title: Acousto-plasmonic hot spots in metallic nano-objects.
abstract: We investigate the acousto-plasmonic dynamics of metallic nano-objects by means of resonant Raman scattering and time-resolved femtosecond transient absorption. We observe an unexpectedly strong acoustic vibration band in the Raman scattering of silver nanocolumns, usually not found in isolated nano-objects. The frequency and the polarization of this unexpected Raman band allow us to assign it to breathing-like acoustic vibration modes. On the basis of full electromagnetic near-field calculations coupled to the elasticity theory, we introduce a new concept of "acousto-plasmonic hot spots" which arise here because of the indented shape of the nanocolumns. These hot spots combine both highly localized surface plasmons and strong shape deformation by the acoustic vibrations at specific sites of the nano-objects. We show that the coupling between breathing-like acoustic vibrations and surface plasmons at the "acousto-plasmonic hot spots" is strongly enhanced, turning almost silent vibration modes into efficient Raman scatterers.
authors.affiliation: Centre d'Elaboration des Materiaux et d'Etudes Structurales CEMES-CNRS, and Université de Toulouse, Toulouse, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Large
authors.forename: Lucien
authors.initials: L
authors.lastname: Saviot
authors.forename: Jérémie
authors.initials: J
authors.lastname: Margueritat
authors.forename: José
authors.initials: J
authors.lastname: Gonzalo
authors.forename: Carmen N
authors.initials: CN
authors.lastname: Afonso
authors.forename: Arnaud
authors.initials: A
authors.lastname: Arbouet
authors.forename: Pierre
authors.initials: P
authors.lastname: Langot
authors.forename: Adnen
authors.initials: A
authors.lastname: Mlayah
authors.forename: Javier
authors.initials: J
authors.lastname: Aizpurua