Extraordinary Light-Induced Local Angular Momentum near Metallic Nanoparticles

Alabastri, Alessandro; Yang, Xiao; Manjavacas, Alejandro; Everitt, Henry O.; Nordlander, Peter

doi:10.1021/acsnano.6b01851

Cited by 38 publications

(32 citation statements)

References 89 publications

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“…30 Strong gradients in the electric elds may induce scattering channels that are absent for standard Raman scattering. 42,43 However, such effects are absent for the large gaps in our nanodimers (20 nm). 13 The large gap size also prevents distinct quantum mechanical effects such as tunnelling of electrons between the discs as well as rapid changes in the gap conguration due to mobile gold atoms.…”

Section: Resultsmentioning

confidence: 80%

“…For example, eld gradients may provide a separate enhancement channel and activate modes in SERS that are not normally Raman active. 13,42,43,51 The large size of the nanodimer gap ensures that eld gradients are sufficiently small. We estimated the second, gradient-related term in the multipole polarizability expansion of the dipole moment and found it to be at least an order of magnitude weaker than the rst term that is related to the magnitude of the electric eld.…”

Section: Discussion Of Sers Enhancement In 6t@cntmentioning

confidence: 99%

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Plasmonic enhancement of SERS measured on molecules in carbon nanotubes

et al. 2017

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We isolated the plasmonic contribution to surface-enhanced Raman scattering (SERS) and found it to be much stronger than expected. Organic dyes encapsulated in single-walled carbon nanotubes are ideal probes for quantifying plasmonic enhancement in a Raman experiment. The molecules are chemically protected through the nanotube wall and spatially isolated from the metal, which prevents enhancement by chemical means and through surface roughness. The tubes carry molecules into SERS hotspots, thereby defining molecular position and making it accessible for structural characterization with atomic-force and electron microscopy. We measured a SERS enhancement factor of 10 on α-sexithiophene (6T) molecules in the gap of a plasmonic nanodimer. This is two orders of magnitude stronger than predicted by the electromagnetic enhancement theory (10). We discuss various phenomena that may explain the discrepancy (including hybridization, static and dynamic charge transfer, surface roughness, uncertainties in molecular position and orientation), but found all of them lacking in enhancement for our probe system. We suggest that plasmonic enhancement in SERS is, in fact, much stronger than currently anticipated. We discuss novel approaches for treating SERS quantum mechanically that appear promising for predicting correct enhancement factors. Our findings have important consequences on the understanding of SERS as well as for designing and optimizing plasmonic substrates.

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Section: Resultsmentioning

confidence: 80%

Section: Discussion Of Sers Enhancement In 6t@cntmentioning

confidence: 99%

Plasmonic enhancement of SERS measured on molecules in carbon nanotubes

et al. 2017

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“…From a practical point of view, while the maximum field enhancements are attractive, the sharp fall off of the induced field, due to the small number of electrons, may limit potential plasmonic applications. Fortunately this does lead to extremely large field gradients that could be useful in exciting higher-order multipole excitations [62,63] and nonlinear effects [64,65] …”

Section: B Field Enhancementsmentioning

confidence: 99%

Quantum plasmonic nanoantennas

2017

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We study plasmonic excitations in the limit of few electrons, in one-atom-thick sodium chains. We compare the excitations to classical localized plasmon modes, and we find for the longitudinal mode a quantum-classical transition around 10 atoms. The transverse mode appears at much higher energies than predicted classically for all chain lengths. The electric field enhancement is also considered, which is made possible by considering the effects of electron-phonon coupling on the broadening of the electronic spectra. Large field enhancements are possible on the molecular level allowing us to consider the validity of using molecules as the ultimate small size limit of plasmonic antennas. Additionally, we consider the case of a dimer system of two sodium chains, where the gap can be considered as a picocavity, and we analyze the charge-transfer states and their dependence on the gap size as well as chain size. Our results and methods are useful for understanding and developing ultrasmall, tunable, and novel plasmonic devices that utilize quantum effects that could have applications in quantum optics, quantum metamaterials, cavity-quantum electrodynamics, and controlling chemical reactions, as well as deepening our understanding of localized plasmons in low-dimensional molecular systems.

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“…This result is understandable since the peak at 1.73 eV exhibits a clear plasmon character as illustrated already in Figure . From a practical point of view, the maximum field enhancements are advantageous for photo‐catalytic applications . In this context, the modulations of E fe due to the pyridine attachment are important (Figure , right panel).…”

Section: Resultsmentioning

confidence: 99%

Electric field amplification of plasmon‐molecule hybrids revealed by first‐principles time dependent density functional theory calculations

Muhammed

John

Mokkath

2019

Int J of Quantum Chemistry

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Using first-principles quantum mechanical calculations, we investigate the electric field amplification in hybrid nanostructures composed of few-atom Ni linear chains attached to an organic molecule. We found that the pristine Ni linear chains exhibit localized plasmons and produce nanoscale hotspot regions, acting as a plasmon-like nanoantenna. We demonstrate that localized plasmons provide massive electric field amplification in the vicinity of the molecule. Besides, we also investigated the active modulation of the optical absorption spectra due to the inclusion of a positive and/or negative electric field in the Hamiltonian. We believe that the results presented in this work are important for the emerging field of cavity induced photo-catalysis and will aid in the realization of new quantum nano-optic devices. K E Y W O R D S plasmon-molecule hybrids, polaritons, TD-DFT | INTRODUCTIONComplex nanostructures that combine the dissimilar/complementary properties of its components provide a unique platform for the design and the implementation of novel devices. In this context, polaritonic nanostructures combining resonantly matched localized surface plasmons (LSPs: collective coherent oscillation of conduction electrons driven by electromagnetic fields) and molecular excitons (electron-hole pairs created by the absorption of photons) offer unprecedented opportunities in controlling light on the nanoscale. [1][2][3][4][5][6][7][8][9][10] Understanding the nature and tunability of polaritonic states are important and triggered the development of new applications including chemical sensors, [11] pH meters, [12] and solar cell, [13] to list a few. It is well-known that LSPs can confine the electromagnetic energy to nanometric volumes, below the diffraction limits, which can produce a local enhancement of the external electromagnetic field nearby the nanosystem. When this happens, the system acts as a plasmonic nanoantenna able to amplify local electric fields at the nanoscale. [14][15][16][17][18][19][20][21][22][23][24][25][26] On the other hand, the molecular emitters and/or quantum dots can also be utilized to modify the plasmonic response of a metal nanostructure through a local modification of the dielectric environment. Previous studies [4] have shown that the highly enhanced electric field can mediate plasmon-exciton coupling near the surfaces of plasmonic nanostructures, known as hotspots. The strong and localized field in a plasmonic hot spot enhances the interaction between LSPRs and the excitons, much as it enhances other molecular excitations.The light scattering/absorption properties of metal nanoparticles with specific size, geometry, and composition have been accurately calculated within a classical electrodynamics framework based on Maxwell's equations. [27][28][29][30][31][32] Despite the successful use of this technique to model the optical properties of a vast number of pristine and hybrid metal nano-objects, it is purely classical, and consequently it cannot describe accurately the plexcitonic sta...

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Extraordinary Light-Induced Local Angular Momentum near Metallic Nanoparticles

Cited by 38 publications

References 89 publications

Plasmonic enhancement of SERS measured on molecules in carbon nanotubes

Plasmonic enhancement of SERS measured on molecules in carbon nanotubes

Quantum plasmonic nanoantennas

Electric field amplification of plasmon‐molecule hybrids revealed by first‐principles time dependent density functional theory calculations

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