Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session L50: Focus Session: Quantum Plasmonics, Metamaterials, and Nanocrystals |
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Chair: Yanwen Wu, University of South Carolina Room: Mile High Ballroom 1D |
Wednesday, March 5, 2014 8:00AM - 8:36AM |
L50.00001: Quantum Plasmonics and Nanoscale Gap Plasmons with graphene, semiconductors and molecules Invited Speaker: Jeremy Baumberg Coupling between plasmonic nano-components generates strongly red-shifted resonances combined with intense local field amplification on the nanoscale. We have combined plasmonics with soft materials to tune this interaction dynamically, accessing the strong coupling domain for gaps below 1nm, reliably made by bottom-up self-assembly. At these distances coupled dipoles cannot describe the response, and a better account comes from gap plasmons. Crucial is the extreme sensitivity to separation, and how quantum tunneling starts to play an influence that can be directly seen at room temperature in ambient conditions. We recently demonstrated how quantum plasmonics controls the very smallest space that light can be squeezed into. We also demonstrate the possibility to track few molecules using surface-enhanced CARS. A new generation of 2D semiconductors coupled to such nano-scale gaps utilizes a nanoparticle on mirror geometry. \\[4pt] [1] \textit{Nature} \textbf{491}, 574 (2012); Revealing the quantum regime in tunnelling plasmonics.\\[0pt] [2] \textit{Nano Letters} \textbf{10}, 1787 (2010); Actively-Tuned Plasmons on Elastomeric Au NP Dimers.\\[0pt] [3] \textit{ACS Nano} \textbf{5}, 3878 (2011); Precise sub-nm plasmonic junctions within Au NP assemblies.\\[0pt] [4] \textit{Nano Lett} doi:10.1021/nl4018463 (2013); Controlling Sub-nm Plasmonic Gaps using Graphene. [Preview Abstract] |
Wednesday, March 5, 2014 8:36AM - 8:48AM |
L50.00002: A single-wavefunction density functional approach to the plasmonic nanostructures in the extreme quantum limit Dafei Jin, Fan Wang, Nicholas Fang We have constructed a single-wavefunction density functional model, which can reproduce the key physical properties of silver, such as its work function, exchange-correlation energy, bulk and surface plasmon frequencies. We apply this model to the studies of silver thin films, nanowires, and silver-dielectric indefinite metamaterials, at the length scale from subnanometers to tens of nanometers. We find that the quantum kinetics of electrons in silver can cause a large nonlocal dependence and blueshift of surface plasmon frequency, when the plasmonic wavelength and the typical size of structures become smaller than 50 nm. Our calculated results can be used to explain the spectrum broadening phenomena observed in recent cathodoluminescence and electron energy loss spectroscopy experiments. [Preview Abstract] |
Wednesday, March 5, 2014 8:48AM - 9:00AM |
L50.00003: Photogeneration of hot plasmonic carriers with metal nanocrystals Alexander Govorov, Hui Zhang, Yurii Gun'ko We investigate the effect of plasmon-assisted carrier injection from metal nanocrystals to a semiconductor contact or to adsorbed molecules. We treat the problem of optically-driven metal nanocrystal using the quantum approach of equation of motion of density matrix. Energy distributions of optically-excited plasmonic carriers are very different in metal nanocrystals with large and small sizes. In large nanocrystals, most excited carriers have very small energies and the electron distribution resembles the case of a plasmon wave in bulk. For gold nanocrystal with smaller sizes (less than 20nm), the energy distribution of hot carriers becomes flat and has a large number of carriers with high energy. Therefore, smaller nanocrystals are preferable for injection of plasmonic carriers into semiconductors or into molecules on the surface. The physical reason for the above behavior is non-conservation of momentum in a nanocrystal. The geometry, type of metal, and orientation of the external electric field are important to obtain high quantum efficiencies of generation and injection of plasmonic electrons. The results obtained in this study can be used to design a variety of plasmonic nano-devices based on hot electron injection for photocatalysis, light-harvesting, and solar cells. [Preview Abstract] |
Wednesday, March 5, 2014 9:00AM - 9:12AM |
L50.00004: Excitation of plasmons in metallic nanostructures by hot electrons in an adjacent semiconductor Jiantao Kong, Chaobin Yang, Juan Merlo, Michael J. Burns, Michael J. Naughton, Krzysztof Kempa It has been shown in a simple model calculation that hot electrons excited in a semiconductor can emit plasmons in an adjacent metallic nanostructure at a very high rate, exceeding that of phonon emission [1]. This effect could provide a possible route to high photovoltaic energy conversion efficiency in a hot electron solar cell. Here, we study this process in specific nanostructures, toward maximizing the effect. In theoretical work, we employ the high fidelity, finite difference time domain (FDTD) simulation technique to study the optical response of the systems considered, combined with quantum mechanical calculation of the scattering rates. We will also discuss fabrication and near and far-field optical measurements of test samples.\\[4pt] [1] K. Kempa, \textit{Phys. Status Solidi RRL} \textbf{7}, 465 (2013). [Preview Abstract] |
Wednesday, March 5, 2014 9:12AM - 9:24AM |
L50.00005: Attosecond Electro-Magnetic Forces Acting on Metal Nanospheres Induced By Relativistic Electrons M.J. Lagos, P.E. Batson, A. Reyes-Coronado, P.M. Echenique, J. Aizpurua Swift electron scattering near nanoscale materials provides information about light-matter behavior, including induced forces. We calculate time-dependent electromagnetic forces acting on 1-1.5 nm metal nanospheres induced by passing swift electrons, finding both impulse-like and oscillatory response forces. Initially, impulse-like forces are generated by a competition between attractive electric forces and repulsive magnetic forces, lasting a few attoseconds (5-10 as). Oscillatory, plasmonic response forces take place later in time, last a few femtoseconds (1- 5 fs), and apparently rely on photon emission by decay of the electron-induced surface plasmons. A comparison of the strength of these two forces suggests that the impulse-like behavior dominates the process, and can transfer significant linear momentum to the sphere. Our results advance understanding of the physics behind the observation of both attractive and repulsive behavior of gold nano-particles induced by electron beams in aberration-corrected electron microscopy. [Preview Abstract] |
Wednesday, March 5, 2014 9:24AM - 9:36AM |
L50.00006: Nanoscale Assemblies of Fluorescent, Few-Atom Silver Clusters Stacy Copp, Danielle Schultz, Nemanja Markesevic, Kira Gardner, Sumant Oemrawsingh, Dirk Bouwmeester, Elisabeth Gwinn Silver clusters with sizes small enough to display high fluorescence quantum yields can be stabilized by DNA. These clusters show evidence for rod-like structure [1], opening up possibilities for new functionalities based on structure-modulated near-field patterning and anisotropic polarization response. We develop DNA clamps to hold two silver clusters composed of 10 and 15 atoms in nanoscale proximity, while retaining the individual structure of each cluster [2]. Thermally modulated fluorescence resonance energy transfer (FRET) verifies assembly formation, with clusters held 5 - 6 nm apart, in the range of the best resolution that can be achieved in DNA scaffolds. The absence of spectral shifts in these dual-cluster FRET pairs, relative to the individual cluster spectra, shows that few-atom silver clusters of different sizes can be sufficiently stable to retain their structural integrity when held within a nanoscale DNA construct. [1] D. Schultz, \textit{et al.}, Adv. Mater. \textbf{25}, 2797 (2013) [2] D. Schultz, \textit{et al.}, ACS Nano, ASAP (DOI: 10.1021/nn4033097). [Preview Abstract] |
Wednesday, March 5, 2014 9:36AM - 9:48AM |
L50.00007: Direct observation of resonant modes in circular cavities by LRM Juan Merlo, Fan Ye, Michael J. Burns, Michael J. Naughton The observation of plasmonic cavities has become an important topic, as a number of novel technologies are being conceived and developed with such systems.\footnote{M. Khajavikhan, A. Simic, M. Katz, J.H. Lee, B. Slutsky, A. Mizrahi, V. Lomakin, Y. Fainman, Nature, 482, 204 (2012).} We present the experimental observation of the resonant plasmon modes in circular cavities by using an alternative scheme of the leakage radiation microscope. The reported method is very simple to implement (wide-field, non-scanning) without sample requirements more than the patterned cavity. The calculation of the cavities' radii for specific excited modes is based on a simple drumhead model.\footnote{F. Ye, M.J. Burns, and M. J. Naughton, Nano Lett. 13, 519 (2013).} Numerical simulations confirm our observations and suggest that the detected field is related to the in-plane components of the modes in the cavity, an expected result when the leakage radiation microscopy is used. [Preview Abstract] |
Wednesday, March 5, 2014 9:48AM - 10:00AM |
L50.00008: Experimental observation of TM propagated modes in nanocoax structures Michael J. Naughton, Binod Rizal, Fan Ye, Michael J. Burns, Juan M. Merlo The nanoscale manipulation of light has become one of the most important research areas in the last years.\footnote{R. R. Oulton, V. J. Sorger, T. Zentgraf, R. M. Ma, C. Gladden, L.Dai, G. Bartal, X. Zhang, Nature 461, 629-632 (2009).} Several studies in nanoscale waveguides have been done and the coaxial waveguide is among the most promising due to its broadband properties.\footnote{D. Pozar, D. ``Microwave Engineering,'' 3rd. Edition. John Wiley and Sons, Inc. USA, 2005.} Here, we report the experimental observation of photonic and plasmonic transverse magnetic mode propagation in a nanocoax structure by use of leakage radiation microscopy and near-field scanning optical microscopy in the visible and near-infrared ranges of the electromagnetic spectrum. Numerical calculations are consistent with our experimental results and suggest that the propagated modes are mainly TM$_{10}$-like (plasmonic) and TM$_{11}$ (photonic) modes, confirming theoretical results previously reported.\footnote{ Peng Y., Wang W., Kempa K., Opt. Express. 3, 1758-1763 (2008).} [Preview Abstract] |
Wednesday, March 5, 2014 10:00AM - 10:12AM |
L50.00009: Meta-Atom Interactions and Coherent Response in RF SQUID Metamaterials Melissa Trepanier, Daimeng Zhang, Oleg Mukhanov, Philipp Jung, Susanne Butz, Alexey Ustinov, Steven Anlage We have designed, fabricated, and measured RF SQUID (radio frequency superconducting quantum interference devices) metamaterials and demonstrated their extreme tunability with temperature, DC magnetic field, and rf current [1]. The SQUID metamaterial can be modelled as an array of weakly coupled oscillators with tunable resonant frequencies. An array of identical SQUIDs under identical conditions will have a coherent collective response regardless of the strength of the interactions between them. In the presence of disorder (nonuniform magnetic flux for instance) the individual SQUIDs in the array may or may not tune coherently. Since we are interested in metamaterial applications, the coherent response is desirable. In this talk we examine the conditions required for the SQUIDs to tune coherently, and compare to experimental data on tuning and nonlinearity in a variety of RF SQUID metamaterials.\\[4pt] [1] M. Trepanier*, Daimeng Zhang*, Oleg Mukhanov, Steven M. Anlage, Phys. Rev. X (in press), arXiv:1308.1410v2 [Preview Abstract] |
Wednesday, March 5, 2014 10:12AM - 10:24AM |
L50.00010: Extremely nonlinear and switchable SQUID metamaterial Daimeng Zhang, Melissa Trepanier, Oleg Mukhanov, Philipp Jung, Susanne Butz, Alexey Ustinov, Steven Anlage We present experimental results on a superconducting metamaterial with remarkably nonlinear and switchable properties in the microwave range. The meta-atoms are RF Superconducting Quantum Interference Devices (SQUIDs), a superconducting loop interrupted by a single Josephson Junction. RF SQUIDs are similar to split-ring resonators except that the inductance is tunable due to the nonlinear Josephson inductance. This metamaterial has high tunability via DC magnetic field, temperature and applied RF power [1]. Here we focus on the nonlinearity in our metamaterial due to the Josephson effect. The intermodulation measurements show a highly nonlinear response from the metamaterial. In an RF power dependence experiment we observed hysteretic behavior in transmission which indicates the metamaterial is a nonlinear multi-state system. As a result, we can control the transmission by switching between metastable states via manipulating the applied RF power. We also observe a unique self-induced transparency of meta-atoms in a certain applied RF power range. This extremely nonlinear metamaterial has potential application for next-generation digital RF receiver systems. \\[4pt] [1] M. Trepanier*, D. Zhang*, O. Mukhanov, S.M. Anlage, Phys. Rev. X (in press), arXiv:1308.1410v2. [Preview Abstract] |
Wednesday, March 5, 2014 10:24AM - 10:36AM |
L50.00011: Band gap variations in ferritin-templated nanocrystals John Colton, Stephen Erickson, Trevor Smith, Richard Watt Ferritin is a 12 nm diameter protein shell with an 8 nm ``cage'' inside that can be used as a template for nanoparticle formation. The native particle is an iron oxide, ferrihydrite, but can be altered or replaced. We have used optical absorption spectroscopy to study the band gap of the ferrihydrite nanoparticles as they age (and become more crystalline), and as they respond to surface interactions with ions in solution. We will also present results of particle composition variations due to incorporation of oxo-anions into the interior of the nanoparticles and substitution of iron with other metals such as cobalt and manganese. [Preview Abstract] |
Wednesday, March 5, 2014 10:36AM - 10:48AM |
L50.00012: Band gap measurements and tunability of ferrihydrite nanocrystals Stephen Erickson, John Colton, Trevor Smith, Richard Watt Ferrihydrite nanocrystals occur naturally within the protein ferritin, a spherical shell with an 8nm wide interior. The nanocrystal core of ferritin can be removed and replaced with a variety of other minerals of a controlled size, allowing for potential to tune their band gap for a variety of applications. However, band gap measurements of even the native ferrihydrite have proven elusive, with reported values of the band gap in the literature ranging from 1.0-3.5 eV. We have resolved these discrepancies using the well-established method of optical absorption spectroscopy, finding evidence of an indirect gap of 2.14 eV and an onset of direct transitions occurring 3.05 eV. A defect-related mid-gap state also exists, with a binding energy of 0.22 eV. Furthermore, we have shown that the band gap can be tuned from (at least) 1.92 - 2.24 eV by controlling the size of the nanocrystals. [Preview Abstract] |
Wednesday, March 5, 2014 10:48AM - 11:00AM |
L50.00013: Multi-functional single electron device at room temperature Chieu Nguyen, Jason Kee Yang Ong, Ravi F. Saraf Smart designs of sub-wavelength structures enable observation of unusual properties of materials as in metamaterials. Typically, Coulomb blockade is observed in array of conducting particles at cryogenic temperature due to local charging of few particles by a single electron in the percolation path. We will report 1-D network of cemented Au nanoparticles in a multi-functional single electron device exhibiting Coulomb blockade at room temperature. The 1-D array is a self-assembled monolayer network spanning between electrodes 10-100$\mu$m apart. It is formed by first bridging the negatively charged 10nm Au NPs with positive ions (Cd2+or Fe3+) followed by cementing with reactive gas to form a robust 2-D network. The network array cemented with CdS and Iron oxide exhibits robust single electron effect at room temperature with electroluminescence (EL) or ferromagnetism, respectively. The nature of EL in this symmetric structure is explained in term of field induced ionization. The EL is specular where the spots are independent of bias magnitude. The magnetic array exhibits ``spin-valve'' behavior with Barkhausen effect. These unique nano materials, fully self-assembled where, properties can be tailored by varying the cement chemistry, have potential applications in solid state lighting. [Preview Abstract] |
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