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  • 1
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    Theory of hysteresis during electron heating of electromagnetic wave scattering by self-organized dust structures in complex plasmas (2015)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2015-07-17
    Description: Dust structuring is a natural and universal process in complex plasmas. The scattering of electromagnetic waves by dust structures is governed by the factor of coherency, i.e., the total number of coherent electrons in a single structure. In the present paper, we consider how the factor of coherency changes due to additional pulse electron heating and show that it obeys a hysteresis. After the end of the pulse heating, the scattering intensity differs substantially from that before heating. There are three necessary conditions for scattering hysteresis: first, the radiation wavelength should be larger than the pattern (structure) size; second, the total number of coherent electrons confined by the structure should be large; and third, the heating pulse duration should be shorter than the characteristic time of dust structure formation. We present the results of numerical calculations using existing models of self-consistent dust structures with either positively or negatively charged dust grains. It is shown that, depending on the grain charge and the ionization rate, two types of hysteresis are possible: one with a final increase of the scattering and the other with a final decrease of the scattering. It is suggested that the hysteresis of coherent scattering can be used as a tool in laboratory experiments and that it can be a basic mechanism explaining the observed hysteresis in radar scattering by noctilucent clouds during active experiments on electron heating in mesosphere.
    Print ISSN: 1070-664X
    Electronic ISSN: 1089-7674
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 2
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    Synchronization of two memristively coupled van der Pol oscillators (2016)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2016-02-26
    Description: The objective of this letter is to convey two essential principles of biological computing— synchronization and memory —in an electronic circuit with two van der Pol (vdP) oscillators coupled via a memristive device. The coupling was mediated by connecting the gate terminals of two programmable unijunction transistors through a resistance-capacitance network comprising an Ag-TiO x -Al memristive device. In the high resistance state the memristance was in the order of MΩ, which leads to two independent self-sustained oscillators characterized by the different frequencies f 1 and f 2 and no phase relation between the oscillations. Depending on the mediated pulse amplitude, the memristive device switched to the low resistance state after a few cycles and a frequency adaptation and phase locking were observed. The experimental results are underlined by theoretically considering a system of two coupled vdP equations. This experiment may pave the way to larger neuromorphic networks in which the coupling parameters (through memristive devices) can vary in time and strength and are able to remember the history of applied electrical potentials.
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 3
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    Semiconductor superlattice diodes for detection of terahertz photons: The role of hybridization of the plasma and polar-optical phonon modes (2014)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2014-08-27
    Description: The current (voltage) responsivity of a superlattice-based diode detector has been studied theoretically in the terahertz frequency band that includes the region of the polar-optical phonon frequencies. Within the framework of an equivalent circuit approach, the electro-dynamical model which allows one to analyze the responsivity taking into account the hybridization of the plasma and polar-optical phonon modes both in the substrate and in the cladding layers of the diode has been suggested. It has been shown that the presence of the plasma and polar-optical phonon modes gives rise to strong features in the frequency dependence of the responsivity, i.e., to the resonance dips and peaks at frequencies of hybridized plasmons and polar-optical phonons. It has been suggested that by judicious engineering of the superlattice-based diodes, it would be possible to enhance substantially their responsivity in the terahertz frequency band.
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 4
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    Coherent scattering of electromagnetic waves by self-organized dust structures: Degree of coherence (2015)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2015-02-25
    Description: It is demonstrated explicitly that the scattering of electromagnetic waves by dust structures can be strongly enhanced as compared to incoherent scattering by random electrons. If the size of the dust structure is much less than the wavelength of the incident radiation, the scattering is coherent. In this case, the scattering is proportional to the square of the total number of electrons in the structure. In the opposite limit, the scattering is incoherent being proportional to the total number of electrons in the structure. The factor describing the degree of coherency is calculated numerically for several models of self-organized structures. It is demonstrated in general way that for sudden heating of electrons, the factor of coherency in scattering by structures can decrease by several orders of magnitude with subsequent increase after the heating is switched off. In laboratory dusty plasmas, the coherent scattering is proposed for diagnostics of universal structuring instability and as a probe for determining the properties typical for self-organized nature of structures that are observed in recent experiments.
    Print ISSN: 1070-664X
    Electronic ISSN: 1089-7674
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 5
    Electronic Resource
    Electronic Resource
    Squeezed state of high-current electron beam (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 1 (1994), S. 741-744 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The results of the computer simulation of an electron beam propagating serially through two coaxial tubes with different radii are presented. It is shown that the virtual cathode in this system may be located in one of two positions depending on the injection current, variation of which yields fast movements of the potential barrier. Under certain conditions, a part of the beam may be in its squeezed state, forming, therefore, a cloud of a dense warm plasma. The qualitative analytical theory based on the consideration of the energy and momentum balance is also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.870819
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  • 6
    Electronic Resource
    Electronic Resource
    Current responsivity of semiconductor superlattice THz-photon detectors (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 3643-3654 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The current responsivity of a semiconductor superlattice THz-photon detector is calculated using an equivalent circuit model which takes into account the finite matching efficiency between a detector antenna and the superlattice in the presence of parasitic losses. Calculations performed for currently available superlattice diodes show that both the magnitudes and the roll-off frequencies of the responsivity are strongly influenced by an excitation of hybrid plasma-Bloch oscillations which are found to be eigenmodes of the system in the THz-frequency band. The expected room temperature values of the responsivity (2–3 A/W in the 1–3 THz-frequency band) range up to several percents of the quantum efficiency e/(h-dash-bar)ω of an ideal superconductor tunnel junction detector. Properly designed semiconductor superlattice detectors may thus demonstrate better room temperature THz-photon responsivity than conventional Schottky junction devices. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369728
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  • 7
    Electronic Resource
    Electronic Resource
    Detection of THz radiation with semiconductor superlattices at polar-optic phonon frequencies (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 1281-1286 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The nonlinear response of GaAs/AlAs superlattices to THz radiation has been analyzed over a wide frequency range (0.1 THz–15 THz), including the range of polar-optic phonon frequencies. Assuming that free electrons in a superlattice subjected to both a static and a THz field perform frequency-modulated damped Bloch oscillations, we have calculated a superlattice current responsivity, i.e., the ratio of the direct current change to the power of the incident radiation. The responsivity of superlattices has been measured in several recent experiments. An equivalent circuit taking into account the resonant properties associated with polar-optic phonons was used in a self-consistent treatment of the problem. It is shown that the responsivity is suppressed at frequencies of infrared-active, transverse polar-optic phonons due to dynamic screening of the THz field by the lattice. In contrast, the responsivity strongly increases at longitudinal polar-optic phonon frequencies due to a large enhancement of the THz field in the superlattice indicated by a longitudinal polar-optic phonon resonance, i.e., by an "anti- screening" effect. The described phenomenon can strongly influence the design and optimization of superlattice-based ultra-fast detectors for THz radiation. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1428802
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  • 8
    Electronic Resource
    Electronic Resource
    Broadband semiconductor superlattice detector for THz radiation (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 1673-1675 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on a broadband GaAs/AlAs superlattice detector for THz radiation; a THz field reduces the current through a superlattice, which is carried by miniband electrons, due to modulation of the Bloch oscillations of the miniband electrons. We studied the detector response, by use of a free electron laser, in a large frequency range (5–12 THz). The responsivity showed strong minima at frequencies of infrared active phonons of the superlattice. A theoretical analysis of the detector delivers an understanding of the role of phonons and gives a characterization of the responsivity. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1352669
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  • 9
    Electronic Resource
    Electronic Resource
    Generation of millimeter waves with a GaAs/AlAs superlattice oscillator (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 1498-1500 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on a semiconductor superlattice oscillator for generation of millimeter waves (frequency 65 GHz). The main element of the oscillator is a doped short-period GaAs/AlAs superlattice with negative differential conductance. The oscillator is due to current oscillations caused by charge density domains. The oscillator delivered, at an efficiency of 0.2% for the conversion of electrical power to radiation power, a power of 100 μW in a bandwidth of the order of 200 kHz. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.121038
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  • 10
    Electronic Resource
    Electronic Resource
    Suppression of current through an Esaki–Tsu GaAs/AlAs superlattice by millimeter wave irradiation (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 1096-1098 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the observation of suppression of the dc current through an Esaki–Tsu GaAs/AlAs superlattice (that shows a negative differential conductance due to Bloch oscillations of miniband electrons) caused by irradiation with millimeter wave radiation (frequency 78 GHz). A theoretical analysis of the dc current indicated that the high-frequency electric current followed the high-frequency field with a response time smaller than the period (∼10−11 s) of the field. Our experiment, with the superlattice at room temperature, demonstrates that the Esaki–Tsu superlattice is suitable for ultrafast millimeter wave detection and other high-frequency applications. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115724
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