On the origin of nonlocal damping in plasmonic monomers and dimers

Abstract

The origin and importance of nonlocal damping is discussed through simulations with the generalized nonlocal optical response (GNOR) theory, in conjunction with timedependent density-functional-theory (TDDFT) calculations and equivalent circuit modeling, for some of the most typical plasmonic architectures: metal-dielectric interfaces, metal-dielectric-metal gaps, spherical nanoparticles, and nanoparticle dimers. It is shown that diffusive damping, as introduced by the convective-diffusive GNOR theory, describes well the enhanced losses and plasmon broadening predicted by ab initio calculations in few-nm particles or few-to-sub-nm gaps. Through the evaluation of a local effective dielectric function, it is shown that absorptive losses appear dominantly close to the metal surface, in agreement with TDDFT and the mechanism of Landau damping due to generation of electron-hole pairs near the interface. Diffusive nonlocal theories provide therefore an efficient means to tackle plasmon damping when electron tunneling can be safely disregarded, without the need to resort to more accurate, but time-consuming fully quantum-mechanical studies.

Role of diffusive surface scattering in nonlocal plasmonics

“…Since, however, the hydrodynamic description is extended in the bulk of the metal, we want to write D surf = D. This assumption is consistent with the results of Fig. 1, where, for the metal-air interface shown in the schematics, we calculate with GNOR, following the examples by Wubs and Mortensen in [65] and Tserkezis et al in [66], an effective dielectric function ε eff (ω) (we focus on the component normal to the interface here), assuming for the metal a plasmon energy ω p = 5 eV, γ = 0.025 eV, v F = 1.07 • 10 6 m s −1 , and a typical value for the diffusion constant D = 2 • 10 −4 m 2 s −1 . These values are chosen as typical for good jellium metals, and do not represent any specific material.…”

Circular Dichroism in Nanoparticle Helices as a Template for Assessing Quantum-Informed Models in Plasmonics

“…Consequently, if a diffusion term is to be included, it must describe processes at the surface of the metal. Indeed, comparison with TD-DFT and modified-damping models shows that GNOR accounts efficiently for surface-enhanced Landau damping [48]. For NP separations of just few Å, a prominent feature left out of the hydrodynamic treatment (by assuming that J ·n = 0 at the metal surface) is the probability of direct electron tunnelling between NPs [18,19].…”

“…Consequently, if a diffusion term is to be included, it must describe processes at the surface of the metal. Indeed, comparison with TD-DFT and modified-damping models shows that GNOR accounts efficiently for surface-enhanced Landau damping [48].…”

Влияние Пространственной Дисперсии В Металлах На Оптические Характеристики Биметаллических Плазмонных Наночастиц

“…Однако теория Друде нуждается в коррекции некоторых квантовых параметров при рассмотрении несферических плазмонных наночастиц. В качестве альтернативы теории Друде исследовательской группой Мортенсена была разработана теория обобщенного нелокального оптического отклика (ОНО) [12]. В наших исследованиях мы используем теорию ОНО, которая уже доказала, что является наиболее подходящим инструментом для анализа частиц ядро−оболочка [13].…”