posted on 2023-01-08, 18:29authored bySamarth Vadia, Johannes Scherzer, Kenji Watanabe, Takashi Taniguchi, Alexander Högele
Chirality is a fundamental
asymmetry phenomenon, with chiral optical
elements exhibiting asymmetric response in reflection or absorption
of circularly polarized light. Recent realizations of such elements
include nanoplasmonic systems with broken-mirror symmetry and polarization-contrasting
optical absorption known as circular dichroism. An alternative route
to circular dichroism is provided by spin-valley polarized excitons
in atomically thin semiconductors. In the presence of magnetic fields,
they exhibit an imbalanced coupling to circularly polarized photons
and thus circular dichroism. Here, we demonstrate that polarization-contrasting
optical transitions associated with excitons in monolayer WSe2 can be transferred to proximal plasmonic nanodisks by coherent
coupling. The coupled exciton–plasmon system exhibits magneto-induced
circular dichroism in a spectrally narrow window of Fano interference,
which we model in a master equation framework. Our work motivates
the use of exciton–plasmon interfaces as building blocks of
chiral metasurfaces for applications in information processing, nonlinear
optics, and sensing.