Interaction of edge exciton polaritons with engineered defects in the van der Waals material Bi2Se3

TL;DR

This study demonstrates that Bi2Se3, a hyperbolic topological insulator, supports room-temperature exciton polaritons and explores their interaction with engineered defects, revealing robustness useful for nanophotonic applications.

Contribution

It provides experimental evidence of hyperbolic edge exciton polaritons in Bi2Se3 and their resilience to defects, advancing understanding of polariton behavior in topological insulators.

Findings

Bi2Se3 supports room-temperature exciton polaritons.

Edge polaritons are affected by engineered defects.

Coupling of localized and propagating polaritons was demonstrated.

Abstract

Hyperbolic materials exhibit unique properties that enable a variety of 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, in addition to being a hyperbolic material, supports room-temperature exciton polaritons. Moreover, we explore the behavior of hyperbolic edge exciton polaritons in Bi2Se3. Edge polaritons are hybrid modes that result from the coupling of the polaritons bound to the upper and lower edges of Bi2Se3 nanoplatelets. In particular, we use electron energy-loss spectroscopy to compare Fabry-P\'erot-like resonances emerging in edge polariton propagation along pristine and artificially structured edges of the nanoplatelets. The experimentally observed scattering of edge polaritons by defect structures was found to be in good agreement with finite-difference time-domain simulations. Moreover, we experimentally proved coupling of localized polaritons in identical open and closed circular nanocavities to the propagating edge polaritons. Our findings are testimony to the extraordinary capability of the hyperbolic polariton propagation to cope with the presence of defects. This provides an excellent basis for applications such as nanooptical circuitry, cloaking at the nanometer scale, as well as nanoscopic quantum technology on the nanoscale.