Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session F14: Graphene: Light Matter Interactions |
Hide Abstracts |
Sponsoring Units: DCMP Chair: David Carey, University of Surrey Room: BCEC 153C |
Tuesday, March 5, 2019 11:15AM - 11:27AM |
F14.00001: Enhanced Raman scattering of graphene using double resonance in silicon photonic crystal nanocavities Hidenori Machiya, Widianta Gomulya, Kotaro Kashiwa, Taiki Inoue, Shohei Chiashi, Shigeo Maruyama, Yuichiro K. Kato We demonstrate enhancements of Raman scattering from graphene on L3 photonic crystals using double resonances, which originate from simultaneous enhancements by a localized guided mode and a cavity mode [1]. By adjusting the photonic crystal cavity parameters, the double resonance [2] can be tuned to the G’ Raman scattering. Excitation wavelength dependence measurements show a large Raman peak enhancement when the excitation and emission wavelengths meet the double resonance condition. Furthermore, spatial imaging measurements are performed to confirm that the enhancement is localized at the cavity, and we find that the enhanced Raman intensity is 60 times larger compared to the on-substrate Raman signal. The observed cavity enhancement of Raman scattering opens up new possibilities for the development of graphene-based light sources for silicon photonics. |
Tuesday, March 5, 2019 11:27AM - 11:39AM |
F14.00002: Photonic Crystals for Nano-Light in Moiré Graphene Superlattices Sai Sunku, GuangXin Ni, Bor-Yuan Jiang, Hyobin Yoo, Aaron Sternbach, McLeod Swinton Alexander, Stauber Tobias, Lin Xiong, Takashi Taniguchi, Kenji Watanabe, Philip Kim, Michael Fogler, Dimitri Basov Twisted bilayer graphene (TBG) consists of two layers of graphene rotated relative to each other. At very small twist angle, the atomic lattices relax and form a periodic array of Bernal-stacked domains separated by solitons. The solitons host topologically protected states and have previously been shown to efficiently scatter propagating surface plasmon polaritons (SPPs) [Jiang et al, Nano Lett, 17:7080 (2017)]. Therefore, an array of such solitons with a periodicity similar to the wavelength of SPPs should act as a photonic crystal for the SPPs. In this work, we use infrared nano-imaging to verify this proposition and demonstrate the interference of propagating SPPs in TBG. Furthermore, our calculations predict that a full plasmonic band gap is possible in this system. |
Tuesday, March 5, 2019 11:39AM - 11:51AM |
F14.00003: Fundamental Limits to graphene plasmonics GuangXin Ni, McLeod Swinton Alexander, Zhiyuan Sun, Lei Wang, Lin Xiong, Kirk W Post, Sai Sunku, Bor-Yuan Jiang, James Hone, Cory R Dean, Michael Fogler, Dimitri Basov Polaritons are hybrid excitations of light and matter that can confine the energy of long-wavelength radiation at the nano-scale. Plasmon polaritons may enable many enigmatic quantum effects including lasing, topological protection, and dipole-forbidden absorption. A necessary condition for realizing such phenomena is a long polariton lifetime, which is notoriously difficult to meet. Plasmon polaritons in graphene provide a platform for exploring light-matter interaction at the nano-scale. However, plasmonic dissipation in graphene has remained substantial and its fundamental limits remained undetermined. Here we use nanometre-scale infrared imaging to investigate propagating plasmon polaritons in high-mobility encapsulated graphene at cryogenic temperatures. In this regime, the propagation of plasmon polaritons is primarily restricted by the dielectric losses of the encapsulated layers, with a minor contribution from electron–phonon interactions. At liquid-nitrogen temperatures, the intrinsic plasmonic propagation length can exceed 50 plasmonic wavelengths, thus setting a record for highly confined and tunable polariton modes. |
Tuesday, March 5, 2019 11:51AM - 12:03PM |
F14.00004: Broadband mid-infrared graphene bolometer Shaofan Yuan, Xiaolong Chen, Bingchen Deng, Qiushi Guo, Cheng Li, Chao Ma, Chen Chen, Kenji Watanabe, Takashi Taniguchi, Fengnian Xia High detection speed, large responsivity, and room-temperature operation are crucial for modern mid-infrared bolometers. The low electronic heat capacity and weak electron-phonon coupling make graphene a remarkable candidate for fast broadband bolometer at room temperature. However, the weak temperature-dependent electrical transport in graphene hinders its applications. Here, we demonstrate ultra-broadband infrared graphene bolometers enabled by the large temperature coefficient of resistance and weak electron-phonon coupling in the intrinsic graphene. Our device has an ultra-broadband photoresponse from 1.3 to 12.2 μm with decent external responsivities at room temperature. Our results show the application potential of pristine graphene in high-speed broadband mid-infrared photodetection. Furthermore, we show that its integration with infrared waveguides, photonic crystals, and plasmonic cavities can significantly improve the performance. |
Tuesday, March 5, 2019 12:03PM - 12:15PM |
F14.00005: Electronic contributions to the Raman spectrum of twisted bilayer graphene Aitor Garcia-Ruiz, Marcin Mucha-Kruczynski, Joshua Thompson, Vladimir Falko Using the continuum model, we study theoretically the purely electronic contributions to the Raman spectrum of twisted bilayer graphene (tBLG) for twist angles close to the magic angle [1]. We show that non-resonant excitations of electron-hole pairs between the first minibands above and below the neutrality point lead to a peak, the position of which is determined by the twist angle. We estimate the quantum efficiency of this Raman feature as ∼10-13, about two orders of magnitude less than the intensity of the G peak [2]. Because of its electronic origin, the new peak provides direct information about the flatness of the first minibands in tBLG. |
Tuesday, March 5, 2019 12:15PM - 12:27PM |
F14.00006: Photonic crystal for graphene plasmons Lin Xiong, Carlos Forsythe, Alexander Swinton McLeod, Minwoo Jung, Sai Sunku, GuangXin Ni, Song Liu, Michael Fogler, James H. Edgar, Gennady Shvets, Cory Dean, Dimitri Basov Recent advancements in high-quality graphene devices enable long-lived surface plasmon polaritons which propagate over several microns. Various tunable parameters including gate voltage, twist angle, and superlattice potential enable efficient control of device functionalities. We used near-field nano-imaging techniques to study graphene plasmonic crystals at cryogenic temperatures. High-mobility graphene is transferred to a periodically patterned SiO2 substrate with Si back-gate. This heterostructure imprints the graphene with 80 nm-scale periodic variations in carrier density under application of a field effect, thus forming a gate-tunable photonic crystal for plasmons. We observed the formation of a selectively engineered full plasmonic bandgap where propagation of plasmons is strongly suppressed within the superlattice. Additionally, we implemented a designed domain wall within the superlattice which simultaneous supports strongly confined 1D plasmons within the plasmonic bandgap. These findings signify a new route towards designer-engineered band-structures to route and manipulate highly confined plasmons within high mobility graphene devices. |
Tuesday, March 5, 2019 12:27PM - 12:39PM |
F14.00007: Probing symmetry breaking in multilayer epitaxial graphene by circularly polarized magneto-infrared spectrscopy Yuxuan Jiang, Zhengguang Lu, James Gigliotti, Claire Berger, Walter de Heer, Dmitry Smirnov, Zhigang Jiang Symmetry breaking in graphene in high magnetic fields has long been an intriguing problem. Here, we report a magneto-infrared transmission spectroscopy study of multilayer epitaxial graphene with circularly polarized light. A four-fold splitting of the zeroth Landau level is found in high magnetic fields and attributed to the lifting of the valley and spin degeneracies and the electron-hole asymmetry. We extract the magnetic field dependence of the splitting gaps and discuss their possible origins. We also observe a surprising electron-hole asymmetry reversal between the monolayer and bilayer graphene components of multilayer epitaxial graphene and propose a possible interpretation. |
Tuesday, March 5, 2019 12:39PM - 12:51PM |
F14.00008: Wide Angle Electronically Tunable Enhanced Light Absorption in Nanopatterned Graphene Alireza Safaei, Sayan Chandra, Michael N. Leuenberger, Debashis Chanda Plasmonics in Dirac systems like graphene shows interesting characteristics because of massless electrons around the Dirac cone. Exciting surface plasmons on graphene is a distinct technique to increase the light absorption with low damping rate and provides the opportunity of electrical tunability of the resonance frequency and high degree of electric field confinement. Here, we demonstrate a novel design of an optical cavity-coupled hexagonal array of nanohole and nanodisk in monolayer CVD-grown graphene to excite Dirac plasmon. We study the surface plasmon lifetimes of the nanopatterns and their role in the enhanced light-matter interaction. By exploiting a high-k gate dielectric to dope the nanopatterned graphene electrostatically, the light absorption enhances to the record values of 60% on nanohole and 90% on nanodisk arrays in the 8-12 mm bandwidth with high spectral tunability. We theoretically and experimentally demonstrate, for the first time, the angular dependency of s- and p- polarized light absorption in nanopatterned graphene. The wide-angle electronically tunable extraordinary light absorption promises graphene-based optoelectronic devices. |
Tuesday, March 5, 2019 12:51PM - 1:03PM |
F14.00009: Theory of entangled-plasmon-pair generation in graphene Zhiyuan Sun, Dimitri Basov, Michael Fogler We study spontaneous parametric down conversion of terahertz photons into entangled plasmon pairs in graphene. This process is permitted by both symmetry and kinematics in a ribbon with an electron density gradient. We show that the conversion rate is maximized |
Tuesday, March 5, 2019 1:03PM - 1:15PM |
F14.00010: Pseudo-Euler equations from nonlinear optics: plasmon-assisted photodetection beyond hydrodynamics Alessandro Principi, Denis Bandurin, Habib Rostami, Marco Corrado Polini A great deal of theoretical and experimental efforts have been devoted in the last decades to the study of long-wavelength photodetection mechanisms in field-effect transistors hosting two-dimensional electron systems. A particularly interesting subclass of these mechanisms is intrinsic and based on the conversion of the incoming electromagnetic radiation into plasmons of a two-dimensional electron system, which resonantly enhance the photoresponse, and subsequent rectification via hydrodynamic nonlinearities. Here we show that such conversion and subsequent rectification occur well beyond the frequency regime in which hydrodynamic theory applies. We consider the nonlinear optical response of generic 2D electron systems and derive pseudo-Euler equations of motion for suitable collective variables. These are solved in one- and two-dimensional geometries for the case of graphene and the results are compared with those of hydrodynamic theory. Significant qualitative differences are found, which are amenable to experimental studies. Our theory expands the knowledge of the fundamental physics behind long-wavelength photodetection. |
Tuesday, March 5, 2019 1:15PM - 1:27PM |
F14.00011: Strong Dirac Photoconductance in Charge Neutral Graphene-Boron Nitride-Graphene Heterostructures Trevor Arp, Jacky Wan, Nathaniel Monroe Gabor Photoexcited hot charge carriers may shed light on the intriguing dynamics of electrons and holes near charge neutrality in very clean graphene. When two graphene layers are separated by thin hexagonal boron nitride (hBN), interlayer photocurrent can occur due to the exponential tail of the hot carrier distribution extending into the valence band of the hBN.[1] Using an ultrafast pulsed laser we excite a graphene-boron nitride-graphene (G-BN-G) heterostructure with photon energy less than the gap of the hBN and observe strong and highly nonlinear interlayer photocurrent as a function of the interlayer voltage. In a fully encapsulated heterostructure (BN-G-BN-G-BN), we find that the differential photoconductance significantly increases when both graphene layers are near charge neutrality. Strikingly, as intralayer voltage is applied near charge neutrality, strong negative differential photoconductance is observed as a function of interlayer voltage. This unusual effect is enhanced at intermediate temperatures ranging from 35 to 70 K. We speculate that this effect is a result of highly anomalous energy transport near the Dirac point. [1] Nature Physics 12, 455–459 (2016) |
Tuesday, March 5, 2019 1:27PM - 1:39PM |
F14.00012: Plasmon−Plasmon Interactions and Radiative Damping of Plasmons in Nanostructured Graphene Vasili Perebeinos While graphene absorbs only 2.3% in the mid infra red (IR) spectral region, graphene plasmons have much stronger absorption in the far IR. Plasmons tunability by the external electric fields and by the spatial confinment offer a promising platform for opto-electronic and sensor applications. In this work [1], we demonstrate both theoretically and experimentally that the plasmon−plasmon and plasmon−radiation interactions modify strongly the plasmon resonance energy, radiative damping, and oscillator strength in graphene nanoribbon arrays. Even for the moderate filling factors of about 50%, plasmon radiative lifetime reduces to a ps time scale from a convetional ns time scale in the isolated graphene nanoribbon. We find scaling of plasmons with respect to the graphene doping level and filling factor, which both modify the strength of the long-range Coulomb and plamson-radiative interactions. The surprisingly large plasmon energy shift and radiative damping significantly affect the graphene-based plasmonic device performance. |
Tuesday, March 5, 2019 1:39PM - 1:51PM |
F14.00013: Optical Properties of Graphene/Al Hetero-film Haozhe Wang, Sidan Fu, Wei Sun Leong, Jifeng Liu, Jing Kong When two metal films stack together forming “hetero-film”, it has been generally accepted that the effective transparency is lower than the respective metal film as a result of the absorption accumulation. Here, we report a counterintuitive phenomenon where transparency of a hetero-film is significantly higher compared to the original metal film. Specifically, we found that by layering one-atom-thick graphene on an aluminum (Al) film, the transparency of the Al film is dramatically increased from ~60% to 80% under 550 nm wavelength light. More surprisingly, similar transparency enhancement is captured when Al film was deposited on the graphene film. Systematic characterizations and numerical simulations were conducted to understand this unusual phenomenon observed in the graphene/Al hetero-film, including Raman, XPS, SEM, AFM analyses. Furthermore, Hall measurements revealed that our graphene/Al hetero-film holds great promise to be used as flexible transparent electrodes. |
Tuesday, March 5, 2019 1:51PM - 2:03PM |
F14.00014: Resistively detected microwave absorption in highly twisted bilayer graphene Liangji Zhang, Justin Lane, Chenyu Zhang, J.I.A. Li, Cory R Dean, Johannes Pollanen Resistively detected microwave absorption measurements of high-mobility two-dimensional (2D) electron systems are a powerful tool to explore the high-frequency spectroscopic and non-equilibrium response of correlated electron states in these systems. We have performed low-temperature magneto-transport experiments on a hexagonal boron nitride and dual graphite encapsulated twisted graphene bilayer while simultaneously irradiating the sample with microwave frequency photons. In this device the twist angle between the graphene flakes is relatively large, leading to a low-energy decoupling of the layers. Dual graphite gates allow us independent control of both the charge carrier density in the bilayer and a displacement electric field perpendicular to the 2D stack. We find that the differential magneto-conductance of the device, defined as the difference in conductance with and without microwave irradiation, shows well-defined oscillations in a large filling factor range down to the lowest Landau level. The dependence of these conductance oscillations on the magnetic field, displacement field, filling factor and microwave frequency will be discussed |
Tuesday, March 5, 2019 2:03PM - 2:15PM |
F14.00015: Resonant terahertz photoresponse and superlattice plasmons in graphene field-effect transistors Denis Bandurin, Dmitry Svintsov, Igor Gayduchenko, Shuigang Xu, Alessandro Principi, Maksim Moskotin, Ivan Tretyakov, Denis Yagodkin, Sergey Zhukov, Takashi Taniguchi, Kenji Watanabe, Irina Grigorieva, Marco Polini, Gregory Goltsman, Andre Geim, Georgy Fedorov Plasmons, collective oscillations of electron systems, can couple light and electric current, and thus can be used to create compact photodetectors, radiation mixers, and spectrometers. Despite the effort, it has proven challenging to implement plasmonic devices operating at THz frequencies. The material capable to meet this challenge is graphene as it supports long-lived electrically-tunable plasmons. In this talk, we will demonstrate plasmon-assisted resonant detection of THz radiation by antenna-coupled graphene FETs that act as both rectifying elements and plasmonic Fabry-Perot cavities amplifying the photoresponse. We will show that by varying the plasmon velocity using gate voltage, our detectors can be tuned between multiple resonant modes, a functionality that we apply to measure plasmons' wavelength and lifetime in graphene as well as to probe collective modes in its moire minibands. Our approach offers a convenient tool for further plasmonic research that is often difficult under non-ambient conditions and promises a viable route for various THz applications. |
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