Interaction of edge exciton polaritons with engineered defects in the hyperbolic material Bi2Se3

Robin Lingstädt,Mario Hentschel,Marko Burghard,Peter A Van Aken,Nahid Talebi,Bruno Gompf,Soudabeh Mashhadi,Harald Giessen

doi:10.1038/s43246-020-00108-9

Abstract

Hyperbolic materials exhibit unique properties that enable intriguing applications in nanophotonics. The topological insulator Bi2Se3 represents a natural hyperbolic optical medium, both in the THz and visible range. Here, using cathodoluminescence spectroscopy and electron energy-loss spectroscopy, we demonstrate that Bi2Se3 supports room-temperature exciton polaritons and explore the behavior of hyperbolic edge exciton polaritons, which are hybrid modes resulting from the coupling of the polaritons bound to the upper and lower edges of Bi2Se3 nanoplatelets. We compare Fabry-Pérot-like resonances emerging in edge polariton propagation along pristine and artificially structured edges and experimentally demonstrate the possibility to steer edge polaritons by means of grooves and nanocavities. The observed scattering of edge polaritons by defect structures is found to be in good agreement with finite-difference time-domain simulations. Our findings reveal the extraordinary capability of hyperbolic polariton propagation to cope with the presence of defects, providing an excellent basis for applications such as nanooptical circuitry, nanoscale cloaking and nanoscopic quantum technology.

Highlights

Hyperbolic materials exhibit unique properties that enable intriguing applications in nanophotonics
A material with a negative real part of the dielectric function in the isotropic plane parallel to the surface εjj is referred to as hyperbolic type-2 (HB2), whereas a material displaying a negative value in the out-of-plane direction ðε?Þ is of hyperbolic type-1 (HB1) character
We use cathodoluminescence spectroscopy to demonstrate for the first time, to the best of our knowledge, that

Summary

Introduction

Hyperbolic materials exhibit unique properties that enable intriguing applications in nanophotonics. We manipulated side planes of 50 nm thin Bi2Se3 nanoplatelets with inhibited grooves or shaped nanocavities using focused ion-beam milling, with the aim of exploring the transmission and scattering behavior of HEEPs and their interaction with localized polaritons To this end, we use electron energy-loss spectroscopy (EELS)[32,33] in a transmission electron microscope (TEM) adapted for investigations in the low-loss energy range, and compare the experimental data with results of finite-difference time-domain (FDTD)[34] simulations. We demonstrate that high-energy HEEPs, owing to their coupling to radiation modes via various mechanisms of energy transfer, are rather robust against the engineered defects

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Conclusion