Laplacian-Level Quantum Hydrodynamic Theory for Plasmonics

An accurate description of the optical response subwavelength metallic particles and nanogap structures is a key problem plasmonics. Quantum hydrodynamic theory (QHT) has emerged as powerful method to calculate nanoparticles (NPs) since it takes into account nonlocality spill-out effects. Nevertheless, absorption spectra NPs obtained with conventional QHT, i.e., incorporating Thomas-Fermi (TF) von Weizsäcker (vW) kinetic energy (KE) contributions, can be affected by several spurious resonances at energies higher than main localized surface plasmon (LSP). These peaks are not present in reference time-dependent density-functional-theory spectra, where, instead, only broad shoulder exists. Moreover, we show here that these incorrectly reduce LSP peak intensity have strong dependence on simulation domain size so proper calculation QHT problematic. In this article, introduce more general accounting for KE contributions depending Laplacian electronic density (q), thus, beyond gradient-only TFvW functional. We employing functional term proportional q2 results an spectrum free peaks, resonance correct numerically stable Bennett state. Finally, novel Laplacian-level very properties different sizes well dimers. Thus, represents novel, efficient, platform study plasmonic systems.4 MoreReceived 5 June 2020Revised 21 October 2020Accepted 24 December 2020DOI:https://doi.org/10.1103/PhysRevX.11.011049Published American Physical Society under terms Creative Commons Attribution 4.0 International license. Further distribution work must maintain attribution author(s) published article’s title, journal citation, DOI.Published SocietyPhysics Subject Headings (PhySH)Research AreasDensity theoryPlasmonicsPlasmonsSurface plasmonsPhysical SystemsNanoparticlesTechniquesClassical electromagnetismDensity approximationsDensity calculationsFree-electron modelGGACondensed Matter, Materials & Applied PhysicsAtomic, Molecular Optical