Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session A30: Focus Session: Graphene Devices: Fabrication, Characterization and Modeling: Plasmons |
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Sponsoring Units: DMP Chair: Dmitri Basov, University of California, San Diego Room: 605 |
Monday, March 3, 2014 8:00AM - 8:12AM |
A30.00001: Efficient nonlinear generation of surface plasmons in graphene and topological insulators Alexey Belyanin, Xianghan Yao, Mikhail Tokman Two-dimensional materials with massless Dirac electrons such as graphene and topological insulators (TIs) support surface plasmon modes with a number of peculiar properties making them an attractive alternative to metal plasmonics. In this theoretical work we show that a coherent surface plasmon mode guided by graphene or a TI surface can be excited with high efficiency through the second-order nonlinear process of difference frequency generation (DFG). Although graphene is an isotropic medium for low-energy electron excitations, the second-order nonlinear susceptibility becomes non-zero when its spatial dispersion is taken into account. In this case the anisotropy is induced by the in-plane wave vectors of obliquely incident or in-plane propagating electromagnetic waves. The dispersion curves of surface plasmons strongly deviate from the photon dispersion already at terahertz (THz) frequencies, leading to a tight vertical confinement and large in-plane wave vector which can be matched to the sum of the photon wave vectors at mid- or even near-IR frequencies. This enables phase-matched DFG of THz plasmons with counter-propagating mid-infrared pump fields. The DFG process can reach efficiencies of 0.01/W and is broadly tunable by gating or varying an angle of incidence. [Preview Abstract] |
Monday, March 3, 2014 8:12AM - 8:24AM |
A30.00002: Measurement of THz radiation from DC heated graphene Jiayue Tong, Martin Muthee, Jun Yan, K. Sigfrid Yngvesson High mobility, tunable broadband optical response, and robust room temperature plasmon excitations have made graphene a promising candidate for THz applications. In this talk, I will discuss our studies of an antenna-coupled graphene THz source on a SiO$_{2}$/Si substrate, coupled through a silicon lens. Our experiments show that graphene samples coupled to a resonant double patch antenna emit strong radiation at about 2 - 2.5 THz. We then characterize the gate dependent THz radiation from heated graphene by simulating the antenna performance and comparing simulation results with experimental measurements. Our work paves the way for making practically useful graphene-based THz sources. [Preview Abstract] |
Monday, March 3, 2014 8:24AM - 8:36AM |
A30.00003: Enhanced control of THz optical conductivity in graphene via optimal extraordinary optical transmission electrode design Sara Arezoomandan, Berardi Sensale-Rodriguez Terahertz (THz) technology has recently arisen much attention for a wide range of applications. One of the major challenges in semiconductor-based THz devices is how to enhance and, therefore more efficiently tune, the material optical conductivity. Graphene due to its extraordinary properties has been extensively used for reconfigurable THz devices. By gating graphene, one can control its electrical thus THz properties. Several gating mechanisms have been proposed, including: Si-substrate, ion-gel, and extraordinary optical transmission (EOT) electrode. However, the optical conductivity swings in CVD graphene are typically limited to the 0.15-1.0mS range. Here we propose a simple device structure consisting of EOT electrode-gated graphene that can effectively achieve an enhancement of its effective optical conductivity swing, e.g. 3.8X effective conductivity enhancement at 2THz and 0.9mS. We accomplished this by optimizing the width/spacing of the metal stripes as well as the separation between graphene and the EOT electrode. The proposed structure does not require the addition of other epitaxially stacked electromagnetic structures (such as additional periodic metallic structures). This configuration shows promise as the active element in low-cost compact THz optoelectronics. [Preview Abstract] |
Monday, March 3, 2014 8:36AM - 8:48AM |
A30.00004: Plasmon anomaly in the dynamical optical conductivity of graphene Kostyantyn Kechedzhi We theoretically consider the manifestation of plasmon collective modes in the frequency dependence of the optical conductivity of disordered graphene. We generalize the equation of motion formalism for Dirac electrons in graphene. We show that the presence of the plasmon pole in the dynamical dielectric function of graphene results in the screening effect of graphene electron gas failing at plasmon frequency. As a result of frequency dependent screening the effective strength of charged impurities varies with frequency. This results in the frequency dependent scattering rate. We predict a characteristic broad feature in the frequency dependence of the optical conductivity of graphene appearing at intermediate frequencies, i.e. larger than the disorder broadening of electron states but smaller than the Fermi energy. We predict that this feature could be observable in graphene on $\mathrm{hBN/SiO_{2}/Si}$ substrate with a relatively thick Boron nitride layer of order $10\mathrm{nm}.$ [Preview Abstract] |
Monday, March 3, 2014 8:48AM - 9:00AM |
A30.00005: The lifetime of Dirac plasmons in graphene Alessandro Principi, Giovanni Vignale, Matteo Carrega, Marco Polini Dirac plasmons in a doped graphene sheet have recently been shown to enable confinement of light to ultrasmall volumes. In this work we calculate the intrinsic lifetime of a Dirac plasmon in a doped graphene sheet by analyzing the role of electron-electron interactions beyond the random phase approximation. The damping mechanism at work is intrinsic since it operates also in disorder-free samples and in the absence of lattice vibrations. We demonstrate that graphene's sublattice-pseudospin degree of freedom suppresses intrinsic plasmon losses with respect to those that occur in ordinary two-dimensional electron liquids. We relate our findings to a microscopic calculation of the homogeneous dynamical conductivity at energies below the single-particle absorption threshold. Finally, we compute the impact of disorder on Dirac plasmon losses and then show that a very reasonable concentration of charged impurities yields a plasmon damping rate which is in good agreement with s-SNOM experimental results. [Preview Abstract] |
Monday, March 3, 2014 9:00AM - 9:12AM |
A30.00006: Electrostatically Controlled Graphene Thermocouple Patrick Herring, Allen Hsu, Nathaniel Gabor, Yong Cheol Shin, Jing Kong, Tomas Palacios, Pablo Jarillo-Herrero Graphene has a broad-band optical absorption ranging from the visible ($\lambda $\textless 532 nm) all the way to the far-infrared ($\lambda $\textgreater 10$\mu$m). Additionally, graphene's optical phonon energy and electrostatically tunable Fermi energy are in the mid-infrared energy range. Together, determining these properties could enable a new generation of carbon-based infrared photodetectors. Electrostatically gated p-n junctions have demonstrated photocurrents in near-IR measurements (850nm), generated primarily through photo-thermoelectric effects. By fabricating electrostatically controlled p-n junctions using chemically vapor grown graphene, we determine the photoresponse mechanism to be primarily thermoelectric in nature at mid-infrared wavelengths and strongly influenced by substrate interactions. [Preview Abstract] |
Monday, March 3, 2014 9:12AM - 9:24AM |
A30.00007: Effect of magnetic field on the plasmons and electron self-energy of gapped graphene Andrii Iurov, Godfrey Gumbs, Danhong Huang The plasmon modes in gapped graphene are calculated in the presence of a uniform perpendicular magnetic field ${\bf B}$. The gap may be produced by external influences on the Dirac cone and include symmetry-breaking perturbations such as multi-layer epitaxially grown graphene, circularly polarized light and an underlying substrate. While one expects the gap to make graphene behave more like conventional 2DEG, we demonstrate the important differences in the plasma excitations and self-energy brought about through the interplay the presence of magnetic field and the symmetry-breaking perturbation. [Preview Abstract] |
Monday, March 3, 2014 9:24AM - 9:36AM |
A30.00008: Graphene Plasmo-Mechanical Structures and Devices Parinita Nene, Jared Strait, Weimin Chan, Christina Manolatou, Paul McEuen, Farhan Rana The manipulation of microstructures with optical forces has generated tremendous interest in recent years. In most cases, the light forces on a dielectric material are induced via the polarization of the medium. The idea of manipulating atomic membranes, like graphene, and related devices with light forces is extremely attractive. But graphene has a small dielectric constant represented by the imaginary part of the optical conductivity. In contrast, in graphene plasmonic structures, the real part of the conductivity is extremely large at the plasmon resonance frequencies. This large current response results in extremely large plasmonic forces between adjacent graphene plasmonic resonators under light illumination. The forces are a result of the charge density associated with the plasmon oscillations and can reach force density values larger than a micro-Newton/micron in plasmonic resonators, such as graphene strips and discs. These plasmonic forces can be tailored to be attractive or repulsive depending on the plasmon mode symmetries. We present results from theoretical and computational models for plasmonic forces, and show several examples of structures and devices that can be manipulated with plasmonic forces, and demonstrate that plasmo-mechanics can be a very effective tool in manipulating and transducing graphene micro- and nano-structures. [Preview Abstract] |
Monday, March 3, 2014 9:36AM - 9:48AM |
A30.00009: Characterization of the plasmon mode of graphene/LaAlO$_3$/SrTiO$_3$ system Weitao Dai, Sangwoo Ryu, Chang-Beom Eom, Cheng Cen Engineering graphene's properties in nanoscale with minimum material degradation is an outstanding challenge in graphene based technologies. Here we present a method targeting at on-demand tuning of 2D plasmon in graphene based on the integration of graphene and a novel complex oxide heterostructure. The recent development of complex oxides has raised the prospect for new classes of electronic devices. In particular, researchers have discovered a high-mobility two-dimensional electron gas forming at the interface between LaAlO$_3$ (LAO) and SrTiO$_3$ (STO). More interestingly, in samples with 3-unit-cell LAO film grown on STO substrate, a biased conducting atomic force microscope probe can locally and reversibly controls the interfacial metal-insulator transition. The close coupling of graphene with these programmable interfacial nanostructures in graphene/LAO/STO heterostructures presents numerous device opportunities. Samples with contacts addressing graphene and oxide interface separately are fabricated. Transport experiments are performed to study the carrier coupling in such hybrid bilayer conducting system. We also report the investigation of plasmonic properties using a variable temperature near field scanning optical microscope. [Preview Abstract] |
Monday, March 3, 2014 9:48AM - 10:00AM |
A30.00010: Electron-phonon coupling in bilayer and single-layer graphene at sub-Kelvin temperatures Chris McKitterick, Heli Vora, Xu Du, Michael Rooks, Daniel Prober Graphene has been proposed by many groups as a detector of terahertz photons$^{1,2,3}$, due to its very small heat capacity and predicted low thermal conductance. We present Johnson noise thermometry measurements of single and bilayer graphene samples fabricated at Stony Brook University and at Yale University. These measurements probe the graphene electron-phonon coupling at sub-Kelvin temperatures. The devices are fabricated with superconducting contacts (NbN at Stony Brook, Al and Nb at Yale) to confine the hot electrons in the graphene device, diminishing the contribution of electron out-diffusion in cooling the electron system. By using commercially-available CVD-grown graphene for some samples, we can define large area sections, allowing us to emphasize the thermal conductance due to electron-phonon coupling. These measurements allow for performance estimates for using similar graphene devices to detect terahertz photons.\\\\ $^1$C. B. McKitterick, D. E. Prober, B. S. Karasik, Journal of Applied Physics 113, 044512 (2013).\\ $^2$H. Vora, P. Kumaravadivel, B. Nielsen, X. Du, Applied Physics Letters 100, 153507 (2012).\\ $^3$K. Fong, K. Schwab, Physical Review X 2, 1 (2012). [Preview Abstract] |
Monday, March 3, 2014 10:00AM - 10:12AM |
A30.00011: Propagation and guiding of exciton polaritons in a patterned microcavity with an embedded graphene layer German Kolmakov, Oleg Berman, Roman Kezerashvili We consider propagation of a Bose-Einstein condensate (BEC) of exciton polaritons formed in a high-quality microcavity with an embedded quantum well or a gapped graphene layer. We study the effects of patterning of the microcavity by using materials with different electric or optical properties that create the potential landscape for the polaritons in the microcavity plane. The landscapes that enable one to guide the polariton BEC propagation and deliver the polaritons to a desired location are discussed. The possibility to govern the polariton propagation in a microcavity with the embedded graphene by dynamically changing the band gap in the graphene layer by means of an external electric field is considered. [Preview Abstract] |
Monday, March 3, 2014 10:12AM - 10:24AM |
A30.00012: Tuning electron-phonon interactions in graphene and its bilayer for sensitive bolometry Heli Vora, Bent Nielsen, Xu Du Graphene's weak electron-phonon coupling and small electronic heat capacity are of considerable advantage for achieving highly sensitive bolometers and fast single photon detectors. Minimizing electron phonon coupling in graphene can be utilized for designing state-of-the-art bolometers. For such purpose, it is important to understand electron-phonon interaction and its dependence on temperature, Fermi energy, disorder and number of layers experimentally. In particular, single and bilayer graphene are expected to show opposite Fermi energy dependence of electron phonon coupling constant. We study graphene-superconductor tunnel junctions, where the superconducting contacts effectively confine the hot electrons inside the graphene absorber, allowing access to phonon cooling regime at low temperatures. We show results on the temperature and doping dependence of electron-phonon coupling in graphene and its bilayer. [Preview Abstract] |
Monday, March 3, 2014 10:24AM - 10:36AM |
A30.00013: Electro-Optical Plasmonic Switch Based On Graphene Suk-Young Park, Kyungsun Moon We have studied an electro-optical plasmonic waveguide, which controls the transmission of incident light by switching the coupling of the surface plasmon polariton (SPP) localized on graphene. It has been previously shown that the propagation length of the SPP localized on the copper surface can be effectively reduced by a factor of two or three by applying external bias potential. In our study, we have demonstrated that the propagation length of the SPP localized on graphene can be dramatically reduced by a factor of ten or so and the wavelength of SPP can be reduced by several hundredths of the incident light as well. This may help develop a nano-scale plasmonic switch. [Preview Abstract] |
Monday, March 3, 2014 10:36AM - 10:48AM |
A30.00014: Probing the graphene-plasmon interaction via ultrafast pump-probe studies of CVD graphene-metal nanostructures Adam Gilbertson, Tyler Roschuk, Dominic Moseley, Themis Sidiropoulos, Yan Francescato, Vincenzo Giannini, Stefan Maier, Rupert Oulton, Lesley Cohen Graphene exhibits ultrafast broadband absorption that has attracted considerable interest for optoelectronic applications. A major hurdle for real applications is the low optical absorption (2.3{\%}) of graphene, limited by its atomic thickness. A promising approach is to integrate graphene with metal nanostructures that concentrate light into nanoscopic volumes, promoting stronger absorption effects.\footnote{T. J. Echtermeyer, et al., Nature Communications 2, (2011).} Here we present progress towards integration of nanostructured metals with commercially available CVD graphene into photoconductive device architectures. Through fs pump-probe measurements conducted at 300K, hot carrier dynamics in these graphene-plasmonic systems have been studied. We will discuss both the spectral and polarization dependent dynamic response of these systems and the impact of the nanostructures on the resulting photoconductive device performance. [Preview Abstract] |
Monday, March 3, 2014 10:48AM - 11:00AM |
A30.00015: Three-dimensional graphene photonic crystal Duanni Huang, Xiaoyin Xiao, Ronen Polsky, David Bruce Burckel, Ting Luk, Igal Brener, Danhong Huang, Wei Pan We perform finite element method (FEM) simulations on a three-dimensional, multi-layer graphene structure patterned by interferometric lithography. The structure shows periodicity and face centered cubic (fcc) symmetry and a lattice constant of 1.7 microns. Initial simulations predict a photonic bandgap centered on a wavelength of 2.5 microns for high dielectric contrast ($\varepsilon_{\mathrm{r\thinspace }}$\textgreater 16). Further simulations modeling graphene as a dispersive material find evidence of surface plasmon activity. We believe the structure shows promise as a 3-D photonic crystal with a tunable bandgap by utilizing the ability to modify the Fermi level and plasma frequency of the material. Such a device may have applications in quantum sensing. Current efforts on this topic focus on experimental verification of the bandgap as well as a deeper understanding of the interaction between electrical and photonic mechanisms within the structure. [Preview Abstract] |
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