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Title: Understanding How Acoustic Vibrations Modulate the Optical Response of Plasmonic Metal Nanoparticles

Measurements of acoustic vibrations in nanoparticles provide a unique opportunity to study mechanical phenomena at nanometer length scales and picosecond time scales. Vibrations in noble-metal nanoparticles have attracted particular attention, because they couple to plasmon resonances in the nanoparticles, leading to strong modulation of optical absorption and scattering. There are three mechanisms that transduce the mechanical oscillations into changes in the plasmon resonance: (1) changes in polarizability due to changes in the nanoparticle geometry; (2) changes in electron density due to changes in the nanoparticle volume and (3) changes in the interband transition energies due to compression/expansion of the nanoparticle (deformation potential). These mechanisms have been studied in the past to explain the origin of the experimental signals; however, a thorough quantitative connection between the coupling of phonon and plasmon modes and separate contribution of each coupling mechanism has not yet been made. Here, we present a numerical method to quantitatively determine the coupling between vibrational and plasmon modes in noble-metal nanoparticles of arbitrary geometries, and apply it to spheres, shells, rods, and cubes in the context of time resolved measurements. We separately determine the parts of the optical response that are due to shape changes, changes in electron density,more » and changes in deformation potential (DP). We further show that coupling is in general strongest when the regions of largest electric field (plasmon mode) and largest displacement (phonon mode) overlap. Lastly, these results clarify reported experimental results, and should help guide future experiments and potential applications.« less
Authors:
ORCiD logo [1] ; ORCiD logo [2] ; ORCiD logo [3]
  1. California State Univ. Long Beach, Long Beach, CA (United States); Argonne National Lab. (ANL), Argonne, IL (United States)
  2. Univ. of Maryland Baltimore County (UMBC), Baltimore, MD (United States); Argonne National Lab. (ANL), Argonne, IL (United States)
  3. Argonne National Lab. (ANL), Argonne, IL (United States). Center for Nanoscale Materials
Publication Date:
Grant/Contract Number:
AC02-06CH11357
Type:
Accepted Manuscript
Journal Name:
ACS Nano
Additional Journal Information:
Journal Volume: 11; Journal Issue: 9; Journal ID: ISSN 1936-0851
Publisher:
American Chemical Society (ACS)
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
77 NANOSCIENCE AND NANOTECHNOLOGY; Acoustic vibrations; Coupling; Nanoparticle; Phonons; Plasmons; Transient Absorption
OSTI Identifier:
1405321

Ahmed, Aftab, Pelton, Matthew, and Guest, Jeffrey R. Understanding How Acoustic Vibrations Modulate the Optical Response of Plasmonic Metal Nanoparticles. United States: N. p., Web. doi:10.1021/acsnano.7b04789.
Ahmed, Aftab, Pelton, Matthew, & Guest, Jeffrey R. Understanding How Acoustic Vibrations Modulate the Optical Response of Plasmonic Metal Nanoparticles. United States. doi:10.1021/acsnano.7b04789.
Ahmed, Aftab, Pelton, Matthew, and Guest, Jeffrey R. 2017. "Understanding How Acoustic Vibrations Modulate the Optical Response of Plasmonic Metal Nanoparticles". United States. doi:10.1021/acsnano.7b04789. https://www.osti.gov/servlets/purl/1405321.
@article{osti_1405321,
title = {Understanding How Acoustic Vibrations Modulate the Optical Response of Plasmonic Metal Nanoparticles},
author = {Ahmed, Aftab and Pelton, Matthew and Guest, Jeffrey R.},
abstractNote = {Measurements of acoustic vibrations in nanoparticles provide a unique opportunity to study mechanical phenomena at nanometer length scales and picosecond time scales. Vibrations in noble-metal nanoparticles have attracted particular attention, because they couple to plasmon resonances in the nanoparticles, leading to strong modulation of optical absorption and scattering. There are three mechanisms that transduce the mechanical oscillations into changes in the plasmon resonance: (1) changes in polarizability due to changes in the nanoparticle geometry; (2) changes in electron density due to changes in the nanoparticle volume and (3) changes in the interband transition energies due to compression/expansion of the nanoparticle (deformation potential). These mechanisms have been studied in the past to explain the origin of the experimental signals; however, a thorough quantitative connection between the coupling of phonon and plasmon modes and separate contribution of each coupling mechanism has not yet been made. Here, we present a numerical method to quantitatively determine the coupling between vibrational and plasmon modes in noble-metal nanoparticles of arbitrary geometries, and apply it to spheres, shells, rods, and cubes in the context of time resolved measurements. We separately determine the parts of the optical response that are due to shape changes, changes in electron density, and changes in deformation potential (DP). We further show that coupling is in general strongest when the regions of largest electric field (plasmon mode) and largest displacement (phonon mode) overlap. Lastly, these results clarify reported experimental results, and should help guide future experiments and potential applications.},
doi = {10.1021/acsnano.7b04789},
journal = {ACS Nano},
number = 9,
volume = 11,
place = {United States},
year = {2017},
month = {8}
}