Department of Physics, The Pennsylvania State University, University Park, PA 16802, USA.
Science. 2020 May 22;368(6493):856-859. doi: 10.1126/science.aba8725.
Topological protection is a universal phenomenon that applies to electronic, photonic, ultracold atomic, mechanical, and other systems. The vast majority of research in these systems has explored the linear domain, where interparticle interactions are negligible. We experimentally observed solitons-waves that propagate without changing shape as a result of nonlinearity-in a photonic Floquet topological insulator. These solitons exhibited distinct behavior in that they executed cyclotron-like orbits associated with the underlying topology. Specifically, we used a waveguide array with periodic variations along the waveguide axis, giving rise to nonzero winding number, and the nonlinearity arose from the optical Kerr effect. This result applies to a range of bosonic systems because it is described by the focusing nonlinear Schrödinger equation (equivalently, the attractive Gross-Pitaevskii equation).
拓扑保护是一种普遍现象，适用于电子、光子、超冷原子、机械等系统。在这些系统中，绝大多数研究都集中在线性领域，其中粒子间相互作用可以忽略不计。我们在光子 Floquet 拓扑绝缘体中实验观察到了孤子-由于非线性而传播时形状不变的波。这些孤子表现出明显的行为，即它们执行与基础拓扑相关的回旋状轨道。具体来说，我们使用了具有沿波导轴周期性变化的波导阵列，产生非零的缠绕数，而非线性则来自光克尔效应。这个结果适用于一系列玻色子系统，因为它由聚焦非线性薛定谔方程（等效地，吸引 Gross-Pitaevskii 方程）描述。
