Time-dependent density functional theory (TDDFT) simulations are conducted on a series of chiral gold nanowires to explore whether an enhancement of circular dichroism at the plasmon resonance is possible and identify its quantummechanical origin. We find that in linear two-dimensional chiral nanowires the dichroic response is suppressed by destructive interference of nearly degenerate components with opposite signs, pointing to this phenomenon as a common and likely origin of the difficulty encountered so far in achieving a plasmonic CD response in experiment and suggesting nevertheless that these opposite components could be “decoupled” by using multiwall arrangements. In contrast, we predict a giant dichroic response for nanowires with three-dimensional helical coiling. We rationalize this finding via an electronic structure analysis of longitudinal and transversal plasmonic excitations and their coupling into chiral components, and we propose a simple formula for the chiral response as a function of structural parameters (nanowire length and coiling number).

Circularly Polarized Plasmons in Chiral Gold Nanowires via Quantum-Mechanical Design

Toffoli, Daniele
Membro del Collaboration Group
;
Russi, Andrea;Fronzoni, Giovanna
Membro del Collaboration Group
;
Coccia, Emanuele
Membro del Collaboration Group
;
Stener, Mauro
Membro del Collaboration Group
;
Fortunelli, Alessandro
Membro del Collaboration Group
2021-01-01

Abstract

Time-dependent density functional theory (TDDFT) simulations are conducted on a series of chiral gold nanowires to explore whether an enhancement of circular dichroism at the plasmon resonance is possible and identify its quantummechanical origin. We find that in linear two-dimensional chiral nanowires the dichroic response is suppressed by destructive interference of nearly degenerate components with opposite signs, pointing to this phenomenon as a common and likely origin of the difficulty encountered so far in achieving a plasmonic CD response in experiment and suggesting nevertheless that these opposite components could be “decoupled” by using multiwall arrangements. In contrast, we predict a giant dichroic response for nanowires with three-dimensional helical coiling. We rationalize this finding via an electronic structure analysis of longitudinal and transversal plasmonic excitations and their coupling into chiral components, and we propose a simple formula for the chiral response as a function of structural parameters (nanowire length and coiling number).
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11368/2992703
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