Laboratory of Wave Engineering, School of Electrical Engineering, EPFL, Station 11, 1015 Lausanne, Switzerland.
Phys Rev Lett. 2019 Aug 2;123(5):053902. doi: 10.1103/PhysRevLett.123.053902.
We demonstrate, both theoretically and experimentally, the concept of nonlinear second-order topological insulators, a class of bulk insulators with quantized Wannier centers and a bulk polarization directly controlled by the level of nonlinearity. We show that one-dimensional edge states and zero-dimensional corner states can be induced in a trivial crystal insulator made of evanescently coupled resonators with linear and nonlinear coupling coefficients, simply by tuning the intensity. This allows global external control over topological phase transitions and switching to a phase with nonzero bulk polarization, without requiring any structural or geometrical changes. We further show how these nonlinear effects enable dynamic tuning of the spectral properties and localization of the topological edge and corner states. Such self-induced second-order topological insulators, which can be found and implemented in a wide variety of physical platforms ranging from electronics to microwaves, acoustics, and optics, hold exciting promises for reconfigurable topological energy confinement, power harvesting, data storage, and spatial management of high-intensity fields.
我们从理论和实验上证明了非线性二阶拓扑绝缘体的概念，这是一类具有量子化的 Wannier 中心和通过非线性程度直接控制的体极化的体绝缘材料。我们表明，通过简单地调节强度，可以在由具有线性和非线性耦合系数的渐逝耦合谐振器构成的平凡晶体绝缘体中诱导出一维边缘态和零维角态。这允许对拓扑相变和切换到具有非零体极化的相进行全局外部控制，而无需任何结构或几何变化。我们还展示了这些非线性效应如何能够动态调整拓扑边缘和角态的谱性质和局域化。这种自诱导的二阶拓扑绝缘体，可以在从电子学到微波、声学和光学等各种物理平台中找到和实现，为可重构拓扑能量限制、功率收集、数据存储以及高强度场的空间管理提供了令人兴奋的前景。
