Bulletin of the American Physical Society
APS March Meeting 2015
Volume 60, Number 1
Monday–Friday, March 2–6, 2015; San Antonio, Texas
Session J15: Focus Session: Transport and Strong Coupling in Plasmonic Nanostructures |
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Sponsoring Units: DMP Chair: Zhe Fei, Argonne National Laboratory Room: 008B |
Tuesday, March 3, 2015 2:30PM - 3:06PM |
J15.00001: Electron and hole dynamics in the electronic and structural phase transitions of VO$_{2}$ Invited Speaker: Richard Haglund The ultrafast, optically induced insulator-to-metal transition (IMT) and the associated structural phase transition (SPT) in vanadium dioxide (VO$_{2})$ have been studied for over a decade. However, only recently have effects due to the combined presence of electron-hole pairs and injected electrons been observed. Here we compare and contrast IMT dynamics when both hot electrons and optically excited electron-hole pairs are involved, in (1) thin films of VO$_{2}$ overlaid by a thin gold foil, in which hot electrons are generated by 1.5~eV photons absorbed in the foil and accelerated through the VO$_{2}$ by an applied electric field; (2) VO$_{2}$ nanoparticles covered with a sparse mesh of gold nanoparticles averaging 20-30 nm in diameter in which hot electrons are generated by resonant excitation and decay of the localized surface plasmon; and (3) bare VO$_{2}$ thin films excited by intense near-single-cycle THz pulses. In the first case, the IMT is driven by excitation of the bulk gold plasmon, and the SPT appears on a few-picosecond time scale. In the second case, density-functional calculations indicate that above a critical carrier density, the addition of a single electron to a 27-unit supercell drives the catastrophic collapse of the coherent phonon associated with, and leading to, the SPT. In the third case, sub-bandgap-energy photons (approximately 0.1~eV) initiate the IMT, but exhibit the same sub-100 femtosecond switching time and coherent phonon dynamics as observed when the IMT is initiated by 1.5~eV photons. This suggests that the underlying mechanism must be quite different, possibly THz-field induced interband tunneling of spatially separated electron-hole pairs. The implications of these findings for ultrafast switching in opto-electronic devices -- such as hybrid VO$_{2}$ silicon ring resonators -- are briefly considered. [Preview Abstract] |
Tuesday, March 3, 2015 3:06PM - 3:18PM |
J15.00002: Plasmonic Hot Carrier Transport and Collection in Nanostructures Adam Jermyn, Ravishankar Sundararaman, Prineha Narang, William Goddard, Harry Atwater Plasmonic resonances provide a promising pathway for efficiently capturing photons from solar radiation and improving photo-catalytic activity via hot carrier generation. Previous calculations have provided the prompt energy-momentum distributions of hot carriers, but have left open the question of their transport to collection surfaces [Accepted in Nature Communications]. As the overall efficiency of plasmonic devices is dependent not just on how many carriers are collected but also on their energy distribution, a transport model which tracks this distribution is of key importance. Here, we provide a first-principles model of this transport based upon at the linearized Boltzmann equation with the diffusive and ballistic regimes handled separately, and investigate the role of geometry on plasmonic hot carrier collection. [Preview Abstract] |
Tuesday, March 3, 2015 3:18PM - 3:30PM |
J15.00003: Controlling the ultrafast hot electron dynamics in hybrid plasmonic nanostructures Hayk Harutyunyan Plasmons hold promise for applications in photonic circuitry because of their ability to squeeze light into sub-wavelength dimensions and also for their ultrafast response times. To this end, it is important to fabricate plasmonic systems that can generate large optical signals at ultrafast timescales. This goal has been accomplished using coherent harmonic generation or wave mixing at metallic nanostructures where the femtosecond plasmonic response is attributed to plasmon dephasing. However, the multi-frequency nature of these optical effects makes their practical use challenging. Plasmonic devises based on Kerr-type nonlinear optical effects, on the other hand, can operate at a single, fundamental frequency. However, the ultrafast response of gold nanostructures so far has been measured to be in the picosecond timescales attributed to electron -- phonon scattering. By designing and fabricating metal-oxide hybrid nanosystems with ultra-high field enhancements we were able to demonstrate much faster, femtosecond dynamics of the optical response. Moreover, our experiments show that the nonlinear optical response can be further tuned in both time and spectral domains by tuning the material composition of our hybrid nanomaterials. Use of the Center for Nanoscale Materials was supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.. [Preview Abstract] |
Tuesday, March 3, 2015 3:30PM - 3:42PM |
J15.00004: Plasmonic Drag Effect: Toward Coupling of Electronic and Plasmonic Components in Nano-Circuits Matthew LePain, David Keene, Vincent Rono, Natalia Noginova, Maxim Durach Plasmonic Drag Effect (PDE) is a phenomenon of rectification of plasmonic optical fields into dc currents or dc polarization in metal nanostructures. Although being a nonlinear effect, PDE is strongly enhanced by resonance and confinement factors and can produce usable pulsed dc voltages of up to several mV in pulsed laser experiments, promising a path to long-awaited opportunities to couple electronic and plasmonic components in nano-circuits. PDE is produced via plasmonic pressure and plasmonic striction rectification forces. In this talk we will discuss the similarities and differences between these forces and possible additional mechanisms of PDE proposed by authors. We will describe generation of DC potential profiles by plasmons in metal nanostructures from both theoretical and experimental perspectives. [Preview Abstract] |
Tuesday, March 3, 2015 3:42PM - 3:54PM |
J15.00005: Exploring Photoswitchable Plasmon-Molecule Interactions at the Single-Molecule and Single-Nanoparticle Levels Mingsong Wang, Bharath Bangalore Rajeeva, Yuebing Zheng Through synergizing the responsiveness of functional molecules and the plasmon-assisted nanoscale localization of light, hybrid nanosystems consisting of molecules and metal nanoparticle have important applications in biochemical detection, drug delivery, and energy conversion. Single-molecule and single-nanoparticle studies of the hybrid nanosystems help eliminate the inevitable heterogeneity from ensemble measurements and provide new insights into the structure-property relations. Along this line, herein, we report our recent advances in designing, measuring and controlling two types of photoswitchable metal-nanoparticle-molecule nanosystems at the single-molecule and single-nanoparticle levels: (1) azobenzene molecules on single metal nanoparticles; and (2) spiropyran molecules on single metal nanoparticles. [Preview Abstract] |
Tuesday, March 3, 2015 3:54PM - 4:06PM |
J15.00006: Multifunctional Diagnostic, Nanothermometer and Photothermal Nano-devices Kory Green, Megan O'Connor, Parminder Kaur, Hong Wang, Shuang Fang Lim In this study, the known therapeutic capabilities of gold nanorods (AuNRs) have been combined with the diagnostic and nanothermometer abilities of upconversion nanoparticles (UCNPs) to develop a system for simultaneous biological imaging, photothermal therapy, and nanothermal sensing. Both the excitation of UCNPs and the finely tuned longitudinal surface plasmon resonance (LSPR) mode of AuNRs lay in a window of relatively high light penetration of tissue in the infra-red. The nanothermometer property of the UCNPs allows direct quantification of the localized temperature of the photothermally heated AuNRs chemically adsorbed to their surface and is free from the bleaching problems inherent in dye thermal sensing systems, especially at high laser fluences required to kill tissue. Spectroscopy on single particles, verified by transmission electron microscopy (TEM), has been performed at varying temperatures to confirm 1) the thermal sensing properties of UCNPs and 2) to finely tune their upconversion enhancement arising from the LSPR coupling of the AuNRs. Preliminary quantification of the localized AuNR temperatures upon photothermal heating will be confirmed through single particle spectroscopy of the attached UCNPs. HeLa cell viability studies have also been performed. [Preview Abstract] |
Tuesday, March 3, 2015 4:06PM - 4:18PM |
J15.00007: Plasmonic Response of Metallic Nanoparticles by Time Dependent Density Functional Theory Emily Townsend, Garnett Bryant Plasmons in metallic nanoparticles (MNPs) hold the potential to carry quantum information. Exploiting this will require a quantum understanding of plasmons in hybrid structures of multiple MNPs and emitters/absorbers. We use real-time, real-space time dependent density functional theory (TDDFT) to examine resonances in the optical response of single and paired MNPs. We consider the character of different resonances (some occur in the core, others near the surface of the MNP) and examine the multiple excitations that constitute these resonances. In both the core and surface resonances we see both plasmon-like sloshing of electrons around the Fermi surface and single-particle-like excitation of electrons from below the Fermi surface to above it. We examine the resonances of a pair of MNPs as a function of their separation distance to see how plasmonic and single-particle excitations mix in these particles. Widely separated pairs behave similarly to individual MNPs, but at closer distances pairs behave like a single, more complicated system. [Preview Abstract] |
Tuesday, March 3, 2015 4:18PM - 4:30PM |
J15.00008: Sweet Plasmonics: Sucrose Macrocrystals of Metal Nanoparticles Pedro Ludwig Hernandez-Martinez, Talha Erdem, Zeliha Soran-Erdem, Vijay Kumar Sharma, Halil Akcali, Ibrahim Akcali, Nikolai Gaponik, Alexander Eychm\"uller, Hilmi Volkan Demir We present a new plasmonic composite structure consisting of gold nanoparticles (Au NPs) incorporated into sucrose macrocrystals, preserving the plasmonic nature of the Au NPs. The resulting quantum efficiency (QE) in this composite material is enhanced via the interplay between the Au NPs and CdTe QDs from 24{\%} to 38{\%}. These results are in agreement with our model that includes electric field enhancement and F\"{o}rster-type energy transfer. Energy transfer is observed by the shortening in the photoluminescence lifetime from 11.0 to 7.40 ns, upon the introduction of Au NPs into the QD incorporated macrocrystals. As a proof of concept, the fluorescence enhancement of green CdTe quantum dots (QDs) via plasmonic coupling with these Au NPs in the sucrose crystals is demonstrated. Thus, ``sweet'' plasmonic crystals are promising for large-scale robust platforms to embed metal nanoparticles. [Preview Abstract] |
Tuesday, March 3, 2015 4:30PM - 4:42PM |
J15.00009: Cross-over from collective strong coupling to quenching in quantum dot-metal nanoparticles assemblies Praveena Mullapudi, Arnab Mukherjee, Sai Sreesh V, J.K. Basu The optical properties for the hybrid structures consisting of gold nanoparticles and CdSe Quantum Dots (QDs) have been widely studied. Compact hybrid monolayer films of gold nano particles (Au NPs) and cadmium selenide (CdSe QDs) with different ratios are prepared using LB method. Suitable tuning of the ratio of QDs and Au NPs at different surface densities leads to enhancement and attenuation of the emission of QDs which acts like a quantum emitters. The net emission enhancement of QDs is maximum, particularly in the case of 0.143 Au NP number fractio ($\varphi _{\mathrm{Au}})$ for both OFF - resonant and ON-resonant cases, and it is even more enhanced in the case of OFF- resonance i.e., when the SPR (surface Plasmon resonance) is not spectrally overlapping with the quantum dot PL maxima.We suggest that this behavior is indicative of a crossover from single particle to collective emission from quantum dots mediated by gold nanoparticles. The ability to control the radiative and non-radiative decay rates and the emission intensity from such assemblies using spectrally and spatially tuned plasmonic sources would be very crucial in the applications of photovoltaic's and nano photonics. [Preview Abstract] |
Tuesday, March 3, 2015 4:42PM - 4:54PM |
J15.00010: Controlling decay dynamics of quantum emitters with Plsmonic self assembly templates S.R.K.Chaitanya Indukuri, J.K. Basu Controlling the emission of quantum dots by tailoring local density of states(LDOS) in self assembled plasmonic template. Using very small diameter gold (Au) spherical nanoantenna within a polymer tem plate randomly dispersed with quantum dots, we show how the photoluminescence intensity and lifetime anisotropy of these dots can be significantly enhanced through LDOS tuning. We also studied the effect of dispersion, wider range of geometric and spectral parameters bringing out the versatility of these functional plasmonic templates. We studied the effect of nano antenna distribution on radiative and non radiative decay rates in the templates. We demonstrated that the decay dynamics in the plasmonic templates can be controlled in a facile manner by changing the filling fraction of the Au nanoparticles. This polarization dependent anisotropic decay dynamics for the quantum emitters is determined by polarization dependent LDOS of the plasmonic templates as demonstrated by FDTD simulations. Our work provides a new method to achieve spontaneous emission intensity and anisotropy enhancement with nanoscale plasmon resonators for applications from controlled photon emitters to light harvesting. [Preview Abstract] |
Tuesday, March 3, 2015 4:54PM - 5:06PM |
J15.00011: Changes of photoluminescence emission from metal/organic hybrid thin films with metal nanoparticle concentration Megumi Kimura, Naoki Tarutani, Masahide Takahashi, Arup Neogi, Ryoko Shimada Metal nanoparticles (NPs) have been attracting research interest in the field of nanophotonics due to the localized surface plasmon (LSP) effect that enhances the electric field around metal NPs. This localization leads to enhancement of light emission from fluorescent molecules in the vicinity of the metal NPs. This study focuses on hybrid thin films consisting of metal NPs (silver: Ag-NPs), organic molecules (anthracene) and a polymer matrix (polyphenylsiloxane glass: PSS) to investigate changes of the enhancement of photoluminescence (PL) emission from anthracene molecules at various Ag-NPs concentration. The integrated PL enhancement factor was reduced at high Ag-NPs concentration due to the aggregation of Ag-NPs, and the LSP resonant energy of Ag-NPs exhibited red-shift for this case. [Preview Abstract] |
Tuesday, March 3, 2015 5:06PM - 5:18PM |
J15.00012: Coupling between Plasmonic Nanostructures and Nitrogen-Vacancy Quantum Emitters Nathaniel Steinsultz, Jinxiao Gong, Min Ouyang In this talk, we will discuss the coupling between plasmonic nanostructures and nitrogen-vacancy (NV) center quantum emitters in diamonds at the nanoscale. We have developed a method to achieve tunable coupling between plasmonic metal nanostructures and NV centers. The effects of the metallic surface plasmon modes on the spontaneous emission rate of the NV centers can be evaluated by measuring the fluorescence lifetime of the NV centers. By coupling the NV center to the surface plasmon modes of the metallic nanoparticles, we observe an enhanced fluorescence rate of NV centers in nanodiamonds that may lead to increased sensitivity in nanoscale sensors. [Preview Abstract] |
Tuesday, March 3, 2015 5:18PM - 5:30PM |
J15.00013: XPS Observations of Crystal Field Splitting in TiO$_{2}$ Thin Films in Quantum Confinement Approach Natalya Sushkova Transition metal oxides attract increased interest due to amazing electrical and magnetic properties and their outstanding applications designated by relative d-band redistributions that are shifted in such a way that narrow bands arranged by localized electrons are situated in the vicinity of E$_{F}$. Different kinds of lattice distortions caused by doping and/or quantum size confinement of TM oxides are assigned to remarkable phenomenon Mott metal-insulator transitions, when mutual metal-oxide orbital arrangement changes dramatically. There is a widespread consensus that strong electron correlations are responsible for that change and magnetic excitation is one of manifestations of these correlations. Here we are presenting XPS study of titanium dioxide nanocrystal formations on silicon substrate with native oxide. The dynamic changes in XPS spectra were used for analysis of TiO$_{2}$ thin films with mass thicknesses up to 2 monolayers formed by redox reactions of sputtered Ti on Si(100) substrate with native oxide implemented \textit{in situ} under UHV conditions. XPS spectra evolution, as a traditional source of information on phase composition, was complemented by the possibility to estimate the morphology and crystal field splitting of formed precipitates. Intensity fluctuations observed for O1s, Si 2p, Ti2p spectra were accompanied by crystal field splitting in Ti2p and on second derivatives of O1s. These fluctuations were followed by noticeable changes in the vicinity of band gap indicating possible Mott metal-insulator transitions. [Preview Abstract] |
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