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  • 1
    Electronic Resource
    Electronic Resource
    Investigation of low-temperature I-V curves of high-quality Nb/Al-AlOx/Nb Josephson junctions (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 1888-1892 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A detailed experimental temperature dependence of the subgap current of high-quality Nb/Al-AlOx/Nb Josephson tunnel junctions is reported. The presence of a pronounced current rise at V(approximately-equal-to)Δ/e is observed. Comparison with the theoretical model for two-particle tunneling is performed, but a substantial disagreement is found. At V〈Δ/e the measured current is in remarkably good agreement with the single particle tunneling predictions down to 2 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351175
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  • 2
    Electronic Resource
    Electronic Resource
    Enhanced ac Josephson effect (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 679-687 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The amplitude of the current steps induced by a rf field in a Josephson junction is strictly related to the stability of the phase-locked state. We show how the ac Josephson effect can be enhanced by means of a proper drive: when two phased ac fields of angular frequencies ω and 2ω are added together, the rf-induced steps have maximum normalized amplitudes larger than the Bessel functions as predicted for a sinusoidal drive. Furthermore, in the limiting case of a driving signal that consists of an impulse train, the stability of the phase-locked state can reach its maximum value, i.e., rf-induced steps as large as the critical current can be obtained. Experimental evidence of the enhanced ac Josephson effect is reported for a highly hysteretic Nb/Al-Al2O3/Nb Josephson tunnel junction. The enhanced ac Josephson effect may open new ways for the understanding of the nonlinear dynamics of Josephson junctions and for the design of more efficient Josephson voltage standard devices.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346798
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  • 3
    Electronic Resource
    Electronic Resource
    Survey of chaos in the rf-biased Josephson junction (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 875-889 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Chaotic behavior in the rf-biased Josephson junction is studied through digital simulations of the Steward–McCumber model. Chaotic states are characterized by Poincare sections, Liapunov exponents, and power spectra. Models are presented which explain some features of the chaotic spectra. The parameter range over which chaotic behavior occurs is determined empirically for a broad range of dc bias, rf bias, and hysteresis parameters for a fixed rf frequency. It is shown that chaos does not occur if either the dc bias or the rf bias is very large. An attempt is made to explain the boundaries of the chaotic region in terms of simple models for chaotic behavior.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.334687
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  • 4
    Electronic Resource
    Electronic Resource
    Intermodulation measurements in Nb superconducting microstrip resonators (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 2898-2905 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The issue of intermodulation distortion in superconducting devices for rf and microwave applications is discussed. The classical frequency conversion theory for nonlinear two-port devices in the small signal limit is shown to apply to microstrip resonators regardless of their geometry and material. Two tone, third order intermodulation measurements allow more sensitive detection of nonlinearity compared to surface impedance measurements, provided a low noise, spurious free experimental setup is adopted. Measurements carried out on high quality Nb meanderline microstrip resonators show that at very low power level nonlinearity is dominated by intrinsic device properties. Film defects start to play a predominant role above a critical power level that strongly depends on the defect's nature. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1286176
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  • 5
    Electronic Resource
    Electronic Resource
    Influence of the idle region on the dynamic properties of window Josephson tunnel junctions (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 2073-2080 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The processes developed in the last years for the fabrication of high quality, reliable all-refractory Josephson tunnel junctions open a window in an insulating region, called the idle region, which provides the passivation of the base electrode all around the junction itself. We report experimental data showing that the phase velocity of electromagnetic waves in the junction barrier can be considerably modified by the presence of the insulating region surrounding the window Josephson tunnel junctions. We have investigated this phenomenon in unidimensional junctions, measuring the asymptotic voltage of the Fiske resonances in the presence of an externally applied magnetic field. We have considered the effect of an idle region: (i) along the long junction dimension and (ii) at the extremities of the junction. When comparing the behavior to that of a bare junction, in the first case the phase velocity has been found to increase and to be affected by dispersion, while in the latter case it decreased and was frequency independent. In order to interpret the main features of the phenomena observed experimentally in terms of basic mechanisms, we propose two simple models for the two different geometrical configurations. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358848
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  • 6
    Electronic Resource
    Electronic Resource
    Model for the fine structure of zero field steps in long Josephson tunnel junctions and its comparison with experiment (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 327-333 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The single fluxon dynamics in the resonant regime has been investigated on high-quality low-loss Nb/Al–AlOx/Nb window Josephson tunnel junctions. A new model accounting for the fine structure of zero field steps in linear junctions is proposed. Depending on the fluxon velocity and on the junction losses, resonances may occur between the fluxon and the plasma waves corresponding to different wave numbers. This mechanism relies on a single proposition that the fluxon experiences an acceleration approaching the nonideal boundaries of the junction. We find good agreement between theory, numerical simulations, and experiments. The presence of the idle region has been proved to play a determinant role for the occurrence of the fine structure. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360834
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  • 7
    Electronic Resource
    Electronic Resource
    Investigation on the properties and the applications of vertically stacked Josephson tunnel junctions (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 3278-3286 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High quality vertically stacked Josephson tunnel junctions have been experimentally studied in the light of their potential applications. They have been realized using a simple fabrication process based on Nb technology. A number of aspects of such new devices were investigated. Among other things, we report on the dc characteristics (and their temperature and magnetic field dependence) of vertical stacks with particular attention to the case in which the intermediate layers are very thin. Furthermore, the Swihart velocities of the electromagnetic waves propagating in double-barrier junctions were measured from the voltages of zero field steps, Fiske steps, and flux flow steps in the current-voltage curve of electrically long devices. Each section is discussed in the light of the potential applications of vertically stacked junctions. We interpret the main features of the phenomena observed experimentally in terms of basic mechanisms. Strong evidence has been found of the proximity effect in thin intermediate layers. Vertically stacked Josephson tunnel junctions seem to be good candidates for applications as particle and photon detectors and high frequency oscillators. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360018
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  • 8
    Electronic Resource
    Electronic Resource
    rf-induced steps in intermediate length Josephson-tunnel junctions (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 5406-5410 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the behavior of the rf-induced steps in unidimensional Josephson-tunnel junctions having overlap geometry and length L≈λj. We have investigated the response of the junctions to the rf current in a range of frequency covering the geometrical resonance of the junctions. The experimental data are compared with the predictions of a model based on a multimode expansion of the junction phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340359
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  • 9
    Electronic Resource
    Electronic Resource
    A new approach for the Jeffreys–Wentzel–Kramers–Brillouin theory (1994)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 35 (1994), S. 6371-6378 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: A new approximation to obtain solutions for the time-independent Schrödinger equation, similar to the classical Jeffreys–Wentzel–Kramers–Brilloin theory, is obtained by means of the theory of continued fractions. A particular case is discussed in detail. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.530680
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  • 10
    Electronic Resource
    Electronic Resource
    Selective trilayer deposition process for fabricating Nb/Al-AlOx/Nb Josephson tunnel junctions (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 3042-3044 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High quality Nb/Al-AlOx/Nb Josephson tunnel junctions have been fabricated using a novel process named the selective trilayer deposition process. The junction is formed on a patterned Nb underlayer through the lift-off deposition of a Nb/Al-AlOx/Nb trilayer. Anodization then provides the insulation between the underlayer and the wiring layer. We show that this easy and simple process is particularly advantageous for the fabrication of many vertically stacked tunnel junctions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111371
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