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in subjects: "Josephson Junctions"

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E-Division semiannual report. Progress report, June 1--December 31, 1977. [Electronics and Instrumentation Division, LASL]

The status of the programs and projects of the Electronics Division is reported for the period of June through December 1977. The presentation is divided into three sections: Research, Engineering Support, and Technical Services. Each of these sections presents the activities and accomplishments of the corresponding branch within the Division. The primary goal of the Research and Development branch is to advance technology for future applications. The primary goal of the Engineering Support bra… more

Date: March 1, 1978

Creator: Kelley, P.A. (comp.)

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Summary and conclusions

This report presents a brief summary of the author's impressions from SQUID 91.

Date: August 1, 1991

Creator: Clarke, J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Macroscopic quantum effects in the zero voltage state of the current biased Josephson junction

When a weak microwave current is applied to a current-biased Josephson tunnel junction in the thermal limit the escape rate from the zero voltage state is enhanced when the microwave frequency is near the plasma frequency of the junction. The resonance curve is markedly asymmetric because of the anharmonic properties of the potential well: this behavior is well explained by a computer simulation using a resistively shunted junction model. This phenomenon of resonant activation enables one to ma… more

Date: May 1, 1985

Creator: Clarke, J.; Devoret, M. H.; Martinis, J. & Esteve, D.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Effect of the subgap conductance on the metastable states in a Josephson tunnel junction

An investigation of the decay rate of metastable states in Josephson tunnel junctions in presence of thermal noise is presented. We have observed that, in the extremely underdamped regime, there is an exponential temperature dependence of the best fit value for the shunt conductance. Such a dependence shows a close relation with the temperature dependence of the subgap conductance, suggesting that the effective conductance for the escape from the metastable states obeys to a quasi-particle ther… more

Date: September 1, 1987

Creator: Cristiano, R.; Pagano, S.; Silvestrini, P.; Gray, K.E. & Liengme, O.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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A Numerical Treatment of the Rf SQUID: I. General Properties andNoise Energy

We investigate the characteristics and noise performance of rf Superconducting Quantum Interference Devices (SQUIDs) by solving the corresponding Langevin equations numerically and optimizing the model parameters with respect to noise energy. After introducing the basic concepts of the numerical simulations, we give a detailed discussion of the performance of the SQUID as a function of all relevant parameters. The best performance is obtained in the crossover region between the dispersive and d… more

Date: January 15, 2007

Creator: Kleiner, Reinhold; Koelle, Dieter & Clarke, John

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Nuclear magnetic resonance experiments with dc SQUID amplifiers

The development and fabrication of dc SQUIDs (Superconducting QUantum Interference Devices) with Nb/Al{sub 2}O{sub 3}/Nb Josephson junctions is described. A theory of the dc SQUID as a radio-frequency amplifier is presented, with an optimization strategy that accounts for the loading and noise contributions of the postamplifier and maximizes the signal-to-noise ratio of the total system. The high sensitivity of the dc SQUID is extended to high field NMR. A dc SQUID is used as a tuned radio-freq… more

Date: November 1, 1990

Creator: Heaney, M.B. (California Univ., Berkeley, CA (USA). Dept. of Physics Lawrence Berkeley Lab., CA (USA))

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Macroscopic quantum tunnelling in a current biased Josephson junction

We discuss in this work an attempt to answer experimentally the question: do macroscopic variables obey quantum mechanics. More precisely, this experiment deals with the question of quantum-mechanical tunnelling of a macroscopic variable, a subject related to the famous Schrodinger's cat problem in the theory of measurement.

Date: November 1, 1984

Creator: Martinis, J. M.; Devoret, M. H.; Clarke, J. & Urbina, C.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Macroscopic quantum tunneling in Josephson tunnel junctions and Coulomb blockade in single small tunnel junctions

Experiments investigating the process of macroscopic quantum tunneling in a moderately-damped, resistively shunted, Josephson junction are described, followed by a discussion of experiments performed on very small capacitance normal-metal tunnel junctions. The experiments on the resistively-shunted Josephson junction were designed to investigate a quantum process, that of the tunneling of the Josephson phase variable under a potential barrier, in a system in which dissipation plays a major role… more

Date: April 1, 1991

Creator: Cleland, A.N.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Josephson oscillations of charge density waves

The formation of charge density waves in solids was originally proposed as a possible mechanism for superconductivity by Froehlich. Although the experimentally discovered materials with charge density waves (CDW)s are found to have finite resistivity as a result of impurity pinning, they nevertheless reveal many interesting features including motion which is analogous to a resistively shunted Josephson junction of superconductors. The noise spectrum of CDW systems is reviewed with particular em… more

Date: January 1, 1985

Creator: Ruvalds, J. & Tua, P.F.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Flux flow, pinning, and resistive behavior in superconducting networks

We have studied the behavior of fluctuation effects in superconducting systems using numerical simulations of XY and Coulomb gas models. Flux flow resistance in two dimensional Josephson junction arrays has been calculated, and related to correlations in vortex structure. Randomness has been introduced, and its effects on the superconducting transition, and vortex mobility, have been studied. We find that randomness destroys phase coherence, yet the randomness induced pinning reduces flux flow … more

Date: October 1, 1991

Creator: Teitel, S.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Superconducting demodulators, differential voltmeters, and transducers

The capabilities of new superconducting measurement devices are reviewed and new applications of this technology are suggested. Specific ways in which these devices may enhance low temperature research in an orbiting laboratory are discussed. 12 refs., 2 figs.

Date: January 1, 1991

Creator: Duncan, R.V.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Nuclear magnetic resonance with dc SQUID (Super-conducting QUantum Interference Device) preamplifiers

Sensitive radio-frequency (rf) amplifiers based on dc Superconducting QUantum Interface Devices (SQUIDS) are available for frequencies up to 200 MHz. At 4.2 K, the gain and noise temperature of a typical tuned amplifier are 18.6 +- 0.5 dB and 1.7 +- 0.5 K at 93 MHz. These amplifiers are being applied to a series of novel experiments on nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR). The high sensitivity of these amplifiers was demonstrated in the observation of ''nuclea… more

Date: August 1, 1988

Creator: Fan, N.Q.; Heaney, M.B.; Clark, J.; Newitt, D.; Wald, L.; Hahn, E.L. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Mode-locking and the transition to chaos in dissipative systems

Dissipative systems with two competing frequencies exhibit transitions to chaos. We have investigated the transition through a study of discrete maps of the circle onto itself, and by constructing and analyzing return maps of differential equations representing some physical systems. The transition is caused by interaction and overlap of mode-locked resonances and takes place at a critical line where the map losses invertibility. At this line the mode-locked intervals trace up a complete Devil'… more

Date: January 1, 1984

Creator: Bak, P.; Bohr, T. & Jensen, M.H.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Charlottesville revisited

A discussion is given of the main areas of research in superconducting devices over the past eleven years. Topics discussed include SQUIDS, high frequency detectors, metrology, voltmeters, thermometers, Josephson junction switches, tunnel junctions, and refrigeration. (PMA)

Date: April 1, 1978

Creator: Clarke, J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Flux flow pinning and resistive behavior in superconducting networks

We have studied the behavior of superconducting networks in terms of XY and Coulomb gas models. The dynamics of frustrated Josephson junction arrays has been simulated, with a view toward understanding the effects of vortex correlations on flux flow resistance. Randomness has been introduced, and its effects on the superconducting transition, and vortex mobility, have been studied. A three dimensional network has been simulated to study the effects of vortex line entanglement in high temperatur… more

Date: October 1, 1990

Creator: Teitel, S.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Dependence of the Josephson coupling of unconventional superconductors on the properties of the tunneling barrier

The Josephson coupling between a conventional and an unconventional superconductor is investigated as a function of the properties of the tunneling barrier. A simple model is adopted for the tunneling probability and it is shown that its variation dramatically affects the I{sub c}R{sub n} product of an s-d, as opposed to an s-s junction. Based on these conclusions, experiments are proposed to probe the symmetry of the order parameter in high temperature superconductors.

Date: May 30, 1994

Creator: Ledvij, M. & Klemm, R. A.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Microstructure and composition of a SNS Josephson junction using CaRuO{sub 3} as the metallic barrier

Superconductor - normal - superconductor (SNS) edge junctions consisting of YBa{sub 2}Cu{sub 3}O{sub 7-x}/CaRuO{sub 3}/YBa{sub 2}Cu{sub 3}O{sub 7-x} were fabricated on (001) LaA1O{sub 3} substrates. These devices display an excess interface resistance which is not well understood but is related to the SN interface and interlayer structure. High-resolution and conventional transmission electron microscopy were employed to investigate the SN interface to determine the structure and possible inter… more

Date: October 1, 1994

Creator: Rozeveld, S.; Merkle, K. L. & Char, K.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Studies in nonlinear problems of energy. Progress report, January 1, 1992--December 31, 1992

Emphasis has been on combustion and flame propagation. The research program was on modeling, analysis and computation of combustion phenomena, with emphasis on transition from laminar to turbulent combustion. Nonlinear dynamics and pattern formation were investigated in the transition. Stability of combustion waves, and transitions to complex waves are described. Combustion waves possess large activation energies, so that chemical reactions are significant only in thin layers, or reaction zones… more

Date: July 1, 1992

Creator: Matkowsky, B. J.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Resonant tunneling in small current-biased Josephson Junctions

Effects of resonant tunneling between bound quantum states of a current-biased Josephson tunnel junction is studied both theoretically and experimentally. Several effects are predicted to arise from resonant tunneling, including a series of voltage peaks along the supercurrent branch of the current-voltage characteristic, and enhanced rate of escape from zero voltage state to voltage state at particular values of bias current. A model is developed to estimate magnitude and duration of voltage p… more

Date: May 1, 1994

Creator: Schmidt, J. M.

Item Type: Thesis or Dissertation

Partner: UNT Libraries Government Documents Department

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Effects of interlayer coupling on the magnetic and transport properties of superconducting multilayers and high-temperature superconductors

The effect of interlayer coupling on the transport properties and dissipation in a magnetic field is reviewed for superconducting multilayers including highly-anisotropic high-temperature superconductors (HTS). For the applied field parallel to the superconducting layers the absence of any Lorentz-force dependence of the dissipation leads to an explanation other than flux motion. This is consistent with a Josephson junction dissipation which dominates flux motion of the insulating regions betwe… more

Date: June 1, 1994

Creator: Gray, K. E.; Hettinger, J. D. & Kim, D. H.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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New Approaches to Quantum Computing Using Nuclear Magnetic Resonance Spectroscopy

The power of a quantum computer (QC) relies on the fundamental concept of the superposition in quantum mechanics and thus allowing an inherent large-scale parallelization of computation. In a QC, binary information embodied in a quantum system, such as spin degrees of freedom of a spin-1/2 particle forms the qubits (quantum mechanical bits), over which appropriate logical gates perform the computation. In classical computers, the basic unit of information is the bit, which can take a value of e… more

Date: February 7, 2003

Creator: Colvin, M. & Krishnan, V. V.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Research and development of superconductivity in the USA

In this paper, the author focuses his attention on the present and potential applications of superconductors -- both the classic low T/sub c/ superconductors such as niobium and its alloys and the new high-T/sub c/ materials. This discussion falls naturally into two broad areas: large scale applications such as magnets and power generators, and small scale applications such as ultrasensitive detectors of electromagnetic radiation and of tiny magnetic fields;

Date: May 1, 1988

Creator: Clarke, J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Flux lattice relaxation, noise and symmetry-breaking in frustrated Josephson junction arrays

The purpose of the present report is to study: (1) Relaxation from an initially random flux state. We wish to exhibit the multiple length and time scales involved in this relaxation, and the influence of thermal fluctuations. This noisy relaxation is controlled by the dynamics of various mesoscopic ``defect`` structures defined with respect to the underlying ground-state flux structure. The defects, their mesoscopic collective patterns, and their dynamics control a complex macroscopic response,… more

Date: 1992

Creator: Gronbech-Jensen, N.; Bishop, A. R. & Lomdahl, P. S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Development, characterization, and applications of high temperature superconductor nanobridge Josephson junctions

A well-controlled, high-yield Josephson junction process in high temperature superconductors (HTS) is necessary for the demonstration of ultra-high-speed devices and circuits which exceed the capabilities of conventional electronics. The authors developed nanobridge Josephson junctions in high quality thin-film YBaCuO with dimensions below 100 nm fabricated using electron-beam nanolithography. They characterized this Josephson junction technology for process yield, junction parameter uniformity… more

Date: March 1, 1994

Creator: Wendt, J. R.; Tigges, C. P.; Hietala, V. M.; Plut, T. A.; Martens, J. S.; Char, K. et al.

Item Type: Report

Partner: UNT Libraries Government Documents Department