Correlative electron and light spectroscopy of strongly-coupled mid-infrared plasmon and phonon polaritons

TL;DR

This study investigates strongly coupled mid-infrared plasmon and phonon polaritons using advanced spectroscopy and modeling, enabling precise characterization and active control of these excitations for potential applications in heat management and nanofocusing.

Contribution

It provides a comprehensive analysis combining electron and light spectroscopy to understand and control coupled polaritonic modes in condensed matter.

Findings

Electron probe enables precise polariton characterization.

Active control over coupling and spectral response demonstrated.

Rigorous description of spectral features applicable to optical systems.

Abstract

The ability to control and modify infrared excitations in condensed matter is of both fundamental and application interests. Here we explore a system supporting low-energy excitations, in particular, mid-infrared localized plasmon modes and phonon polaritons that are tuned to be strongly coupled. We study the coupled modes by using far-field infrared spectroscopy, state-of-the-art monochromated electron energy-loss spectroscopy, numerical simulations and analytical modeling. We demonstrate that the electron probe facilitates a precise characterization of polaritons constituting the coupled system, and enables an active control over the coupling and the resulting sample response both in frequency and space. Our work establishes a rigorous description of the spectral features observed in light- and localized electron-based spectroscopies, which can be extended to analogous optical systems with applications in heat management, and electromagnetic field concentration or nanofocusing.