservation laws can be efficiently described by a generalized Gibbs ensemble if the steady state of the system is unique. However, such a description can fail if there are multiple steady state solutions, for example, a bistability. In this case domains and domain walls may form. In one-dimensional (1D) systems any type of noise (thermal or non-thermal) will in general lead to a proliferation of such domains. We study this physics in a 1D spin chain with two approximate conservation laws, energy and the $z$-component of the total magnetization. A bistability in the magnetization is induced by the coupling to suitably chosen Lindblad operators. We analyze the theory for a weak coupling strength $ε$ to the non-equilibrium bath. In this limit, we argue that one can use hydrodynamic approximations which describe the system locally in terms of space- and time-dependent Lagrange parameters. Here noise terms enforce the creation of domains, where the typical width of a domain wall goes as $\sim 1/\sqrtε$ while the density of domain walls is exponentially small in $1/\sqrtε$. This is shown by numerical simulations of a simplified hydrodynamic equation in the presence of noise.
