论文标题
floquet修饰的$ \ Mathcal {pt} $ - 对称SSH模型中的真实边缘模式
Real Edge Modes in a Floquet-modulated $\mathcal{PT}$-symmetric SSH model
论文作者
论文摘要
非热汉密尔顿人提供了一个简单的图片,用于分析具有自然或诱发的增益和损失的系统;然而,通常,这种哈密顿人具有复杂的能量和相应的非正常异态本质。只要哈密顿人具有$ \ Mathcal {pt} $对称性,则可以找到一个完全真实的征兆的制度。在静态$ \ MATHCAL {PT} $ - 简单的Su-Schrieffer-Heeger模型的对称扩展中,已经证明与任何边缘状态相关的能量保证是复杂的。转到时间依赖的系统意味着必须在调制本身的有效时间尺度上进行对哈密顿量的处理,从而使比静态情况更复杂的阶段发生。已经证明,在特定的定期驾驶类别中,可以在高驾驶频率下实现真正的拓扑阶段。在本文中,我们通过使用简单的两步定期调制来显示此过程的详细信息。我们获得了有效的浮雕汉密尔顿的严格表达,并将其对称性与构成调制步骤的原始汉密尔顿人的对称性进行了比较。有效哈密顿量的$ \ Mathcal {pt} $相位取决于调制频率以及增益/损失强度。此外,$ \ Mathcal {pt} $ - 不间断的阶段的拓扑非平地式阶段在高频情况下都在高频且下方具有真实特征值的高度定位的边缘状态,尽管在较小的参数空间范围内。
Non-Hermitian Hamiltonians provide a simple picture for analyzing systems with natural or induced gain and loss; however, in general, such Hamiltonians feature complex energies and a corresponding non-orthonormal eigenbasis. Provided that the Hamiltonian has $\mathcal{PT}$ symmetry, it is possible to find a regime in which the eigenspectrum is completely real. In the case of static $\mathcal{PT}$-symmetric extensions of the simple Su-Schrieffer-Heeger model, it has been shown that the energies associated with any edge states are guaranteed to be complex. Moving to a time-dependent system means that treatment of the Hamiltonian must be done at the effective time-scale of the modulation itself, allowing for more intricate phases to occur than in the static case. It has been demonstrated that with particular classes of periodic driving, achieving a real topological phase at high driving frequency is possible. In the present paper, we show the details of this process by using a simple two-step periodic modulation. We obtain a rigorous expression for the effective Floquet Hamiltonian and compare its symmetries to those of the original Hamiltonians which comprise the modulation steps. The $\mathcal{PT}$ phase of the effective Hamiltonian is dependent on the modulation frequency as well as the gain/loss strength. Furthermore, the topologically nontrivial regime of the $\mathcal{PT}$-unbroken phase admits highly-localized edge states with real eigenvalues in both the high frequency case and below it, albeit within a smaller extent of the parameter space.