title: Fano Transparency in Rounded Nanocube Dimers Induced by Gap Plasmon Coupling.
abstract: Homodimers of noble metal nanocubes form model plasmonic systems where the localized plasmon resonances sustained by each particle not only hybridize but also coexist with excitations of a different nature: surface plasmon polaritons confined within the Fabry-Perot cavity delimited by facing cube surfaces (i.e., gap plasmons). Destructive interference in the strong coupling between one of these highly localized modes and the highly radiating longitudinal dipolar plasmon of the dimer is responsible for the formation of a Fano resonance profile and the opening of a spectral window of anomalous transparency for the exciting light. We report on the clear experimental evidence of this effect in the case of 50 nm silver and 160 nm gold nanocube dimers studied by spatial modulation spectroscopy at the single particle level. A numerical study based on a plasmon mode analysis leads us to unambiguously identify the main cavity mode involved in this process and especially the major role played by its symmetry. The Fano depletion dip is red-shifted when the gap size is decreasing. It is also blue-shifted and all the more pronounced that the cube edge rounding is large. Combining nanopatch antenna and plasmon hybridization descriptions, we quantify the key role of the face-to-face distance and the cube edge morphology on the spectral profile of the transparency dip.
authors.affiliation: Univ Lyon, Université Claude Bernard Lyon , CNRS, Institut Lumière Matière, F-69622 Villeurbanne, France.
authors.forename: Michel
authors.identifier: 0000-0001-5620-2056
authors.initials: M
authors.lastname: Pellarin
authors.affiliation: Univ Lyon, Université Claude Bernard Lyon , CNRS, Institut Lumière Matière, F-69622 Villeurbanne, France.
authors.forename: Julien
authors.initials: J
authors.lastname: Ramade
authors.affiliation: Univ Lyon, Université Claude Bernard Lyon , CNRS, Institut Lumière Matière, F-69622 Villeurbanne, France.
authors.forename: Jan Michael
authors.initials: JM
authors.lastname: Rye
authors.affiliation: Univ Lyon, Université Claude Bernard Lyon , CNRS, Institut Lumière Matière, F-69622 Villeurbanne, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Bonnet
authors.affiliation: Univ Lyon, Université Claude Bernard Lyon , CNRS, Institut Lumière Matière, F-69622 Villeurbanne, France.
authors.forename: Michel
authors.initials: M
authors.lastname: Broyer
authors.affiliation: Univ Lyon, Université Claude Bernard Lyon , CNRS, Institut Lumière Matière, F-69622 Villeurbanne, France.
authors.forename: Marie-Ange
authors.initials: MA
authors.lastname: Lebeault
authors.affiliation: Univ Lyon, Université Claude Bernard Lyon , CNRS, Institut Lumière Matière, F-69622 Villeurbanne, France.
authors.forename: Jean
authors.initials: J
authors.lastname: Lermé
authors.affiliation: NIMBE, CEA, CNRS, Université Paris-Saclay, CEA Saclay , 91191 Gif-sur-Yvette, France.
authors.forename: Sylvie
authors.initials: S
authors.lastname: Marguet
authors.affiliation: Fiber and Polymer Technology, Royal Institute of Technology (KTH) , Teknikringen 56, SE-100 44 Stockholm, Sweden.
authors.forename: Julien R G
authors.initials: JR
authors.lastname: Navarro
authors.affiliation: Univ Lyon, Université Claude Bernard Lyon , CNRS, Institut Lumière Matière, F-69622 Villeurbanne, France.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Cottancin
keywords: fano resonance; gap plasmon; gold nanocubes; nanoparticle dimers; plasmonic coupling; plasmonic nanoantennas; silver nanocubes