nl9b03534_si_001.pdf (1.41 MB)
Download fileVisualizing Spatial Variations of Plasmon–Exciton Polaritons at the Nanoscale Using Electron Microscopy
journal contribution
posted on 2019-10-28, 19:03 authored by Andrew
B. Yankovich, Battulga Munkhbat, Denis G. Baranov, Jorge Cuadra, Erik Olsén, Hugo Lourenço-Martins, Luiz H. G. Tizei, Mathieu Kociak, Eva Olsson, Timur ShegaiPolaritons are compositional light-matter
quasiparticles that have
enabled remarkable breakthroughs in quantum and nonlinear optics,
as well as in material science. Recently, plasmon–exciton polaritons
(plexcitons) have been realized in hybrid material systems composed
of transition metal dichalcogenide (TMDC) materials and metal nanoparticles,
expanding polaritonic concepts to room temperature and nanoscale systems
that also benefit from the exotic properties of TMDC materials. Despite
the enormous progress in understanding TMDC-based plexcitons using
optical-based methods, experimental evidence of plexcitons formation
has remained indirect and mapping their nanometer-scale characteristics
has remained an open challenge. Here, we demonstrate that plexcitons
generated by a hybrid system composed of an individual silver nanoparticle
and a few-layer WS2 flake can be spectroscopically mapped
with nanometer spatial resolution using electron energy loss spectroscopy
in a scanning transmission electron microscope. Experimental anticrossing
measurements using the absorption-dominated extinction signal provide
the ultimate evidence for plexciton hybridization in the strong coupling
regime. Spatially resolved EELS maps reveal the existence of unexpected
nanoscale variations in the deep-subwavelength nature of plexcitons
generated by this system. These findings pioneer new possibilities
for in-depth studies of the local atomic structure dependence of polariton-related
phenomena in TMDC hybrid material systems with nanometer spatial resolution.