Abstract
Abstract Plasmonic materials have long been exploited for enhanced spectroscopy, integrated nanophotonic circuits, sensing, light harvesting, etc. Damping is the key factor that limits their performance and restricts the development of the field. Optical characterization of single nanoparticle at low temperature is ideal for investigating the damping of plasmons but is usually technically impractical due to the sample vibration from the cryostat and the surface adsorption during the cooling process. In this work, we use a vibration-free cryostat to investigate the temperature-dependent dark-field scattering spectroscopy of a single Au nanowire on top of a Au film. This allows us to extract the contribution of electron-phonon scattering to the damping of plasmons without performing statistics over different target nanoparticles. The results show that the full width at half-maximum of the plasmon resonance increases by an amount of 5.8%, over the temperature range of 5−150 K. Electromagnetic calculations reveal that the temperature-insensitive dissipation channels into photons or surface plasmon polaritons on the Au film contribute up to 64% of the total dissipations at the plasmon resonance. This explains why the reduction of plasmon linewidth seems small at the single-particle level. This study provides a more explicit measurement on the damping process of the single plasmonic nanostructure, which serves as basic knowledge in the applications of nanoplasmonic materials.
Highlights
The local electromagnetic field around a metallic nanostructure can be enhanced by orders of magnitude due to the excitation of localized surface plasmon resonance (LSPR) [1,2,3], a phenomenon that has been widely used in enhanced spectroscopy [4,5,6], sensing [7,8,9], and strong light-matter interaction [10,11,12], etc
We used a home-made oblique-incidence DF microscopy combined with a vibration-free cryostat to investigate the temperature-dependent DF scattering spectroscopy of a single Au-NWOM system (Figure 1A)
We explored the relationship at higher temperatures range (150 ∼ 246 K, see Supplementary S2), which shows the full width at half-maximum (FWHM) gradually homogeneous broadening as the temperature increases
Summary
The local electromagnetic field around a metallic nanostructure can be enhanced by orders of magnitude due to the excitation of localized surface plasmon resonance (LSPR) [1,2,3], a phenomenon that has been widely used in enhanced spectroscopy [4,5,6], sensing [7,8,9], and strong light-matter interaction [10,11,12], etc. Plasmonic materials inevitably suffer from remarkable energy dissipation arising from both radiative and non-radiative damping [15, 16] The former converts plasmons into free-space photons; the latter annihilates plasmons and creates electron-hole excitations via electron-phonon scattering [17], electron-surface scattering [18] and electron-electron scattering [19]. These damping channels jointly determine the lifetime of surface plasmons, ranging from a few femtoseconds to tens of femtoseconds. Investigating electron-phonon scattering damping variation with temperature is crucial to either understanding the basic dissipation physics or promoting further developments of the plasmonic applications
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