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High field magneto-transport in high mobility gated InSb/InAlSb quantum well heterostructures  [PDF]
A. M. Gilbertson,W. R. Branford,M. Fearn,L. Buckle,P. D. Buckle,T. Ashley,L. F. Cohen
Physics , 2009, DOI: 10.1103/PhysRevB.79.235333
Abstract: We present high field magneto-transport data from a range of 30nm wide InSb/InAlSb quantum wells. The low temperature carrier mobility of the samples studied ranged from 18.4 to 39.5 m2V-1s-1 with carrier densities between 1.5x1015 and 3.28x1015 m-2. Room temperature mobilities are reported in excess of 6 m2V-1s-1. It is found that the Landau level broadening decreases with carrier density and beating patterns are observed in the magnetoresistance with non-zero node amplitudes in samples with the narrowest broadening despite the presence of a large g-factor. The beating is attributed to Rashba splitting phenomenon and Rashba coupling parameters are extracted from the difference in spin populations for a range of samples and gate biases. The influence of Landau level broadening and spin-dependent scattering rates on the observation of beating in the Shubnikov-de Haas oscillations is investigated by simulations of the magnetoconductance. Data with non-zero beat node amplitudes are accompanied by asymmetric peaks in the Fourier transform, which are successfully reproduced by introducing a spin-dependent broadening in the simulations. It is found that the low-energy (majority) spin up state suffers more scattering than the high-energy (minority) spin down state and that the absence of beating patterns in the majority of (lower density) samples can be attributed to the same effect when the magnitude of the level broadening is large.
Rapid Scanning Terahertz Time-Domain Magnetospectroscopy with a Table-Top Repetitive Pulsed Magnet  [PDF]
G. T. Noe,Q. Zhang,J. Lee,E. Kato,G. L. Woods,H. Nojiri,J. Kono
Physics , 2014, DOI: 10.1364/AO.53.005850
Abstract: We have performed terahertz time-domain magnetospectroscopy by combining a rapid scanning terahertz time-domain spectrometer based on the electronically coupled optical sampling method with a table-top mini-coil pulsed magnet capable of producing magnetic fields up to 30 T. We demonstrate the capability of this system by measuring coherent cyclotron resonance oscillations in a high-mobility two-dimensional electron gas in GaAs and interference-induced terahertz transmittance modifications in a magnetoplasma in lightly doped n-InSb.
Terahertz magneto-spectroscopy of transient plasmas in semiconductors  [PDF]
M. A. Zudov,A. P. Mitchell,A. H. Chin,J. Kono
Physics , 2002, DOI: 10.1063/1.1589601
Abstract: Using synchronized near-infrared (NIR) and terahertz (THz) lasers, we have performed picosecond time-resolved THz spectroscopy of transient carriers in semiconductors. Specifically, we measured the temporal evolution of THz transmission and reflectivity after NIR excitation. We systematically investigated transient carrier relaxation in GaAs and InSb with varying NIR intensities and magnetic fields. Using this information, we were able to determine the evolution of the THz absorption to study the dynamics of photocreated carriers. We developed a theory based on a Drude conductivity with time-dependent density and density-dependent scattering lifetime, which successfully reproduced the observed plasma dynamics. Detailed comparison between experimental and theoretical results revealed a linear dependence of the scattering frequency on density, which suggests that electron-electron scattering is the dominant scattering mechanism for determining the scattering time. In InSb, plasma dynamics was dramatically modified by the application of a magnetic field, showing rich magneto-reflection spectra, while GaAs did not show any significant magnetic field dependence. We attribute this to the small effective masses of the carriers in InSb compared to GaAs, which made the plasma, cyclotron, and photon energies all comparable in the density, magnetic field, and wavelength ranges of the current study.
Low temperature terahertz spectroscopy of n-InSb through a magnetic field driven metal-insulator transition  [PDF]
X. P. A. Gao,J. Y. Sohn,S. A. Crooker
Physics , 2006, DOI: 10.1063/1.2356105
Abstract: We use fiber-coupled photoconductive emitters and detectors to perform terahertz (THz) spectroscopy of lightly-doped n-InSb directly in the cryogenic (1.5 K) bore of a high-field superconducting magnet. We measure transmission spectra from 0.1-1.1 THz as the sample is driven through a metal-insulator transition (MIT) by applied magnetic field. In the low-field metallic state, the data directly reveal the plasma edge and magneto-plasmon modes. With increasing field, a surprisingly broad band (0.3-0.8 THz) of low transmission appears at the onset of the MIT. This band subsequently collapses and evolves into the sharp 1s -> 2p- transition of electrons `frozen' onto isolated donors in the insulating state.
Feasibility of electron cyclotron autoresonance acceleration by a short terahertz pulse  [PDF]
Yousef I. Salamin,Jian-Xing Li,Benjamin J. Galow,Christoph H. Keitel
Physics , 2015, DOI: 10.1364/OE.23.017560
Abstract: A vacuum autoresonance accelerator scheme for electrons, which employs terahertz radiation and currently available magnetic fields, is suggested. Based on numerical simulations, parameter values, which could make the scheme experimentally feasible, are identified and discussed.
Room temperature broadband coherent terahertz emission induced by dynamical photon drag in graphene  [PDF]
J. Maysonnave,S. Huppert,F. Wang,S. Maero,C. Berger,W. de Heer,T. B. Norris,L. A. De Vaulchier,S. Dhillon,J. Tignon,R. Ferreira,J. Mangeney
Physics , 2014, DOI: 10.1021/nl502684j
Abstract: Nonlinear couplings between photons and electrons in new materials give rise to a wealth of interesting nonlinear phenomena. This includes frequency mixing, optical rectification or nonlinear current generation, which are of particular interest for generating radiation in spectral regions that are difficult to access, such as the terahertz gap. Owing to its specific linear dispersion and high electron mobility at room temperature, graphene is particularly attractive for realizing strong nonlinear effects. However, since graphene is a centrosymmetric material, second-order nonlinearities a priori cancel, which imposes to rely on less attractive third-order nonlinearities. It was nevertheless recently demonstrated that dc-second-order nonlinear currents as well as ultrafast ac-currents can be generated in graphene under optical excitation. The asymmetry is introduced by the excitation at oblique incidence, resulting in the transfer of photon momentum to the electron system, known as the photon drag effect. Here, we show broadband coherent terahertz emission, ranging from about 0.1-4 THz, in epitaxial graphene under femtosecond optical excitation, induced by a dynamical photon drag current. We demonstrate that, in contrast to most optical processes in graphene, the next-nearest-neighbor couplings as well as the distinct electron-hole dynamics are of paramount importance in this effect. Our results indicate that dynamical photon drag effect can provide emission up to 60 THz opening new routes for the generation of ultra-broadband terahertz pulses at room temperature.
Terahertz dynamics of a topologically protected state: quantum Hall effect plateaus near cyclotron resonance in a GaAs/AlGaAs heterojunction  [PDF]
A. V. Stier,C. T. Ellis,H. Zhang,D. Eason,G. Strasser,B. D. McCombe T. Morimoto,H. Aoki,J. Cerne
Physics , 2011, DOI: 10.1103/PhysRevLett.115.247401
Abstract: We measure the Hall conductivity of a two-dimensional electron gas formed at a GaAs/AlGaAs heterojunction in the terahertz regime close to the cyclotron resonance frequency by employing a highly sensitive Faraday rotation method coupled with electrical gating of the sample to change the electron density. We observe clear plateau-and step-like features in the Faraday rotation angle vs. electron density and magnetic field (Landau-level filling factor), which are the high frequency manifestation of quantum Hall plateaus - a signature of topologically protected edge states. The results are compared to a recent dynamical scaling theory.
毫米波-太赫兹电子回旋器件的几个基础问题
Several fundamental challenges of millimeter-to-terahertz electron cyclotron devices
 [PDF]

杜朝海,罗里,刘濮鲲
- , 2015, DOI: 10.13700/j.bh.1001-5965.2015.0231
Abstract: 摘要 探索和发展更高频率和更高功率水平的电磁波源是电子器件长期以来的重要发展方向.本文介绍了基于电子回旋脉塞原理发展起来的电子回旋器件,该类器件在毫米波-太赫兹波段具有高功率的优势.系统探讨了电子回旋器件所面临的欧姆损耗、模式竞争以及对强磁场的依赖性等几个基础问题,指出在深入研究模式竞争机理的基础上发展高阶模式和高次谐波系统将有助于推动电子回旋器件实现高功率、高效率和高稳定性,这对促进器件向太赫兹频段发展具有参考意义.
Abstract:It is always an important tendency of the electronic power devices to explore and develop electromagnetic radiation sources operating on higher frequency and with higher power capability. The cyclotron electron device which was developed based on the mechanism of the electron cyclotron maser and with the excellent advantage of radiating high power in millimeter-to-terahertz range was introduced. It systematically discussed about the fundamental challenges encountered by the electron cyclotron devices, including the strong ohmic dissipation problem, the mode competition problem, and the unavoidable dependency on operating with strong magnetic field. Finally, it was proposed that, on the basis of fully exploring the physical mechanism of the mode competition, to develop higher order mode circuit and higher harmonic interaction system would be very helpful to realize the high power, high efficiency and high stability cyclotron electron devices, which is of important reference for guiding devices development towards terahertz band.
Direct surface cyclotron resonance terahertz emission from a quantum cascade structure  [PDF]
Fran?ois-Régis Jasnot,Louis-Anne De Vaulchier,Yves Guldner,Gérald Bastard,Angela Vasanelli,Christophe Manquest,Carlo Sirtori,Mattias Beck,Jér?me Faist
Physics , 2012, DOI: 10.1063/1.3692572
Abstract: A strong magnetic field applied along the growth direction of a semiconductor quantum well gives rise to a spectrum of discrete energy states, the Landau levels. By combining quantum engineering of a quantum cascade structure with a static magnetic field, we can selectively inject electrons into the excited Landau level of a quantum well and realize a tunable surface emitting device based on cyclotron emission. By applying the appropriate magnetic field between 0 and 12 T, we demonstrate emission from a single device over a wide range of frequencies (1-2 THz and 3-5 THz).
Shape and Size Dependence of Electronic Properties of InSb Diamondoids and Nanocrystals: A Density Functional Theory Study  [PDF]
Mudar Ahmed Abdulsattar,Thamer R. Sultan,Ahmed M. Saeed
Advances in Condensed Matter Physics , 2013, DOI: 10.1155/2013/713267
Abstract: Shape and size dependence of electronic properties of InSb diamondoids and nanocrystals is investigated using density functional theory. Cluster and large unit cell methods are combined with molecular orbital methods to obtain electronic structure of InSb diamondoids and nanocrystals. Starting from the simple molecules of hydrogenated InSb clusters such as InSbH6, In3Sb3H12, InSb-diamantane, InSb-tetramantane, and InSb-hexamantane and ending with InSb large unit cell method we were able to obtain the electronic structure of a wide range of InSb nanostructures. Results showed that energy gap and In–Sb bond lengths generally decrease as the number of atoms increases with remarkable dependence on the shape of the molecule or nanocrystal. Atomic charges, tetrahedral angles, and bond lengths are used to compare different sizes, locations, and shapes of InSb diamondoids and nanocrystals. 1. Introduction InSb is a unique semiconductor. It has one of the largest lattice constants and one of the smallest energy gaps. These properties give InSb the opportunity to cover some applications that no other semiconductor can be used for. As an example, the small energy gap (0.17?eV [1]) nominated InSb to be used in infrared devices and other applications. These applications span photodiodes [2], thermal imaging [3], terahertz radiation [4], and so forth. Transforming materials to their nanoscale size change, many of their properties. These changes include their electronic, mechanical, and optical properties. InSb nanoparticles undergo these changes that might include new applications as is the case for other materials. In the present work we introduce InSb diamondoids as a molecular limit and building blocks for larger nanocrystals. These molecules (diamondoids) are well known and found in nature as cage like molecules that resemble the tetrahedral bonding of carbon [5]. Cage like molecules other than carbon are found in nature or synthesized with a variety of atoms such as Si, P, and N compounds. We shall show that even numbered diamondoids (diamantane, tetramantane, and hexamantane) can also form stable molecules for the III–V InSb semiconductor compound. Odd numbered diamondoids (adamantane, triamantane, etc.) produce molecules with unequal number of In and Sb atoms. 2. Theory Geometrical optimization method is used in the present work to obtain the electronic structure of InSb molecules and nanocrystals (Figure 1.) These include the following: InSbH6, In3Sb3H12, InSb-diamantane, InSb-tetramantane, and InSb-hexamantane. Figure 1: Shape of geometrically optimized (a)
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