Noh Jiho, Huang Sheng, Chen Kevin P, Rechtsman Mikael C
Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
Department of Electrical and Computer Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA.
Phys Rev Lett. 2018 Feb 9;120(6):063902. doi: 10.1103/PhysRevLett.120.063902.
We experimentally demonstrate topological edge states arising from the valley-Hall effect in two-dimensional honeycomb photonic lattices with broken inversion symmetry. We break the inversion symmetry by detuning the refractive indices of the two honeycomb sublattices, giving rise to a boron nitridelike band structure. The edge states therefore exist along the domain walls between regions of opposite valley Chern numbers. We probe both the armchair and zigzag domain walls and show that the former become gapped for any detuning, whereas the latter remain ungapped until a cutoff is reached. The valley-Hall effect provides a new mechanism for the realization of time-reversal-invariant photonic topological insulators.
我们通过实验证明了在具有破缺反演对称性的二维蜂窝状光子晶格中，由谷霍尔效应产生的拓扑边缘态。我们通过失谐两个蜂窝子晶格的折射率来打破反演对称性，从而产生类似氮化硼的能带结构。因此，边缘态沿着具有相反谷陈数的区域之间的畴壁存在。我们探测了扶手椅形和锯齿形畴壁，结果表明，对于任何失谐，前者都会出现能隙，而后者在达到截止之前一直保持无隙状态。谷霍尔效应为实现时间反演不变的光子拓扑绝缘体提供了一种新机制。
