Cui, L., An, S., Yit Loong Lee, H., Liu, G.-X., Wang, H., Wang, H.-Y., Wu, L., Dong, Z., & Wang, L. (2024). Dynamic Ultrastrong Coupling in a 2 nm Gap Plasmonic Cavity at the Sub-Picosecond Scale. Nano Letters, 24(30), 9337–9344. https://doi.org/10.1021/acs.nanolett.4c02288
Abstract:
Localized surface plasmon resonances (LSPRs) can enhance the electromagnetic fields on metallic nanostructures upon light illumination, providing an approach for manipulating light−matter interactions at the sub-wavelength scale. However, currently, there is no thorough investigation of the physical mechanism in the dynamic formation of the strongly coupled LSPRs on sub-5 nm plasmonic cavities at the sub-picosecond scale. In this work, through femtosecond broadband transient absorption spectroscopy, we
reveal the dynamic ultrastrong coupling processes in a nanoparticle-in-trench (NPiT) structure containing 2 nm gap cavities, and demonstrate a coherent motional coupling between vibrating AuNPs and the nanogaps. We achieve a maximum Rabi splitting energy of ∼660 meV in the sub-picosecond hot-electron relaxation time scale under the resonant excitation of the nanogap cavity’s LSPR, reaching the ultrastrong coupling regime. This leads to a change of global vibration modes for the 2 nm gap cavity, potentially related to the dynamical Casimir effect with nanogap resonators.
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Funding Info:
This research / project is supported by the Agency for Science, Technology and Research - Advanced Manufacturing and Engineering (AME) Individual Research Grant
Grant Reference no. : A20E5c0093
This research / project is supported by the Agency for Science, Technology and Research - Career Development Award Grant
Grant Reference no. : C210112019
This research / project is supported by the Agency for Science, Technology and Research - Manufacturing, Trade, and Connectivity (MTC) Individual Research Grant
Grant Reference no. : M21K2c0116
This research / project is supported by the Agency for Science, Technology and Research - Manufacturing, Trade, and Connectivity (MTC) Individual Research Grant
Grant Reference no. : M22K2c0088
This research is supported by core funding from: Agency for Science, Technology and Research DELTA-Q 2.0 Programme
Grant Reference no. : C230917005
This research / project is supported by the National Research Foundation, Singapore - Quantum Engineering Programme 2.0
Grant Reference no. : NRF2021-QEP2-03-P09, NRF2021-QEP2-02-P03
This research / project is supported by the National Research Foundation, Singapore - Competitive Research Programme
Grant Reference no. : NRF-CRP26 2021-0004