Bulletin of the American Physical Society
APS March Meeting 2016
Volume 61, Number 2
Monday–Friday, March 14–18, 2016; Baltimore, Maryland
Session B24: Optical Effects Near Metallic NanostructuresFocus
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Sponsoring Units: DMP Chair: Latha Venkataraman, Columbia University Room: 323 |
Monday, March 14, 2016 11:15AM - 11:51AM |
B24.00001: \textbf{Optical functionality of plasmon-exciton nanomaterials in the strong coupling regime} Invited Speaker: Maxim Sukharev Understanding optical plasmon-exciton interaction in hybrid plasmonic nanostructures is important for tuning the optical response, e.g. for applications in nonlinear optics, organic solar cells, or organic light-emitting diodes. In developing such nanostructures, the strong coupling phenomena play crucial role allowing to efficiently transfer energy between plasmons and molecular excitons on a femtosecond time scale. In this talk I will discuss modeling aspects of various optical phenomena at plasmonic interfaces using Maxwell-Bloch equations in three dimensions. Various plasmonic systems including periodic V-grooves, bowtie antennas, nanowires, periodic hole arrays, and others will be considered. In particular, I will demonstrate that one can design hybrid nanomaterials with highly pronounced Fano resonances using femtosecond lasers. I will show that it is possible to use ultra-short laser pulses to materials with desired properties and functionality. Electromagnetic energy transport in systems composed of closely spaced nanowires in a presence of molecular excitons will also be discussed. [Preview Abstract] |
Monday, March 14, 2016 11:51AM - 12:03PM |
B24.00002: Surface Enhance Infrared Absorption in nanogap structures Yajing Li, Pavlo Zolotavin, Douglas Natelson Understanding the energy dissipation at the interface of molecules and metal nanostructures is of interest. We fabricate self-aligned gold nanostructures with nanometer-scale interelectrode spacing. Those gold nanostructures support highly hybridized plasmon modes with great enhanced local electric field. Previous studies have proven those structures to be suitable substrates for surface-enhanced Raman spectroscopy with single-molecule sensitivity, which enables the study of molecular vibrational and electronic physics. We propose those structures as possible probes of the energy dissipation at the nanometer gap. By measuring the absorption spectrum of molecules assembled in the junction, we can estimate the local filed intensity at the gap and discuss the plasmonic responses of these self-aligned structures under infrared excitation. [Preview Abstract] |
Monday, March 14, 2016 12:03PM - 12:15PM |
B24.00003: Optically induced changes to the tunneling properties of molecular junctions. Pavlo Zolotavin, Charlotte Evans, Douglas Natelson We report increased conductance under laser illumination in plasmonically active atomic scale gold junction in a cryogenic environment (substrate temperatures down to 4 K). Additionally, we observe changes in the bias dependence of differential conductance, which we attribute to local heating due to the illumination. We differentiate between plasmon and direct gold absorption by investigating the polarization dependence of the observed temperature change. The effect is quantified by measuring optically induced changes in the resistance of the metal nanowire and by the change in the magnitude of simultaneously measured Johnson-Nyquist noise. A combination of these techniques provides independent measurements of effective lattice and electronic temperatures. Unlike previous experiments at room temperature and 80 K, we report a substantially larger light-driven temperature increase of 80-120K for devices fabricated on SiO$_{\mathrm{2}}$/Si substrates held at substrate temperatures as low as 4 K. The implications of the observed behavior for electronic transport in single molecular junctions with plasmonically active nanowire leads will be discussed. [Preview Abstract] |
Monday, March 14, 2016 12:15PM - 12:27PM |
B24.00004: Propagating plasmon excitation of molecular junctions for spectroscopy Charlotte Evans, Pavlo Zolotavin, Douglas Natelson Electronic transport and simultaneous optical measurements on molecule-containing junctions can provide critical information about the dissipation of energy through inelastic processes. Gold bowtie nanostructures have been used for electronic transport and as plasmonically active substrates for surface-enhanced Raman scattering (SERS), conventionally with exciting light incident directly on the molecular junction. Electromigrating these devices created interelectrode nanogaps with single-molecule sensitivity in which the Raman scattering rate is dominated by plasmonically enhanced electromagnetic fields due to the presence of the metal nanojunction near the molecules of interest. Direct optical excitation of the junction region, however, can cause heating of the metal, molecular instability via conformational and chemical changes, and breakdown over time. Adding metallic gratings to the electrode design enables the excitation of propagating plasmon modes that can couple into the junction region without direct excitation by far-field radiation. We will present preliminary data on how the addition of these gratings affects single-molecule SERS and the electrical properties of the molecules in these junctions. [Preview Abstract] |
Monday, March 14, 2016 12:27PM - 12:39PM |
B24.00005: Enhancement of Resonant Energy Transfer Due to Evanescent-wave from the Metal Amrit Poudel, Xin Chen, Mark Ratner The high density of evanescent modes in the vicinity of a metal leads to enhancement of the near-field Forster resonant energy transfer (FRET) rate. We present a mathematical formulation based on classical electromagnetic theory using the dyadic Greens function and investigate the effect of metallic environment using material permittivity in local and nonlocal limits, which provides better estimates of the transfer rate at small separations from the metal. Furthermore, we present a general formula of FRET rate for multiple donors and acceptors in the presence of arbitrary dielectric environment and discuss the path interference effect on FRET rate. [Preview Abstract] |
Monday, March 14, 2016 12:39PM - 12:51PM |
B24.00006: Two-photon up-conversion affected by inter-molecule correlations near metallic nanostructure Yoshiki Osaka, Nobuhiko Yokoshi, Hajime Ishihara Optical antennas, which consist of metallic nanostructures, concentrate free-propagating light into localized surface plasmons (LSP). Such a localized field enables effective interactions between light and molecules nearby the metal surfaces. However, as the light intensity decreases to single-photon level, large dissipation in the metals always inhibits the effective photon-molecule interaction via LSP. We have theoretically elucidated that controlling quantum interference in an antenna-molecule coupled system strongly suppresses the photon-dissipations, and leads to efficient two-photon processes in the molecule. However, it is difficult to prepare only one molecule nearby the metal. Therefore, as a beachhead into a multi-molecule system, we will consider the case that two photons couple with two molecules under one LSP. In rapid intuition, the appearance of the second molecule seemingly damages the up-conversion process. In the presentation, we reveal that controlling the inter-molecule interaction could resolve the difficulty, and lead to the efficient up-conversion through the quantum interference among three-bodies, i.e., LSP and two molecules. [Preview Abstract] |
Monday, March 14, 2016 12:51PM - 1:03PM |
B24.00007: Finite-Difference Time-Domain (FDTD) Modeling of Gold Core-Shell Structures with Different Shell Morphology for Surface-Enhanced Raman Spectroscopy (SERS) Zohre Gorunmez, Debrina Jana, Jie He, Laura Sagle, Thomas Beck Core-shell (CS) nanostructures have received attention in recent years due to their usefulness in applications ranging from catalysis to cancer treatment. SERS has been shown to be one of the most sensitive techniques for molecular detection, achieving single molecule detection. It has been established that the electromagnetic mechanism (EM) provides the main contribution to SERS enhancement due to the normal Raman spectroscopy arising from coupling of both the incident and re-emitted fields. The FDTD technique has been developed to provide numerical solutions to Maxwell’s time-dependent curl equations in order to promise modeling capabilities for EM enhancement of SERS. Herein, we apply this method to the study of three morphologically different gold core-shell nanoparticles to investigate their contributions to SERS. In these structures, the dye/probe molecule resides in between the shell and the core and only the shell morphology is altered. The data shows that the surface plasmon resonances (PRs) influencing the SERS of the probe molecules, due to the coupling of the core and shell, are tunable by changing the shell morphologies and CS structures with sharp features on their surfaces highlight larger enhancements due to stronger localized surface PRs. [Preview Abstract] |
Monday, March 14, 2016 1:03PM - 1:15PM |
B24.00008: Block copolymer based design of highly sensitive substrates for detecting single molecules by surface enhanced Raman scattering Atikur Rahman, Charles Black Surface enhanced Raman spectroscopy (SERS) relies on substrates with nanometer-scale curvature in order to concentrate and amplify the incident electromagnetic field to increase the spectroscopic signature of Raman scattering. The localization and amplification of incident light is maximum between two plasmonic nanostructures called as ``hot spot''. Here, we report a new, scalable method for fabricating high-performance SERS substrates based on self-assembly of nanostructured block copolymer thin films. Due to the high spatial density and extremely high field strengths of substrate hot spots, these substrate are capable of enhancing Raman scattering signals from target molecules by more than 10 billion times. We will describe the process of fabricating these remarkable diagnostic tools, which are \textasciitilde cm$^{\mathrm{2}}$ area substrates composed of an extremely high density (\textasciitilde 10$^{\mathrm{11}}$ /cm$^{\mathrm{2}})$ of hexagonally-arranged Au or Ag nanoparticles positioned atop \textasciitilde 70nm tall silicon nanopillars. Key to the substrate performance is the sub-5 nm separation between particles, which we control with nm level precision. By systematically varying the gap between nanoparticles, we demonstrate that both the high hotspot density and sub 5nm hot spot gap are necessary to achieve the highest degree of enhancement of the Raman signal. The enormous enhancements provided by these substrates make possible the detection of single molecules. [Preview Abstract] |
Monday, March 14, 2016 1:15PM - 1:27PM |
B24.00009: ABSTRACT WITHDRAWN |
Monday, March 14, 2016 1:27PM - 1:39PM |
B24.00010: A condensed matter field theory for quantum plasmonics Fouad Ballout, Ortwin Hess In recent years plasmonics has advanced to ever decreasing length scales reaching dimensions comparable to the de broglie wavelength of an electron, which has a manifest influence on the plasmon dispersion relation. The associated phenomenology lies beyond the reach of the classical drude free electron theory or its nonlocal extension and adequate models are needed to address the quantum matter aspects of light-matter interaction that are responsible for plasmonicquantum size effects. We present on the basis of the jellium model a quantum field theory of surface-plasmon polaritons in which they emerge as extended objects as a result of an inhomogeneous condensation of bosons around a topological singularity describing the surface. The benefit of this approach lies in relating the electromagnetic fields belonging to such a macroscopic quantum state with the surface topology and nonlocal responsefunction (expressed in terms of the retarded photon self-energy) of the delimited electron gas sustaining that state. [Preview Abstract] |
Monday, March 14, 2016 1:39PM - 1:51PM |
B24.00011: Combining magneto-optics with plasmonics in gold-nickel nanoparticle arrays Mikko Kataja, Sara Pourjamal, Nicol\'{o} Maccaferri, Paolo Vavassori, Tommi Hakala, Mikko Huttunen, P\"{a}ivi T\"{o}rm\"{a}, Sebastiaan van Dijken Periodic arrays of metallic nanoantennas support intense surface lattice resonances (SLRs) with very narrow linewidths that arise from radiative coupling between the surface plasmon polaritons of the individual nanoparticles. Combining plasmonic systems with active components such as magneto-optical materials opens up new possibilities for active optical devices. Here, we present a new versatile method of integrating ferromagnetic and noble metal plasmonic nanostructures leading to strong magneto-optical responses in conjuncture with drastically enhanced optical reflectivity. The structures under study consist of nickel and gold nanoparticles that are ordered into periodic checkerboard arrays. The gold constituent of these hybrid arrays guarantees intense optical reflectivity. Yet, compared to pure nickel arrays, the magneto-optical signal is practically retained. Local analyses of the radiation fields indicate that the nickel and gold nanoparticles both actively contribute to the magneto-optical activity of the hybrid lattice via radiative coupling. The results also demonstrate that the size of the noble metal nanoparticles can be used to tailor magneto-optical spectra, providing a new tool for designer magneto-optical materials. [Preview Abstract] |
Monday, March 14, 2016 1:51PM - 2:03PM |
B24.00012: Surface lattice resonances and magneto-optical response in magnetic nanoparticle arrays Tommi Hakala, Mikko Kataja, Aleksi Julku, Mikko Huttunen, Sebastiaan van Dijken, Paivi Torma We show that periodic rectangular arrays of magnetic nanoparticles display collective surface plasmon modes which are coupled by the radiation fields from each particle. The two directions of the lattice are coupled by the magnetic-field-controllable spin-orbit coupling in the nanoparticles. When breaking the symmetry of the lattice, we find that the optical response shows Fano-type surface lattice resonances whose frequency is determined by the periodicity orthogonal to the polarization of the incident field. In striking contrast, the magneto-optical Kerr response is controlled by the period in the parallel direction. The spectral separation of the response for longitudinal and orthogonal excitations provides versatile tuning of narrow and intense magneto-optical resonances. [Preview Abstract] |
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