# Investigation of hybrid plasmons in a highly crystalline Bi2Se3/C60 heterostructure using low-loss electron energy loss spectroscopy

## TL;DR

This paper explores how combining a topological insulator with a molecular layer can control plasmons for use in nanoscale devices.

## Contribution

The study demonstrates a new method to grow highly crystalline Bi2Se3/C60 heterostructures and reveals unexpected π state hybridization.

## Key findings

- Bi2Se3/C60 heterostructures show significant hybridization of π states at the interface.
- 2D plasmons are quenched in the heterostructure despite weak van der Waals interactions.
- Momentum-resolved EELS and DFT confirm interfacial charge dipoles influence plasmon behavior.

## Abstract

Topological Insulators (TIs) present an interesting materials platform for nanoscale, high frequency devices because they support high mobility, low scattering electronic transport within confined surface states. However, a robust methodology to control the properties of surface plasmons in TIs has yet to be developed. Surface doping of TIs with molecules may provide tunable control of the two-dimensional plasmons in Bi2Se3, but exploration of such heterostructures is still at an early stage and usually confined to monolayers. We have grown heterostructures of Bi2Se3/C60 with exceptional crystallinity. Electron energy loss spectroscopy (EELS) reveals significant hybridisation of π states at the interface, despite the expectation for only weak van der Waals interactions, including quenching of 2D plasmons. Momentum-resolved EELS measurements are used to probe the plasmon dispersion, with Density Functional Theory predictions providing an interpretation of results based on interfacial charge dipoles. This work provides growth methodology and characterization of highly crystalline TI/molecular interfaces that can be engineered for plasmonic applications in energy, communications and sensing.

Topological insulators offer promising potential for nanoscale, high-frequency devices, yet controlling surface plasmon properties remains challenging. Here, the authors grow Bi2Se3/C60 heterostructures with exceptional crystallinity, using electron energy loss spectroscopy and density functional theory to reveal significant π state hybridization and quenching of 2D plasmons.