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Generation of Hot Electrons with Chiral Metamaterial Perfect Absorbers: Giant Optical Chirality for Polarization-Sensitive Photochemistry
journal contribution
posted on 2019-11-12, 18:34 authored by Wenhao Wang, Lucas V. Besteiro, Tianji Liu, Cuo Wu, Jiachen Sun, Peng Yu, Le Chang, Zhiming Wang, Alexander O. GovorovChiral plasmonic
metamaterials have shown very interesting possibilities
as chiral optical absorbers for circularly polarized light detection,
as their optical response can be manipulated through the careful design
of their geometry. Exhibiting the generation of hot electrons, chiral
plasmonic nanostructures can be potentially used for polarization-sensitive
photochemistry and chiral photocatalysis, in which the excited hot
electrons induce surface reactions. In this study, we show that chiral
metamaterial perfect absorbers (MMPAs) can be utilized for plasmon-induced
polarization-sensitive photochemistry involving hot electrons, with
extremely strong differential chiral responses. The calculated nearly
perfect optical absorption (∼98%) of metamaterials demonstrate
that the MMPAs can strongly absorb the photons and direct a significant
part of the radiant energy to the generation of energetic (hot) carriers.
Through the elaborate design of the plasmonic antenna geometry, we
theoretically present a MMPA exhibiting a very large circular dichroism
in its optical response. In addition, the greatly asymmetric electromagnetic
field enhancement response of the MMPA to left and right circularly
polarized light leads to a large chiral effect in the hot electron
generation. In our calculations with the optimized designs, the g-factor reaches a value of 1.52, close to the theoretical
upper limit of 2, higher than that of chiral colloidal nanocrystals
with plasmonic resonances and much higher than for any chiral molecules.
The remarkably strong chiral effect in hot electron generation, predicted
in our study, suggests that plasmonic MMPAs can be used in polarization-sensitive
photochemical applications and for photodetection.