Novel plasmons in quantum anomalous Hall systems*

We find that the inverted band structure with the Mexican-hat dispersion could enhance the interband correlation leading to a strong intrinsic plasmon excitation. Its frequency ranges from several meV to tens of meV and can be effectively tuned by the external fields. The electron-hole asymmetric term splits the peak of the plasmon excitation into double peaks. The fate and properties of this plasmon excitation can also act as a probe to characterize the topological phases even in lightly doped systems. We numerically demonstrate the impact of band inversion on plasmon excitations in magnetically doped thin films of three-dimensional strong topological insulators, which support the quantum anomalous Hall states (QAHE). We also study the chiral edge plasmons in QAHE and find many new and remarkable features of chiral edge plasmons. Our work thus sheds some new light on the potential applications of topological materials in plasmonics.
References: PRL 119, 266804 (2017); Furu Zhang, Jianhui Zhou, and Yugui Yao, In preparation (2018).