Plasmons in molecules: Microscopic characterization based on orbital transitions and momentum conservation

Krauter, Caroline M.; Schirmer, J.; Jacob, Christoph R.; Pernpointner, Markus; Dreuw, Andreas

doi:10.1063/1.4894266

Cited by 30 publications

(87 citation statements)

References 74 publications

(74 reference statements)

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“…This correlation is analogous to the nearly-linear relationship between metal nanorod plasmon wavelength and nanorod length and is in agreement with the effect of spatial confinement of a charge distribution. 22,29 We also observed a linear redshift with increasing index of refraction of the surrounding environment. 30 .…”

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confidence: 74%

“…17,18 Insights from recent Time-Dependent Density Functional Theory [18][19][20] (TDDFT) and Random Phase Approximation 21,22 (RPA) theoretical work imply that molecular-scale systems support some excitation modes which are indeed collective in nature. The description of a molecular plasmon as a collective electronic excitation rather than a single-electron transition, is supported by three primary attributes: (1) The strong dependence on the electron-electron interaction strength; (2) The excitation 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 being a superposition of many elementary single-electron excitations (i.e.…”

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confidence: 98%

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Molecular Plasmonics

et al. 2015

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Graphene supports surface plasmons that have been observed to be both electrically and geometrically tunable in the mid- to far-infrared spectral regions. In particular, it has been demonstrated that graphene plasmons can be tuned across a wide spectral range spanning from the mid-infrared to the terahertz. The identification of a general class of plasmonic excitations in systems containing only a few dozen atoms permits us to extend this versatility into the visible and ultraviolet. As appealing as this extension might be for active nanoscale manipulation of visible light, its realization constitutes a formidable technical challenge. We experimentally demonstrate the existence of molecular plasmon resonances in the visible for ionized polycyclic aromatic hydrocarbons (PAHs), which we reversibly switch by adding, then removing, a single electron from the molecule. The charged PAHs display intense absorption in the visible regime with electrical and geometrical tunability analogous to the plasmonic resonances of much larger nanographene systems. Finally, we also use the switchable molecular plasmon in anthracene to demonstrate a proof-of-concept low-voltage electrochromic device.

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confidence: 74%

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confidence: 98%

Molecular Plasmonics

et al. 2015

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“…coupled with transition densities showing oscillating dipolar charge distributions (13,30,31), this is indicative of resonances exhibiting collective electron motion.…”

Section: Significancementioning

confidence: 85%

“…While many properties of nanoscale plasmons are well described by classical electromagnetic theory, in the few-atom quantum limit this description breaks down for the systems that still exhibit plasmonic behavior (10,11), thus requiring a fully quantum treatment. From a quantum-mechanical perspective, plasmons can be described as coherent superpositions of individual electron-hole pair transitions that emerge when the Coulomb interaction between excited states is switched on (12)(13)(14)(15).…”

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confidence: 99%

Lifetime dynamics of plasmons in the few-atom limit

Chapkin

Bursi

Stec

et al. 2018

Proc. Natl. Acad. Sci. U.S.A.

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Polycyclic aromatic hydrocarbon (PAH) molecules are essentially graphene in the subnanometer limit, typically consisting of 50 or fewer atoms. With the addition or removal of a single electron, these molecules can support molecular plasmon (collective) resonances in the visible region of the spectrum. Here, we probe the plasmon dynamics in these quantum systems by measuring the excited-state lifetime of three negatively charged PAH molecules: anthanthrene, benzo[ghi]perylene, and perylene. In contrast to the molecules in their neutral state, these three systems exhibit far more rapid decay dynamics due to the deexcitation of multiple electron-hole pairs through molecular plasmon "dephasing" and vibrational relaxation. This study provides a look into the distinction between collective and single-electron excitation dynamics in the purely quantum limit and introduces a conceptual framework with which to visualize molecular plasmon decay.

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“…However, at the nanoscale, single-particle and plasmonic excitations are intrinsically mixed [18], and how to recognize a plasmonic excitation is still an unsolved problem.A few approaches have been recently proposed attempting to classify the plasmonic character of the excitations of nanosystems. [11,[19][20][21][22][23][24] In particular, Bernadotte et al [11] formulated, in the framework of time-dependent density-functional theory (TDDFT), a scaling approach based on the different dependence of the energies of the excitations of nanosystems on the Coulomb kernel. Along this line, Krauter et al[23] demonstrated that the electronic wave function of plasmons, at the time-dependent Hartree-Fock level, is described by the superposition of several electron configurations, i.e.…”

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Quantifying the Plasmonic Character of Optical Excitations in Nanostructures

et al. 2016

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The identification of plasmons in systems below ∼10 nm in size is a tremendous challenge. Any sharp distinction of the excitation character (non-plasmonic vs plasmonic) becomes blurred in this range of sizes, where quantum effects become important. Here we define a plasmonicicty index that quantifies the plasmonic character of selected optical excitations in small nanostructures, starting from first principles calculations, based on (TD)DFT. This novel approach allows us to overcome the aforementioned problems, providing a direct and quantitative classification of the plasmonic character of the excitations. We show its usefulness for model metallic nanoparticles, a prototypical C-based molecule and a paradigmatic hybrid system. Our results indicate that the plasmonicity index can be exploited to solve previously unsolvable problems about the plasmonic character of complex systems, not predictable a priori.Localized surface plasmon resonances in nanostrucures interact strongly with light allowing the confinement of electromagnetic energy down to deep subwavelength regions [1,2]. This, together with their easy tunability [3], robustness [4] and field enhancement properties [5], provides a powerful tool to manipulate light at the nanoscale, below the diffraction limit. Thus, plasmons have become of paramount importance for a wide range of applications [6][7][8] spanning from light harvesting[9] to biosensing [10]. In general terms, plasmons can be defined as electronic collective excitations that arise when the Coulomb interaction between excited states is switched on [11]. However, their theoretical description at the microscopic level is still an open and controversial issue [12]. In large nanoparticles optical and plasmonic properties are generally described by electrodynamics of continuous media, exploiting semiclassical models of the frequencydependent dielectric function [13][14][15] and the identification of plasmons is straightforward. This description has been very useful for designing applications, but fails to convey a microscopic understanding of what plasmons are. Nanoparticles and their excitations are composed of electrons and nuclei like ordinary molecules. Therefore, it must be possible to understand their excited states, including plasmons, in terms of the same elementary electron and hole excitations routinely used to interpret molecular excited states. Notably, such a microscopic description is mandatory when the system size reaches 1-2 nanometers, where the dielectric description breaks down and quantum finite-size effects [2,16] as well as the details of the atomic structure[17] play a crucial role. However, at the nanoscale, single-particle and plasmonic excitations are intrinsically mixed [18], and how to recognize a plasmonic excitation is still an unsolved problem.A few approaches have been recently proposed attempting to classify the plasmonic character of the excitations of nanosystems. [11,[19][20][21][22][23][24] In particular, Bernadotte et al. [11] formulated, in the framework of tim...

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Plasmons in molecules: Microscopic characterization based on orbital transitions and momentum conservation

Cited by 30 publications

References 74 publications

Molecular Plasmonics

Molecular Plasmonics

Lifetime dynamics of plasmons in the few-atom limit

Quantifying the Plasmonic Character of Optical Excitations in Nanostructures

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