Smith Thomas Benjamin, Kocabas Coskun, Principi Alessandro
Department of Physics and Astronomy, School of Natural Sciences, Faculty of Science and Engineering, University of Manchester, Oxford Road, Manchester, M13 9PY, United Kingdom.
The National Graphene Institute, University of Manchester, Booth Street East, Manchester, M13 9PL, United Kingdom.
J Phys Condens Matter. 2021 May 26;33(26). doi: 10.1088/1361-648X/abf7e0.
We study topological surface-plasmon-polaritons at optical frequencies in tri-harmonic diffraction gratings formed at a metal-dielectric interface. The latter are shown to well approximate a bipartite Kronig-Penney model. Topologically protected localised modes are then predicted to occur at the edges of the grating and at defects formed by the combination of two mirror antisymmetric corrugations, whose bulk invariant is a step-wise varying Zak phase in both cases. An interesting special case wherein the defect state is in-fact forbidden is also observed that reveals the fragility of such states despite their topological nature.
我们研究了在金属-电介质界面形成的三谐波衍射光栅中光频下的拓扑表面等离激元极化激元。结果表明，后者能很好地近似二分的克勒尼希-彭尼模型。然后预测拓扑保护的局域模会出现在光栅边缘以及由两个镜面对称波纹组合形成的缺陷处，在这两种情况下，其体不变量都是一个阶梯式变化的扎克相位。还观察到一个有趣的特殊情况，即缺陷态实际上是被禁止的，这揭示了此类状态尽管具有拓扑性质但仍具有脆弱性。
