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Sample records for nuclear josephson effect

  1. Momentum-Space Josephson Effects

    Science.gov (United States)

    Hou, Junpeng; Luo, Xi-Wang; Sun, Kuei; Bersano, Thomas; Gokhroo, Vandna; Mossman, Sean; Engels, Peter; Zhang, Chuanwei

    2018-03-01

    The Josephson effect is a prominent phenomenon of quantum supercurrents that has been widely studied in superconductors and superfluids. Typical Josephson junctions consist of two real-space superconductors (superfluids) coupled through a weak tunneling barrier. Here we propose a momentum-space Josephson junction in a spin-orbit coupled Bose-Einstein condensate, where states with two different momenta are coupled through Raman-assisted tunneling. We show that Josephson currents can be induced not only by applying the equivalent of "voltages," but also by tuning tunneling phases. Such tunneling-phase-driven Josephson junctions in momentum space are characterized through both full mean field analysis and a concise two-level model, demonstrating the important role of interactions between atoms. Our scheme provides a platform for experimentally realizing momentum-space Josephson junctions and exploring their applications in quantum-mechanical circuits.

  2. Applications of Josephson effect

    International Nuclear Information System (INIS)

    Benacka, S.

    Week coupling superconducting systems are described, such as the tunnel system, the bridge-type system, the whisker connection of two superconductors, and the Clark SLUG (Superconducting Low-Inductance Undulatory Galvanometer). The equivalent diagram is presented. If the power supply resistance is greater than the barrier resistance, the hysteresis occurs of the volt-ampere characteristics as a function of the inherent capacitance and inductance of the system. In the opposite case, hysteresis decays and the negative differential resistance region may be effective. The d.c. and high-='requency SQUID (Superconducting Quantum Interference Device) systems are described. The whisker and bridge types are mainly used in the high-frequency region. These systems may be used as sources of electromagnetic radiation of up to 10 THz. The generated out.out is in the order of 10 -10 W. (J.B.)

  3. Josephson effect far-infrared detector

    International Nuclear Information System (INIS)

    Shapiro, S.

    1971-01-01

    Four Josephson effect schemes for detection of far-infrared radiation are reviewed: Video broad-band detection, regenerative detection, conventional mixing for monochromatic signals, and self-mixing or frequency conversion. (U.S.)

  4. Response of high Tc superconducting Josephson junction to nuclear radiation

    International Nuclear Information System (INIS)

    Ding Honglin; Zhang Wanchang; Zhang Xiufeng

    1992-10-01

    The development of nuclear radiation detectors and research on high T c superconducting nuclear radiation detectors are introduced. The emphases are the principle of using thin-film and thick-film Josephson junctions (bridge junction) based on high T c YBCO superconductors to detect nuclear radiation, the fabrication of thin film and thick-film Josephson junction, and response of junction to low energy gamma-rays of 59.5 keV emitted from 241 Am and beta-rays of 546 keV. The results show that a detector for measuring nuclear radiation spectrum made of high T c superconducting thin-film or thick-film, especially, thick-film Josephson junction, certainly can be developed

  5. The Josephson effect in atomic contacts

    International Nuclear Information System (INIS)

    Chauvin, M.

    2005-11-01

    The Josephson effect appears when a weak-link establishes phase coherence between two superconductors. A unifying theory of this effect emerged in the 90's within the framework of mesoscopic physics. Based on two cornerstone concepts, conduction channels and Andreev reflection, it predicts the current-phase relation for the most basic weak-link: a single conduction channel of arbitrary transmission. This thesis illustrates this mesoscopic point of view with experiments on superconducting atomic size contacts. In particular, we have focused on the supercurrent peak around zero voltage, put into evidence the ac Josephson currents in a contact under constant bias voltage (Shapiro resonances and photon assisted multiple Andreev reflections), and performed direct measurements of the current-phase relation. (author)

  6. Effect of environment fluctuations on a Josephson current

    International Nuclear Information System (INIS)

    Galaktionov, A.V.

    2017-01-01

    Highlights: • Josephson current is influenced differently by environment fluctuations. • Two types of environment are studied: ohmic and resonant-mode one. • A crossover to a Josephson π-junction is possible for both of them. - Abstract: An influence of an electromagnetic environment on a Josephson current through a tunnel junction is studied with the aid of Ambegaokar-Eckern-Schön effective action. Two types of environment are investigated: one, characterized by a resonant mode, and an ohmic one. The crossover to a Josephson π-junction is possible for both of them. In addition the resonant-mode environment results in an increase of a Josephson current when the ratio of the doubled superconducting gap to the frequency of the mode is close to an integer number.

  7. Josephson technology

    International Nuclear Information System (INIS)

    Drangeid, K.E.

    1983-01-01

    The author presents an introduction to Josephson junctions. After an introduction to the physical principles of superconductivity and the Josephson effect some applications are described with special regards to the implementation in digital circuits. (HSI)

  8. The Josephson effect in atomic contacts; Effect Josephson dans les contacts atomiques

    Energy Technology Data Exchange (ETDEWEB)

    Chauvin, M

    2005-11-15

    The Josephson effect appears when a weak-link establishes phase coherence between two superconductors. A unifying theory of this effect emerged in the 90's within the framework of mesoscopic physics. Based on two cornerstone concepts, conduction channels and Andreev reflection, it predicts the current-phase relation for the most basic weak-link: a single conduction channel of arbitrary transmission. This thesis illustrates this mesoscopic point of view with experiments on superconducting atomic size contacts. In particular, we have focused on the supercurrent peak around zero voltage, put into evidence the ac Josephson currents in a contact under constant bias voltage (Shapiro resonances and photon assisted multiple Andreev reflections), and performed direct measurements of the current-phase relation. (author)

  9. Anomalous Josephson effect controlled by an Abrikosov vortex

    Science.gov (United States)

    Mironov, S.; Goldobin, E.; Koelle, D.; Kleiner, R.; Tamarat, Ph.; Lounis, B.; Buzdin, A.

    2017-12-01

    The possibility of a fast and precise Abrikosov vortex manipulation by a focused laser beam opens the way to create laser-driven Josephson junctions. We theoretically demonstrate that a vortex pinned in the vicinity of the Josephson junction generates an arbitrary ground state phase which can be equal not only to 0 or π but to any desired φ0 value in between. Such φ0 junctions have many peculiar properties and may be effectively controlled by the optically driven Abrikosov vortex. Also we theoretically show that the Josephson junction with the embedded vortex can serve as an ultrafast memory cell operating at sub THz frequencies.

  10. Quantum synchronization effects in intrinsic Josephson junctions

    International Nuclear Information System (INIS)

    Machida, M.; Kano, T.; Yamada, S.; Okumura, M.; Imamura, T.; Koyama, T.

    2008-01-01

    We investigate quantum dynamics of the superconducting phase in intrinsic Josephson junctions of layered high-T c superconductors motivated by a recent experimental observation for the switching rate enhancement in the low temperature quantum regime. We pay attention to only the capacitive coupling between neighboring junctions and perform large-scale simulations for the Schroedinger equation derived from the Hamiltonian considering the capacitive coupling alone. The simulation focuses on an issue whether the switching of a junction induces those of the other junctions or not. The results reveal that the superconducting phase dynamics show synchronous behavior with increasing the quantum character, e.g., decreasing the junction plane area and effectively the temperature. This is qualitatively consistent with the experimental result

  11. Josephson effects in a Bose–Einstein condensate of magnons

    International Nuclear Information System (INIS)

    Troncoso, Roberto E.; Núñez, Álvaro S.

    2014-01-01

    A phenomenological theory is developed, that accounts for the collective dynamics of a Bose–Einstein condensate of magnons. In terms of such description we discuss the nature of spontaneous macroscopic interference between magnon clouds, highlighting the close relation between such effects and the well known Josephson effects. Using those ideas, we present a detailed calculation of the Josephson oscillations between two magnon clouds, spatially separated in a magnonic Josephson junction. -- Highlights: •We presented a theory that accounts for the collective dynamics of a magnon-BEC. •We discuss the nature of macroscopic interference between magnon-BEC clouds. •We remarked the close relation between the above phenomena and Josephson’s effect. •We remark the distinctive oscillations that characterize the Josephson oscillations

  12. Josephson effects in a Bose–Einstein condensate of magnons

    Energy Technology Data Exchange (ETDEWEB)

    Troncoso, Roberto E., E-mail: r.troncoso.c@gmail.com [Centro para el Desarrollo de la Nanociencia y la Nanotecnología, CEDENNA, Avda. Ecuador 3493, Santiago 9170124 (Chile); Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Casilla 487-3, Santiago (Chile); Núñez, Álvaro S., E-mail: alnunez@dfi.uchile.cl [Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Casilla 487-3, Santiago (Chile)

    2014-07-15

    A phenomenological theory is developed, that accounts for the collective dynamics of a Bose–Einstein condensate of magnons. In terms of such description we discuss the nature of spontaneous macroscopic interference between magnon clouds, highlighting the close relation between such effects and the well known Josephson effects. Using those ideas, we present a detailed calculation of the Josephson oscillations between two magnon clouds, spatially separated in a magnonic Josephson junction. -- Highlights: •We presented a theory that accounts for the collective dynamics of a magnon-BEC. •We discuss the nature of macroscopic interference between magnon-BEC clouds. •We remarked the close relation between the above phenomena and Josephson’s effect. •We remark the distinctive oscillations that characterize the Josephson oscillations.

  13. Josephson effects in Nb3Sn microbridges

    International Nuclear Information System (INIS)

    Lee, T.W.; Falco, C.M.

    1981-01-01

    Josephson effects in long narrow Nb/sub 3/Sn microbridges at temperatures up to 17 K were studied. These microbridges are formed by photolithographic techniques and subsequently subjected to controlled electrical discharges to modifY the intrinsic T/sub c/ of the bridge region. The bridges exhibit 10 GHz microwave steps in their I-V characteristics whose amplitudes are in agreement with the Resistively Shunted Junction (RSJ) model. I-V characteristics can be fit assuming an effective temperature approximately 15 K above the bath temperature. Structures in the I-V characteristics in the absence of microwaves were also investigated. It was demonstrated that phase-slip centers are induced at weak superconducting positions along the bridge when the S-N boundarY of an expanding hot spot reaches within a thermal healing distance. The critical current of the phase-slip center thus formed exhibits a temperature dependence (1-T/T/sub c/)/one-half/ insteady of the usual mean field result (1-T/T/sub c/)/sup 3/2/. 12 refs

  14. Effect of surface losses on soliton propagation in Josephson junctions

    DEFF Research Database (Denmark)

    Davidson, A.; Pedersen, Niels Falsig; Pagano, S.

    1986-01-01

    We have explored numerically the effects on soliton propagation of a third order damping term in the modified sine-Gordon equation. In Josephson tunnel junctions such a term corresponds physically to quasiparticle losses within the metal electrodes of the junction. We find that this loss term pla...

  15. The Josephson and Quantum Hall effect in metrology

    International Nuclear Information System (INIS)

    Lifka, E.

    1990-01-01

    This first generation of DC voltage standards based upon the Josephson effect made use of one tunnel junction coupled with microwaves via an external resonator. The needed output voltage level of 1 V was derived either by means of room temperature resistive divider or the cryogenic current comparator from the quantized microwave-induced voltage drop on the Josephson tunnel junction. In order to increase the accuracy of th standard, series arrays of Josephson tunnel junctions, in which the quantized voltage drops are added together thus providing reference voltage of several hundreds mV, are commonly used in some national laboratories. As the radiating frequency used is 70 GHz or higher the actual sample containing tunnel junction array takes form of an millimeter wave integrated circuit feeded by the thin film fin-line. This improved DC voltage standard has relative uncertainty lower by an amount which equals to the contribution of the resistive divider and allied measuring circuitry. This paper traces the present and future of studies involving the use of the Josephson and Quantum Hall Effect in meteorology

  16. Josephson effect in point contacts between 'f-wave' superconductors

    International Nuclear Information System (INIS)

    Mahmoodi, R.; Shevchenko, S.N.; Kolesnichenko, Yu.A

    2002-01-01

    A stationary Josephson effect in point contacts between triplet superconductors is analyzed theoretically for most probable models of the order parameter in UPt 3 and Sr 2 RuO 4 . The consequence of misorientation of crystals in the superconducting banks on this effect is considered. We show that different models for the order parameter lead to quit different current-phase relations. For certain angles of misorientation a boundary between superconductors can generate a spontaneous current parallel to the surface. In a number of cases the state with a zero Josephson current and minimum of the free energy corresponds to a spontaneous phase difference. This phase difference depends on the misorientation angle and may possess any value. We conclude that experimental investigations of the current-phase relations of small junctions can be used for determination of the order parameter symmetry in the superconductors mentioned above

  17. Self-field effects in window-type Josephson tunnel junctions

    DEFF Research Database (Denmark)

    Monaco, Roberto; Koshelets, Valery P; Mukhortova, Anna

    2013-01-01

    The properties of Josephson devices are strongly affected by geometrical effects such as those associated with the magnetic field induced by the bias current. The generally adopted analysis of Owen and Scalapino (1967 Phys. Rev. 164, 538) for the critical current, Ic, of an in-line Josephson tunnel...

  18. Josephson effect in high-Tc superconductors and in structures using them

    International Nuclear Information System (INIS)

    Kupriyanov, M.Yu.; Likharev, K.K.

    1990-01-01

    A review of the investigations of the Josephson effect in HTS materials and HTS Josephson structures is represented. The influence of the synthesis conditions and a surface etching on the surface properties of the HTS/Ag(Au) are briefly discussed. On the basis of these results the experimental data obtained in various types of the Josephson junctions (point contacts, tunnel junctions, weak links, break and bulk junctions and crystal type break junctions) are considered. These data are compared with theoretical results obtained from different BCS models of the Josephson junctions. It is concluded that now it is impossible to make either the conclusion on the applicability of the BCS theory for HTS superconductors or the unambiguous identification of the principal physical structure of the junctions. The directions of the future experimental investigations of the Josephson effect in HTS tunnel junctions and weak links are discussed

  19. Interactions between electrons, mesoscopic Josephson effect and asymmetric current fluctuations

    Science.gov (United States)

    Huard, B.

    2006-07-01

    This article discusses three experiments on the properties of electronic transport at the mesoscopic scale. The first one allowed to measure the energy exchange rate between electrons in a metal contaminated by a very weak concentration of magnetic impurities. The role played by magnetic impurities in the Kondo regime on those energy exchanges is quantitatively investigated, and the global measured exchange rate is larger than expected. The second experiment is a measurement of the current-phase relation in a system made of two superconductors linked through a single atom. We thus provide quantitative support for the recent description of the mesoscopic Josephson effect. The last experiment is a measurement of the asymmetry of the current fluctuations in a mesoscopic conductor, using a Josephson junction as a threshold detector. Cet ouvrage décrit trois expériences portant sur les propriétés du transport électronique à l'échelle mésoscopique. La première a permis de mesurer le taux d'échange d'énergie entre électrons dans un métal contenant une très faible concentration d'impuretés magnétiques. Nous avons validé la description quantitative du rôle des impuretés magnétiques dans le régime Kondo sur ces échanges énergétiques et aussi montré que le taux global d'échange est plus fort que prévu. La seconde expérience est une mesure de la relation courant-phase dans un système constitué de deux supraconducteurs couplés par un seul atome. Elle nous a permis de conforter quantitativement la récente description de l'effet Josephson mésoscopique. La dernière expérience est unemesure de l'asymétrie des fluctuations du courant dans un conducteur mésoscopique en utilisant une Jonction Josephson comme détecteur de seuil.

  20. Effect of colored noise on an overdamped Josephson junction

    Science.gov (United States)

    Genchev, Z. D.

    2001-03-01

    In this paper my attention is restricted to stochastic differential equation in phase function φ(t), describing an overdamped Josephson junction. I accept the RSJ (resistively shunted junction) modeling, when the contact characterized by resistance R and critical current I c is under the action of a given direct current I and stochastic current source Ĩ(t) (=0) : {ℏ}/{2 eR }{dφ }/{dt }+I csinφ=I+ Ĩ(t). In our case the thermal noise is a Gaussian process and obeys the Johnson-Nyquistr correlation law C(t)== {ℏ}/{2πR}∫ -∞∞dω ω coth{ℏω}/{2k BT }cosωt. The effective Fokker-Planck equation is derived and the current-voltage characteristics (CVCs) of the Josephson junction are calculated for weakly colored noise. In the limit limℏ→0C(t)= {2k BT }/{R}δ(t) the well-known results for white noise are recovered.

  1. Josephson effect in SIFS junctions at arbitrary scattering

    International Nuclear Information System (INIS)

    Pugach, N. G.; Kupriyanov, M. Yu.; Goldobin, E.; Koelle, D.; Kleiner, R.

    2011-01-01

    Full text: The interplay between dirty and clean limits in Superconductor-Ferromagnet-Superconductor (SFS) Josephson junctions is a subject of intensive theoretical studies. SIFS junctions, containing an additional insulator (I) barrier are interesting as potential logic elements in superconducting circuits, since their critical current I c can be tuned over a wide range, still keeping a high I c R N product, where R N is the normal resistance of the junction. They are also a convenient model system for a comparative study of the 0-π transitions for arbitrary relations between characteristic lengths of the F-layer: the layer thickness d, the mean free path l, the magnetic length ξ H =v F /2H, and the nonmagnetic coherence length ξ 0 =v F /2πT, where v F is the Fermi velocity, H is the exchange magnetic energy, and T is the temperature. The spatial variations of the order parameter are described by the complex coherent length in the ferromagnet ξ F -1 = ξ 1 -1 + iξ 2 -1 . It is well known, that in the dirty limit (l 1,2 ) described by the Usadel equations both ξ 1 2 = ξ 2 2 = v F l/3H. In this work the spatial distribution of the anomalous Green's functions and the Josephson current in the SIFS junction are calculated. The linearized Eilenberger equations are solved together with the Zaitsev boundary conditions. This allows comparing the dirty and the clean limits, investigating a moderate disorder, and establishing the applicability limits of the Usadel equations for such structures. We demonstrate that for an arbitrary relation between l, ξ H , and d the spatial distribution of the anomalous Green's function can be approximated by a single exponent with reasonable accuracy, and we find its effective decay length and oscillation period for several values of ξ H , l and d. The role of different types of the FS interface is analyzed. The applicability range of the Usadel equation is established. The results of calculations have been applied to the

  2. AC Josephson effect in YBa2Cu3O7-δ bicrystal grain boundary junctions

    International Nuclear Information System (INIS)

    Fischer, G.M.; Andreev, A.V.; Divin, Y.Ya.; Freltoft, T.; Mygind, J.; Pedersen, N.F.; Shen Yueqiang; Vase, P.

    1994-01-01

    The ac Josephson effect in YBa 2 Cu 3 O 7-δ bicrystal grain boundary junctions was studied in the temperature range from 4K to 90K. Junctions with widths from 0.2 to 50 μm were made on SrTiO 3 bicrystal substrates by laser ablation and e-beam lithography. The linewidth of the Josephson oscillations is derived from the shape of the dc voltage response to low-intensity, f = 70 GHz radiation at voltages V ≅ (h/2e) f, assuming the RSJ model. The effect of the size on the Josephson behavior of this type of high-T c junctions was studied. Close to T c the linewidth of the Josephson oscillations was shown to be determined by thermal fluctuations. (orig.)

  3. Effect of Impurities on the Josephson Current through Helical Metals: Exploiting a Neutrino Paradigm

    Science.gov (United States)

    Ghaemi, Pouyan; Nair, V. P.

    2016-01-01

    In this Letter we study the effect of time-reversal symmetric impurities on the Josephson supercurrent through two-dimensional helical metals such as on a topological insulator surface state. We show that, contrary to the usual superconducting-normal metal-superconducting junctions, the suppression of the supercurrent in the superconducting-helical metal-superconducting junction is mainly due to fluctuations of impurities in the junctions. Our results, which are a condensed matter realization of a part of the Mikheyev-Smirnov-Wolfenstein effect for neutrinos, show that the relationship between normal state conductance and the critical current of Josephson junctions is significantly modified for Josephson junctions on the surface of topological insulators. We also study the temperature dependence of the supercurrent and present a two fluid model which can explain some of the recent experimental results in Josephson junctions on the edge of topological insulators.

  4. The role of magnetic fields for curvature effects in Josephson junction

    Energy Technology Data Exchange (ETDEWEB)

    Jarmoliński, A.; Dobrowolski, T., E-mail: dobrow@up.krakow.pl

    2017-06-01

    The large area Josephson junction is considered. On the basis of Maxwell equations the influence of the magnetic field on fluxion dynamics is considered. The presented studies show that assumptions presumed in the literature do not restrict experimental settings adopted in the considerations of the fluxion movement in the Josephson junction. It is shown that the particular orientation of the magnetic fields is not needed in order to study physical effects of curvature and therefore they do not restrict the experimental arrangements.

  5. Effect of quasi-particle injection on retrapping current of Josephson junction

    OpenAIRE

    Utsunomiya, K.; Yagi, Ryuta

    2006-01-01

    We report that the energy dissipation of Josephson junction can be controlled by quasi-particle injection. We fabricated two Josephson junctions on the narrow aluminum wire and controlled the energy dissipation of one junction by quasi-particle injection from the other. We observed the retrapping current increased as the quasi-particles were injected. We also studied the heating effect of our measurement.

  6. Possible resonance effect of axionic dark matter in Josephson junctions.

    Science.gov (United States)

    Beck, Christian

    2013-12-06

    We provide theoretical arguments that dark-matter axions from the galactic halo that pass through Earth may generate a small observable signal in resonant S/N/S Josephson junctions. The corresponding interaction process is based on the uniqueness of the gauge-invariant axion Josephson phase angle modulo 2π and is predicted to produce a small Shapiro steplike feature without externally applied microwave radiation when the Josephson frequency resonates with the axion mass. A resonance signal of so far unknown origin observed by C. Hoffmann et al. [Phys. Rev. B 70, 180503(R) (2004)] is consistent with our theory and can be interpreted in terms of an axion mass m(a)c2=0.11  meV and a local galactic axionic dark-matter density of 0.05  GeV/cm3. We discuss future experimental checks to confirm the dark-matter nature of the observed signal.

  7. Stationary Josephson effect in a weak-link between nonunitary triplet superconductors

    International Nuclear Information System (INIS)

    Rashedi, G; Kolesnichenko, Yu.A.

    2005-01-01

    A stationary Josephson effect in a weak-link between misorientated nonunitary triplet superconductors is investigated theoretically. The non-self-consistent quasiclassical Eilenberger equation for this system has been solved analytically. As an application of this analytical calculation, the current-phase diagrams are plotted for the junction between two nonunitary bipolar f-wave superconducting banks. A spontaneous current parallel to the interface between superconductors has been observed. Also, the effect of misorientation between crystals on the Josephson and spontaneous currents is studied. Such experimental investigations of the current-phase diagrams can be used to test the pairing symmetry in the above-mentioned superconductors

  8. On the Josephson effect between superconductors in singlet and triplet spin-pairing states

    International Nuclear Information System (INIS)

    Pals, J.A.; Haeringen, W. van

    1977-01-01

    An expression is derived for the Josephson current between two weakly coupled superconductors of which one or both have pairs in a spin-triplet state. It is shown that there can be no Josephson effect up to second order in the transition matrix elements between a superconductor with spin-triplet pairs and one with spin-singlet pairs if the coupling between the two superconductors can be described with a spin-conserving tunnel hamiltonian. This is shown to offer a possibility to investigate experimentally whether a particular superconductor has spin-triplet pairs by coupling it weakly to a well-known spin-singlet pairing superconductor. (Auth.)

  9. Anomalous Josephson Effect between Even-and Odd-Frequency Superconductors

    NARCIS (Netherlands)

    Tanaka, Yukio; Golubov, Alexandre Avraamovitch; Kashiwaya, Satoshi; Ueda, Masahito

    2007-01-01

    We demonstrate that, contrary to standard wisdom, the lowest-order Josephson coupling is possible between odd- and even-frequency superconductors. The origin of this effect is the induced odd- (even-)frequency pairing component at the interface of bulk even- (odd-)frequency superconductors. The

  10. Self-pumping effects and radiation linewidth of Josephson flux-flow oscillators

    DEFF Research Database (Denmark)

    Koshelets, V.P.; Shitov, S.V.; Shchukin, A.V.

    1997-01-01

    Flux-flow oscillators (FFO's) are being developed for integration with a SIS mixer for use in submillimeter wave receivers, The present work contains a detailed experimental study of the dc, microwave, and noise properties of Nb-AlOx-Nb FFO's, A model based on the Josephson self-pumping effect...

  11. Effect of cross-type bias in a two-dimensional array of short Josephson junctions

    DEFF Research Database (Denmark)

    Filatrella, G.; Pedersen, Niels Falsig; Wiesenfeld, K.

    1998-01-01

    We investigate numerically the effect of cross-type bias on two-dimensional arrays of short Josephson junctions. We have demonstrated that, for the simplest circuit, this type of bias is able to phase lock the junctions yielding a substantial improvement over ordinary biasing schemes. (C) 1998...

  12. Coherent charge fluctuations in Josephson junctions and the oscillations of the effective capacitance

    International Nuclear Information System (INIS)

    Krive, I.V.; Rozhavsky, A.S.

    1990-07-01

    We predict novel voltage oscillations of the effective capacitance of small Josephson junctions. This macroscopic effect involves coherent charge fluctuations with charge 2e, leading to a period of oscillations, V c = 2e/C, where C is the junction capacitance. The amplitude of the effect decreases with temperature as exp(-π 2 T/ε c ), where ε c = (2e) 2 /C. (author). 6 refs

  13. AC Josephson effect without superconductivity, and other effects of radio frequency quantum nanoelectronics

    Science.gov (United States)

    Waintal, Xavier; Gaury, Benoit; Weston, Joseph

    With single coherent electron sources and electronic interferometers now available in the lab, the time resolved dynamics of electrons can now be probed directly. I will discuss how a fast raise of voltage propagates inside an electronic interferometer and leads to an oscillating current of well controled frequency. This phenomena is the normal counterpart to the AC josephson effect. I will also briefly advertize our software for computing quantum transport properties, Kwant (http://kwant-project.org) and its time-dependent extension T-Kwant.

  14. Numerical study of self-field effects on dynamics of Josephson-junction arrays

    International Nuclear Information System (INIS)

    Phillips, J.R.; Van der Zant, H.S.J.; White, J.; Orlando, T.P.

    1994-01-01

    We consider the influence of self-induced magnetic fields on dynamic properties of arrays of resistively and capacitively shunted Josephson junctions. Self-field effects are modeled by including mutual inductance interactions between every cell in the array. We find that it is important to include all mutual inductance interactions in order to understand the dynamic properties of the array, in particular subharmonic structure arising under AC current bias. (orig.)

  15. Effect of transparency on the Josephson junction between D-wave superconductors

    International Nuclear Information System (INIS)

    Rashedi, G

    2008-01-01

    In this paper, a dc Josephson junction between two singlet superconductors (d-wave and s-wave) with arbitrary reflection coefficient has been investigated theoretically following the famous paper [Y. Tanaka and S. Kashiwaya 1996 Phys. Rev. B 53, R11957]. For the case of High T c superconductors, the c-axes are parallel to an interface with finite transparency and their ab-planes have a mis-orientation. The effect of transparency and mis-orientation on the currents is studied both analytically and numerically. It is observed that, the current phase relations are totally different from the case of ideal transparent Josephson junctions between d-wave superconductors and two s-wave superconductors. This apparatus can be used to demonstrate d-wave order parameter in High T c superconductors

  16. Polaron effects on the dc- and ac-tunneling characteristics of molecular Josephson junctions

    Science.gov (United States)

    Wu, B. H.; Cao, J. C.; Timm, C.

    2012-07-01

    We study the interplay of polaronic effect and superconductivity in transport through molecular Josephson junctions. The tunneling rates of electrons are dominated by vibronic replicas of the superconducting gap, which show up as prominent features in the differential conductance for the dc and ac current. For relatively large molecule-lead coupling, a features that appears when the Josephson frequency matches the vibron frequency can be identified with an over-the-gap structure observed by Marchenkov [Nat. Nanotech. 1748-338710.1038/nnano.2007.2182, 481 (2007)]. However, we are more concerned with the weak-coupling limit, where resonant tunneling through the molecular level dominates. We find that certain features involving both Andreev reflection and vibron emission show an unusual shift of the bias voltage V at their maximum with the gate voltage Vg as V˜(2/3)Vg. Moreover, due to the polaronic effect, the ac Josephson current shows a phase shift of π when the bias eV is increased by one vibronic energy quantum ℏωv. This distinctive even-odd effect is explained in terms of the different sign of the coupling to vibrons of electrons and of Andreev-reflected holes.

  17. Study of a high critical temperature superconductor through Josephson effect and tunnel spectroscopy

    International Nuclear Information System (INIS)

    Grison, X.

    2000-11-01

    This work, mainly experimental, is dedicated to the study of the Josephson effect and the tunnel spectroscopy of superconducting films. Thin films of YBa 2 Cu 3 O 7-δ oriented towards [0,0,1], [1,0,3], [1,1,0] or [1,0,0] axis have been made. The results concerning the [0,0,1] orientation are consistent with an order parameter having a d(x 2 -y 2 ) symmetry but with a small component of s symmetry due to the orthorombicity of YBa 2 Cu 3 O 7δ . The results concerning the [1,1,0] orientation show the existence (near (1,1,0)-type surfaces) of an order parameter whose symmetry is d(x 2 -y 2 ) ± i*s or more likely d(x 2 - y 2 ) ± i*d(xy). The latter term implies the breaking of the time reversing symmetry. The i*d(xy) component is responsible for the Josephson coupling along the [1,1,0] axis, which means that the coupling is not or is little carried by the Andreev bound states contrarily to recent predictions. It is also shown that Josephson junctions can be fabricated by using ion irradiation. (A.C.)

  18. Observation of the Josephson effect on Ba-122 iron pnictide single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Hasan, Noor; Schmidt, Stefan; Doering, Sebastian; Tympel, Volker; Schmidl, Frank; Seidel, Paul [Friedrich-Schiller- Universitaet Jena, Institut fuer Festkoerperphysik, Helmholtzweg 5, 07743 Jena (Germany); Wolf, Thomas [Karlsruhe Institute of Technology, Institut fuer Festkoerperphysik, Hermann-von- Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany)

    2015-07-01

    Since the discovery of the first Fe-based superconductors in 2006, extensive effort has been directed characterizing and modeling the novel properties of these exotic materials. Therefore Josephson junction offer ways to investigate the fundamental properties of iron pnictides. We use Ba(Fe{sub 1-x}Co{sub x}){sub 2}As{sub 2} single crystals, prepared by a self-flux method, with an optimal Co concentration of 0.065 (critical temperature T{sub c}=23.5 K). We realize Josephson junctions along the c-axis. To prepare them a newly developed surface polishing as well as standard thin film technologies are used. The artificial barrier consists of thin sputtered layers of various materials, normal conductors as well as insulators. A thermally evaporated double layer film of Pb and In was used as the counter electrode. For the characterization of the Josephson effect we will present temperature dependent I-V characteristics as well as I{sub c} R{sub n} - T dependencies and measurements under microwave radiation, including. Additionally results from tunneling and Andreev spectroscopy i.e temperature dependent dI/dV - V spectra are shown.

  19. Method of manufacturing Josephson junction integrated circuits

    International Nuclear Information System (INIS)

    Jillie, D.W. Jr.; Smith, L.N.

    1985-01-01

    Josephson junction integrated circuits of the current injection type and magnetically controlled type utilize a superconductive layer that forms both Josephson junction electrode for the Josephson junction devices on the integrated circuit as well as a ground plane for the integrated circuit. Large area Josephson junctions are utilized for effecting contact to lower superconductive layers and islands are formed in superconductive layers to provide isolation between the groudplane function and the Josephson junction electrode function as well as to effect crossovers. A superconductor-barrier-superconductor trilayer patterned by local anodization is also utilized with additional layers formed thereover. Methods of manufacturing the embodiments of the invention are disclosed

  20. A programmable quantum current standard from the Josephson and the quantum Hall effects

    Energy Technology Data Exchange (ETDEWEB)

    Poirier, W., E-mail: wilfrid.poirier@lne.fr; Lafont, F.; Djordjevic, S.; Schopfer, F.; Devoille, L. [Quantum metrology group, Laboratoire National de métrologie et d' Essais, 29 avenue Roger Hennequin, 78197 Trappes (France)

    2014-01-28

    We propose a way to realize a programmable quantum current standard (PQCS) from the Josephson voltage standard and the quantum Hall resistance standard (QHR) exploiting the multiple connection technique provided by the quantum Hall effect (QHE) and the exactness of the cryogenic current comparator. The PQCS could lead to breakthroughs in electrical metrology like the realization of a programmable quantum current source, a quantum ampere-meter, and a simplified closure of the quantum metrological triangle. Moreover, very accurate universality tests of the QHE could be performed by comparing PQCS based on different QHRs.

  1. Strong mechanically induced effects in DC current-biased suspended Josephson junctions

    Science.gov (United States)

    McDermott, Thomas; Deng, Hai-Yao; Isacsson, Andreas; Mariani, Eros

    2018-01-01

    Superconductivity is a result of quantum coherence at macroscopic scales. Two superconductors separated by a metallic or insulating weak link exhibit the AC Josephson effect: the conversion of a DC voltage bias into an AC supercurrent. This current may be used to activate mechanical oscillations in a suspended weak link. As the DC-voltage bias condition is remarkably difficult to achieve in experiments, here we analyze theoretically how the Josephson effect can be exploited to activate and detect mechanical oscillations in the experimentally relevant condition with purely DC current bias. We unveil how changing the strength of the electromechanical coupling results in two qualitatively different regimes showing dramatic effects of the oscillations on the DC-voltage characteristic of the device. These include the appearance of Shapiro-type plateaus for weak coupling and a sudden mechanically induced retrapping for strong coupling. Our predictions, measurable in state-of-the-art experimental setups, allow the determination of the frequency and quality factor of the resonator using DC only techniques.

  2. Coherent Cooper pair tunneling in systems of Josephson junctions: effects of quasiparticle tunneling and of the electromagnetic environment

    NARCIS (Netherlands)

    Maassen van den Brink, A.; Odintsov, A.A.; Bobbert, P.A.; Schön, G.

    1991-01-01

    Small capacitance tunnel junctions show single electron effects and, in the superconducting state, the coherent tunneling of Cooper pairs. We study these effects in a system of two Josephson junctions, driven by a voltage source with a finite impedance. Novel features show up in theI–V

  3. Theory of Josephson effect in d-wave superconductor/diffusive ferromagnet/d-wave superconductor junctions

    NARCIS (Netherlands)

    Yokoyama, T.; Tanaka, Y.; Golubov, Alexandre Avraamovitch

    2007-01-01

    We study Josephson effect in d-wave superconductor/diffusive ferromagnet/d-wave superconductor junctions, changing the exchange field and the angles between the normal to the interfaces and the crystal axes of d-wave superconductors. We find a 0–π transition at a certain value of the exchange field.

  4. Coherent oscillations between two weakly coupled Bose-Einstein condensates: Josephson effects, π oscillations, and macroscopic quantum self-trapping

    International Nuclear Information System (INIS)

    Raghavan, S.; Smerzi, A.; Fantoni, S.; Shenoy, S.R.

    2001-03-01

    We discuss the coherent atomic oscillations between two weakly coupled Bose-Einstein condensates. The weak link is provided by a laser barrier in a (possibly asymmetric) double-well trap or by Raman coupling between two condensates in different hyperfine levels. The boson Josephson junction (BJJ) dynamics is described by the two-mode nonlinear Gross-Pitaevskii equation that is solved analytically in terms of elliptic functions. The BJJ, being a neutral, isolated system, allows the investigations of dynamical regimes for the phase difference across the junction and for the population imbalance that are not accessible with superconductor Josephson junctions (SJJ's). These include oscillations with either or both of the following properties: (i) the time-averaged value of the phase is equal to π (π-phase oscillations); (ii) the average population imbalance is nonzero, in states with macroscopic quantum self-trapping. The (nonsinusoidal) generalization of the SJJ ac and plasma oscillations and the Shapiro resonance can also be observed. We predict the collapse of experimental data (corresponding to different trap geometries and the total number of condensate atoms) onto a single universal curve for the inverse period of oscillations. Analogies with Josephson oscillations between two weakly coupled reservoirs of 3 He-B and the internal Josephson effect in 3 He-A are also discussed. (author)

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

    International Nuclear Information System (INIS)

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

    1987-09-01

    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 thermal activation mechanism. The introduction of this effective conductance into the lifetime expression for the zero-voltage states leads to significant changes in the width of the switching current distributions. A comparisons of the experimental data with the proposed model is reported. 7 refs., 2 figs

  6. Effects of the phase periodicity on the quantum dynamics of a resistively shunted Josephson junction

    International Nuclear Information System (INIS)

    Zwerger, W.; Dorsey, A.T.; Fisher, M.P.A.

    1986-01-01

    A phenomenological model is introduced for the dissipative quantum dynamics of the phase phi across a current-biased Josephson junction. The model is invariant under phi→phi+2π. This enables us to restrict phi to the interval 0 to 2π, equating phi+2π with phi, and study the role played by the resulting nontrivial topology. Using Feynman's influence functional theory it is shown that the dissipation suppresses interference between paths with different winding numbers. For Ohmic dissipation this interference is completely destroyed, and phi can effectively be treated as an extended coordinate. This justifies the use of the usual washboard potential description of a current-biased junction even in the quantum case, provided an Ohmic dissipation mechanism is present

  7. Effect of single Abrikosov vortices on the properties of Josephson tunnel junctions

    International Nuclear Information System (INIS)

    Golubov, A.A.; Kupriyanov, M.Yu.

    1987-01-01

    The effect of single Abrikosov vortices, trapped in the electrodes of a Josephson tunnel junction perpendicularly to the junction surface, on the tunnel current through the junction is studied within the framework of the microscopic theory. The current-voltage characteristic and the critical junction current I c are calculated for temperatures 0 c . It is shown that if the vortices at the junction are misaligned, singularities on the current-voltage characteristic appear at eV Δ (T), and in some cases the magnitude of suppression of I c may be of the order of magnitude of I c itself. The temperature dependence of the critical current is calculated for the case of one of the electrodes being a two-dimensional superconducting film in which the creation of opposite sign vortex pairs is significant

  8. Annealing effect on the reproducibility of Josephson Junctions made by ion irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Sirena, M; Matzen, S; Bergeal, N; Lesueur, J [Laboratoire Photons Et Matiere, CNRS, ESPCI, 10 Rue Vauquelin 75231 Paris (France) (France); Faini, G [Laboratoire de Photonique et Nanostructures, Route de Nozay, 91460 Marcoussis (France) (France); Bernard, R; Briatico, J; Crete, D [UMR-CNRS/THALES, Route D128, 91767 Palaiseau (France) (France)], E-mail: martin.sirena@espci.fr

    2008-02-01

    We have studied the annealing effects on the transport properties of High Tc Josephson Junctions (JJ) made by ion irradiation. Several JJ were measured for different annealing times and the experimental data were compared to numerical simulations. We have successfully used a vacancy-interstitial annihilation mechanism to describe the evolution of the JJ coupling temperature (T{sub J}) and the homogeneity of a JJ array, related to the evolution of the defects density mean value and its distribution width. For sufficient long annealing times (t > 600 min), {delta}T{sub J} was significatively reduced. This result appears to be very encouraging for future applications where the spread in JJ characteristics has to be as low as possible.

  9. Annealing effect on the reproducibility of Josephson Junctions made by ion irradiation

    International Nuclear Information System (INIS)

    Sirena, M; Matzen, S; Bergeal, N; Lesueur, J; Faini, G; Bernard, R; Briatico, J; Crete, D

    2008-01-01

    We have studied the annealing effects on the transport properties of High Tc Josephson Junctions (JJ) made by ion irradiation. Several JJ were measured for different annealing times and the experimental data were compared to numerical simulations. We have successfully used a vacancy-interstitial annihilation mechanism to describe the evolution of the JJ coupling temperature (T J ) and the homogeneity of a JJ array, related to the evolution of the defects density mean value and its distribution width. For sufficient long annealing times (t > 600 min), ΔT J was significatively reduced. This result appears to be very encouraging for future applications where the spread in JJ characteristics has to be as low as possible

  10. Solitonic excitations in collisions of superfluid nuclei a qualitatively new phenomenon distinct from the Josephson effect

    Science.gov (United States)

    Sekizawa, Kazuyuki; Wlazłowski, Gabriel; Magierski, Piotr

    2017-11-01

    Recently, we have reported a novel role of pairing in low-energy heavy ion reactions at energies above the Coulomb barrier, which may have a detectable impact on reaction outcomes, such as the kinetic energy of fragments and the fusion cross section [arXiv:1611.10261, arXiv:1702.00069]. The phenomenon mimics the one studied experimentally with ultracold atomic gases, where two clouds of fermionic superfluids with different phases of the pairing fields are forced to merge, inducing various excitation modes of the pairing field. Although it originates from the phase difference of the pairing fields, the physics behind it is markedly different from the so-called Josephson effect. In this short contribution, we will briefly outline the results discussed in our recent papers and explain relations with the field of ultracold atomic gases.

  11. Signatures of granular superconductivity and Josephson effects in macroscopic measurements: the case of new superconductors

    Directory of Open Access Journals (Sweden)

    S Senoussi

    2006-09-01

    Full Text Available   We report systematic investigations of the magnetic superconducting properties of the new superconducting materials (NS: New high temperature superconductors (HTS, Organic superconductors (OS, fullerenes, carbon nanotubes, MgB2 etc. We show that, contrary to conventional superconductors where the superconducting state can be coherent over several tenths of km, the macroscopic coherence range lc of the NS is often as short as 0.1 to 10 µm typically. As a consequence, the magnetic properties are dominated by granular-like effects as well as Josephson coupling between grains. Here, we concentrate on HTS ceramics and organic superconductors exclusively. In the first case we observe three distinct regimes: (i At very low field (H < 5 Oe to say all the grains are coupled via Josephson effect and lc can be considered as infinite. (2 At intermediate field (5 < H < 50 Oe, typically the grains are gradually decoupled by H and/or T. (iii At higher fields all the grains are decoupled and lc roughly coincides with the diameter of the metallurgical grains. The case of OS is more subtle and is connected with a kind of order-disorder transition that occurs in most of them. For instance, in this study, we exploit quenched disorder (after crossing such a transition in the -(BEDT-TTF2Cu[N(CN2]Br layered organic superconductor to get new insights on both the superconducting state (T £ 11.6 K and the glassy transition at Tg, by studying the superconducting properties as functions of annealing time and annealing temperature around the glassy transition. Our main result is that the data can be described by a percolation molecular cluster model in which the topology and the growth of the molecular clusters obey an Ising spin-glass-like model with Tg ≈ 80 K for the hydrogenated compound and Tg ≈ 55 K for the fully deuterated one.

  12. Effective boundary field theory for a Josephson junction chain with a weak link

    International Nuclear Information System (INIS)

    Giuliano, Domenico; Sodano, Pasquale

    2005-01-01

    We show that a finite Josephson junction (JJ) chain, ending with two bulk superconductors, and with a weak link at its center, may be regarded as a condensed matter realization of a two-boundary sine-Gordon model. Computing the partition function yields a remarkable analytic expression for the DC Josephson current as a function of the phase difference across the chain. We show that, in a suitable range of the chain parameters, there is a crossover of the DC Josephson current from a sinusoidal to a sawtooth behavior, which signals a transition from a regime where the boundary term is an irrelevant operator to a regime where it becomes relevant

  13. Quantum ratchets, the orbital Josephson effect, and chaos in Bose-Einstein condensates

    Science.gov (United States)

    Carr, Lincoln D.; Heimsoth, Martin; Creffield, Charles E.; Sols, Fernando

    2014-03-01

    In a system of ac-driven condensed bosons we study a new type of Josephson effect occurring between states sharing the same region of space and the same internal atom structure. We first develop a technique to calculate the long-time dynamics of a driven interacting many-body system. For resonant frequencies, this dynamics can be shown to derive from an effective time-independent Hamiltonian which is expressed in terms of standard creation and annihilation operators. Within the subspace of resonant states, and if the undriven states are plane waves, a locally repulsive interaction between bosons translates into an effective attraction. We apply the method to study the effect of interactions on the coherent ratchet current of an asymmetrically driven boson system. We find a wealth of dynamical regimes which includes Rabi oscillations, self-trapping and chaotic behavior. In the latter case, a full quantum many-body calculation deviates from the mean-field results by predicting large quantum fluctuations of the relative particle number. Moreover, we find that chaos and entanglement, as defined by a variety of widely used and accepted measures, are overlapping but distinct notions. Funded by Spanish MINECO, the Ramon y Cajal program (CEC), the Comunidad de Madrid through Grant Microseres, the Heidelberg Center for Quantum Dynamics, and the NSF.

  14. Proximity effects and Josephson currents in ferromagnet. Spin-triplet superconductors junctions

    International Nuclear Information System (INIS)

    Terrade, Damien

    2015-01-01

    Spin-triplet superconductivity, first attached to the description of 3 He, is now generally considered to also occur in heavy-fermions compounds and in perovskite ruthenium oxide Sr 2 RuO 4 . The latter material is especially interesting since many experiments show strong evidences for a unitary chiral spin-triplet state. Moreover, the recent fabrication of thin heterostructures made of ferromagnetic SrRuO 3 on the top of Sr 2 RuO 4 strongly encourages new theoretical studies on the interplay between spin-triplet superconductor and ferromagnet in similar fashion to spin-singlet superconductors. Using an extended tight-binding Hamiltonian to model the superconductor, we discuss in this thesis the specific proximity effects of such interface by solving self-consistently the Bogoliubov-De Gennes equations on two- and three-dimensional lattices in the ballistic limit. We obtain the spatial profile of the superconducting order parameters at the interface as well as the spin-polarisation and the current across the Josephson junctions. In contrast to heterostructures made of spin-singlet superconductor, we show that the physical properties at the interface are not only controlled by the strength of the magnetization inside the ferromagnet but also by its orientation due to the existence of a finite pair spin projection of the spin-triplet Cooper pairs. We analyse in the first part the spin-polarisation and the Gibbs free energy at the three-dimensional ferromagnet-chiral spin-triplet superconductor interface. Then, the second part of the thesis is dedicated to the study of the Josephson junctions made of a chiral spin-triplet superconductor and a ferromagnetic barrier. More precisely, we analyse the existence of 0-π state transitions in two- and three-dimensional junctions with respect to the strength and the orientation of the magnetization. Finally, we study the proximity effects at the interface of helical spin-triplet superconductors. They differ from the chiral

  15. Josephson effect in Al/Bi{sub 2}Se{sub 3}/Al coplanar hybrid devices

    Energy Technology Data Exchange (ETDEWEB)

    Galletti, L., E-mail: luca.galletti@unina.it [Dipartimento di Scienze Fisiche, Università degli Studi di Napoli Federico II, I-80126 Napoli (Italy); CNR-SPIN Napoli, Complesso Universitario di Monte Sant’Angelo, 80126 Napoli (Italy); Charpentier, S. [Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-41296 Göteborg (Sweden); Lucignano, P.; Massarotti, D. [Dipartimento di Scienze Fisiche, Università degli Studi di Napoli Federico II, I-80126 Napoli (Italy); CNR-SPIN Napoli, Complesso Universitario di Monte Sant’Angelo, 80126 Napoli (Italy); Arpaia, R. [Dipartimento di Scienze Fisiche, Università degli Studi di Napoli Federico II, I-80126 Napoli (Italy); Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-41296 Göteborg (Sweden); Tafuri, F. [CNR-SPIN Napoli, Complesso Universitario di Monte Sant’Angelo, 80126 Napoli (Italy); Dipartimento di Ingegneria Industriale e dell’Informazione, Seconda Università di Napoli, I-81031 Aversa (CE) (Italy); Bauch, T. [Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-41296 Göteborg (Sweden); Suzuki, Y. [University of Tsukuba, Institute of Materials Science, Tsukuba 305, Ibaraki (Japan); Tagliacozzo, A. [Dipartimento di Scienze Fisiche, Università degli Studi di Napoli Federico II, I-80126 Napoli (Italy); Kadowaki, K. [University of Tsukuba, Institute of Materials Science, Tsukuba 305, Ibaraki (Japan); Lombardi, F. [Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-41296 Göteborg (Sweden)

    2014-08-15

    Highlights: • Superconducting proximity effect induced in Al/Bi{sub 2}Se{sub 3}/Al coplanar hybrid devices. • Comparative study of Al/Bi{sub 2}Se{sub 3} interfaces with various buffer layers. • Towards a Josephson super-current through the edge states of topological insulators. - Abstract: The edge states of Topological Insulators (TI) are protected against backscattering, thanks to the topological properties arising from their band structure. Coupling a TI to a superconductor (S) can induce unconventional effects, including the creation of Majorana bound states (MBS). The fabrication of coplanar hybrid devices is a fundamental step to pave the way to the understanding of proximity effects in topologically non-trivial systems, and to a large variety of experiments aimed at the possible detection of MBS. We discuss the feasibility and some relevant properties of Al–Bi{sub 2}Se{sub 3}–Al coplanar proximity devices. Special attention is devoted to the design of the junction, aimed at enhancing the coupling between the electrodes and the TI.

  16. Effect of parallel transport currents on the d-wave Josephson junction

    International Nuclear Information System (INIS)

    Rashedi, Gholamreza

    2009-01-01

    In this paper, the non-local mixing of coherent current states in d-wave superconducting banks is investigated. The superconducting banks are connected via a ballistic point contact. The banks have mis-orientation and phase difference. Furthermore, they are subjected to a tangential transport current along the ab plane of d-wave crystals and parallel to the interface between the superconductors. The effects of mis-orientation and external transport current on the current-phase relations and current distributions are the subjects of this paper. It is observed that, at values of phase difference close to 0, π and 2π, the current distribution may have a vortex-like form in the vicinity of the point contact. The current distribution of the above-mentioned junction between d-wave superconductors is totally different from the junction between s-wave superconductors. The interesting result which this study shows is that spontaneous and Josephson currents are observed for the case of φ = 0.

  17. Effect of exciton pairing on the stationary Josephson current in superconductor-semimetal-superconductor junctions

    International Nuclear Information System (INIS)

    Itskovich, I.F.; Shekhter, R.I.

    1983-01-01

    The effect of exciton pairing of charge carriers in a semimetal on the stationary Josephson current in superconductor-semimetal-superconductor junctions is considered. It is shown that the phase transition of the semimetal interlayer into an exciton dielectric state for T/sub γ/< T/sub c/ (T/sub γ/, T/sub c/ are the superconducting and exciton transition temperatures, respectively) is accompanied by a kink on the critical current j/sub c/ versus temperature curve at the point T = T/sub γ/. A sharp nonmonotonic temperature dependence of the reduced current j/sub c//j/sub c/0 (j/sub c/0 is the critical current at T/sub γ/ = 0) is also possible in the range T< T/sub γ/. At low temperatures T<< v/sub 1,2//d<< T/sub γ/ (v/sub 1,2/ are the Fermi velocities of the carriers in the semimetal, d is the thickness of the interlayer) the critical current of the superconductor-semimetal-superconductor junction is exponentially smaller than the current in the absence of exciton pairing

  18. Extended Josephson Relation and Abrikosov lattice deformation

    International Nuclear Information System (INIS)

    Matlock, Peter

    2012-01-01

    From the point of view of time-dependent Ginzburg Landau (TDGL) theory, a Josephson-like relation is derived for an Abrikosov vortex lattice accelerated and deformed by applied fields. Beginning with a review of the Josephson Relation derived from the two ingredients of a lattice-kinematics assumption in TDGL theory and gauge invariance, we extend the construction to accommodate a time-dependent applied magnetic field, a Floating-Kernel formulation of normal current, and finally lattice deformation due to the electric field and inertial effects of vortex-lattice motion. The resulting Josephson-like relation, which we call an Extended Josephson Relation, applies to a much wider set of experimental conditions than the original Josephson Relation, and is explicitly compatible with the considerations of TDGL theory.

  19. Josephson effect in superfluid helium 3 during flow through small hole

    International Nuclear Information System (INIS)

    Kopnin, N.B.

    1986-01-01

    The Josephson current flowing in helium 3 through a small hole near the critical temperature is calculated. In diffusion particle reflection from vessel walls the critical current is proportional to (T c -T) 2 , and in mirror reflection it is proportional to (T c -T)

  20. External magnetic field and self-field effects in stacked long Josephson junctions

    DEFF Research Database (Denmark)

    Carapella, G.; Costabile, G.; Mygind, Jesper

    1996-01-01

    We have fabricated and tested samples consisting of two long stacked Josephson junctions with direct access to the intermediate electrode, whose thickness is smaller than London penetration depth lambda(L). The electrodes are patterned so that the junctions can be independently biased in the over...

  1. Microstructure of Josephson junctions: Effect on supercurrent transport in YBCO grain boundary and barrier layer junctions

    International Nuclear Information System (INIS)

    Merkle, K.L.; Huang, Y.

    1998-01-01

    The electric transport of high-temperature superconductors, such as YBa 2 Cu 3 O 7-x (YBCO), can be strongly restricted by the presence of high-angle grain boundaries (GB). This weak-link behavior is governed by the macroscopic GB geometry and the microscopic grain boundary structure and composition at the atomic level. Whereas grain boundaries present a considerable impediment to high current applications of high T c materials, there is considerable commercial interest in exploiting the weak-link-nature of grain boundaries for the design of microelectronic devices, such as superconducting quantum interference devices (SQUIDs). The Josephson junctions which form the basis of this technology can also be formed by introducing artificial barriers into the superconductor. The authors have examined both types of Josephson junctions by EM techniques in an effort to understand the connection between microstructure/chemistry and electrical transport properties. This knowledge is a valuable resource for the design and production of improved devices

  2. Bond and flux-disorder effects on the superconductor-insulator transition of a honeycomb array of Josephson junctions

    Science.gov (United States)

    Granato, Enzo

    2018-05-01

    We study the effects of disorder on the zero-temperature quantum phase transition of a honeycomb array of Josephson junctions in a magnetic field with an average of fo flux quantum per plaquette. Bond disorder due to spatial variations in the Josephson couplings and magnetic flux disorder due to variations in the plaquette areas are considered. The model can describe the superconductor-insulator transition in ultra-thin films with a triangular pattern of nanoholes. Path integral Monte Carlo simulations of the equivalent (2 + 1)-dimensional classical model are used to study the critical behavior and estimate the universal resistivity at the transition. The results show that bond disorder leads to a rounding of the first-order phase transition for fo = 1 / 3 to a continuous transition. For integer fo, the decrease of the critical coupling parameter with flux disorder is significantly different from that of the same model defined on a square lattice. The results are compared with recent experimental observations on nanohole thin films with geometrical disorder and external magnetic field.

  3. Josephson junction arrays

    International Nuclear Information System (INIS)

    Bindslev Hansen, J.; Lindelof, P.E.

    1985-01-01

    In this review we intend to cover recent work involving arrays of Josephson junctions. The work on such arrays falls naturally into three main areas of interest: 1. Technical applications of Josephson junction arrays for high-frequency devices. 2. Experimental studies of 2-D model systems (Kosterlitz-Thouless phase transition, commensurate-incommensurate transition in frustrated (flux) lattices). 3. Investigations of phenomena associated with non-equilibrium superconductivity in and around Josephson junctions (with high current density). (orig./BUD)

  4. Quasiparticle Green's function theory of the Josephson effect in chiral p-wave superconductor/diffusive normal metal/chiral p-wave superconductor junctions

    NARCIS (Netherlands)

    Sawa, Y.; Yokoyama, T.; Tanaka, Y.; Golubov, Alexandre Avraamovitch

    2007-01-01

    We study the Josephson effect in chiral p-wave superconductor/diffusive normal metal (DN)/chiral p-wave superconductor (CP/DN/CP) junctions using quasiclassical Green's function formalism with proper boundary conditions. The px+ipy-wave symmetry of superconducting order parameter is chosen which is

  5. Theory of Josephson effect in Sr2RuO4/diffusive normal metal/Sr2RuO4 junctions

    NARCIS (Netherlands)

    Sawa, Y.; Yokoyama, T.; Tanaka, Y.; Golubov, Alexandre Avraamovitch

    2007-01-01

    We derive a generalized Nazarov’s boundary condition for diffusive normal metal (DN)/chiral p-wave superconductor (CP) interface including the macroscopic phase of the superconductor. The Josephson effect is studied in CP/DN/CP junctions solving the Usadel equations under the above boundary

  6. Fractional Solitons in Excitonic Josephson Junctions

    OpenAIRE

    Hsu, Ya-Fen; Su, Jung-Jung

    2015-01-01

    The Josephson effect is especially appealing to physicists because it reveals macroscopically the quantum order and phase. In excitonic bilayers the effect is even subtler due to the counterflow of supercurrent as well as the tunneling between layers (interlayer tunneling). Here we study, in a quantum Hall bilayer, the excitonic Josephson junction: a conjunct of two exciton condensates with a relative phase ? 0 applied. The system is mapped into a pseudospin ferromagnet then described numeric...

  7. Squeezed States in Josephson Junctions.

    Science.gov (United States)

    Hu, X.; Nori, F.

    1996-03-01

    We have studied quantum fluctuation properties of Josephson junctions in the limit of large Josephson coupling energy and small charging energy, when the eigenstates of the system can be treated as being nearly localized. We have considered(X. Hu and F. Nori, preprints.) a Josephson junction in a variety of situations, e.g., coupled to one or several of the following elements: a capacitor, an inductor (in a superconducting ring), and an applied current source. By solving an effective Shrödinger equation, we have obtained squeezed vacuum (coherent) states as the ground states of a ``free-oscillating'' (linearly-driven) Josephson junction, and calculated the uncertainties of its canonical momentum, charge, and coordinate, phase. We have also shown that the excited states of the various systems we consider are similar to the number states of a simple harmonic oscillator but with different fluctuation properties. Furthermore, we have obtained the time-evolution operators for these systems. These operators can make it easier to calculate the time-dependence of the expectation values and fluctuations of various quantities starting from an arbitrary initial state.

  8. Spatio-temporal effects in a perturbed Sine-Gordan system: A long Josephson junction

    International Nuclear Information System (INIS)

    Nana, L.; Crepin Kofane, T.

    2003-12-01

    A collective coordinate approach is applied to study chaotic responses induced by an applied driven signal on the long Josephson junction influenced by a constant dc-driven field. We derive a nonlinear equation for a collective variable of the breather and the Melnikov method is then used to demonstrate the existence of irregular behavior in breather-fluxon-antifluxon pair transitions. Additionally, numerical simulations show that the theoretical predictions are well reproduced. Results obtained using these perturbative analysis are in good agreement with numerical simulations of the dynamics of the junction. (author)

  9. Josephson junctions array resonators

    Energy Technology Data Exchange (ETDEWEB)

    Gargiulo, Oscar; Muppalla, Phani; Mirzaei, Iman; Kirchmair, Gerhard [Institute for Quantum Optics and Quantum Information, Innsbruck (Austria)

    2016-07-01

    We present an experimental analysis of the self- and cross-Kerr effect of extended plasma resonances in Josephson junction chains. The chain consists of 1600 individual junctions and we can measure quality factors in excess of 10000. The Kerr effect manifests itself as a frequency shift that depends linearly on the number of photons in a resonant mode. By changing the input power we are able to measure this frequency shift on a single mode (self-kerr). By changing the input power on another mode while measuring the same one, we are able to evaluate the cross-kerr effect. We can measure the cross-Kerr effect by probing the resonance frequency of one mode while exciting another mode of the array with a microwave drive.

  10. Radio-Frequency Illuminated Superconductive Disks: Reverse Josephson Effects and Implications for Precise Measuring of Proposed Gravity Effects

    Science.gov (United States)

    Noever, David A.; Koczor, Ronald J.

    1998-01-01

    We have previously reported results using a high precision gravimeter to probe local gravity changes in the neighborhood of large bulk-processed high-temperature superconductors. It have been indicated three essential components to achieve anomalous gravity effects, namely large, two-layer high-temperature YBCO superconductors, magnetic levitation and AC input in the form of radio-frequency (RF) electromagnetic fields. We report experiments on RF-illuminated (1-15 MHz) superconducting disks with corresponding gravity readings indicating an apparent increase in observed gravity of approximately 3-5 x l0(exp -5)cm/sq s, above and to the side of the superconductor. In this preliminary study, RF- illumination is achieved using a series of large radius (15 cm) spiral antenna with RF power inputs equal to or greater than 90 W. The observed gravitational modification range is significantly lower than the 2.1% gravity modification. The error analyses of thermal and electromagnetic interference in a magnetically shielded gravimeter with vacuum enclosures, Faraday cages and shielded instrument leads, are outlined both experimentally and theoretically. The nearly exact correspondence between the peak gravity effects reported and the well-known peak in AC resistance in superconductors (2-7 MHz, owing to reverse Josephson quantum effects) suggests that electrical resistance will arise in this frequency range and subsequently any trapped magnetic fields in the superconductor may disperse partially into the measuring instrument's local environment. Implications for propulsion initiatives and RF-heating in superconductors will be discussed.

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

    International Nuclear Information System (INIS)

    Clarke, J.; Devoret, M.H.; Martinis, J.; Esteve, D.

    1985-05-01

    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 make in situ measurements of the capacitance and resistance shunting the junction, including contributions from the complex impedance presented by the current leads. For the relatively large area junctions studied in these experiments, the external capacitive loading was relatively unimportant, but the damping was entirely dominated by the external resistance

  12. Phase synchronisation in mutually coupled chaotic Josephson junctions: Effect of asymmetry and incommensurate frequencies

    International Nuclear Information System (INIS)

    Al-Khawaja, S.

    2011-01-01

    In this paper, synchronising two coupled ratchet Josephson junctions subjected to a quasiperiodic field is achieved. In the limit of weak perturbation of irrational frequencies equal to the square root of the transcendental number π and for small damping parameters, phase locking occurs as the coupling between both junctions is increased. It turns out that the transition from non-synchronous to synchronous chaotic state does not involve attractors appearing and disappearing. The undertaken symmetry analysis of the system demonstrates the suppression of the massive phase fluctuations as the coupling rises, allowing chaos synchronisation between both junctions to take place. The calculations also reveal the persistence of the synchronous state for high coupling strengths, taking into consideration the symmetry particularity of the external drive and potential. (author)

  13. Phase Synchronisation in Mutually Coupled Chaotic Josephson Junctions: Effect of Asymmetry and Incommensurate Frequencies

    International Nuclear Information System (INIS)

    Sameer Al-Khawaja

    2010-01-01

    In this paper, synchronising two coupled ratchet Josephson junctions subjected to a quasiperiodic field is achieved. In the limit of weak perturbation of irrational frequencies equal to the square root of the transcendental number π and for small damping parameters, phase locking occurs as the coupling between both junctions is increased. It turns out that the transition from non-synchronous to synchronous chaotic state does not involve attractors appearing and disappearing. The undertaken symmetry analysis of the system demonstrates the suppression of the massive phase fluctuations as the coupling rises, allowing chaos synchronisation between both junctions to take place. The calculations also reveal the persistence of the synchronous state for high coupling strengths, taking into consideration the symmetry particularity of the external drive and potential. (author)

  14. Macroscopic weak superconductivity of an NXN Josephson junction array below the Kosterlitz-Thouless transition

    International Nuclear Information System (INIS)

    Shenoy, S.R.; Karlsruhe Univ.

    1983-07-01

    A two-dimensional NXN array of coupled Josephson junctions, each of size tau 0 and Josephson length lambdasub(JO)>>tau 0 , is shown to exhibit macroscopic weak superconductivity. The Josephson phase coherence here extends across the array, vanishing discontinuously at the Kosterlitz-Thouless transition temperature. The transverse size Ntau 0 must be smaller than a few times the effective Josephson screening length lambdasub(J)sup(eff) proportional to lambdasub(JO), for a sharp transition to be seen. (author)

  15. Shapiro and parametric resonances in coupled Josephson junctions

    International Nuclear Information System (INIS)

    Gaafar, Ma A; Shukrinov, Yu M; Foda, A

    2012-01-01

    The effect of microwave irradiation on the phase dynamics of intrinsic Josephson junctions in high temperature superconductors is investigated. We compare the current-voltage characteristics for a stack of coupled Josephson junctions under external irradiation calculated in the framework of CCJJ and CCJJ+DC models.

  16. Effect of quantum noise and tunneling on the fluctuational voltage-current characteristics and the lifetime of the zero-voltage state in Josephson junctions

    International Nuclear Information System (INIS)

    Mel'nikov, V.I.; Suetoe, A.

    1986-01-01

    The minima of the potential energy for the dynamical variable phi of a Josephson junction are separated by barriers of height hI/sub c//e, where I/sub c/ is the critical current. At low temperatures, T hΩ/2π (Ω is the Josephson plasma frequency). We consider this problem for high-quality junctions (RCΩ>>1, R and C are the resistance and the capacitance of the junction), accounting for the effect of a Johnson-Nyquist noise and quantum tunneling at the barrier top. With a simplifying assumption, we derive a pair of integral equations containing an energy variable for the steady-state distribution of phi and phi-dot, and solve it by a modification of the Wiener-Hopf method. The result is a formula for the current dependence of the fluctuational voltage, valid for currents I 2 <<1

  17. Modern aspects of Josephson dynamics and superconductivity electronics

    CERN Document Server

    Askerzade, Iman; Cantürk, Mehmet

    2017-01-01

    In this book new experimental investigations of properties of Josephson junctions and systems are explored with the help of recent developments in superconductivity. The theory of the Josephson effect is presented taking into account the influence of multiband and anisotropy effects in new superconducting compounds. Anharmonicity effects in current-phase relation on Josephson junctions dynamics are discussed. Recent studies in analogue and digital superconductivity electronics are presented. Topics of special interest include resistive single flux quantum logic in digital electronics. Application of Josephson junctions in quantum computing as superconducting quantum bits are analyzed. Particular attention is given to understanding chaotic behaviour of Josephson junctions and systems. The book is written for graduate students and researchers in the field of applied superconductivity.

  18. Coherent tunneling of Bose-Einstein condensates: Exact solutions for Josephson effects and macroscopic quantum self-trapping

    International Nuclear Information System (INIS)

    Raghavan, S.; Fantoni, S.; Shenoy, S.R.; Smerzi, A.

    1997-07-01

    We consider coherent atomic tunneling between two weakly coupled Bose-Einstein condensates (BEC) at T = 0 in (possibly asymmetric) double-well trap. The condensate dynamics of the macroscopic amplitudes in the two wells is modeled by two Gross-Pitaevskii equations (GPE) coupled by a tunneling matrix element. The evolution of the inter-well fractional population imbalance (related to the condensate phase difference) is obtained in terms of elliptic functions, generalizing well-known Josephson effects such as the 'ac' effect, the 'plasma oscillations', and the resonant Shapiro effect, to the nonsiusoidal regimes. We also present exact solutions for a novel 'macroscopic quantum self-trapping' effect arising from nonlinear atomic self-interaction in the GPE. The coherent BEC tunneling signatures are obtained in terms of the oscillations periods and the Fourier spectrum of the imbalance oscillations, as a function of the initial values of GPE parameters. Experimental procedures are suggested to make contact with theoretical predictions. (author). 44 refs, 8 figs

  19. Fractional Solitons in Excitonic Josephson Junctions

    Science.gov (United States)

    Su, Jung-Jung; Hsu, Ya-Fen

    The Josephson effect is especially appealing because it reveals macroscopically the quantum order and phase. Here we study this effect in an excitonic Josephson junction: a conjunct of two exciton condensates with a relative phase ϕ0 applied. Such a junction is proposed to take place in the quantum Hall bilayer (QHB) that makes it subtler than in superconductor because of the counterflow of excitonic supercurrent and the interlayer tunneling in QHB. We treat the system theoretically by first mapping it into a pseudospin ferromagnet then describing it by the Landau-Lifshitz-Gilbert equation. In the presence of interlayer tunneling, the excitonic Josephson junction can possess a family of fractional sine-Gordon solitons that resemble the static fractional Josephson vortices in the extended superconducting Josephson junctions. Interestingly, each fractional soliton carries a topological charge Q which is not necessarily a half/full integer but can vary continuously. The resultant current-phase relation (CPR) shows that solitons with Q =ϕ0 / 2 π are the lowest energy states for small ϕ0. When ϕ0 > π , solitons with Q =ϕ0 / 2 π - 1 take place - the polarity of CPR is then switched.

  20. Flux Cloning in Josephson Transmission Lines

    International Nuclear Information System (INIS)

    Gulevich, D.R.; Kusmartsev, F.V.

    2006-01-01

    We describe a novel effect related to the controlled birth of a single Josephson vortex. In this phenomenon, the vortex is created in a Josephson transmission line at a T-shaped junction. The 'baby' vortex arises at the moment when a 'mother' vortex propagating in the adjacent transmission line passes the T-shaped junction. In order to give birth to a new vortex, the mother vortex must have enough kinetic energy. Its motion can also be supported by an externally applied driving current. We determine the critical velocity and the critical driving current for the creation of the baby vortices and briefly discuss the potential applications of the found effect

  1. Stochasticity in the Josephson map

    International Nuclear Information System (INIS)

    Nomura, Y.; Ichikawa, Y.H.; Filippov, A.T.

    1996-04-01

    The Josephson map describes nonlinear dynamics of systems characterized by standard map with the uniform external bias superposed. The intricate structures of the phase space portrait of the Josephson map are examined on the basis of the tangent map associated with the Josephson map. Numerical observation of the stochastic diffusion in the Josephson map is examined in comparison with the renormalized diffusion coefficient calculated by the method of characteristic function. The global stochasticity of the Josephson map occurs at the values of far smaller stochastic parameter than the case of the standard map. (author)

  2. Josephson shift registers

    International Nuclear Information System (INIS)

    Przybysz, J.X.

    1989-01-01

    This paper gives a review of Josephson shift register circuits that were designed, fabricated, or tested, with emphasis on work in the 1980s. Operating speed is most important, since it often limits system performance. Older designs used square-wave clocks, but most modern designs use offset sine waves, with either two or three phases. Operating margins and gate bias uniformity are key concerns. The fastest measured Josephson shift register operated at 2.3 GHz, which compares well with a GaAs shift register that consumes 250 times more power. The difficulties of high-speed testing have prevented many Josephson shift registers from being operated at their highest speeds. Computer simulations suggest that 30-GHz operation is possible with current Nb/Al 2 O 3 /Nb technology. Junctions with critical current densities near 10 kA/cm 2 would make 100-GHz shift registers feasible

  3. Quasioptical Josephson oscillator

    International Nuclear Information System (INIS)

    Wengler, M.J.; Pance, A.; Liu, B.

    1991-01-01

    This paper discusses the authors' work with large 2-dimensional arrays of Josephson junctions for submillimeter power generation. The basic design of the Quasioptical Josephson Oscillator (QJO) is presented. The reasons for each design decision are discussed. Superconducting devices have not yet been fabricated, but scale models and computer simulations have been done. A method for characterizing array rf coupling structures is described, and initial results with this method are presented. Microwave scale models of the radiation structure are built and a series of measurements are made with a network analyzer

  4. Equivalent Josephson junctions

    International Nuclear Information System (INIS)

    Boyadzhiev, T.L.; ); Semerdzhieva, E.G.; Shukrinov, Yu.M.; Fiziko-Tekhnicheskij Inst., Dushanbe

    2008-01-01

    The magnetic field dependences of critical current are numerically constructed for a long Josephson junction with a shunt- or resistor-type microscopic inhomogeneities and compared to the critical curve of a junction with exponentially varying width. The numerical results show that it is possible to replace the distributed inhomogeneity of a long Josephson junction by an inhomogeneity localized at one of its ends, which has certain technological advantages. It is also shown that the critical curves of junctions with exponentially varying width and inhomogeneities localized at the ends are unaffected by the mixed fluxon-antifluxon distributions of the magnetic flux [ru

  5. Effects of c-axis Josephson coupling on dissipation, flux dynamics and the mechanism of high-Tc superconductivity

    International Nuclear Information System (INIS)

    Gray, K.E.; Hettinger, J.D.

    1995-01-01

    Measurements of the c-axis transport in highly anisotropic HTS materials strongly indicate that Josephson coupling is involved. This conclusion affects various properties of the HTS cuprates, including the irreversibility behavior for transport in the ab planes, the direct c-axis transport and potentially the mechanism of Cooper pairing

  6. Josephson junctions with ferromagnetic interlayer

    International Nuclear Information System (INIS)

    Wild, Georg Hermann

    2012-01-01

    We report on the fabrication of superconductor/insulator/ferromagnetic metal/superconductor (Nb/AlO x /Pd 0.82 Ni 0.18 /Nb) Josephson junctions (SIFS JJs) with high critical current densities, large normal resistance times area products, and high quality factors. For these junctions, a transition from 0- to π-coupling is observed for a thickness d F =6 nm of the ferromagnetic Pd 0.82 Ni 0.18 interlayer. The magnetic field dependence of the critical current of the junctions demonstrates good spatial homogeneity of the tunneling barrier and ferromagnetic interlayer. Magnetic characterization shows that the Pd 0.82 Ni 0.18 has an out-of-plane anisotropy and large saturation magnetization indicating negligible dead layers at the interfaces. A careful analysis of Fiske modes up to about 400 GHz provides valuable information on the junction quality factor and the relevant damping mechanisms. Whereas losses due to quasiparticle tunneling dominate at low frequencies, at high frequencies the damping is explained by the finite surface resistance of the junction electrodes. High quality factors of up to 30 around 200 GHz have been achieved. They allow to study the junction dynamics, in particular the switching probability from the zero-voltage into the voltage state with and without microwave irradiation. The experiments with microwave irradiation are well explained within semi-classical models and numerical simulations. In contrast, at mK temperature the switching dynamics without applied microwaves clearly shows secondary quantum effects. Here, we could observe for the first time macroscopic quantum tunneling in Josephson junctions with a ferromagnetic interlayer. This observation excludes fluctuations of the critical current as a consequence of an unstable magnetic domain structure of the ferromagnetic interlayer and affirms the suitability of SIFS Josephson junctions for quantum information processing.

  7. Josephson junctions with ferromagnetic interlayer

    Energy Technology Data Exchange (ETDEWEB)

    Wild, Georg Hermann

    2012-03-04

    We report on the fabrication of superconductor/insulator/ferromagnetic metal/superconductor (Nb/AlO{sub x}/Pd{sub 0.82}Ni{sub 0.18}/Nb) Josephson junctions (SIFS JJs) with high critical current densities, large normal resistance times area products, and high quality factors. For these junctions, a transition from 0- to {pi}-coupling is observed for a thickness d{sub F}=6 nm of the ferromagnetic Pd{sub 0.82}Ni{sub 0.18} interlayer. The magnetic field dependence of the critical current of the junctions demonstrates good spatial homogeneity of the tunneling barrier and ferromagnetic interlayer. Magnetic characterization shows that the Pd{sub 0.82}Ni{sub 0.18} has an out-of-plane anisotropy and large saturation magnetization indicating negligible dead layers at the interfaces. A careful analysis of Fiske modes up to about 400 GHz provides valuable information on the junction quality factor and the relevant damping mechanisms. Whereas losses due to quasiparticle tunneling dominate at low frequencies, at high frequencies the damping is explained by the finite surface resistance of the junction electrodes. High quality factors of up to 30 around 200 GHz have been achieved. They allow to study the junction dynamics, in particular the switching probability from the zero-voltage into the voltage state with and without microwave irradiation. The experiments with microwave irradiation are well explained within semi-classical models and numerical simulations. In contrast, at mK temperature the switching dynamics without applied microwaves clearly shows secondary quantum effects. Here, we could observe for the first time macroscopic quantum tunneling in Josephson junctions with a ferromagnetic interlayer. This observation excludes fluctuations of the critical current as a consequence of an unstable magnetic domain structure of the ferromagnetic interlayer and affirms the suitability of SIFS Josephson junctions for quantum information processing.

  8. Josephson junction spectrum analyzer for millimeter and submillimeter wavelengths

    International Nuclear Information System (INIS)

    Larkin, S.Y.; Anischenko, S.E.; Khabayev, P.V.

    1994-01-01

    A prototype of the Josephson-effect spectrum analyzer developed for the millimeter-wave band is described. The measurement results for spectra obtained in the frequency band from 50 to 250 GHz are presented

  9. Josephson junction spectrum analyzer for millimeter and submillimeter wavelengths

    Energy Technology Data Exchange (ETDEWEB)

    Larkin, S.Y.; Anischenko, S.E.; Khabayev, P.V. [State Research Center, Kiev (Ukraine)

    1994-12-31

    A prototype of the Josephson-effect spectrum analyzer developed for the millimeter-wave band is described. The measurement results for spectra obtained in the frequency band from 50 to 250 GHz are presented.

  10. HTSC-Josephson step contacts

    International Nuclear Information System (INIS)

    Herrmann, K.

    1994-03-01

    In this work the properties of josephson step contacts are investigated. After a short introduction into Josephson step contacts the structure, properties and the Josphson contacts of YBa 2 Cu 3 O 7-x high-T c superconductors is presented. The fabrication of HTSC step contacts and the microstructure is discussed. The electric properties of these contacts are measured together with the Josephson emission and the magnetic field dependence. The temperature dependence of the stationary transport properties is given. (WL)

  11. Fractional Josephson vortices in two-gap superconductor long Josephson junctions

    Science.gov (United States)

    Kim, Ju

    2014-03-01

    We investigated the phase dynamics of long Josephson junctions (LJJ) with two-gap superconductors in the broken time reversal symmetry state. In this LJJ, spatial phase textures (i-solitons) can be excited due to the presence of two condensates and the interband Joesphson effect between them. The presence of a spatial phase texture in each superconductor layer leads to a spatial variation of the critical current density between the superconductor layers. We find that this spatial dependence of the crtitical current density can self-generate magnetic flux in the insulator layer, resulting in Josephson vortices with fractional flux quanta. Similar to the situation in a YBa2 Cu3O7 - x superconductor film grain boundary, the fractionalization of a Josephson vortex arises as a response to either periodic or random excitation of i-solitions. This suggests that magnetic flux measurements may be used to probe i-soliton excitations in multi-gap superconductor LJJs.

  12. Curved Josephson junction

    International Nuclear Information System (INIS)

    Dobrowolski, Tomasz

    2012-01-01

    The constant curvature one and quasi-one dimensional Josephson junction is considered. On the base of Maxwell equations, the sine–Gordon equation that describes an influence of curvature on the kink motion was obtained. It is showed that the method of geometrical reduction of the sine–Gordon model from three to lower dimensional manifold leads to an identical form of the sine–Gordon equation. - Highlights: ► The research on dynamics of the phase in a curved Josephson junction is performed. ► The geometrical reduction is applied to the sine–Gordon model. ► The results of geometrical reduction and the fundamental research are compared.

  13. Electromagnetic waves in single- and multi-Josephson junctions

    International Nuclear Information System (INIS)

    Matsumoto, Hideki; Koyama, Tomio; Machida, Masahiko

    2008-01-01

    The terahertz wave emission from the intrinsic Josephson junctions is one of recent topics in high T c superconductors. We investigate, by numerical simulation, properties of the electromagnetic waves excited by a constant bias current in the single- and multi-Josephson junctions. Nonlinear equations of phase-differences are solved numerically by treating the effects of the outside electromagnetic fields as dynamical boundary conditions. It is shown that the emitted power of the electromagnetic wave can become large near certain retrapping points of the I-V characteristics. An instability of the inside phase oscillation is related to large amplitude of the oscillatory waves. In the single- (or homogeneous mutli-) Josephson junctions, electromagnetic oscillations can occur either in a form of standing waves (shorter junctions) or by formation of vortex-antivortex pairs (longer junctions). How these two effects affects the behavior of electromagnetic waves in the intrinsic Josephson junctions is discussed

  14. Josephson tunneling and nanosystems

    OpenAIRE

    Ovchinnikov, Yurii; Kresin, Vladimir

    2010-01-01

    Josephson tunneling between nanoclusters is analyzed. The discrete nature of the electronic energy spectra, including their shell ordering, is explicitly taken into account. The treatment considers the two distinct cases of resonant and non-resonant tunneling. It is demonstrated that the current density greatly exceeds the value discussed in the conventional theory. Nanoparticles are shown to be promising building blocks for nanomaterials-based tunneling networks.

  15. Modeling Bloch oscillations in ultra-small Josephson junctions

    Science.gov (United States)

    Vora, Heli; Kautz, Richard; Nam, Sae Woo; Aumentado, Jose

    In a seminal paper, Likharev et al. developed a theory for ultra-small Josephson junctions with Josephson coupling energy (Ej) less than the charging energy (Ec) and showed that such junctions demonstrate Bloch oscillations which could be used to make a fundamental current standard that is a dual of the Josephson volt standard. Here, based on the model of Geigenmüller and Schön, we numerically calculate the current-voltage relationship of such an ultra-small junction which includes various error processes present in a nanoscale Josephson junction such as random quasiparticle tunneling events and Zener tunneling between bands. This model allows us to explore the parameter space to see the effect of each process on the width and height of the Bloch step and serves as a guide to determine whether it is possible to build a quantum current standard of a metrological precision using Bloch oscillations.

  16. Magnetic properties of slablike Josephson-junction arrays

    International Nuclear Information System (INIS)

    Chen, D.; Sanchez, A.; Hernando, A.

    1994-01-01

    Magnetic properties of infinitely long and wide slablike Josephson-junction arrays (JJA's) consisting of 2N+1 rows of grains are calculated for the dc Josephson effect with gauge-invariant phase differences. When N is large, the intergranular magnetization curve, M J (H), of the JJA's in low fields approaches that of uniform Josephson junctions with lengths equal to the thicknesses of the JJA's, but in a larger field interval, its amplitude is dually modulated with periods determined by the junction and void areas. M J (H) curves for small N are more complicated. The concept of Josephson vortices and the application of the results to high-T c superconductors are discussed

  17. Transport properties of Josephson contacts with ferromagnetic tunnel barriers; Transporteigenschaften von Josephson-Kontakten mit ferromagnetischer Tunnelbarriere

    Energy Technology Data Exchange (ETDEWEB)

    Sprungmann, Dirk

    2010-01-28

    The combination of the Josephson and the proximity effect is possible by the introduction of a ferromagnetic barrier into a Josephson contact resulting in a so called π coupling. The supra current through these contacts is flowing in the reverse direction. Specific new electronic circuits such as phase shifting devices are possible, for instance for high-speed analog-digital transducers. In the frame of this thesis SIFS Josephson contacts were studied, with a barrier consisting of a thin insulating Al2Ox barrier layer and a ferromagnetic thin film. For the ferromagnetic material weak ferromagnetic Ni(0.6)Cu(0.4), the strong ferromagnetic Fe(0.25)Co(0.75) and the ternary Heusler alloys Co2MnSn and Cu2MnAl were used. Josephson contacts with π coupling were realized with the NiCu alloy, triplet superconductivity seems to appear with the Heusler systems.

  18. Influence of surface losses and the self-pumping effect on current-voltage characteristics of a long Josephson junction

    DEFF Research Database (Denmark)

    Pankratov, A.L.; Sobolev, A.S.; Koshelets, V.P.

    2007-01-01

    We have numerically investigated the dynamics of a long linear Josephson tunnel junction with overlap geometry. Biased by a direct current (dc) and an applied dc magnetic field, the junction has important applications as tunable high frequency oscillator [flux-flow oscillator (FFO......) placed at both ends of the FFO. In our model, the damping parameter depends both on the spatial coordinate and on the amplitude of the ac voltage. In order to find the dc current-voltage curves, the damping parameter has to be calculated self-consistently by successive approximations and time integration...

  19. Parity violation effects in the Josephson junction of a p-wave superconductor

    International Nuclear Information System (INIS)

    Belov, Nikolay A.; Harman, Zoltán

    2016-01-01

    The phenomenon of the parity violation due to weak interaction may be studied with superconducting systems. Previous research considered the case of conventional superconductors. We here theoretically investigate the parity violation effect in an unconventional p-wave ferromagnetic superconductor, and find that its magnitude can be increased by three orders of magnitude, as compared to results of earlier studies. For potential experimental observations, the superconductor UGe_2 is suggested, together with the description of a possible experimental scheme allowing one to effectively measure and control the phenomenon. Furthermore, we put forward a setup for a further significant enhancement of the signature of parity violation in the system considered.

  20. Thermally activated phase slippage in high-Tc grain-boundary Josephson junctions

    International Nuclear Information System (INIS)

    Gross, R.; Chaudhari, P.; Dimos, D.; Gupta, A.; Koren, G.

    1990-01-01

    The effect of thermally activated phase slippage (TAPS) in YBa 2 Cu 3 O 7 grain-boundary Josephson junctions has been studied. TAPS has been found to be responsible for the dc noise voltage superimposed on the dc Josephson current near the transition temperature. Because of the reduced Josephson coupling energy of the grain-boundary junctions, which is caused by a reduced superconducting order parameter at the grain-boundary interface, TAPS is present over a considerable temperature range. The implications of TAPS on the applicability of high-T c Josephson junctions are outlined

  1. Thermally activated phase slippage in high- T sub c grain-boundary Josephson junctions

    Energy Technology Data Exchange (ETDEWEB)

    Gross, R.; Chaudhari, P.; Dimos, D.; Gupta, A.; Koren, G. (IBM Thomas J. Watson Research Center, P.O. Box 218, Yorktown Heights, New York 10598 (USA))

    1990-01-08

    The effect of thermally activated phase slippage (TAPS) in YBa{sub 2}Cu{sub 3}O{sub 7} grain-boundary Josephson junctions has been studied. TAPS has been found to be responsible for the dc noise voltage superimposed on the dc Josephson current near the transition temperature. Because of the reduced Josephson coupling energy of the grain-boundary junctions, which is caused by a reduced superconducting order parameter at the grain-boundary interface, TAPS is present over a considerable temperature range. The implications of TAPS on the applicability of high-{ital T}{sub {ital c}} Josephson junctions are outlined.

  2. Josephson Metamaterial with a Widely Tunable Positive or Negative Kerr Constant

    Science.gov (United States)

    Zhang, Wenyuan; Huang, W.; Gershenson, M. E.; Bell, M. T.

    2017-11-01

    We report on the microwave characterization of a novel one-dimensional Josephson metamaterial composed of a chain of asymmetric superconducting quantum interference devices with nearest-neighbor coupling through common Josephson junctions. This metamaterial demonstrates a strong Kerr nonlinearity, with a Kerr constant tunable over a wide range, from positive to negative values, by a magnetic flux threading the superconducting quantum interference devices. The experimental results are in good agreement with the theory of nonlinear effects in Josephson chains. The metamaterial is very promising as an active medium for Josephson traveling-wave parametric amplifiers; its use facilitates phase matching in a four-wave-mixing process for efficient parametric gain.

  3. Resistive transition of two-dimensional arrays of proximity-effect Josephson junctions

    International Nuclear Information System (INIS)

    Abraham, D.W.

    1983-01-01

    Results of measurements on large arrays of PbBi/Cu proximity-effect junctions are presented. Extrapolation of the critical current measured at low temperature to the region at and above T/sub c/ allows us to describe the initial drop in resistance by a simple model of the proximity effect, and also to define an effective temperature T' = E/sub J/(T/sub c/)T/E/sub J/(T) for describing the vortex-unbinding transition. This extrapolation has also allowed comparison of the magnitude of the universal jump in the renormalized coupling strength E/sub J/(T) with prediction, after allowance for renormalization effects. A simple decomposition of the vortex population above T/sub c/ into a sum of thermally-generated and currents-split components allows us to compare data taken at finite voltage sensitivity with theory. This idea is used to understand the broadened universal scaling of this data in a form consistent with the theory of Halperin and Nelson, suitably modified for array samples. Except for temperatures very near the transition temperature, these results can differ significantly from the continuum results of Halperin and Nelson and may be more appropriate for description of junction arrays and some granular films. New experimental data are also presented which show a periodic variation of the resistance of these arrays with the magnetic flux per cell in units of the flux quantum, including a secondary minimum at the half-quantum points. A simple model is presented which accounts for the existence, shape, and magnitude of this periodic variation in terms of vortex core energies. Observations of the current dependence of this periodic variation are presented, and a qualitative model of this effect is discussed

  4. Influence of effective electron interaction on critical current of Josephson weak links

    International Nuclear Information System (INIS)

    Kupriyanov, M.Yu.; Likharev, K.K.; Lukichev, V.F.

    1981-01-01

    On the basis of microscopic theory of superconductivity, the dc Josphson effect in weak links of the type of variable thickness bridges or high ohmic interlayer sandwiches is studied. The Isub(C)Rsub(N) product is calculatied as a function of temperature T and weak link length L for various amplitudes and both signs of effective electron-electron interaction constant lambda. If the weak link material is superconducting with critical temperature Tsub(C) > 0 (lambda > 0), the maximum value of Isub(C)Rsub(N) product (under condition of the singlevalued Isub(S)(phi) relationship) can be achieved at L approx. <= 3xisup(*) when Tsub(C) approx. <= Tsub(CS)/2, and at L=(4 / 6)xisup(*) when Tsub(C) = Tsub(CS). Electron repulsion inside the weak link (lambda < 0) results in some reduction of the Isub(C)Rsub(N) product in comparison with the case of 'really normal' weak link material (lambda = 0). (orig.)

  5. Phase-dependent noise in Josephson junctions

    Science.gov (United States)

    Sheldon, Forrest; Peotta, Sebastiano; Di Ventra, Massimiliano

    2018-03-01

    In addition to the usual superconducting current, Josephson junctions (JJs) support a phase-dependent conductance related to the retardation effect of tunneling quasi-particles. This introduces a dissipative current with a memory-resistive (memristive) character that should also affect the current noise. By means of the microscopic theory of tunnel junctions we compute the complete current autocorrelation function of a Josephson tunnel junction and show that this memristive component gives rise to both a previously noted phase-dependent thermal noise, and an undescribed non-stationary, phase-dependent dynamic noise. As experiments are approaching ranges in which these effects may be observed, we examine the form and magnitude of these processes. Their phase dependence can be realized experimentally as a hysteresis effect and may be used to probe defects present in JJ based qubits and in other superconducting electronics applications.

  6. Effect of Abrikosov vortices on Josephson junction currents in high temperature superconductors

    International Nuclear Information System (INIS)

    Mitchell, E.; Mueller, K.-H.

    2000-01-01

    Full text: The current-carrying capacity of high temperature superconductors (HTS) is limited by the weak links which form between individual grains. We investigate the role of Abrikosov vortices (AV) and inhomogeneities at the intergrain boundary by examining the high magnetic field characteristics of HTS thin film grain boundary junctions. We model the effects of junction inhomogeneity, AV's and vortex pinning by solving the inhomogeneous London equation. The calculations show that both inhomogeneities and the presence of AV's improve the current-carrying capacity across grain boundaries at high magnetic fields. Our experimental measurements of the irreversibility of the junction critical current density J c (H a ) find good agreement with the model

  7. Tunable Nitride Josephson Junctions.

    Energy Technology Data Exchange (ETDEWEB)

    Missert, Nancy A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Henry, Michael David [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Lewis, Rupert M. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Howell, Stephen W. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Wolfley, Steven L. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Brunke, Lyle Brent [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Wolak, Matthaeus [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2017-12-01

    We have developed an ambient temperature, SiO2/Si wafer - scale process for Josephson junctions based on Nb electrodes and Ta x N barriers with tunable electronic properties. The films are fabricated by magnetron sputtering. The electronic properties of the TaxN barriers are controlled by adjusting the nitrogen flow during sputtering. This technology offers a scalable alternative to the more traditional junctions based on AlOx barriers for low - power, high - performance computing.

  8. Accurate Control of Josephson Phase Qubits

    Science.gov (United States)

    2016-04-14

    for Bits and Atoms and Department of Physics, MIT, Cambridge , Massachusetts 02139, USA 2Solid State and Photonics Laboratory, Stanford University...computing to simulate tun- neling effects in Josephson junction qubits, illustrating how quantum computing is useful in modeling and simulating the...Computation and Quantum Information ~ Cambridge University Press, Cambridge , 2000!. 2 J. I. Cirac and P. Zoller, Phys. Rev. Lett. 74, 4091 ~1995!. 3 Y

  9. Phase-locked Josephson soliton oscillators

    DEFF Research Database (Denmark)

    Holst, T.; Hansen, Jørn Bindslev; Grønbech-Jensen, N.

    1991-01-01

    Detailed experimental characterization of the phase-locking at both DC and at microwave frequencies is presented for two closely spaced Josephson soliton (fluxon) oscillators. In the phase-locked state, the radiated microwave power exhibited an effective gain. With one common bias source......, a frequency tunability of the phase-locked oscillators up to 7% at 10 GHz was observed. The interacting soliton oscillators were modeled by two inductively coupled nonlinear transmission lines...

  10. Distributed amplifier using Josephson vortex flow transistors

    International Nuclear Information System (INIS)

    McGinnis, D.P.; Beyer, J.B.; Nordman, J.E.

    1986-01-01

    A wide-band traveling wave amplifier using vortex flow transistors is proposed. A vortex flow transistor is a long Josephson junction used as a current controlled voltage source. The dual nature of this device to the field effect transistor is exploited. A circuit model of this device is proposed and a distributed amplifier utilizing 50 vortex flow transistors is predicted to have useful gain to 100 GHz

  11. Restored symmetries, quark puzzle, and the Pomeron as a Josephson current. [Clustering effects, quantum supercurrents, cross sections, phase transitions, narrowing gap mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Mendes, R V [Instituto de Fisica e Matematica, Lisbon (Portugal)

    1976-07-01

    A special type of symmetry is studied, wherein manifest invariance is restored by direct integration over a set of spontaneously broken ground states. In addition to invariant states and multiplets these symmetry realizations are shown to lead, in general, to clustering effects and quantum supercurrents. A systematic exploration of these symmetry realizations is proposed, mostly in physical situations where it has so far been believed that the only consequences of the symmetry are invariant states and multiplets. An application of these ideas to the quark system yields a possible explanation for the unobservability of free quarks and an interpretation of the Pomeron as a generalized Josephson current. Furthermore, the 'narrowing gap mechanism' suggests an explanation for the behavior of the e/sup +/ e/sup -/ ..-->.. hadrons cross section and a speculation on an approaching phase transition in hadronic production and the observation of free quarks.

  12. Josephson comparator switching time

    Energy Technology Data Exchange (ETDEWEB)

    Herr, Quentin P; Miller, Donald L; Przybysz, John X [Northrop Grumman, Baltimore, MD (United States)

    2006-05-15

    Comparator performance can be characterized in terms of both sensitivity and decision time. Delta-sigma analogue-to-digital converters are tolerant of sensitivity errors but require short decision time due to feedback. We have analysed the Josephson comparator using the numerical solution of the Fokker-Planck equation, which describes the time evolution of the ensemble probability distribution. At balance, the result is essentially independent of temperature in the range 5-20 K. There is a very small probability, 1 x 10{sup -14}, that the decision time will be longer than seven single-flux-quantum pulse widths, defined as Phi{sub 0}/(I{sub c}R{sub n}). For junctions with a critical current density of 4.5 kA, this decision time is only 20 ps. Decision time error probability decreases rapidly with lengthening time interval, at a rate of two orders of magnitude per pulse width. We conclude that Josephson comparator performance is quite favourable for analogue-to-digital converter applications.

  13. Fractional flux quanta in Josephson junctions

    Energy Technology Data Exchange (ETDEWEB)

    Goldobin, E.; Buckenmaier, K.; Gaber, T.; Kemmler, M.; Pfeiffer, J.; Koelle, D.; Kleiner, R. [Physikalisches Inst. - Experimentalphysik II, Univ. Tuebingen (Germany); Weides, M.; Kohlstedt, H. [Center of Nanoelectronic Systems for Information Technology (CNI), Research Centre Juelich (Germany); Siegel, M. [Inst. fuer Mikro- und Nanoelektronische Systeme, Univ. Karlsruhe (Germany)

    2007-07-01

    Fractional Josephson vortices may appear in the so-called 0-{kappa} Josephson junctions ({kappa} is an arbitrary number) and carry magnetic flux {phi}, which is a fraction of the magnetic flux quantum {phi}{sub 0}{approx}2.07 x 10{sup -15} Wb. Their properties are very different from the usual integer fluxons: they are pinned, and often represent the ground state of the system with spontaneous circulating supercurrent. They behave as well controlled macroscopic spins and can be used to construct bits, qubits, tunable photonic crystals and to study the (quantum) physics of spin systems. In this talk we discuss recent advances in 0-{pi} junction technology and present recent experimental results: evidence of the spontaneous flux in the ground state, spectroscopy of the fractional vortex eigenfrequencies and observation of dynamics effects related to the flipping of the fractional vortices. (orig.)

  14. Improving nuclear regulatory effectiveness

    International Nuclear Information System (INIS)

    2001-01-01

    Ensuring that nuclear installations are operated and maintained in such a way that their impact on public health and safety is as low as reasonably practicable has been and will continue to be the cornerstone of nuclear regulation. In the past, nuclear incidents provided the main impetus for regulatory change. Today, economic factors, deregulation, technological advancements, government oversight and the general requirements for openness and accountability are leading regulatory bodies to review their effectiveness. In addition, seeking to enhance the present level of nuclear safety by continuously improving the effectiveness of regulatory bodies is seen as one of the ways to strengthen public confidence in the regulatory systems. This report covers the basic concepts underlying nuclear regulatory effectiveness, advances being made and future requirements. The intended audience is primarily nuclear safety regulators, but government authorities, nuclear power plant operators and the general public may also be interested. (author)

  15. Josephson plasma resonance in vortex filament state of high temperature superconductors

    International Nuclear Information System (INIS)

    Matsuda, Yuji; Gaifullin, M.B.

    1996-01-01

    High temperature superconductors have the crystalline structure in which two-dimensional CuO 2 planes are piled in layers, consequently, the anisotropy of electroconductivity arises, and this brings about stable and low energy Josephson plasma in superconducting state. Also as to the vortex filament state of high temperature superconductors, the effect of thermal fluctuation due to low dimensionality, short coherence length and high transition temperature becomes conspicuous. In reality, these plasma and vortex filament state are related closely. Light reflection and plasma edge in superconducting state, Josephson plasma resonance in the vortex filament state of BiO 2 Sr 2 CaCu 2 O 8+δ , the plasma vibration in Josephson junction, Josephson plasma in magnetic field, Josephson plasma in the liquid state of vortex filament, Josephson plasma in the solid state of vortex filament, and Josephson plasma in parallel magnetic field are reported. The Josephson plasma resonance is the experimental means for exploring vortex filament state from microscopic standpoint, and its development hereafter is expected. (K.I.)

  16. Manufacturing technology for practical Josephson voltage normals

    International Nuclear Information System (INIS)

    Kohlmann, Johannes; Kieler, Oliver

    2016-01-01

    In this contribution we present the manufacturing technology for the fabrication of integrated superconducting Josephson serial circuits for voltage normals. First we summarize some foundations for Josephson voltage normals and sketch the concept and the setup of the circuits, before we describe the manufacturing technology form modern practical Josephson voltage normals.

  17. Observation of supercurrent in graphene-based Josephson junction

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Libin; Li, Sen; Kang, Ning [Key Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics, Peking University, Beijing 100871 (China); Xu, Chuan; Ren, Wencai [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China)

    2015-07-01

    Josephson junctions with a normal metal region sandwiched between two superconductors (S) are known as superconductor- normal-superconductor (SNS) structures. It has attracted significant attention especially when changing the normal metal with graphene, which allow for high tunability with the gate voltage and to study the proximity effect of the massless Dirac fermions. Here we report our work on graphene-based Josephson junction with a new two dimensional superconductor crystal, which grown directly on graphene, as superconducting electrodes. At low temperature, we observer proximity effect induced supercurrent flowing through the junction. The temperature and the magnetic field dependences of the critical current characteristics of the junction are also studied. The critical current exhibits a Fraunhofer-type diffraction pattern against magnetic field. Our experiments provided a new route of fabrication of graphene-based Josephson junction.

  18. Planar Josephson tunnel junctions in a transverse magnetic field

    DEFF Research Database (Denmark)

    Monacoa, R.; Aarøe, Morten; Mygind, Jesper

    2007-01-01

    demagnetization effects imposed by the tunnel barrier and electrodes geometry are important. Measurements of the junction critical current versus magnetic field in planar Nb-based high-quality junctions with different geometry, size, and critical current density show that it is advantageous to use a transverse......Traditionally, since the discovery of the Josephson effect in 1962, the magnetic diffraction pattern of planar Josephson tunnel junctions has been recorded with the field applied in the plane of the junction. Here we discuss the static junction properties in a transverse magnetic field where...

  19. A nanoscale gigahertz source realized with Josephson scanning tunneling microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Jäck, Berthold, E-mail: b.jaeck@fkf.mpg.de; Eltschka, Matthias; Assig, Maximilian; Etzkorn, Markus; Ast, Christian R. [Max-Planck-Institut für Festkörperforschung, 70569 Stuttgart (Germany); Hardock, Andreas [Institut für Theoretische Elektrotechnik, Technische Universität Hamburg-Harburg, 21079 Hamburg (Germany); Kern, Klaus [Max-Planck-Institut für Festkörperforschung, 70569 Stuttgart (Germany); Institut de Physique de la Matière Condensée, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne (Switzerland)

    2015-01-05

    Using the AC Josephson effect in the superconductor-vacuum-superconductor tunnel junction of a scanning tunneling microscope (STM), we demonstrate the generation of GHz radiation. With the macroscopic STM tip acting as a λ/4-monopole antenna, we first show that the atomic scale Josephson junction in the STM is sensitive to its frequency-dependent environmental impedance in the GHz regime. Further, enhancing Cooper pair tunneling via excitations of the tip eigenmodes, we are able to generate high-frequency radiation. We find that for vanadium junctions, the enhanced photon emission can be tuned from about 25 GHz to 200 GHz and that large photon flux in excess of 10{sup 20 }cm{sup −2} s{sup −1} is reached in the tunnel junction. These findings demonstrate that the atomic scale Josephson junction in an STM can be employed as a full spectroscopic tool for GHz frequencies on the atomic scale.

  20. Microwave oscillator using arrays of long Josephson junctions

    International Nuclear Information System (INIS)

    Pagano, S.; Monaco, R.; Costabile, G.

    1989-01-01

    The authors report on measurements performed on integrated superconducting devices based on arrays of long Josephson tunnel junctions operating in the resonant fluxon oscillation regime (i.e. biased on the Zero Field Steps). The electromagnetic coupling among the junction causes a mutual phase-locking of the fluxon oscillations with a corresponding increase of the emitted power and a decrease of the signal linewidth. This phase-locked state can be controlled by means of an external dc bias current and magnetic field. The effect of the generated microwave signal has been observed on a small Josephson tunnel junction coupled to the array via a microstrip transmission line. The feasibility of the reported devices as local oscillators in an integrated microwave Josephson receiver is discussed

  1. Implementation of the Grover search algorithm with Josephson charge qubits

    International Nuclear Information System (INIS)

    Zheng Xiaohu; Dong Ping; Xue Zhengyuan; Cao Zhuoliang

    2007-01-01

    A scheme of implementing the Grover search algorithm based on Josephson charge qubits has been proposed, which would be a key step to scale more complex quantum algorithms and very important for constructing a real quantum computer via Josephson charge qubits. The present scheme is simple but fairly efficient, and easily manipulated because any two-charge-qubit can be selectively and effectively coupled by a common inductance. More manipulations can be carried out before decoherence sets in. Our scheme can be realized within the current technology

  2. Microwave Josephson generation in thin film superconducting bridges

    International Nuclear Information System (INIS)

    Gubankov, V.N.; Koshelets, V.P.; Ovsyannikov, G.A.

    1975-01-01

    Thin-film bridges have some advantage over other types of superconducting weak links: good definition of electromagnetic parameters and of weak region geometry. Up to now Josephson properties of bridges have been investigated by using indirect methods (the effect of magnetic field on the critical current I 0 , the bridge behavior in a microwave field, etc.). Direct experimental observation of Josephson radiation from autonomous thin film bridges is reported. Microwave radiation in tin bridges of 'variable' thickness has been investigated where the thickness of the film forming the bridge is far less than the thickness of the bank films. (Auth.)

  3. Fluxon dynamics in long annular Josephson tunnel junctions

    DEFF Research Database (Denmark)

    Martucciello, N.; Mygind, Jesper; Koshelets, V.P.

    1998-01-01

    Single-fluxon dynamics has been experimentally investigated in high-quality Nb/Al-AlOx/Nb annular Josephson tunnel junctions having a radius much larger than the Josephson penetration depth. Strong evidence of self-field effects is observed. An external magnetic field in the barrier plane acts...... on the fluxon as a periodic potential and lowers its average speed. Further, the results of perturbative calculations do not fit the experimental current-voltage profile and, provided the temperature is low enough, this profile systematically shows pronounced deviations from the smooth predicted form...

  4. Gravitation at the Josephson Junction

    Directory of Open Access Journals (Sweden)

    Victor Atanasov

    2018-01-01

    Full Text Available A geometric potential from the kinetic term of a constrained to a curved hyperplane of space-time quantum superconducting condensate is derived. An energy conservation relation involving the geometric field at every material point in the superconductor is demonstrated. At a Josephson junction the energy conservation relation implies the possibility of transforming electric energy into geometric field energy, that is, curvature of space-time. Experimental procedures to verify that the Josephson junction can act as a voltage-to-curvature converter are discussed.

  5. Josephson junctions with ferromagnetic alloy interlayer

    Energy Technology Data Exchange (ETDEWEB)

    Himmel, Nico

    2015-07-23

    Josephson junctions are used as active devices in superconducting electronics and quantum information technology. Outstanding properties are their distinct non-linear electrical characteristics and a usually sinusoidal relation between the current and the superconducting phase difference across the junction. In general the insertion of ferromagnetic material in the barrier of a Josephson junction is associated with a suppression of superconducting correlations. But also new phenomena can arise which may allow new circuit layouts and enhance the performance of applications. This thesis presents a systematic investigation for two concepts to fabricate Josephson junctions with a rather uncommon negative critical current. Such devices exhibit an intrinsic phase slip of π between the electrodes, so they are also known as π junctions. Both studies go well beyond existing experiments and in one system a π junction is shown for the first time. All the thin film junctions are based on superconducting Nb electrodes. In a first approach, barriers made from Si and Fe were investigated with respect to the realisation of π junctions by spin-flip processes. The distribution of Fe in the Si matrix was varied from pure layers to disperse compounds. The systematic fabrication of alloy barriers was facilitated by the development of a novel timing-based combinatorial sputtering technique for planetary deposition systems. An orthogonal gradient approach allowed to create binary layer libraries with independent variations of thickness and composition. Second, Nb vertical stroke AlO{sub x} vertical stroke Nb vertical stroke Ni{sub 60}Cu{sub 40} vertical stroke Nb (SIsFS) double barrier junctions were experimentally studied for the occurrence of proximity effect induced order parameter oscillations. Detailed dependencies of the critical current density on the thickness of s-layer and F-layer were acquired and show a remarkable agreement to existing theoretical predictions. Especially

  6. Josephson junctions with ferromagnetic alloy interlayer

    International Nuclear Information System (INIS)

    Himmel, Nico

    2015-01-01

    Josephson junctions are used as active devices in superconducting electronics and quantum information technology. Outstanding properties are their distinct non-linear electrical characteristics and a usually sinusoidal relation between the current and the superconducting phase difference across the junction. In general the insertion of ferromagnetic material in the barrier of a Josephson junction is associated with a suppression of superconducting correlations. But also new phenomena can arise which may allow new circuit layouts and enhance the performance of applications. This thesis presents a systematic investigation for two concepts to fabricate Josephson junctions with a rather uncommon negative critical current. Such devices exhibit an intrinsic phase slip of π between the electrodes, so they are also known as π junctions. Both studies go well beyond existing experiments and in one system a π junction is shown for the first time. All the thin film junctions are based on superconducting Nb electrodes. In a first approach, barriers made from Si and Fe were investigated with respect to the realisation of π junctions by spin-flip processes. The distribution of Fe in the Si matrix was varied from pure layers to disperse compounds. The systematic fabrication of alloy barriers was facilitated by the development of a novel timing-based combinatorial sputtering technique for planetary deposition systems. An orthogonal gradient approach allowed to create binary layer libraries with independent variations of thickness and composition. Second, Nb vertical stroke AlO x vertical stroke Nb vertical stroke Ni 60 Cu 40 vertical stroke Nb (SIsFS) double barrier junctions were experimentally studied for the occurrence of proximity effect induced order parameter oscillations. Detailed dependencies of the critical current density on the thickness of s-layer and F-layer were acquired and show a remarkable agreement to existing theoretical predictions. Especially a variation of

  7. Linewidth of Josephson oscillations in YBa2Cu3O7-x grain-boundary junctions

    DEFF Research Database (Denmark)

    Divin, Yu. Ya.; Mygind, Jesper; Pedersen, Niels Falsig

    1993-01-01

    The AC Josephson effect in YBa2Cu3O7-x grain-boundary junctions (GBJs) was studied in the temperature range from 4 K to 90 K. The temperature dependence of the linewidth of millimeter-wave Josephson oscillations was measured, and it is shown that the derived effective noise temperature of GBJ mig...... Josephson oscillations observed at 77 K was equal to 380 MHz, which demonstrates the applicability of GBJ, particularly in the field of radiation spectroscopy, even at liquid nitrogen temperatures...

  8. Josephson junctions of multiple superconducting wires

    Science.gov (United States)

    Deb, Oindrila; Sengupta, K.; Sen, Diptiman

    2018-05-01

    We study the spectrum of Andreev bound states and Josephson currents across a junction of N superconducting wires which may have s - or p -wave pairing symmetries and develop a scattering matrix based formalism which allows us to address transport across such junctions. For N ≥3 , it is well known that Berry curvature terms contribute to the Josephson currents; we chart out situations where such terms can have relatively large effects. For a system of three s -wave or three p -wave superconductors, we provide analytic expressions for the Andreev bound-state energies and study the Josephson currents in response to a constant voltage applied across one of the wires; we find that the integrated transconductance at zero temperature is quantized to integer multiples of 4 e2/h , where e is the electron charge and h =2 π ℏ is Planck's constant. For a sinusoidal current with frequency ω applied across one of the wires in the junction, we find that Shapiro plateaus appear in the time-averaged voltage across that wire for any rational fractional multiple (in contrast to only integer multiples in junctions of two wires) of 2 e /(ℏ ω ) . We also use our formalism to study junctions of two p -wave and one s -wave wires. We find that the corresponding Andreev bound-state energies depend on the spin of the Bogoliubov quasiparticles; this produces a net magnetic moment in such junctions. The time variation of these magnetic moments may be controlled by an external voltage applied across the junction. We discuss experiments which may test our theory.

  9. Chaos controlling problems for circuit systems with Josephson junction

    International Nuclear Information System (INIS)

    Gou, X-F; Wang, X; Xie, J-L

    2008-01-01

    The complex dynamical characters of the Josephson junction circuit system are studied and the tunnel effect is considered. The dynamical equation of the system is established. The route from periodic motion to chaos is illustrated using bifurcation diagram. An adscititious coupling controller is constructed to control the chaos

  10. Micromagnetic modeling of critical current oscillations in magnetic Josephson junctions

    NARCIS (Netherlands)

    golovchanskiy, I.A.; Bol'ginov, V.V.; Stolyarov, V.S.; Abramov, N.N.; Ben Hamida, A.; Emelyanova, O.V.; Stolyarov, B.S.; Kupriyanov, M..Y.; Golubov, Alexandre Avraamovitch; Ryazanov, V.V.

    2016-01-01

    In this work we propose and explore an effective numerical approach for investigation of critical current dependence on applied magnetic field for magnetic Josephson junctions with in-plane magnetization orientation. This approach is based on micromagnetic simulation of the magnetization reversal

  11. Josephson current at atomic scale: Tunneling and nanocontacts using a STM

    International Nuclear Information System (INIS)

    Rodrigo, J.G.; Crespo, V.; Vieira, S.

    2006-01-01

    Using a scanning tunneling microscope, STM, with a superconducting tip, we have measured the Josephson current in atomic size tunnel junctions and contacts with a small number of quantum channels of conduction. We analyze our results in terms of the Ivanchenko and Zil'berman model for phase diffusion. The effect of the thermal energy and the electromagnetic environment on the Josephson current is discussed in terms of the transmissions of the individual quantum channels. These results suppose an initial step to the control of Scanning Josephson Spectroscopy at atomic level

  12. Propagation and generation of Josephson radiation in superconductor/insulator superlattices

    International Nuclear Information System (INIS)

    Auvil, P.R.; Ketterson, J.B.

    1987-01-01

    The wave propagation and generation characteristics of a metal-insulator superlattice are calculated in a low-field Landau--Ginzburg model, including Josephson coupling through the insulating layers. It is shown that a significant increase in the phase velocity of the electromagnetic waves propagating in the superlattice occurs when the thickness of the superconducting layers becomes much less than the London penetration depth, suggesting that increased output of Josephson radiation may be achieved from such structures. Wave generation via the ac Josephson effect (in the presence of applied dc electric and magnetic fields) is studied for both parallel and series driven multilayer structures

  13. Manufacturing technology for practical Josephson voltage normals; Fertigungstechnologie fuer praxistaugliche Josephson-Spannungsnormale

    Energy Technology Data Exchange (ETDEWEB)

    Kohlmann, Johannes; Kieler, Oliver [Physikalisch-Technische Bundesanstalt (PTB), Braunschweig (Germany). Arbeitsgruppe 2.43 ' ' Josephson-Schaltungen' '

    2016-09-15

    In this contribution we present the manufacturing technology for the fabrication of integrated superconducting Josephson serial circuits for voltage normals. First we summarize some foundations for Josephson voltage normals and sketch the concept and the setup of the circuits, before we describe the manufacturing technology form modern practical Josephson voltage normals.

  14. Logic design of Josephson network. II

    International Nuclear Information System (INIS)

    Nakajima, K.; Onodera, Y.

    1978-01-01

    By numerical calculations of the differential-difference sine-Gordon equation, we have discussed the discrete Josephson-junction transmission lines which are constructed of a series of small-area Josephson junctions connected by superconducting strips. It is shown that the discrete Josephson lines containing D lines, N lines, T turning points, and S turning points are elementarily characterized by the discreteness parameter (2πLI/sub c//Phi 0 )/sup 1/2/. On the discrete Josephson logic circuits there exists a region of forbidden propagation in the (2πLI/sub c//Phi 0 )/sup 1/2/-γ (bias-current parameter) plane for single flux quanta. A single flux quantum can be stuffed in a small area of the discrete Josephson logic circuits. The discrete circuits can be conveniently and easily linked to each other, in a practical fabrication of a Josephson network

  15. Influence of thermal fluctuations on Cherenkov radiation from fluxons in dissipative Josephson systems

    DEFF Research Database (Denmark)

    Antonov, A. A.; Pankratov, A. L.; Yulin, A. V.

    2000-01-01

    The nonlinear dynamics of fluxons in Josephson systems with dispersion and thermal fluctuations is analyzed using the "quasiparticle" approach to investigate the influence of noise on the Cherenkov radiation effect. Analytical expressions for the stationary amplitude of the emitted radiation...

  16. Vertical Josephson Interferometer for Tunable Flux Qubit

    Energy Technology Data Exchange (ETDEWEB)

    Granata, C [Istituto di Cibernetica ' E. Caianiello' del Consiglio Nazionale delle Ricerche, I- 80078, Pozzuoli (Italy); Vettoliere, A [Istituto di Cibernetica ' E. Caianiello' del Consiglio Nazionale delle Ricerche, I- 80078, Pozzuoli (Italy); Lisitskiy, M [Istituto di Cibernetica ' E. Caianiello' del Consiglio Nazionale delle Ricerche, I- 80078, Pozzuoli (Italy); Rombetto, S [Istituto di Cibernetica ' E. Caianiello' del Consiglio Nazionale delle Ricerche, I- 80078, Pozzuoli (Italy); Russo, M [Istituto di Cibernetica ' E. Caianiello' del Consiglio Nazionale delle Ricerche, I- 80078, Pozzuoli (Italy); Ruggiero, B [Istituto di Cibernetica ' E. Caianiello' del Consiglio Nazionale delle Ricerche, I- 80078, Pozzuoli (Italy); Corato, V [Dipartimento di Ingegneria dell' Informazione, Seconda Universita di Napoli, I-8 1031, Aversa (Italy) and Istituto di Cibernetica ' E. Caianiello' del CNR, I-80078, Pozzuoli (Italy); Russo, R [Dipartimento di Ingegneria dell' Informazione, Seconda Universita di Napoli, I-8 1031, Aversa (Italy) and Istituto di Cibernetica ' E. Caianiello' del CNR, I-80078, Pozzuoli (Italy); Silvestrini, P [Dipartimento di Ingegneria dell' Informazione, Seconda Universita di Napoli, I-8 1031, Aversa (Italy) and Istituto di Cibernetica ' E. Caianiello' del CNR, I-80078, Pozzuoli (Italy)

    2006-06-01

    We present a niobium-based Josephson device as prototype for quantum computation with flux qubits. The most interesting feature of this device is the use of a Josephson vertical interferometer to tune the flux qubit allowing the control of the off-diagonal Hamiltonian terms of the system. In the vertical interferometer, the Josephson current is precisely modulated from a maximum to zero with fine control by a small transversal magnetic field parallel to the rf superconducting loop plane.

  17. Josephson shift register design and layout

    International Nuclear Information System (INIS)

    Przybysz, J.X.; Buttyan, J.; Blaugher, R.D.

    1989-01-01

    Integrated circuit chips were designed and fabricated, based on Josephson shift register circuit that simulated operation at 25 GHz using the SPICE program. The 6.25 mm square chip featured a twelve-gate, four-stage shift register fabricated with Nb/AlO/sub x//Nb Josephson junctions with a design value of 2000 A/cm/sup 2/ critical current density. SUPERCOMPACT, a general program for the design of monolithic microwave integrated circuits, was used to model the effects of layout geometry on the uniformity and phase coherence of logic gate bias currents. Gate bias resistors were treated as resistive transmission lines. A layout geometry for the superconductive transmission lines and thin film bias resistors was developed. The original SPICE-designed circuit was modified as a result of these calculations. Modeling indicated that bias current variations could be limited to 3% for all possible logic states of the shift register, and phase coherence of the gates could be maintained to within 2 degrees of 10 Ghz. The fundamental soundness of the circuit design was demonstrated by the proper operation of fabricated shift registers

  18. Nonlinear optical control of Josephson coupling in cuprates

    Energy Technology Data Exchange (ETDEWEB)

    Casandruc, Eliza

    2017-03-15

    In High-T{sub C} cuprates superconducting Cu-O planes alternate with insulating layers along the crystallographic c-axis, making the materials equivalent to Josephson junctions connected in series. The most intriguing consequence is that the out-of-plane superconducting transport occurs via Cooper pairs tunneling across the insulating layers and can be predicted by the Josephson tunneling equations. Nonlinear interaction between light fields and the superconducting carriers serves as a powerful dynamical probe of cuprates, while offering opportunities for controlling them in an analogous fashion to other stimuli such as pressure and magnetic fields. The main goal of this thesis work is to use intense transient light fields to control the interlayer superconducting transport on ultrafast time scales. This was achieved by tuning the wavelength of such light pulses to completely different ranges, in order to either directly excite Josephson Plasma Waves in the nonlinear regime, or efficiently melt the competing charge and spin order phase, which in certain cuprates quenches the Josephson tunneling at equilibrium. In a first study, I have utilized strong field terahertz transients with frequencies tuned to the Josephson plasma resonance (JPR) to coherently control the c-axis superconducting transport. The Josephson relations have a cubic nonlinearity which is exploited to achieve two related, albeit slightly different, phenomena. Depending on the driving pulse, solitonic breathers were excited with narrow-band multi-cycle pulses in La{sub 1.84}Sr{sub 0.16}CuO{sub 4} while broad-band half-cycle pulses were employed to achieve a parametric amplification of Josephson Plasma Waves in La{sub 1.905}Ba{sub 0.095}CuO{sub 4}. These experiments are supported by extensive modeling, showing exceptional agreement. A comprehensive study illustrates the strong enhancement of the nonlinear effects near the JPR frequency. Then, I turned to investigate the competition between

  19. Superconductor-Insulator transition in a single Josephson junction

    International Nuclear Information System (INIS)

    Sonin, E.B.; PenttilA, J.S.; Parts, O.; Hakonen, P.J.; Paalanen, M.A.

    1999-01-01

    For ultra small Josephson junctions, when quantum effects become important, dissipative phase transition (DPT) has been predicted. The physical origin of this transition is the suppression of macroscopic quantum tunneling of the phase by tile interaction with dissipative quantum-mechanical environment. Macroscopic quantum tunneling destroys superconductivity of a junction, whereas suppression of tunneling restores superconductivity. Hence, this transition is often called a superconductor-insulator transition (SIT). SIT was predicted for various systems, but its detection in a single Josephson junction is of principal importance since it is the simplest system where this transition is expected, without any risk of being masked by other physical processes, as is possible in more complicated systems like regular or' random Josephson junction arrays. In this Letter we present results of our measurements on R = dV/dI vs. I curves, for a variety of single small isolated Josephson junctions, shunted and un shunted, with different values of capacitance C and normal state tunneling resistance RT. We have detected a crossover. between two types of RI-curves with an essentially different behavior at small currents. On the basis of this crossover, we are able to map out the whole phase diagram for a Josephson junction. The position of the observed phase boundary did not agree with that expected from the original theory. However, the theory revised to take into account a finite accuracy of our voltage measurements (viz., the minimum voltage which we are able to detect), explains well the observed phase diagram. Our important conclusion is that the concept of dissipative phase transition (DPT) and superconductor-insulator transition (SIT) are not completely identical as assumed before. Both are accompanied by the sign change of the thermo resistance, which is traditionally considered as a signature of SIT. Thus any DPT is SIT, but not vice versa. We argue that the real signature

  20. Josephson junctions and circle maps

    Energy Technology Data Exchange (ETDEWEB)

    Bak, P; Bohr, T; Jensen, M H; Christiansen, P V

    1984-01-01

    The return map of a differential equation for the current driven Josephson junction, or the damped driven pendulum, is shown numerically to be a circle map. Phase locking, noise and hysteresis, can thus be understood in a simple and coherent way. The transition to chaos is related to the development of a cubic inflection point. Recent theoretical results on universal behavior at the transition to chaos can readily be checked experimentally by studying I-V characteristics. 17 references, 1 figure.

  1. Dynamics of Josephson junction arrays

    International Nuclear Information System (INIS)

    Hadley, P.

    1989-01-01

    The dynamics of Josephson junction arrays is a topic that lies at the intersection of the fields of nonlinear dynamics and Josephson junction technology. The series arrays considered here consist of several rapidly oscillating Josephson junctions where each junction is coupled equally to every other junction. The purpose of this study is to understand phaselocking and other cooperative dynamics of this system. Previously, little was known about high dimensional nonlinear systems of this sort. Numerical simulations are used to study the dynamics of these arrays. Three distinct types of periodic solutions to the array equations were observed as well as period doubled and chaotic solutions. One of the periodic solutions is the symmetric, in-phase solution where all of the junctions oscillate identically. The other two periodic solutions are symmetry-broken solutions where all of the junction do not oscillate identically. The symmetry-broken solutions are highly degenerate. As many as (N - 1) stable solutions can coexist for an array of N junctions. Understanding the stability of these several solutions and the transitions among them is vital to the design of useful devices

  2. Ultimately short ballistic vertical graphene Josephson junctions

    Science.gov (United States)

    Lee, Gil-Ho; Kim, Sol; Jhi, Seung-Hoon; Lee, Hu-Jong

    2015-01-01

    Much efforts have been made for the realization of hybrid Josephson junctions incorporating various materials for the fundamental studies of exotic physical phenomena as well as the applications to superconducting quantum devices. Nonetheless, the efforts have been hindered by the diffusive nature of the conducting channels and interfaces. To overcome the obstacles, we vertically sandwiched a cleaved graphene monoatomic layer as the normal-conducting spacer between superconducting electrodes. The atomically thin single-crystalline graphene layer serves as an ultimately short conducting channel, with highly transparent interfaces with superconductors. In particular, we show the strong Josephson coupling reaching the theoretical limit, the convex-shaped temperature dependence of the Josephson critical current and the exceptionally skewed phase dependence of the Josephson current; all demonstrate the bona fide short and ballistic Josephson nature. This vertical stacking scheme for extremely thin transparent spacers would open a new pathway for exploring the exotic coherence phenomena occurring on an atomic scale. PMID:25635386

  3. Nuclear energy and greenhouse effect

    International Nuclear Information System (INIS)

    Strub, R.A.

    1991-01-01

    The contribution of nuclear power plants against the greenhouse effects is evaluated, not only nuclear energy is unable to fight greenhouse effect increase but long life wastes endanger environment. 8 refs

  4. Dynamics of a nanoscale Josephson junction probed by scanning tunneling microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ast, Christian R.; Jaeck, Berthold; Eltschka, Matthias; Etzkorn, Markus [Max-Planck-Institut fuer Festkoerperforschung, Stuttgart (Germany); Kern, Klaus [Max-Planck-Institut fuer Festkoerperforschung, Stuttgart (Germany); Institut de Physique de la Matiere Condensee, EPFL, Lausanne (Switzerland)

    2015-07-01

    The Josephson effect is an intriguing phenomenon as it presents an interplay of different energy scales, such as the Josephson energy ε{sub J} (critical current), charging energy ε{sub C}, and temperature T. Using a scanning tunneling microscope (STM) operating at a base temperature of 15 mK, we create a nanoscale superconductor-vacuum-superconductor tunnel junction in an extremely underdamped regime (Q>>10). We observe extremely small retrapping currents also owing to strongly reduced ohmic losses in the well-developed superconducting gaps. While formally operating in the zero temperature limit, i.e. the temperature T is smaller than the Josephson plasma frequency ω{sub J} (k{sub B}T<<ℎω{sub J}=√(8ε{sub J}ε{sub C})), experimentally other phenomena, such as stray photons, may perturb the Josephson junction, leading to an effectively higher temperature. The dynamics of the Josephson junction can be addressed experimentally by looking at characteristic parameters, such as the switching current and the retrapping current. We discuss the dynamics of the Josephson junction in the context of reaching the zero temperature limit.

  5. Psychological effects of nuclear warfare

    International Nuclear Information System (INIS)

    Mickley, G.A.

    1987-01-01

    This report is divided into five parts. (1) Discussion of the psychological milieu before a nuclear confrontation. (2) Acute psychological reactions to nuclear warfare (some of which may reflect, in part, direct radiogenic alteration of nervous system functions). (3) Chronic psychological effects of a nuclear confrontation. (4) Issues concerning treatment of these psychological changes. (5) Prevention of adverse psychological reactions to nuclear warfare

  6. RF assisted switching in magnetic Josephson junctions

    Science.gov (United States)

    Caruso, R.; Massarotti, D.; Bolginov, V. V.; Ben Hamida, A.; Karelina, L. N.; Miano, A.; Vernik, I. V.; Tafuri, F.; Ryazanov, V. V.; Mukhanov, O. A.; Pepe, G. P.

    2018-04-01

    We test the effect of an external RF field on the switching processes of magnetic Josephson junctions (MJJs) suitable for the realization of fast, scalable cryogenic memories compatible with Single Flux Quantum logic. We show that the combined application of microwaves and magnetic field pulses can improve the performances of the device, increasing the separation between the critical current levels corresponding to logical "0" and "1." The enhancement of the current level separation can be as high as 80% using an optimal set of parameters. We demonstrate that external RF fields can be used as an additional tool to manipulate the memory states, and we expect that this approach may lead to the development of new methods of selecting MJJs and manipulating their states in memory arrays for various applications.

  7. Miniaturization of Josephson logic circuits

    International Nuclear Information System (INIS)

    Ko, H.; Van Duzer, T.

    1985-01-01

    The performances of Current Injection Logic (CIL) and Resistor Coupled Josephson Logic (RCJL) have been evaluated for minimum features sizes ranging from 5 μm to 0.2 μm. The logic delay is limited to about 10 ps for both the CIL AND gate and the RCJL OR gate biased at 70% of maximum bias current. The maximum circuit count on an 6.35 x 6.35 chip is 13,000 for CIL gates and 20,000 for RCJL gates. Some suggestions are given for further improvements

  8. Josephson tunnel junction microwave attenuator

    DEFF Research Database (Denmark)

    Koshelets, V. P.; Shitov, S. V.; Shchukin, A. V.

    1993-01-01

    A new element for superconducting electronic circuitry-a variable attenuator-has been proposed, designed, and successfully tested. The principle of operation is based on the change in the microwave impedance of a superconductor-insulator-superconductor (SIS) Josephson tunnel junction when dc biased...... at different points in the current-voltage characteristic. Both numerical calculations based on the Tien-Gordon theory and 70-GHz microwave experiments have confirmed the wide dynamic range (more than 15-dB attenuation for one stage) and the low insertion loss in the ''open'' state. The performance of a fully...

  9. Josephson oscillation and self-trapping in momentum space

    Science.gov (United States)

    Zheng, Yi; Feng, Shiping; Yang, Shi-Jie

    2018-04-01

    The Creutz ladder model is studied in the presence of unconventional flux induced by complex tunneling rates along and between the two legs. In the vortex phase, the double-minima band structure is regarded as a double well. By introducing a tunable coupling between the two momentum minima, we demonstrate a phenomenon of Josephson oscillations in momentum space. The condensate density locked in one of the momentum valleys is referred to as macroscopic quantum self-trapping. The on-site interaction of the lattice provides an effective analogy to the double-well model within the two-mode approximation which allows for a quantitative understanding of the Josephson effect and the self-trapping in momentum space.

  10. Shot noise in YBCO bicrystal Josephson junctions

    DEFF Research Database (Denmark)

    Constantinian, K.Y.; Ovsyannikov, G.A.; Borisenko, I.V.

    2003-01-01

    We measured spectral noise density in YBCO symmetric bicrystal Josephson junctions on sapphire substrates at bias voltages up to 100 mV and T 4.2 K. Normal state resistance of the Josephson junctions, R-N = 20-90 Omega and ICRN up to 2.2 mV have been observed in the experimental samples. Noise...... may explain the experimentally measured linewidth broadening of Josephson oscillations at mm and submm wave frequencies in high-Tc superconducting junctions. Experimental results are discussed in terms of bound states existing at surfaces of d-wave superconducting electrodes....

  11. Parametric frequency conversion in long Josephson junctions

    International Nuclear Information System (INIS)

    Irie, F.; Ashihara, S.; Yoshida, K.

    1976-01-01

    Current steps at voltages corresponding to the parametric coupling between an applied r.f. field and junction resonant modes have been observed in long Josephson tunnel junctions in the flux-flow state. The observed periodic variations of the step height due to the applied magnetic field are explained quantitatively by a perturbational analysis using Josephson phase equations. The present study demonstrates that the moving vortex array can serve as a coherent pump wave for signal waves propagating in the barrier region, which indicates, as a result, the possibility of traveling-wave parametric devices with long Josephson tunnel junctions. (author)

  12. Using ion irradiation to make high-Tc Josephson junctions

    International Nuclear Information System (INIS)

    Bergeal, N.; Lesueur, J.; Sirena, M.; Faini, G.; Aprili, M.; Contour, J. P.; Leridon, B.

    2007-01-01

    In this article we describe the effect of ion irradiation on high-T c superconductor thin film and its interest for the fabrication of Josephson junctions. In particular, we show that these alternative techniques allow to go beyond most of the limitations encountered in standard junction fabrication methods, both in the case of fundamental and technological purposes. Two different geometries are presented: a planar one using a single high-T c film and a mesa one defined in a trilayer structure

  13. Magnetic interference patterns in 0-pi superconductor/insulator/ferromagnet/superconductor Josephson junctions: Effects of asymmetry between 0 and pi regions

    OpenAIRE

    Kemmler, M.; Weides, M.; Goldobin, E.; Weiler, M.; Opel, M.; Goennenwein, S.T.B.; Vasenko, A.S.; Golubov, A.A.; Kohlstedt, H.; Koelle, D.; Kleiner, R.

    2010-01-01

    We present a detailed analysis of the dependence of the critical current I-c on an in-plane magnetic field B of 0, pi, and 0-pi superconductor-insulator-ferromagnet-superconductor Josephson junctions. I-c(B) of the 0 and the pi junction closely follows a Fraunhofer pattern, indicating a homogeneous critical current density j(c)(x). The maximum of I-c(B) is slightly shifted along the field axis, pointing to a small remanent in-plane magnetization of the F-layer along the field axis. I-c(B) of ...

  14. Majorana splitting from critical currents in Josephson junctions

    Science.gov (United States)

    Cayao, Jorge; San-Jose, Pablo; Black-Schaffer, Annica M.; Aguado, Ramón; Prada, Elsa

    2017-11-01

    A semiconducting nanowire with strong Rashba spin-orbit coupling and coupled to a superconductor can be tuned by an external Zeeman field into a topological phase with Majorana zero modes. Here we theoretically investigate how this exotic topological superconductor phase manifests in Josephson junctions based on such proximitized nanowires. In particular, we focus on critical currents in the short junction limit (LN≪ξ , where LN is the junction length and ξ is the superconducting coherence length) and show that they contain important information about nontrivial topology and Majoranas. This includes signatures of the gap inversion at the topological transition and a unique oscillatory pattern that originates from Majorana interference. Interestingly, this pattern can be modified by tuning the transmission across the junction, thus providing complementary evidence of Majoranas and their energy splittings beyond standard tunnel spectroscopy experiments, while offering further tunability by virtue of the Josephson effect.

  15. Quantum and thermal phase escape in extended Josephson systems

    International Nuclear Information System (INIS)

    Kemp, A.

    2006-01-01

    In this work I examine phase escape in long annular Josephson tunnel junctions. The sine-Gordon equation governs the dynamics of the phase variable along the junction. This equation supports topological soliton solutions, which correspond to quanta of magnetic flux trapped in the junction barrier. For such Josephson vortices an effective potential is formed by an external magnetic field, while a bias current acts as a driving force. Both together form a metastable potential well, which the vortex is trapped in. When the driving force exceeds the pinning force of the potential, the vortex escapes and the junction switches to the voltage state. At a finite temperature the driving force fluctuates. If the junction's energy scale is small, the phase variable can undergo a macroscopic quantum tunneling (MQT) process at temperatures below the crossover temperature. Without a vortex trapped, the metastable state is not a potential minimum in space, but a potential minimum at zero phase difference. (orig.)

  16. Thermal and quantum depinning of a fractional Josephson vortex

    Energy Technology Data Exchange (ETDEWEB)

    Goldobin, Edward; Gaber, Tobias; Buckenmaier, Kai; Kienzle, Uta; Sickinger, Hanna; Koelle, Dieter; Kleiner, Reinhold [Physikalische Institut, University of Tuebingen, Auf der Morgenstelle 14, 72076 Tuebingen (Germany); Meckbach, Max; Kaiser, Christoph; Il' in, Konstantin; Siegel, Michael [Institut fuer Mikro- und Nanoelektronische Systeme, University of Karlsruhe, Hertzstrasse 16, 76187, Karlsruhe (Germany)

    2011-07-01

    We investigate the bias current induced depinning of a fractional Josephson vortex in a 0-{kappa} Josephson junction, where the {kappa}-discontinuity of the phase is induced by current injectors. At high temperatures T>or similar 100 mK the depinning is governed by thermal fluctuations. By measuring a depinning current histogram and extracting the effective barrier height vs. {kappa}, one can see the signatures of fractional vortex escape. At low T

  17. Quantum and thermal phase escape in extended Josephson systems

    Energy Technology Data Exchange (ETDEWEB)

    Kemp, A.

    2006-07-12

    In this work I examine phase escape in long annular Josephson tunnel junctions. The sine-Gordon equation governs the dynamics of the phase variable along the junction. This equation supports topological soliton solutions, which correspond to quanta of magnetic flux trapped in the junction barrier. For such Josephson vortices an effective potential is formed by an external magnetic field, while a bias current acts as a driving force. Both together form a metastable potential well, which the vortex is trapped in. When the driving force exceeds the pinning force of the potential, the vortex escapes and the junction switches to the voltage state. At a finite temperature the driving force fluctuates. If the junction's energy scale is small, the phase variable can undergo a macroscopic quantum tunneling (MQT) process at temperatures below the crossover temperature. Without a vortex trapped, the metastable state is not a potential minimum in space, but a potential minimum at zero phase difference. (orig.)

  18. Dissipative effects on a generation scheme of a W state in an array of coupled Josephson junctions

    Energy Technology Data Exchange (ETDEWEB)

    Migliore, R [Institute of Biophysics, National Research Council, via Ugo La Malfa 153, 90146 Palermo (Italy); Scala, M; Napoli, A; Messina, A [Dipartimento di Fisica dell' Universita di Palermo, Via Archirafi 36, 90123 Palermo (Italy); Yuasa, K [Waseda Institute for Advanced Study, Waseda University, Tokyo 169-8050 (Japan); Nakazato, H, E-mail: rosanna@fisica.unipa.it, E-mail: matteo.scala@fisica.unipa.it [Department of Physics, Waseda University, Okubo 3-4-1, Shinjuku, Tokyo 169-8555 (Japan)

    2011-04-14

    The dynamics of an open quantum system, consisting of three superconducting qubits interacting with independent reservoirs, is investigated to elucidate the effects of the environment on a unitary generation scheme of W states (Migliore R et al 2006 Phys. Rev. B 74 104503). To this end a microscopic master equation is constructed and its exact resolution predicts the generation of a Werner-like state instead of the W state. A comparison between our model and a more intuitive phenomenological model is also considered, in order to find the limits of the latter approach in the case of structured reservoirs.

  19. Microwave integrated circuit for Josephson voltage standards

    Science.gov (United States)

    Holdeman, L. B.; Toots, J.; Chang, C. C. (Inventor)

    1980-01-01

    A microwave integrated circuit comprised of one or more Josephson junctions and short sections of microstrip or stripline transmission line is fabricated from thin layers of superconducting metal on a dielectric substrate. The short sections of transmission are combined to form the elements of the circuit and particularly, two microwave resonators. The Josephson junctions are located between the resonators and the impedance of the Josephson junctions forms part of the circuitry that couples the two resonators. The microwave integrated circuit has an application in Josephson voltage standards. In this application, the device is asymmetrically driven at a selected frequency (approximately equal to the resonance frequency of the resonators), and a d.c. bias is applied to the junction. By observing the current voltage characteristic of the junction, a precise voltage, proportional to the frequency of the microwave drive signal, is obtained.

  20. Coplanar strips for Josephson voltage standard circuits

    International Nuclear Information System (INIS)

    Schubert, M.; May, T.; Wende, G.; Fritzsch, L.; Meyer, H.-G.

    2001-01-01

    We present a microwave circuit for Josephson voltage standards. Here, the Josephson junctions are integrated in a microwave transmission line designed as coplanar strips (CPS). The new layout offers the possibility of achieving a higher scale of integration and to considerably simplify the fabrication technology. The characteristic impedance of the CPS is about 50 Ω, and this should be of interest for programmable Josephson voltage standard circuits with SNS or SINIS junctions. To demonstrate the function of the microwave circuit design, conventional 10 V Josephson voltage standard circuits with 17000 Nb/AlO x /Nb junctions were prepared and tested. Stable Shapiro steps at the 10 V level were generated. Furthermore, arrays of 1400 SINIS junctions in this microwave layout exhibited first-order Shapiro steps. Copyright 2001 American Institute of Physics

  1. Field modulation of the critical current in magnetic Josephson junctions

    International Nuclear Information System (INIS)

    Blamire, M G; Smiet, C B; Banerjee, N; Robinson, J W A

    2013-01-01

    The dependence of the critical current of a simple Josephson junction on the applied magnetic field is well known and, for a rectangular junction, gives rise to the classic ‘Fraunhofer’ modulation with periodic zeros at the fields that introduce a flux quantum into the junction region. Much recent work has been performed on Josephson junctions that contain magnetic layers. The magnetization of such layers introduces additional flux into the junction and, for large junction areas or strong magnetic materials, can significantly distort the modulation of the critical current and strongly suppress the maximum critical current. The growing interest in junctions that induce odd-frequency triplet pairing in a ferromagnet, and the need to make quantitative comparisons with theory, mean that a full understanding of the role of magnetic barriers in controlling the critical current is necessary. This paper analyses the effect of magnetism and various magnetic configurations on Josephson critical currents; the overall treatment applies to junctions of general shape, but the specific cases of square and rectangular junctions are considered. (paper)

  2. Josephson supercurrent in a topological insulator without a bulk shunt

    International Nuclear Information System (INIS)

    Snelder, M; Molenaar, C G; Golubov, A A; Van der Wiel, W G; Hilgenkamp, H; Golden, M S; Brinkman, A; Pan, Y; Wu, D; Huang, Y K; De Visser, A

    2014-01-01

    A Josephson supercurrent has been induced into the three-dimensional topological insulator Bi 1.5 Sb 0.5 Te 1.7 Se 1.3 . We show that the transport in Bi 1.5 Sb 0.5 Te 1.7 Se 1.3 exfoliated flakes is dominated by surface states and that the bulk conductivity can be neglected at the temperatures where we study the proximity induced superconductivity. We prepared Josephson junctions with widths in the order of 40 nm and lengths in the order of 50–80 nm on several Bi 1.5 Sb 0.5 Te 1.7 Se 1.3 flakes and measured down to 30 mK. The Fraunhofer patterns unequivocally reveal that the supercurrent is a Josephson supercurrent. The measured critical currents are reproducibly observed on different devices and upon multiple cooldowns, and the critical current dependence on temperature as well as magnetic field can be well explained by diffusive transport models and geometric effects. (paper)

  3. Branching in current-voltage characteristics of intrinsic Josephson junctions

    International Nuclear Information System (INIS)

    Shukrinov, Yu M; Mahfouzi, F

    2007-01-01

    We study branching in the current-voltage characteristics of the intrinsic Josephson junctions of high-temperature superconductors in the framework of the capacitively coupled Josephson junction model with diffusion current. A system of dynamical equations for the gauge-invariant phase differences between superconducting layers for a stack of ten intrinsic junctions has been numerically solved. We have obtained a total branch structure in the current-voltage characteristics. We demonstrate the existence of a 'breakpoint region' on the current-voltage characteristics and explain it as a result of resonance between Josephson and plasma oscillations. The effect of the boundary conditions is investigated. The existence of two outermost branches and correspondingly two breakpoint regions for the periodic boundary conditions is shown. One branch, which is observed only at periodic boundary conditions, corresponds to the propagating of the plasma mode. The second one corresponds to the situation when the charge oscillations on the superconducting layers are absent, excluding the breakpoint. A time dependence of the charge oscillations at breakpoints is presented

  4. Development of a Josephson vortex two-state system based on a confocal annular Josephson junction

    DEFF Research Database (Denmark)

    Monaco, Roberto; Mygind, Jesper; Koshelets, Valery P.

    2018-01-01

    We report theoretical and experimental work on the development of a Josephson vortex two-state system based on a confocal annular Josephson tunnel junction (CAJTJ). The key ingredient of this geometrical configuration is a periodically variable width that generates a spatial vortex potential...

  5. Josephson Thermal Memory

    Science.gov (United States)

    Guarcello, Claudio; Solinas, Paolo; Braggio, Alessandro; Di Ventra, Massimiliano; Giazotto, Francesco

    2018-01-01

    We propose a superconducting thermal memory device that exploits the thermal hysteresis in a flux-controlled temperature-biased superconducting quantum-interference device (SQUID). This system reveals a flux-controllable temperature bistability, which can be used to define two well-distinguishable thermal logic states. We discuss a suitable writing-reading procedure for these memory states. The time of the memory writing operation is expected to be on the order of approximately 0.2 ns for a Nb-based SQUID in thermal contact with a phonon bath at 4.2 K. We suggest a noninvasive readout scheme for the memory states based on the measurement of the effective resonance frequency of a tank circuit inductively coupled to the SQUID. The proposed device paves the way for a practical implementation of thermal logic and computation. The advantage of this proposal is that it represents also an example of harvesting thermal energy in superconducting circuits.

  6. Biological effects of nuclear weapons

    International Nuclear Information System (INIS)

    Frischauf, H.

    1983-01-01

    Prompt and delayed biological effects of nuclear weapons are discussed. The response to excess pressure on man is estimated, the acute radiation syndrome caused by different radiation doses and cancerogenous and genetic effects are described. Medical care after a nuclear explosion would be difficult and imperfect. (M.J.)

  7. Topology-induced critical current enhancement in Josephson networks

    International Nuclear Information System (INIS)

    Silvestrini, P.; Russo, R.; Corato, V.; Ruggiero, B.; Granata, C.; Rombetto, S.; Russo, M.; Cirillo, M.; Trombettoni, A.; Sodano, P.

    2007-01-01

    We investigate the properties of Josephson junction networks with inhomogeneous architecture. The networks are shaped as 'square comb' planar lattices on which Josephson junctions link superconducting islands arranged in the plane to generate the pertinent topology. Compared to the behavior of reference linear arrays, the temperature dependencies of the Josephson currents of the branches of the network exhibit relevant differences. The observed phenomena evidence new and surprising behavior of superconducting Josephson arrays

  8. Topology-induced critical current enhancement in Josephson networks

    Energy Technology Data Exchange (ETDEWEB)

    Silvestrini, P. [Dipartimento d' Ingegneria dell' Informazione, Seconda Universita di Napoli, Aversa (Italy); Istituto di Cibernetica ' E. Caianiello' del CNR, Pozzuoli (Italy)], E-mail: p.silvestrini@cib.na.cnr.it; Russo, R. [Istituto di Cibernetica ' E. Caianiello' del CNR, Pozzuoli (Italy); Corato, V. [Dipartimento d' Ingegneria dell' Informazione, Seconda Universita di Napoli, Aversa (Italy); Ruggiero, B.; Granata, C.; Rombetto, S.; Russo, M. [Istituto di Cibernetica ' E. Caianiello' del CNR, Pozzuoli (Italy); Cirillo, M. [Dipartimento di Fisica and INFM, Universita di Roma ' Tor Vergata' , 00173 Roma (Italy); Trombettoni, A. [International School for Advanced Studies and Sezione INFN, Via Beirut 2/4, 34104 Trieste (Italy); Sodano, P. [International School for Advanced Studies and Sezione INFN, Via Beirut 2/4, 34104 Trieste (Italy); Dipartimento di Fisica, Universita di Perugia, 06123 Perugia, and Sezione INFN, Perugia (Italy); Progetto Lagrange, Fondazione C.R.T. e Fondazione I.S.I., Dipartimento di Fisica, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10124 Torino (Italy)

    2007-10-29

    We investigate the properties of Josephson junction networks with inhomogeneous architecture. The networks are shaped as 'square comb' planar lattices on which Josephson junctions link superconducting islands arranged in the plane to generate the pertinent topology. Compared to the behavior of reference linear arrays, the temperature dependencies of the Josephson currents of the branches of the network exhibit relevant differences. The observed phenomena evidence new and surprising behavior of superconducting Josephson arrays.

  9. Realization of φ Josephson junctions with a ferromagnetic interlayer

    International Nuclear Information System (INIS)

    Sickinger, Hanna Sabine

    2014-01-01

    In this thesis, φ Josephson junctions based on 0-π junctions with a ferromagnetic interlayer are studied. Josephson junctions (JJs) with a ferromagnetic interlayer can have a phase drop of 0 or π in the ground state, depending on the thickness of the ferromagnet (0 JJs or π JJs). Also, 0-π JJs can be realized, where one segment of the junction (if taken separately) is in the 0 state, while the other segment is in the π state. One can use these π Josephson junctions as a device in superconducting circuits, where it provides a constant phase shift, i.e., it acts as a π phase battery. A generalization of a π JJ is a φ JJ, which has the phase ±φ in the ground state. The value of φ can be chosen by design and tuned in the interval 0<φ<π. The φ JJs used in this experiment were fabricated as 0-π JJs with asymmetric current densities in the 0 and π facets. This system can be described by an effective current-phase relation which is tunable by an externally applied magnetic field. The first experimental evidence of such a φ JJ is presented in this thesis. In particular it is demonstrated that (a) a φ JJ has two ground states +φ and -φ, (b) the unknown state can be detected (read out) by measuring the critical current I c (I c+ or I c- ), and (c) a particular state can be prepared by applying a magnetic field or a special bias sweep sequence. These properties of a φ JJ can be utilized, for example, as a memory cell (classical bit). Furthermore, a φ Josephson junction can be used as a deterministic ratchet. This is due to the tunable asymmetry of the potential that can be changed by the external magnetic field. Rectification curves are observed for the overdamped and the underdamped case. Moreover, experimental data of the retrapping process of the phase of a φ Josephson junction depending on the temperature is presented.

  10. Chemical effects of nuclear transformations

    Energy Technology Data Exchange (ETDEWEB)

    Bulbulian, S

    1982-06-01

    A brief survey of the present state of knowledge on the chemical effects of nuclear transformations is presented. The recoil energy produced by these transformations in the nuclide is often sufficiently high to disrupt the chemical ligands between these particular atoms affected by the nuclear transformations, while the rest of their molecules. It also contains a discussion of the different annealing processes that produce the cancellation of the chemical change produced by the nuclear transformation.

  11. Inter-band phase fluctuations in macroscopic quantum tunneling of multi-gap superconducting Josephson junctions

    Energy Technology Data Exchange (ETDEWEB)

    Asai, Hidehiro, E-mail: hd-asai@aist.go.jp [Electronics and Photonics Research Institute (ESPRIT), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568 (Japan); Ota, Yukihiro [CCSE, Japan Atomic Energy Agency, Kashiwa, Chiba 277-8587 (Japan); Kawabata, Shiro [Electronics and Photonics Research Institute (ESPRIT), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568 (Japan); Nori, Franco [CEMS, RIKEN, Wako-shi, Saitama 351-0198 (Japan); Physics Department, University of Michigan, Ann Arbor, MI 48109-1040 (United States)

    2014-09-15

    Highlights: • We study MQT in Josephson junctions composed of multi-gap superconductors. • We derive a formula of the MQT escape rate for multiple phase differences. • We investigate the effect of inter-band phase fluctuation on MQT. • The MQT escape rate is significantly enhanced by the inter-band phase fluctuation. - Abstract: We theoretically investigate macroscopic quantum tunneling (MQT) in a hetero Josephson junction formed by a conventional single-gap superconductor and a multi-gap superconductor. In such Josephson junctions, phase differences for each tunneling channel are defined, and the fluctuation of the relative phase differences appear which is referred to as Josephson–Leggett’s mode. We take into account the effect of the fluctuation in the tunneling process and calculate the MQT escape rate for various junction parameters. We show that the fluctuation of relative phase differences drastically enhances the escape rate.

  12. Inter-band phase fluctuations in macroscopic quantum tunneling of multi-gap superconducting Josephson junctions

    International Nuclear Information System (INIS)

    Asai, Hidehiro; Ota, Yukihiro; Kawabata, Shiro; Nori, Franco

    2014-01-01

    Highlights: • We study MQT in Josephson junctions composed of multi-gap superconductors. • We derive a formula of the MQT escape rate for multiple phase differences. • We investigate the effect of inter-band phase fluctuation on MQT. • The MQT escape rate is significantly enhanced by the inter-band phase fluctuation. - Abstract: We theoretically investigate macroscopic quantum tunneling (MQT) in a hetero Josephson junction formed by a conventional single-gap superconductor and a multi-gap superconductor. In such Josephson junctions, phase differences for each tunneling channel are defined, and the fluctuation of the relative phase differences appear which is referred to as Josephson–Leggett’s mode. We take into account the effect of the fluctuation in the tunneling process and calculate the MQT escape rate for various junction parameters. We show that the fluctuation of relative phase differences drastically enhances the escape rate

  13. Nuclear explosions and their effects

    Energy Technology Data Exchange (ETDEWEB)

    1958-01-01

    A brief historical background is given of the development of the atomic bomb. Also included is an account of the Hiroshima-Nagasaki bombing, plus some information on the testing and production of nuclear weapons by the United States, United Kingdom, and Russia. More detailed consideration is given to the following: the scientific principles of fission and fusion explosions; the energy released in fission and the radioactivity of fission products; blast, thermal, and radiologicalal effects of nuclear explosions; long-term radiological hazards from fall-out; and genetic effects of nuclear explosions. A brief account is given of the fission chain process, the concept of critical size, and the principles of implosion as applied to nuclear explosions. Limited information is presented on the controlled release of thermonuclear energy and catalyzed fusion reaction. Discussions are included on dose rates from radiation sources inside and outside the body, the effect of nuclear explosions on the weather, and the contamination of fish and marine organisms.

  14. Parity Anomaly and Spin Transmutation in Quantum Spin Hall Josephson Junctions.

    Science.gov (United States)

    Peng, Yang; Vinkler-Aviv, Yuval; Brouwer, Piet W; Glazman, Leonid I; von Oppen, Felix

    2016-12-23

    We study the Josephson effect in a quantum spin Hall system coupled to a localized magnetic impurity. As a consequence of the fermion parity anomaly, the spin of the combined system of impurity and spin-Hall edge alternates between half-integer and integer values when the superconducting phase difference across the junction advances by 2π. This leads to characteristic differences in the splittings of the spin multiplets by exchange coupling and single-ion anisotropy at phase differences, for which time-reversal symmetry is preserved. We discuss the resulting 8π-periodic (or Z_{4}) fractional Josephson effect in the context of recent experiments.

  15. The pulse-driven AC Josephson voltage normal; Das pulsgetriebene AC-Josephson-Spannungsnormal

    Energy Technology Data Exchange (ETDEWEB)

    Kieler, Oliver [Physikalisch-Technische Bundesanstalt (PTB), Braunschweig (Germany). Arbeitsgruppe 2.43 ' ' Josephson-Schaltungen' '

    2016-09-15

    In this contribution quantum precise alternating-voltage sources are presented, which make the generation of arbitrary wave forms with highest spectral purity with a high bandwidth from DC up to the MHz range possible. Heartpiece of these Josephson voltage normals is a serial circuit of many thousand Josephson contacts, which make by irradiation with high-frequency radiation (microwaves) the generation of highly precise voltage values possible. Thereby in the current-voltage characteristics stages of constant voltage, so called Shapiro stages, occur. Illustratively these stages can be described by the transfer of a certain number of flux quanta through the Josephson contacts.

  16. Nuclear war effects studied

    Science.gov (United States)

    Widespread starvation resulting from changes in climate in the aftermath of a large-scale nuclear war could kill far more people than would the bombs themselves. That prediction was made in a recent study by the Scientific Committee on Problems of the Environment (SCOPE), an a rm of the International Council of Scientific Unions (ICSU). “Noncombatant and combatant countries alike” would risk mass starvation; SCOPE predicted that all told, 2.5 billion people could die as a result of crop failures and breakdowns in food distribution after a nuclear war.

  17. Hybrid Josephson-CMOS Memory in Advanced Technologies and Larger Sizes

    International Nuclear Information System (INIS)

    Liu, Q; Van Duzer, T; Fujiwara, K; Yoshikawa, N

    2006-01-01

    Recent progress on demonstrating components of the 64 kb Josephson-CMOS hybrid memory has encouraged exploration of the advancement possible with use of advanced technologies for both the Josephson and CMOS parts of the memory, as well as considerations of the effect of memory size on access time and power dissipation. The simulations to be reported depend on the use of an approximate model for 90 nm CMOS at 4 K. This model is an extension of the one we developed for 0.25 μm CMOS and have already verified. For the Josephson parts, we have chosen 20 kA/cm 2 technology, which was recently demonstrated. The calculations show that power dissipation and access time increase rather slowly with increasing size of the memory

  18. Spectroscopy of fractional Josephson vortex molecules

    Energy Technology Data Exchange (ETDEWEB)

    Goldobin, Edward; Gaber, Tobias; Buckenmaier, Kai; Kienzle, Uta; Sickinger, Hanna; Koelle, Dieter; Kleiner, Reinhold [Physikalisches Institut - Experimentalphysik II, Center for Collective Quantum Phenomena, Universitaet Tuebingen, Auf der Morgenstelle 14, D-72076 Tuebingen (Germany)

    2010-07-01

    Using tiny current injectors we create {kappa} discontinuities of the Josephson phase in a long Josephson junction. The junction reacts at the discontinuities by creating fractional Josephson vortices of size {lambda}{sub J} pinned at them. Such vortices carry the flux {phi}, which is a fraction of the magnetic flux quantum {phi}{sub 0}{approx}2.07 x 10{sup -15} Wb. Being pinned, a fractional vortex has an eigenfrequency (localized mode), which depends on {kappa} and applied bias current, and which lays within the plasma gap. If one considers a molecule consisting of several coupled fractional vortices, the eigenfrequency will split into several modes. We report on spectroscopy of a fractional vortex molecule performed in the thermal regime.

  19. A Josephson radiation comb generator.

    Science.gov (United States)

    Solinas, P; Gasparinetti, S; Golubev, D; Giazotto, F

    2015-07-20

    We propose the implementation of a Josephson Radiation Comb Generator (JRCG) based on a dc superconducting quantum interference device (SQUID) driven by an external magnetic field. When the magnetic flux crosses a diffraction node of the critical current interference pattern, the superconducting phase undergoes a jump of π and a voltage pulse is generated at the extremes of the SQUID. Under periodic drive this allows one to generate a sequence of sharp, evenly spaced voltage pulses. In the frequency domain, this corresponds to a comb-like structure similar to the one exploited in optics and metrology. With this device it is possible to generate up to several hundreds of harmonics of the driving frequency. For example, a chain of 50 identical high-critical-temperature SQUIDs driven at 1 GHz can deliver up to a 0.5 nW at 200 GHz. The availability of a fully solid-state radiation comb generator such as the JRCG, easily integrable on chip, may pave the way to a number of technological applications, from metrology to sub-millimeter wave generation.

  20. Directional Amplification with a Josephson Circuit

    Directory of Open Access Journals (Sweden)

    Baleegh Abdo

    2013-07-01

    Full Text Available Nonreciprocal devices perform crucial functions in many low-noise quantum measurements, usually by exploiting magnetic effects. In the proof-of-principle device presented here, on the other hand, two on-chip coupled Josephson parametric converters (JPCs achieve directionality by exploiting the nonreciprocal phase response of the JPC in the transmission-gain mode. The nonreciprocity of the device is controlled in situ by varying the amplitude and phase difference of two independent microwave pump tones feeding the system. At the desired working point and for a signal frequency of 8.453 GHz, the device achieves a forward power gain of 15 dB within a dynamical bandwidth of 9 MHz, a reverse gain of -6  dB, and suppression of the reflected signal by 8 dB. We also find that the amplifier adds a noise equivalent to less than 1.5 photons at the signal frequency (referred back to the input. It can process up to 3 photons at the signal frequency per inverse dynamical bandwidth. With a directional amplifier operating along the principles of this device, qubit and readout preamplifier could be integrated on the same chip.

  1. Fluxon dynamics in long Josephson junctions in the presence of a temperature gradient or spatial nonuniformity

    DEFF Research Database (Denmark)

    Krasnov, V.M.; Oboznov, V.A.; Pedersen, Niels Falsig

    1997-01-01

    Fluxon dynamics in nonuniform Josephson junctions was studied both experimentally and theoretically. Two types of nonuniform junctions were considered: the first type had a nonuniform spatial distribution of critical and bias currents and the second had a temperature gradient applied along...... the junction. An analytical expression for the I-V curve in the presence of a temperature gradient or spatial nonuniformity was derived. It was shown that there is no static thermomagnetic Nernst effect due to Josephson fluxon motion despite the existence of a force pushing fluxons in the direction of smaller...

  2. Improving ion irradiated high Tc Josephson junctions by annealing: The role of vacancy-interstitial annihilation

    International Nuclear Information System (INIS)

    Sirena, M.; Matzen, S.; Bergeal, N.; Lesueur, J.; Faini, G.; Bernard, R.; Briatico, J.; Crete, D. G.

    2007-01-01

    The authors have studied the annealing effect in the transport properties of high T c Josephson junctions (JJs) made by ion irradiation. Low temperature annealing (80 deg. C) increases the JJ coupling temperature (T J ) and the I c R n product, where I c is the critical current and R n the normal resistance. They have found that the spread in JJ characteristics can be reduced by sufficient long annealing times, increasing the reproducibility of ion irradiated Josephson junctions. The characteristic annealing time and the evolution of the spread in the JJ characteristics can be explained by a vacancy-interstitial annihilation process rather than by an oxygen diffusion one

  3. Loss models for long Josephson junctions

    DEFF Research Database (Denmark)

    Olsen, O. H.; Samuelsen, Mogens Rugholm

    1984-01-01

    A general model for loss mechanisms in long Josephson junctions is presented. An expression for the zero-field step is found for a junction of overlap type by means of a perturbation method. Comparison between analytic solution and perturbation result shows good agreement.......A general model for loss mechanisms in long Josephson junctions is presented. An expression for the zero-field step is found for a junction of overlap type by means of a perturbation method. Comparison between analytic solution and perturbation result shows good agreement....

  4. Dynamical properties of weakly coupled Josephson systems

    International Nuclear Information System (INIS)

    Lee, K.H.; Xia, T.K.; Stroud, D.

    1990-01-01

    This paper reviews recent work on the dynamical behavior of coupled resistively-shunted Josephson junctions, with emphasis on our own calculations. The authors present a model which allows for the inclusion of finite temperature, disorder, d.c. and a.c. applied currents, and applied magnetic fields. The authors discuss applications to calculations of critical currents and IV characteristics; harmonic generation and microwave absorption by finite clusters of Josephson junctions; critical energies for vortex depinning; and quantized voltage plateaus in arrays subjected to combined d.c. and a.c. currents. Possible connections to the behavior of granular high-temperature superconductors are briefly discussed

  5. Microscopic tunneling theory of long Josephson junctions

    DEFF Research Database (Denmark)

    Grønbech-Jensen, N.; Hattel, Søren A.; Samuelsen, Mogens Rugholm

    1992-01-01

    We present a numerical scheme for solving a nonlinear partial integro-differential equation with nonlocal time dependence. The equation describes the dynamics in a long Josephson junction modeled by use of the microscopic theory for tunneling between superconductors. We demonstrate that the detai......We present a numerical scheme for solving a nonlinear partial integro-differential equation with nonlocal time dependence. The equation describes the dynamics in a long Josephson junction modeled by use of the microscopic theory for tunneling between superconductors. We demonstrate...

  6. Impedance metrology with Josephson voltage normals; Impedanzmetrologie mit Josephson-Spannungsnormalen

    Energy Technology Data Exchange (ETDEWEB)

    Bauer, Stephan; Palafox, Luis [Physikalisch-Technische Bundesanstalt (PTB), Braunschweig (Germany). Arbeitsgruppe 2.63 ' ' Josephson-Effekt, Spannung' '

    2016-09-15

    This article first explains the fundamental principle of an impedance measurement bridge on the base of Josephson voltage normals, before both types of measurement bridges realized in the PTB are more precisely discussed.

  7. Hybrid Josephson-CMOS memory: a solution for the Josephson memory problem

    International Nuclear Information System (INIS)

    Duzer, Theodore van; Feng Yijun; Meng Xiaofan; Whiteley, Stephen R; Yoshikawa, Nobuyuki

    2002-01-01

    The history of the development of superconductive memory for Josephson digital systems is presented along with the several current proposals. The main focus is on a proposed combination of the highly developed CMOS memory technology with Josephson peripheral circuits to achieve memories of significant size with subnanosecond access time. Background material is presented on the cryogenic operation of CMOS. Simulations and experiments on components of memory with emphasis on the important input interface amplifier are presented

  8. Phase transition in a modified square Josephson-junction array

    CERN Document Server

    Han, J

    1999-01-01

    We study the phase transition in a modified square proximity-coupled Josephson-junction array with small superconducting islands at the center of each plaquette. We find that the modified square array undergoes a Kosterlitz-Thouless-Berezinskii-like phase transition, but at a lower temperature than the simple square array with the same single-junction critical current. The IV characteristics, as well as the phase transition, resemble qualitatively those of a disordered simple square array. The effects of the presence of the center islands in the modified square array are discussed.

  9. Steady-state properties of Josephson junctions with direct conductivity

    International Nuclear Information System (INIS)

    Zubkov, A.A.; Kupriyanov, M.Y.; Semenov, V.K.

    1981-01-01

    A new criterion for determining the kinetic inductance of Josephson junctions is introduced. The effects of temperature T, the critical temperatures of the superconducting electrodes T/sub c/1 and T/sub c/2, and the weak-link length on the kinetic inductance of ''dirty'' junctions with direct conductivity are analyzed within the framework of the Usadel equations. Numerical calculations show that both a large characteristic voltage and a nearly harmonic dependence of the current on the phase difference of the superconducting-electrode wave functions cannot be obtained by varying the junction parameters

  10. Generation of cluster states with Josephson charge qubits

    International Nuclear Information System (INIS)

    Zheng, Xiao-Hu; Dong, Ping; Xue, Zheng-Yuan; Cao, Zhuo-Liang

    2007-01-01

    A scheme for the generation of the cluster states based on the Josephson charge qubits is proposed. The two-qubit generation case is introduced first, and then generalized to multi-qubit case. The successful probability and fidelity of current multi-qubit cluster state are both 1.0. The scheme is simple and can be easily manipulated, because any two charge qubits can be selectively and effectively coupled by a common inductance. More manipulations can be realized before decoherence sets in. All the devices in the scheme are well within the current technology

  11. 0-π phase-controllable thermal Josephson junction

    Science.gov (United States)

    Fornieri, Antonio; Timossi, Giuliano; Virtanen, Pauli; Solinas, Paolo; Giazotto, Francesco

    2017-05-01

    Two superconductors coupled by a weak link support an equilibrium Josephson electrical current that depends on the phase difference ϕ between the superconducting condensates. Yet, when a temperature gradient is imposed across the junction, the Josephson effect manifests itself through a coherent component of the heat current that flows opposite to the thermal gradient for |ϕ| heat currents can be inverted by adding a π shift to ϕ. In the static electrical case, this effect has been obtained in a few systems, for example via a ferromagnetic coupling or a non-equilibrium distribution in the weak link. These structures opened new possibilities for superconducting quantum logic and ultralow-power superconducting computers. Here, we report the first experimental realization of a thermal Josephson junction whose phase bias can be controlled from 0 to π. This is obtained thanks to a superconducting quantum interferometer that allows full control of the direction of the coherent energy transfer through the junction. This possibility, in conjunction with the completely superconducting nature of our system, provides temperature modulations with an unprecedented amplitude of ∼100 mK and transfer coefficients exceeding 1 K per flux quantum at 25 mK. Then, this quantum structure represents a fundamental step towards the realization of caloritronic logic components such as thermal transistors, switches and memory devices. These elements, combined with heat interferometers and diodes, would complete the thermal conversion of the most important phase-coherent electronic devices and benefit cryogenic microcircuits requiring energy management, such as quantum computing architectures and radiation sensors.

  12. Nuclear effects hardened shelters

    International Nuclear Information System (INIS)

    Lindke, P.

    1990-01-01

    This paper reports on the Houston Fearless 76 Government Projects Group that has been actively engaged for more than twenty-five years as a sub-contractor and currently as a prime contractor in the design, manufacture, repair and logistics support of custom mobile ground stations and their equipment accommodations. Other associated products include environmental control units (ECU's), mobilizers for shelters and a variety of mobile power generation units (MPU's). Since 1984, Houston Fearless 76 has designed and manufactured four 8 foot by 8 foot x 22 foot nuclear hardened mobile shelters. These shelters were designed to contain electronic data processing/reduction equipment. One shelter is currently being operated by the Air Force as a Defense Intelligence Agency (DIA) approved and certified Special Compartmented Information Facility (SCIF). During the development and manufacturing process of the shelters, we received continual technical assistance and design concept evaluations from Science Applications International Corporation (SAIC) Operations Analysis and Logistics Engineering Division and the Nondestructive Inspection Lab at McClellan AFB. SAIC was originally employed by the Air Force to design the nuclear hardening specifications applied to these shelters

  13. Quark effects in nuclear structure

    International Nuclear Information System (INIS)

    Watt, A.

    1987-01-01

    Some experimental data in nuclear structure physics cannot be explained on the assumption that nuclei consist of inert protons and neutrons. The quark model attributes a definite internal structure to nucleons and implies that their properties should change when embedded in a nucleus. This article reviews some of the experimental evidence for these effects and discusses some new aspects of nuclear structure predicted by the quark model

  14. Ballistic Josephson junctions based on CVD graphene

    Science.gov (United States)

    Li, Tianyi; Gallop, John; Hao, Ling; Romans, Edward

    2018-04-01

    Josephson junctions with graphene as the weak link between superconductors have been intensely studied in recent years, with respect to both fundamental physics and potential applications. However, most of the previous work was based on mechanically exfoliated graphene, which is not compatible with wafer-scale production. To overcome this limitation, we have used graphene grown by chemical vapour deposition (CVD) as the weak link of Josephson junctions. We demonstrate that very short, wide CVD-graphene-based Josephson junctions with Nb electrodes can work without any undesirable hysteresis in their electrical characteristics from 1.5 K down to a base temperature of 320 mK, and their gate-tuneable critical current shows an ideal Fraunhofer-like interference pattern in a perpendicular magnetic field. Furthermore, for our shortest junctions (50 nm in length), we find that the normal state resistance oscillates with the gate voltage, consistent with the junctions being in the ballistic regime, a feature not previously observed in CVD-graphene-based Josephson junctions.

  15. Cavity syncronisation of underdamped Josephson junction arrays

    DEFF Research Database (Denmark)

    Barbara, P.; Filatrella, G.; Lobb, C.

    2003-01-01

    the junctions in the array and an electromagnetic cavity. Here we show that a model of a one-dimensional array of Josephson junctions coupled to a resonator can produce many features of the coherent be havior above threshold, including coherent radiation of power and the shape of the array current...

  16. Josephson plasma resonance in superconducting multilayers

    DEFF Research Database (Denmark)

    Pedersen, Niels Falsig

    1999-01-01

    We derive an analytical solution for the josephson plasma resonance of superconducting multilayers. This analytical solution is derived mainly for low T-c systems with magnetic coupling between the superconducting layers, but many features of our results are more general, and thus an application...... to the recently derived plasma resonance phenomena for high T-c superconductors of the BSCCO type is discussed....

  17. Josephson plasma resonance in superconducting multilayers

    DEFF Research Database (Denmark)

    Pedersen, Niels Falsig; Sakai, S

    1998-01-01

    We derive an analytical solution for the Josephson plasma resonance of superconducting multilayers. This analytical solution is derived mainly for low-T-c systems with magnetic coupling between the superconducting layers. but many features of our results are more general, and thus an application...

  18. Transient chaos in weakly coupled Josephson junctions

    Energy Technology Data Exchange (ETDEWEB)

    Koch, B P; Bruhn, B

    1988-01-01

    This paper considers periodic excitations and coupling of nonlinear Josephson oscillators. The Melnikov method is used to prove the existence of horseshoes in the dynamics. The coupling of two systems yields a reduction of the chaos threshold in comparison with the corresponding threshold of a single system. For some selected parameter values the theoretical predictions are checked by numerical methods.

  19. Fluxon density waves in long Josephson junctions

    DEFF Research Database (Denmark)

    Olsen, O. H.; Ustinov, A. V.; Pedersen, Niels Falsig

    1993-01-01

    Numerical simulations of the multiple fluxon dynamics stimulated by an external oscillating force applied at a boundary of a long Josephson junction are presented. The calculated IV characteristics agree well with a recent experimental observation of rf-induced satellite flux-flow steps. The volt...... density waves....

  20. Dissipative current in SIFS Josephson junctions

    NARCIS (Netherlands)

    Vasenko, A.; Kawabata, S.; Golubov, Alexandre Avraamovitch; Kupriyanov, M. Yu; Hekking, F.W.J.

    2010-01-01

    We investigate superconductor/insulator/ferromagnet/superconductor (SIFS) tunnel Josephson junctions in the dirty limit, using the quasiclassical theory. We consider the case of a strong tunnel barrier such that the left S layer and the right FS bilayer are decoupled. We calculate quantitatively the

  1. Characterization and Modeling of Superconducting Josephson Junction Arrays at Low Voltage and Liquid Helium Temperatures

    Science.gov (United States)

    2016-09-01

    both from SSC Pacific) and Marc Tukeman, Chuck Vinson and Mr. Mark Flemon with the procurement process . We acknowledge Deep Gupta, Saad Sarwana, and...superconductor-ionic quantum memory and computation devices. iv CONTENTS EXECUTIVE SUMMARY...Josephson effect makes these measurements useful for characterization and calibration of superconducting quantum memory and computational devices

  2. Influence of the cos-phi conductance on fluxons propagating in long Josephson junctions

    DEFF Research Database (Denmark)

    Olsen, O. H.; Samuelsen, Mogens Rugholm

    1982-01-01

    The influence of a cosφ conductance on the motion of fluxons in long and narrow Josephson junctions is investigated by numerical computations and by a perturbation analysis. It turns out that the presence of the cosφ term will have opposite effects on the motion of a fluxon and on plasma waves or...

  3. Quantitative description of hysteresis loops induced by rf radiation in long Josephson junctions

    DEFF Research Database (Denmark)

    Olsen, Ole H.; Samuelsen, Mogens Rugholm

    1991-01-01

    The effect of an applied rf signal on the radiation emitted from a long Josephson junction is examined by means of a model based on the sine-Gordon equation. This system exhibits a variety of interesting phenomena, e.g., chaos and hysteresis. The hysteresis loop is examined in detail. These simple...

  4. Transparent Semiconductor-Superconductor Interface and Induced Gap in an Epitaxial Heterostructure Josephson Junction

    NARCIS (Netherlands)

    Kjaergaard, M.; Suominen, H. J.; Nowak, M.P.; Akhmerov, A.R.; Shabani, J.; Palmstrøm, C. J.; Nichele, F.; Marcus, C.M.

    2017-01-01

    Measurement of multiple Andreev Reflection (MAR) in a Josephson junction made from an InAs quantum well heterostructure with epitaxial aluminum is used to quantify a highly transparent effective semiconductor-superconductor interface with near-unity transmission. The observed temperature

  5. Markovian Dynamics of Josephson Parametric Amplification

    Directory of Open Access Journals (Sweden)

    W. Kaiser

    2017-09-01

    Full Text Available In this work, we derive the dynamics of the lossy DC pumped non-degenerate Josephson parametric amplifier (DCPJPA. The main element in a DCPJPA is the superconducting Josephson junction. The DC bias generates the AC Josephson current varying the nonlinear inductance of the junction. By this way the Josephson junction acts as the pump oscillator as well as the time varying reactance of the parametric amplifier. In quantum-limited amplification, losses and noise have an increased impact on the characteristics of an amplifier. We outline the classical model of the lossy DCPJPA and derive the available noise power spectral densities. A classical treatment is not capable of including properties like spontaneous emission which is mandatory in case of amplification at the quantum limit. Thus, we derive a quantum mechanical model of the lossy DCPJPA. Thermal losses are modeled by the quantum Langevin approach, by coupling the quantized system to a photon heat bath in thermodynamic equilibrium. The mode occupation in the bath follows the Bose-Einstein statistics. Based on the second quantization formalism, we derive the Heisenberg equations of motion of both resonator modes. We assume the dynamics of the system to follow the Markovian approximation, i.e. the system only depends on its actual state and is memory-free. We explicitly compute the time evolution of the contributions to the signal mode energy and give numeric examples based on different damping and coupling constants. Our analytic results show, that this model is capable of including thermal noise into the description of the DC pumped non-degenerate Josephson parametric amplifier.

  6. Markovian Dynamics of Josephson Parametric Amplification

    Science.gov (United States)

    Kaiser, Waldemar; Haider, Michael; Russer, Johannes A.; Russer, Peter; Jirauschek, Christian

    2017-09-01

    In this work, we derive the dynamics of the lossy DC pumped non-degenerate Josephson parametric amplifier (DCPJPA). The main element in a DCPJPA is the superconducting Josephson junction. The DC bias generates the AC Josephson current varying the nonlinear inductance of the junction. By this way the Josephson junction acts as the pump oscillator as well as the time varying reactance of the parametric amplifier. In quantum-limited amplification, losses and noise have an increased impact on the characteristics of an amplifier. We outline the classical model of the lossy DCPJPA and derive the available noise power spectral densities. A classical treatment is not capable of including properties like spontaneous emission which is mandatory in case of amplification at the quantum limit. Thus, we derive a quantum mechanical model of the lossy DCPJPA. Thermal losses are modeled by the quantum Langevin approach, by coupling the quantized system to a photon heat bath in thermodynamic equilibrium. The mode occupation in the bath follows the Bose-Einstein statistics. Based on the second quantization formalism, we derive the Heisenberg equations of motion of both resonator modes. We assume the dynamics of the system to follow the Markovian approximation, i.e. the system only depends on its actual state and is memory-free. We explicitly compute the time evolution of the contributions to the signal mode energy and give numeric examples based on different damping and coupling constants. Our analytic results show, that this model is capable of including thermal noise into the description of the DC pumped non-degenerate Josephson parametric amplifier.

  7. The Effects of Nuclear Weapons

    Energy Technology Data Exchange (ETDEWEB)

    Glasstone, Samuel

    1964-02-01

    This book is a revision of "The Effects of Nuclear Weapons" which was issued in 1957. It was prepared by the Defense Atomic Support Agency of the Department of Defense in coordination with other cognizant governmental agencies and was published by the U.S. Atomc Energy Commission. Although the complex nature of nuclear weapons effects does not always allow exact evaluation, the conclusions reached herein represent the combined judgment of a number of the most competent scientists working the problem. There is a need for widespread public understanding of the best information available on the effects of nuclear weapons. The purpose of this book is to present as accurately as possible, within the limits of national security, a comprehensive summary of this information.

  8. Quark effects in nuclear physics

    International Nuclear Information System (INIS)

    Miller, G.A.

    1983-01-01

    A phenomenological approach which enables the size of quark effects in various nuclear processes is discussed. The principle of conservation of probability provides significant constraints on six quark wave functions. Using this approach, it is found that the low-energy proton-proton weak interaction can be explained in terms of W and Z boson exchanges between quarks. That the value of the asymptotic ratio of D to S state wave functions is influenced (at the 5% level) by quark effects, is another result of our approach. We have not discovered a nuclear effect that can be uniquely explained by quark-quark interactions. However it does seem that quark physics is very relevant for nuclear physics. 52 references

  9. The effective nuclear potential

    International Nuclear Information System (INIS)

    Skyrme, T.H.R.

    1994-01-01

    An empirical analyses is made of the mean effective internucleon potential required in the shell-model description of nuclei, allowing for the presence of many-body effects as suggested by current theory. A consistent description is found in which the effective two-body interaction acts almost entirely in even states, and the many-body effects are simulated by a repulsive three-body contact interaction. The strength of the two-body interaction is consistent with that expressed by the free scattering matrix of the two-nucleon system, and that of the three-body interaction with the 'rearrangement energy' calculated in the many-body theory. (author). 21 refs, 2 figs, 7 tabs

  10. Isotope effects on nuclear shielding

    International Nuclear Information System (INIS)

    Hansen, P.E.

    1983-01-01

    This review concentrates upon empirical trends and practical uses of mostly secondary isotope effects, both of the intrinsic and equilibrium types. The text and the tables are arranged in the following fashion. The most 'popular' isotope effect is treated first, deuterium isotope effects on 13 C nuclear shielding, followed by deuterium on 1 H nuclear shieldings, etc. Focus is thus on the isotopes producing the effect rather than on the nuclei suffering the effect. After a brief treatment of each type of isotope effect, general trends are dealt with. Basic trends of intrinsic isotope effects such as additivity, solvent effects, temperature effects, steric effects, substituent effects and hyperconjugation are discussed. Uses of isotope effects for assignment purposes, in stereochemical studies, in hydrogen bonding and in isotopic tracer studies are dealt with. Kinetic studies, especially of phosphates, are frequently performed by utilizing isotope effects. In addition, equilibrium isotope effects are treated in great detail as these are felt to be new and very important and may lead to new uses of isotope effects. Techniques used to obtain isotope effects are briefly surveyed at the end of the chapter. (author)

  11. BIPM direct on-site Josephson voltage standard comparisons: 20 years of results

    International Nuclear Information System (INIS)

    Solve, Stephane; Stock, Michael

    2012-01-01

    The discovery of the Josephson effect has for the first time given national metrology institutes (NMIs) the possibility of maintaining voltage references which are stable in time. In addition, the introduction in 1990 of a conventional value for the Josephson constant, K J-90 , has greatly improved world-wide consistency among representations of the volt. For 20 years, the Bureau International des Poids et Mesures (BIPM) has conducted an ongoing, direct, on-site key comparison of Josephson voltage standards among NMIs under the denominations BIPM.EM-K10.a (1 V) and BIPM.EM-K10.b (10 V) in the framework of the mutual recognition arrangement (CIPM MRA). The results of 41 comparisons illustrate the consistency among primary voltage standards and have demonstrated that a relative total uncertainty of a few parts in 10 10 is achievable if a few precautions are taken with regard to the measurement set-up. Of particular importance are the grounding, efficient filters and high insulation resistance of the measurement leads, and clean microwave distribution along the propagation line to the Josephson array. This paper reviews the comparison scheme and technical issues that need to be taken into account to achieve a relative uncertainty at the level of a few parts in 10 10 or even a few parts in 10 11 in the best cases. (paper)

  12. Josephson admittance spectroscopy application for frequency analysis of broadband THz antennas

    International Nuclear Information System (INIS)

    Volkov, O Yu; Divin, Yu Yu; Gubankov, V N; Gundareva, I I; Pavlovskiy, V V

    2010-01-01

    Application of Josephson admittance spectroscopy for the spectral analysis of a broad-band log-periodic superconducting antenna was demonstrated at the frequency range from 50 to 700 GHz. The [001]-tilt YBa 2 Cu 3 O 7-x bicrystal Josephson junctions, integrated with sinuous log-periodic YBa 2 Cu 3 O 7-x antennas, were fabricated on NdGaO 3 bicrystal substrates. A real part of the antenna admittance ReY(f) as a function of the frequency f was reconstructed from the modification of the dc current-voltage characteristic of the junction, induced by the antenna. Resonance features were observed in the recovered ReY(f)-spectra with a periodicity in the logarithmic frequency scale, corresponding to log-periodic geometry of the antenna. The ReY(f)-spectra, recovered by Josephson spectroscopy, were compared with the ReY(f)-spectra, obtained by CAD simulation, and both spectra were shown to be similar in their main features. A value of 23 was obtained for an effective permittivity of the NdGaO3 bicrystal substrates by fitting simulated data to those obtained from Josephson spectroscopy.

  13. Q factor and resonance amplitude of Josephson tunnel junctions

    International Nuclear Information System (INIS)

    Broom, R.F.; Wolf, P.

    1977-01-01

    The surface impedance of the superconducting films comprising the electrodes of Josephson tunnel junctions has been derived from the BCS theory in the extreme London limit. Expressions have been obtained for (i) the dependence of the penetration depth lambda on frequency and temperature, and (ii) the quality factor Q of the junction cavity, attributable to surface absorption in the electrodes. The effect of thin electrodes (t 9 or approx. = lambda) is also included in the calculations. Comparison of the calculated frequency dependence of lambda with resonance measurements on Pb-alloy and all-Nb tunnel junctions yields quite good agreement, indicating that the assumptions made in the theory are reasonable. Measurements of the (current) amplitude of the resonance peaks of the junctions have been compared with the values obtained from inclusion of the calculated Q in the theory by Kulik. In common with observations on microwave cavities by other workers, we find that a small residual conductivity must be added to the real part of the BCS value. With its inclusion, good agreement is found between calculation and experiment, within the range determined by the simplifying assumptions of Kulik's theory. From the results, we believe the calculation of Q to be reasonably accurate for the materials investigated. It is shown that the resonance amplitude of Josephson junctions can be calculated directly from the material constants and a knowledge of the residual conductivity

  14. Climatic effects of nuclear war

    International Nuclear Information System (INIS)

    Covey, C.

    1985-01-01

    Global climatic consequences of a nuclear war have, until recently, been assumed to be insignificant compared with the obviously devastating direct effects from blast, heat, and short-term fallout. But a number of investigations carried out over the past few years indicate that climatic impact could actually be severe enough to threaten the global ecosystem significantly, including regions that may not have been directly involved in the war. This change in perception comes as researchers realize that the fires ignited by nuclear explosions would generate so much smoke that, even spread over a large portion of Earth's surface, densities could be high enough to block most of the sunlight normally reaching the ground. As a result, temperatures could decrease below freezing in a nuclear winter lasting weeks to months. Smoke from fires is what would make nuclear winter so severe. Of necessity, theoretical models are relied upon to estimate the climatic impact of nuclear war. The models incorporate many uncertain assumptions, particularly regarding the small-scale details of smoke production by fires

  15. The Effects of Nuclear Weapons

    Science.gov (United States)

    1977-01-01

    34Nuclear Explosion Effects Practice No. 42, 1961. on Structui’es and Protective Construction-A * ARMOUR RESEARCH FOUNDATION, "A Sim- Selected Bibliography...34 U.S. Atomic Energy p1e Method of Evaluating Blast Effects on Commission, April 1961, TID-3092. Buildihigs," Armour Research Foundation, PI(KERINU, E...stripes have been destroyed by the heat fiom the therm. al radiation. lion points could receive thermal radia- as shades, curtains, and drapes . Of

  16. Common features of a vortex structure in long exponentially shaped Josephson junctions and Josephson junctions with inhomogeneities

    International Nuclear Information System (INIS)

    Boyadjiev, T.L.; Semerdjieva, E.G.; Shukrinov, Yu.M.

    2007-01-01

    We study the vortex structure in three different models of the long Josephson junction: the exponentially shaped Josephson junction and the Josephson junctions with the resistor and the shunt inhomogeneities in the barrier layer. For these three models the critical curves 'critical current-magnetic field' are numerically constructed. We develop the idea of the equivalence of the exponentially shaped Josephson junction and the rectangular junction with the distributed inhomogeneity and demonstrate that at some parameters of the shunt and the resistor inhomogeneities in the ends of the junction the corresponding critical curves are very close to the exponentially shaped one

  17. Josephson Circuits as Vector Quantum Spins

    Science.gov (United States)

    Samach, Gabriel; Kerman, Andrew J.

    While superconducting circuits based on Josephson junction technology can be engineered to represent spins in the quantum transverse-field Ising model, no circuit architecture to date has succeeded in emulating the vector quantum spin models of interest for next-generation quantum annealers and quantum simulators. Here, we present novel Josephson circuits which may provide these capabilities. We discuss our rigorous quantum-mechanical simulations of these circuits, as well as the larger architectures they may enable. This research was funded by the Office of the Director of National Intelligence (ODNI) and the Intelligence Advanced Research Projects Activity (IARPA) under Air Force Contract No. FA8721-05-C-0002. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of ODNI, IARPA, or the US Government.

  18. Josephson tunnel junctions in niobium films

    International Nuclear Information System (INIS)

    Wiik, Tapio.

    1976-12-01

    A method of fabricating stable Josephson tunnel junctions with reproducible characteristics is described. The junctions have a sandwich structure consisting of a vacuum evaporated niobium film, a niobium oxide layer produced by the glow discharge method and a lead film deposited by vacuum evaporation. Difficulties in producing thin-film Josephson junctions are discussed. Experimental results suggest that the lower critical field of the niobium film is the most essential parameter when evaluating the quality of these junctions. The dependence of the lower critical field on the film thickness and on the Ginzburg-Landau parameter of the film is studied analytically. Comparison with the properties of the evaporated films and with the previous calculations for bulk specimens shows that the presented model is applicable for most of the prepared samples. (author)

  19. Relaxation oscillation logic in Josephson junction circuits

    International Nuclear Information System (INIS)

    Fulton, T.A.

    1981-01-01

    A dc powered, self-resetting Josephson junction logic circuit relying on relaxation oscillations is described. A pair of Josephson junction gates are connected in series, a first shunt is connected in parallel with one of the gates, and a second shunt is connected in parallel with the series combination of gates. The resistance of the shunts and the dc bias current bias the gates so that they are capable of undergoing relaxation oscillations. The first shunt forms an output line whereas the second shunt forms a control loop. The bias current is applied to the gates so that, in the quiescent state, the gate in parallel with the second shunt is at V O, and the other gate is undergoing relaxation oscillations. By controlling the state of the first gate with the current in the output loop of another identical circuit, the invert function is performed

  20. Electrical analog of a Josephson junction

    International Nuclear Information System (INIS)

    Goldman, A.M.

    1979-01-01

    It is noted that a mathematical description of the phase-coupling of two oscillators synchronized by a phase-lock-loop under the influence of thermal white noise is analogous to that of the phase coupling of two superconductors in a Josephson junction also under the influence of noise. This analogy may be useful in studying threshold instabilities of the Josephson junction in regimes not restricted to the case of large damping. This is of interest because the behavior of the mean voltage near the threshold current can be characterized by critical exponents which resemble those exhibited by an order parameter of a continuous phase transition. As it is possible to couple a collection of oscillators together in a chain, the oscillator analogy may also be useful in exploring the dynamics and statistical mechanics of coupled junctions

  1. Towards a 16 kilobit, subnanosecond Josephson RAM

    International Nuclear Information System (INIS)

    Herr, Q.P.; Eaton, L.

    1999-01-01

    A critical component of ultrahigh-speed Josephson logic systems is compatible memory. We are developing a fast Josephson memory that could be used as a small memory or first-level cache. Performance goals include sub-ns access and cycle time, 16 kbit cm -2 integration scale, low power consumption and appreciable yield. Initial test results on circuits fabricated in TRW's standard Nb integrated circuit process indicate that all these goals may be achieved. A 5 bit parallel decoder and 1 kbit memory array have been tested at 0.5 GHz. The maximum operating frequency of the memory array was limited by the test equipment. Circuit density is consistent with 16 kbit cm -2 . The top-level architecture has been chosen to achieve high throughput and low skew. The architecture is word organized, multiported and interleaved. (author)

  2. Neutron induced permanent damage in Josephson junctions

    International Nuclear Information System (INIS)

    Mueller, G.P.; Rosen, M.

    1982-01-01

    14 MeV neutron induced permanent changes in the critical current density of Josephson junctions due to displacement damage in the junction barrier are estimated using a worst case model and the binary collision simulation code MARLOWE. No likelihood of single event hard upsets is found in this model. It is estimated that a fluence of 10 18 -10 19 neutrons/cm 2 are required to change the critical current density by 5%

  3. Defect formation in long Josephson junctions

    DEFF Research Database (Denmark)

    Gordeeva, Anna; Pankratov, Andrey

    2010-01-01

    We study numerically a mechanism of vortex formation in a long Josephson junction within the framework of the one-dimensional sine-Gordon model. This mechanism is switched on below the critical temperature. It is shown that the number of fluxons versus velocity of cooling roughly scales according...... to the power law with the exponent of either 0.25 or 0.5 depending on the temperature variation in the critical current density....

  4. Hysteresis development in superconducting Josephson junctions

    International Nuclear Information System (INIS)

    Refai, T.F.; Shehata, L.N.

    1988-09-01

    The resistively and capacitive shunted junction model is used to investigate hysteresis development in superconducting Josephson junctions. Two empirical formulas that relate the hysteresis width and the quasi-particle diffusion length in terms of the junctions electrical parameters, temperature and frequency are obtained. The obtained formulas provide a simple tool to investigate the full potentials of the hysteresis phenomena. (author). 9 refs, 3 figs

  5. Nonlinearity in superconductivity and Josephson junctions

    International Nuclear Information System (INIS)

    Lazarides, N.

    1995-01-01

    Within the framework of the Bardeen, Cooper and Schrieffers (BCS) theory, the influence of anisotropy on superconducting states are investigated. Crystal anisotropy exists in un-conventional low temperature superconductors as e.g. U 1-x Th x Be 13 and in high temperature superconductors. Starting from a phenomenological pairing interaction of the electrons or holes, the BCS approach is used to derive a set of coupled nonlinear algebraic equations for the momentum dependent gap parameter. The emphasis is put on bifurcation phenomena between s-, d-wave and mixed s- and d-wave symmetry and the influence on measurable quantities as the electron specific heat, spin susceptibility and Josephson tunnelling. Pitch-fork and perturbed pitch-fork bifurcations have been found separating s- and d-wave superconducting states from mixed s- and d-wave states. The additional superconducting states give rise to jumps in the electron specific heat below the transition temperature. These jumps are rounded in the case of perturbed pitch-fork bifurcations. An experiment to measure the sign of the interlayer interaction using dc SQUIDS is suggested. The Ambegaokar-Baratoff formalism has been used for calculating the quasiparticle current and the two phase coherent tunnelling currents in a Josephson junction made of anisotropic superconductors. It is shown that anisotropy can lead to a reduction in the product of the normal resistance and the critical current. For low voltages across the junction the usual resistively shunted Josephson model can be used. Finally, bunching in long circular Josephson junctions and suppression of chaos in point junctions have been investigated. (au) 113 refs

  6. Josephson junction in superconducting oxides thick films. Jonction Josephson en couche epaisse d'oxydes supraconducteurs

    Energy Technology Data Exchange (ETDEWEB)

    Gunther, C; Monfort, Y; Lam Chok Sing, M; Bloyet, D; Brousse, T; Provost, J; Raveau, B [Institut des Sciences de la Matiere du Rayonnement, 14 - Caen (FR)

    1992-02-01

    Constrictions engraved in YBaCuO thick films fabricated by screen printing on YSZ substrate (J{sub c} > 3 000 A/cm{sup 2} at 77 K) have been studied. Microwave irradiation of the devices at LN{sub 2} showed distinct Shapiro steps demonstrating the presence intrinsic Josephson junctions. The latter have an I{sub c}(T) dependence fitting (1 - T/T{sub c}){sup 2} characteristic of SNS junctions. Furthermore, dc SQUID effects have also been observed with a peak-to-peak response {approx equal} 0.2 {mu}V and with a magnetic field periodicity extending through several hundred of {phi}{sub o}. An energy resolution close to 3 x 10{sup -29} J/Hz is estimated for our constriction operating in the white noise frequency range (f > 50 Hz) at 77 K. This sensitivity is adequate to use this flux sensor in many applications: geomagnetism, magnetocardiology,... 19 refs; 7 figs.

  7. Y-junction of superconducting Josephson chains

    International Nuclear Information System (INIS)

    Giuliano, Domenico; Sodano, Pasquale

    2009-01-01

    We show that, for pertinent values of the fabrication and control parameters, an attractive finite coupling fixed point emerges in the phase diagram of a Y-junction of superconducting Josephson chains. The new fixed point arises only when the dimensionless flux f piercing the central loop of the network equals π and, thus, does not break time-reversal invariance; for f≠π, only the strongly coupled fixed point survives as a stable attractive fixed point. Phase slips (instantons) have a crucial role in establishing this transition: we show indeed that, at f=π, a new set of instantons-the W-instantons-comes into play to destabilize the strongly coupled fixed point. Finally, we provide a detailed account of the Josephson current-phase relationship along the arms of the network, near each one of the allowed fixed points. Our results evidence remarkable similarities between the phase diagram accessible to a Y-junction of superconducting Josephson chains and the one found in the analysis of quantum Brownian motion on frustrated planar lattices

  8. Edge currents in frustrated Josephson junction ladders

    Science.gov (United States)

    Marques, A. M.; Santos, F. D. R.; Dias, R. G.

    2016-09-01

    We present a numerical study of quasi-1D frustrated Josephson junction ladders with diagonal couplings and open boundary conditions, in the large capacitance limit. We derive a correspondence between the energy of this Josephson junction ladder and the expectation value of the Hamiltonian of an analogous tight-binding model, and show how the overall superconducting state of the chain is equivalent to the minimum energy state of the tight-binding model in the subspace of one-particle states with uniform density. To satisfy the constraint of uniform density, the superconducting state of the ladder is written as a linear combination of the allowed k-states of the tight-binding model with open boundaries. Above a critical value of the parameter t (ratio between the intra-rung and inter-rung Josephson couplings) the ladder spontaneously develops currents at the edges, which spread to the bulk as t is increased until complete coverage is reached. Above a certain value of t, which varies with ladder size (t = 1 for an infinite-sized ladder), the edge currents are destroyed. The value t = 1 corresponds, in the tight-binding model, to the opening of a gap between two bands. We argue that the disappearance of the edge currents with this gap opening is not coincidental, and that this points to a topological origin for these edge current states.

  9. Fractional Josephson vortices: oscillating macroscopic spins

    Energy Technology Data Exchange (ETDEWEB)

    Gaber, T.; Buckenmaier, K.; Koelle, D.; Kleiner, R.; Goldobin, E. [Universitaet Tuebingen, Physikalisches Institut - Experimentalphysik II, Tuebingen (Germany)

    2007-11-15

    Fractional Josephson vortices carry a magnetic flux {phi}, which is a fraction of the magnetic flux quantum {phi}{sub 0}{approx}2.07 x 10{sup -15} Wb. We consider a fractional vortex which spontaneously appears at a phase discontinuity. Its properties are very different from the properties of the usual integer fluxon. In particular, a fractional vortex is pinned and may have one of two possible polarities - just like a usual spin 1/2 particle. The fractional vortex may also oscillate around its equilibrium position with an eigenfrequency which is expected to be within the Josephson plasma gap. Using microwave spectroscopy, we investigate the dependence of the eigenfrequency of a fractional Josephson vortex on its magnetic flux {phi} and on the bias current. The experimental results are in good agreement with theoretical predictions. Positive result of this experiment is a cornerstone for further investigation of more complex fractional vortex systems such as fractional vortex molecules and tunable bandgap materials. (orig.)

  10. Josephson cross-sectional model experiment

    International Nuclear Information System (INIS)

    Ketchen, M.B.; Herrell, D.J.; Anderson, C.J.

    1985-01-01

    This paper describes the electrical design and evaluation of the Josephson cross-sectional model (CSM) experiment. The experiment served as a test vehicle to verify the operation at liquid-helium temperatures of Josephson circuits integrated in a package environment suitable for high-performance digital applications. The CSM consisted of four circuit chips assembled on two cards in a three-dimensional card-on-board package. The chips (package) were fabricated in a 2.5-μm (5-μm) minimum linewidth Pb-alloy technology. A hierarchy of solder and pluggable connectors was used to attach the parts together and to provide electrical interconnections between parts. A data path which simulated a jump control sequence and a cache access in each machine cycle was successfully operated with cycle times down to 3.7 ns. The CSM incorporated the key components of the logic, power, and package of a prototype Josephson signal processor and demonstrated the feasibility of making such a processor with a sub-4-ns cycle time

  11. Vortex dynamics in two-dimensional Josephson junction arrays with asymmetrically bimodulated potential

    International Nuclear Information System (INIS)

    Nie, Qing-Miao; Zhang, Sha-Sha; Chen, Qing-Hu; Zhou, Wei

    2012-01-01

    On the basis of resistively-shunted junction dynamics, we study vortex dynamics in two-dimensional Josephson junction arrays with asymmetrically single and bimodulated periodic pinning potential for the full range of vortex density f. The ratchet effect occurring at a certain range of temperature, current, and f, is observed in our simulation. We explain the microscopic behavior behind this effect by analyzing the vortex distribution and interaction. The reversal of the ratchet effect can be observed at several f values for a small driven current. This effect is stronger when the asymmetric potential is simultaneously introduced in two directions. -- Highlights: ► The ratchet effect in Josephson junction arrays strongly depends on vortex density. ► The reversed ratchet effect can be observed at several f for a small current. ► The interaction between vortices can explain the reversed ratchet effect. ► The ratchet effect is enhanced by injecting the bimodulated asymmetric potential.

  12. Nuclear energy: biological effects and environmental impact

    International Nuclear Information System (INIS)

    Boonefaes, M.

    1987-01-01

    This thesis is concerned with the large development of nuclear power plants and the recent nuclear catastrophe which has made clear how the hazards resulting from radioactivity affect public health and the environment. Environmental effects of nuclear power plants operating in normal conditions are small, but to obtain nuclear power plants of reduced radioactivity, optimization of their design, construction, operation and waste processing plays a decisive role. Biological effects of ionizing radiations and environmental impacts of Nuclear Power plants are developed [fr

  13. Climatic effects of nuclear war

    International Nuclear Information System (INIS)

    Turco, R.P.; Toon, O.B.; Ackerman, T.P.; Pollack, J.B.; Sagan, C.

    1984-01-01

    Recent findings by this group confirmed by workers in Europe, the US and the USSR, suggest that the long-term climatic effects of a major nuclear war are likely to be much severer and farther-reaching than had been supposed. In the aftermath of such a war vast areas of the earth could be subjected to prolonged darkness, abnormally low temperatures, violent windstorms, toxic smog and persistent radioactive fallout - in short, the combination of conditions that has come to be known as nuclear winter. In brief, the authors' initial results, published in Science in December, 1983, showed that the potential global atmospheric and climatic consequences of nuclear war...are serious. Significant hemispherical attenuation of the solar radiation flux and subfreezing land temperatures may be caused by fine dust raised in high-yield nuclear surface bursts and by smoke from city and forest fires ignited by airbursts of all yields. Subsequent studies, based on more powerful models of the general circulation of the earth's atmosphere, have tended to confirm both the validity of the authors' investgative approach and the main thrust of their findings. Most of this article is devoted to reviewing the current state of knowledge on this vital issue

  14. Radiation Effects in Nuclear Ceramics

    Directory of Open Access Journals (Sweden)

    L. Thomé

    2012-01-01

    Full Text Available Due to outstanding physicochemical properties, ceramics are key engineering materials in many industrial domains. The evaluation of the damage created in ceramics employed in radiative media is a challenging problem for electronic, space, and nuclear industries. In this latter field, ceramics can be used as immobilization forms for radioactive wastes, inert fuel matrices for actinide transmutation, cladding materials for gas-cooled fission reactors, and structural components for fusion reactors. Information on the radiation stability of nuclear materials may be obtained by simulating the different types of interactions involved during the slowing down of energetic particles with ion beams delivered by various types of accelerators. This paper presents a review of the radiation effects occurring in nuclear ceramics, with an emphasis on recent results concerning the damage accumulation processes. Energetic ions in the KeV-GeV range are used to explore the nuclear collision (at low energy and electronic excitation (at high energy regimes. The recovery by electronic excitation of the damage created by ballistic collisions (SHIBIEC process is also addressed.

  15. Long Josephson Junction Stack Coupled to a Cavity

    DEFF Research Database (Denmark)

    Madsen, Søren Peder; Pedersen, Niels Falsig; Groenbech-Jensen, N.

    2007-01-01

    A stack of inductively coupled long Josephson junctions are modeled as a system of coupled sine-Gordon equations. One boundary of the stack is coupled electrically to a resonant cavity. With one fluxon in each Josephson junction, the inter-junction fluxon forces are repulsive. We look at a possible...... transition, induced by the cavity, to a bunched state....

  16. Numerical simulations of flux flow in stacked Josephson junctions

    DEFF Research Database (Denmark)

    Madsen, Søren Peder; Pedersen, Niels Falsig

    2005-01-01

    We numerically investigate Josephson vortex flux flow states in stacked Josephson junctions, motivated by recent experiments trying to observe the vortices in a square vortex lattice when a magnetic field is applied to layered high-Tc superconductors of the Bi2Sr2CaCu2Ox type. By extensive...

  17. Critical current of Josephson contacts with accidental position of vortexes

    International Nuclear Information System (INIS)

    Fistul', M.V.

    1989-01-01

    Josephson contact critical current dependence on magnetic field under different concentrations of Abrikosov vortices (AV) in superconducting shores is found. Pinned vortex concentration as well as correlation in the vortex position can be determined by Josephson current dependence on magnetic field

  18. Superconducting states and depinning transitions of Josephson ladders

    International Nuclear Information System (INIS)

    Barahona, M.; Strogatz, S.H.; Orlando, T.P.

    1998-01-01

    We present analytical and numerical studies of pinned superconducting states of open-ended Josephson ladder arrays, neglecting inductances but taking edge effects into account. Treating the edge effects perturbatively, we find analytical approximations for three of these superconducting states emdash the no-vortex, fully frustrated, and single-vortex states emdash as functions of the dc bias current I and the frustration f. Bifurcation theory is used to derive formulas for the depinning currents and critical frustrations at which the superconducting states disappear or lose dynamical stability as I and f are varied. These results are combined to yield a zero-temperature stability diagram of the system with respect to I and f. To highlight the effects of the edges, we compare this dynamical stability diagram to the thermodynamic phase diagram for the infinite system where edges have been neglected. We briefly indicate how to extend our methods to include self-inductances. copyright 1998 The American Physical Society

  19. Josephson oscillations and noise temperatures in YBa2Cu3O7-x grain-boundary junctions

    DEFF Research Database (Denmark)

    Yu, Ya. Divin; Mygind, Jesper; Pedersen, Niels Falsig

    1992-01-01

    The ac Josephson effect was studied in YBa2Cu3O7−x grain-boundary junctions (GBJ) in the temperature range from 4 to 90 K. The temperature dependence of the linewidth of millimeter-wave Josephson oscillations was measured and it is shown that the derived effective noise temperatures may be as low...... as the physical temperature in the temperature range investigated. In the millimeter-wave range, linewidths as low as 380 MHz were found at liquid-nitrogen temperatures. Applied Physics Letters is copyrighted by The American Institute of Physics....

  20. The Effects of Nuclear Weapons

    Energy Technology Data Exchange (ETDEWEB)

    Glasstone, Samuel

    1957-06-01

    This handbook prepared by the Armed Forces Special Weapons Project of the Department of Defense in coordination with other cognizant government agencies and published by the United States Atomic Energy Commission, is a comprehensive summary of current knowledge on the effects of nuclear weapons. The effects information contained herein is calculated for yields up to 20 megatons and the scaling laws for hypothetically extending the calculations beyond this limit are given. The figure of 20 megatons however is not be taken as an indication of capabilities or developments.

  1. Influence of coupling parameter on current-voltage characteristics of intrinsic Josephson junctions in high-T c superconductors

    International Nuclear Information System (INIS)

    Shukrinov, Yu.M.; Mahfouzi, F.

    2006-01-01

    We study the current-voltage characteristics of intrinsic Josephson junctions in high-T c superconductors by numerical calculations and in framework of capacitively coupled Josephson junctions model we obtain the total number of branches. The influence of the coupling parameter α on the current-voltage characteristics at fixed parameter β (β 2 1/β c , where β c is McCumber parameter) and the influence of α on β-dependence of the current-voltage characteristics are investigated. We obtain the α-dependence of the branch's slopes and branch's endpoints. The presented results show new features of the coupling effect on the scheme of hysteresis jumps in current-voltage characteristics of intrinsic Josephson junctions in high-T c superconductors

  2. Climatic effects of nuclear war

    International Nuclear Information System (INIS)

    Crutzen, P.J.

    1987-01-01

    Although considerable further research has been conducted since the writing of the Scientific Committee on Problems of the Environment (SCOPE) study, the main conclusions reached in early 1986 about the potential climatic, atmospheric, chemical, ecological, and agricultural consequences of a nuclear war are still valid, also taking into account the latest research results by Thompson and Schneider (1986). The main finding of the SCOPE study is that severe, large-scale, possibly global, climatic disturbances could result from a nuclear war in which a substantial fraction (10% or more) of the combustible materials in the NATO and Warsaw Pact nations would burn, producing several tens of million tonnes of soot. This could be caused by nuclear attacks on less than a hundred of the most important urban and industrial centres of these nations. As a consequence, it is estimated that surface temperatures might drop by more than 10 deg. C over a large fraction of the continents in the northern hemisphere and that rainfall could also be strongly reduced. These effects could last for weeks, maybe years. In many parts of the northern hemisphere agricultural productivity would be severely reduced, contributing to serious food shortages. 37 refs, 5 figs, 4 tabs

  3. Health and environmental effects of nuclear weapons

    International Nuclear Information System (INIS)

    1993-01-01

    This report briefly reviews previous WHO work on the health consequences of nuclear war and concentrates on current information about the effects of nuclear weapons on health, and related environmental problems. 15 refs

  4. Overview of climatic effects of nuclear winter

    International Nuclear Information System (INIS)

    Jones, E.M.; Malone, R.C.

    1985-01-01

    A general description of the climatic effects of a nuclear war are presented. This paper offers a short history of the subject, a discussion of relevant parameters and physical processes, and a description of plausible nuclear winter scenario. 9 refs

  5. Experiments on intrinsic and thermally induced chaos in an rf-driven Josephson junction

    DEFF Research Database (Denmark)

    Davidson, A.; Dueholm, B.; Beasley, M. R.

    1986-01-01

    We report detailed measurements of low-frequency noise due to microwaves applied to a real Josephson tunnel junction. An intrinsically chaotic region is apparently identified, but the effects of thermal noise are shown to be significant. In particular we show experimental data that we interpret a...... as evidence for thermally activated hopping and thermally affected chaos. The data are only in qualitative accord with recent ideas regarding the effect of thermal noise on intermittent chaos....

  6. Studies of chaos and thermal noise in a driven Josephson junction using an electronic analog

    International Nuclear Information System (INIS)

    Pegrum, C.M.; Gurney, W.S.C.; Nisbet, R.M.

    1989-01-01

    Using an electronic analog of a resistively shunted driven Josephson junction, the authors have demonstrated a number of effects, including the appearance of a devil's staircase in the current-voltage characteristic, the onset of chaos, and the effect of noise on these phenomena. The authors stress that the analog is simple, but models the junction behavior with a high degree of accuracy and detail

  7. Nuclear famine: The indirect effects of nuclear war

    International Nuclear Information System (INIS)

    Harwell, M.A.; Harwell, C.C.

    1986-01-01

    The indirect effects of a nuclear war, especially as mediated by disruption in food availability, could be much more extensive than the direct effects. Furthermore, this risk is especially severe for noncombatant countries - for the 4 billion or so humans expected to survive the immediate period after a nuclear war relatively physically unharmed. Thus, a fundamentally different picture of the post-nuclear-war world results, where a large-scale nuclear war between the United States and the Soviet Union would probably result in more eventual fatalities in India than in the United States and the Soviet Union combined, and more people would die on the African continent than in all of Europe. Rather than reflecting images of Hiroshima and Nagasaki, a modern nuclear war would, for most of the people of the world, much more resemble current images of Ethiopia and the Sudan

  8. Doubled Shapiro steps in a topological Josephson junction

    Science.gov (United States)

    Li, Yu-Hang; Song, Juntao; Liu, Jie; Jiang, Hua; Sun, Qing-Feng; Xie, X. C.

    2018-01-01

    We study the transport properties of a superconductor-quantum spin Hall insulator-superconductor hybrid system in the presence of microwave radiation. Instead of adiabatic analysis or use of the resistively shunted junction model, we start from the microscopic Hamiltonian and calculate the d.c. current directly with the help of the nonequilibrium Green's function method. The numerical results show that (i) the I-V curves of background current due to multiple Andreev reflections exhibit a different structure from those in the conventional junctions, and (ii) all Shapiro steps are visible and appear one by one at high frequencies, while at low frequencies, the steps evolve exactly as the Bessel functions and the odd steps are completely suppressed, implying a fractional Josephson effect.

  9. Synchronisation of Josephson vortices in multi-junction systems

    DEFF Research Database (Denmark)

    Filatrella, G.; Pedersen, Niels Falsig; Wiesenfeld, K.

    2006-01-01

    , is modified by the coupling among the junctions, so the motion of the flux quanta in the various layers is affected by the flux dynamics in all other layers. Two basic states are possible: a synchronous motion, where all junctions are reflected at the edge at the same instant, and an out-of-phase motion......, that is mainly to retrieve the above described synchronous motion. We discuss the physics behind synchronization of nonlinear elements and we review applications to Josephson arrays. We discuss in the framework of a general model for synchronization, the Kuramoto model, a mechanism that can possibly enhance...... synchronization, such as coupling to a resonant cavity. We present a version of the Kuramoto model that might include the effects of the strong interaction between the oscillators and the cavity. (c) 2005 Elsevier B.V. All rights reserved....

  10. Quark effects in nuclear physics

    International Nuclear Information System (INIS)

    Scholten, O.

    1990-01-01

    The magnitude of the quark effect for low-energy nuclear physics is investigated. Coulomb energy is studied in the A=3 system in order to determine the effect of the composite structure of the nucleon. In the actual calculations a non-relativistic quark-cluster model description has been used. A nucleon size b=0.617 fm, the width of the relative wave function Φ of the quarks in the nucleon, has been assumed. It is concluded that the contribution to Coulomb energies due to quark effects are significant compared to the observed Nolen-Schiffer anomaly. However these do not provide the long searched for 'smoking gun'. When the free parameters that appear in the calculation are adjusted to reproduce the same charge form factor, the calculated anomalies are not significantly different. 2 figs., 2 tabs., 8 refs.2

  11. Ferromagnetic Josephson Junctions for Cryogenic Memory

    Science.gov (United States)

    Niedzielski, Bethany M.; Gingrich, Eric C.; Khasawneh, Mazin A.; Loloee, Reza; Pratt, William P., Jr.; Birge, Norman O.

    2015-03-01

    Josephson junctions containing ferromagnetic materials are of interest for both scientific and technological purposes. In principle, either the amplitude of the critical current or superconducting phase shift across the junction can be controlled by the relative magnetization directions of the ferromagnetic layers in the junction. Our approach concentrates on phase control utilizing two junctions in a SQUID geometry. We will report on efforts to control the phase of junctions carrying either spin-singlet or spin-triplet supercurrent for cryogenic memory applications. Supported by Northorp Grumman Corporation and by IARPA under SPAWAR Contract N66001-12-C-2017.

  12. Phase locking between Josephson soliton oscillators

    DEFF Research Database (Denmark)

    Holst, T.; Hansen, Jørn Bindslev; Grønbech-Jensen, N.

    1990-01-01

    We report observations of phase-locking phenomena between two Josephson soliton (fluxon) oscillators biased in self-resonant modes. The locking strength was measured as a function of bias conditions. A frequency tunability of the phase-locked oscillators up to 7% at 10 GHz was observed. Two coupled...... perturbed sine-Gordon equations were derived from an equivalent circuit consisting of inductively coupled, nonlinear, lossy transmission lines. These equations were solved numerically to find the locking regions. Good qualitative agreement was found between the experimental results and the calculations...

  13. A Josephson ternary associative memory cell

    International Nuclear Information System (INIS)

    Morisue, M.; Suzuki, K.

    1989-01-01

    This paper describes a three-valued content addressable memory cell using a Josephson complementary ternary logic circuit named as JCTL. The memory cell proposed here can perform three operations of searching, writing and reading in ternary logic system. The principle of the memory circuit is illustrated in detail by using the threshold-characteristics of the JCTL. In order to investigate how a high performance operation can be achieved, computer simulations have been made. Simulation results show that the cycle time of memory operation is 120psec, power consumption is about 0.5 μW/cell and tolerances of writing and reading operation are +-15% and +-24%, respectively

  14. Harmonic synchronization in resistively coupled Josephson junctions

    International Nuclear Information System (INIS)

    Blackburn, J.A.; Gronbech-Jensen, N.; Smith, H.J.T.

    1994-01-01

    The oscillations of two resistively coupled Josephson junctions biased only by a single dc current source are shown to lock harmonically in a 1:2 mode over a significant range of bias current, even when the junctions are identical. The dependence of this locking on both junction and coupling parameters is examined, and it is found that, for this particular two-junction configuration, 1:1 locking can never occur, and also that a minimum coupling coefficient is needed to support harmonic locking. Some issues related to subharmonic locking are also discussed

  15. delta-biased Josephson tunnel junctions

    DEFF Research Database (Denmark)

    Monaco, R.; Mygind, Jesper; Koshelet, V.

    2010-01-01

    Abstract: The behavior of a long Josephson tunnel junction drastically depends on the distribution of the dc bias current. We investigate the case in which the bias current is fed in the central point of a one-dimensional junction. Such junction configuration has been recently used to detect...... the persistent currents circulating in a superconducting loop. Analytical and numerical results indicate that the presence of fractional vortices leads to remarkable differences from the conventional case of uniformly distributed dc bias current. The theoretical findings are supported by detailed measurements...

  16. Exponentially tapered Josephson flux-flow oscillator

    DEFF Research Database (Denmark)

    Benabdallah, A.; Caputo, J. G.; Scott, Alwyn C.

    1996-01-01

    We introduce an exponentially tapered Josephson flux-flow oscillator that is tuned by applying a bias current to the larger end of the junction. Numerical and analytical studies show that above a threshold level of bias current the static solution becomes unstable and gives rise to a train...... of fluxons moving toward the unbiased smaller end, as in the standard flux-flow oscillator. An exponentially shaped junction provides several advantages over a rectangular junction including: (i) smaller linewidth, (ii) increased output power, (iii) no trapped flux because of the type of current injection...

  17. The effects of nuclear weapons

    International Nuclear Information System (INIS)

    Barnaby, F.; Rotblat, J.

    1982-01-01

    At least 40% of the population of Hiroshima and 26% of that of Nagasaki were killed in the nuclear attacks. The early and late effects in these two cities and in relation to present weaponry are briefly discussed. The effects of blast, heat and initial and delayed radiation are outlined. Neutron and gamma doses as functions of slant distances for bombs of various specified yields are presented. Dose rates for fallout at various times after explosions in terms of wind velocity and various cloud formations are also outlined. In Western Europe there are only 145 cities with populations of over 200,000. It is concluded that the destruction of these cities would kill in a short time more than one third of the population of Western Europe, and in a nuclear world war, not only would a fair part of the urban population in the Northern Hemisphere be killed by fire and blast, and most of the survivors by radiation, but much of the rural population would be killed by radiation from fallout. Many millions in the Southern Hemisphere would also be killed by fallout radiation. (U.K.)

  18. The Effects of Nuclear Weapons. Third edition

    Energy Technology Data Exchange (ETDEWEB)

    Glasstone, S; Dolan, P J

    1977-01-01

    Since the last edition of ''The Effects of Nuclear Weapons'' in 1962 much new information has become available concerning nuclear weapon effects. This has come in part from the series of atmospheric tests, including several at very high altitudes, conducted in the Pacific Ocean area in 1962. In addition, laboratory studies, theoretical calculations, and computer simulations have provided a better understanding of the various effects. A new chapter has been added on the electromagnetic pulse. The chapter titles are as follows: general principles of nuclear explosions; descriptions of nuclear explosions; air blast phenomena in air and surface bursts; air blast loading; structural damage from air blast; shock effects of surface and subsurface bursts; thermal radiation and its effects; initial nuclear radiation; residual nuclear radiation and fallout; radio and radar effects; the electromagnetic pulse and its effects; and biological effects. (LTN)

  19. Investigations of the structure of Nb-NbO/sub x/-Pb Josephson tunnel elements

    International Nuclear Information System (INIS)

    Koehler, H.J.; Seidel, P.; Weber, P.; Bluethner, K.; Linke, S.; Haedrich, T.; Berthel, K.H.

    1983-01-01

    Nb-NbO/sub x/-Pb tunnel junctions with tunnel areas of 100x100 μm 2 to 3x3 μm 2 are investigated. The temperature dependence of the current-voltage characteristic, of the effective niobium energy gap and of the critical Josephson current are compared with the BCS curves. The deviation of the experimentally determined values is caused by a proximity layer. With a proximity effect model the parameters of this proximity layer can be found by fitting the calculated values to the experimental values. Moreover, current density distribution in tunnel junctions are determined, which can be calculated from the dependence of the critical Josephson current on the magnetic field by means of a theoretical model. The dependences of the current density distributions on tunnel areas and the changes in time are investigated. (author)

  20. Some chaotic features of intrinsically coupled Josephson junctions

    International Nuclear Information System (INIS)

    Kolahchi, M.R.; Shukrinov, Yu.M.; Hamdipour, M.; Botha, A.E.; Suzuki, M.

    2013-01-01

    Highlights: ► Intrinsically coupled Josephson junctions model a high-T c superconductor. ► Intrinsically coupled Josephson junctions can act as a chaotic nonlinear system. ► Chaos could be due to resonance overlap. ► Avoiding parameters that lead to chaos is important for the design of resonators. -- Abstract: We look for chaos in an intrinsically coupled system of Josephson junctions. This study has direct applications for the high-T c resonators which require coherence amongst the junctions

  1. The pulse-driven AC Josephson voltage normal

    International Nuclear Information System (INIS)

    Kieler, Oliver

    2016-01-01

    In this contribution quantum precise alternating-voltage sources are presented, which make the generation of arbitrary wave forms with highest spectral purity with a high bandwidth from DC up to the MHz range possible. Heartpiece of these Josephson voltage normals is a serial circuit of many thousand Josephson contacts, which make by irradiation with high-frequency radiation (microwaves) the generation of highly precise voltage values possible. Thereby in the current-voltage characteristics stages of constant voltage, so called Shapiro stages, occur. Illustratively these stages can be described by the transfer of a certain number of flux quanta through the Josephson contacts.

  2. Phase transition in nonuniform Josephson arrays: Monte Carlo simulations

    Science.gov (United States)

    Lozovik, Yu. E.; Pomirchy, L. M.

    1994-01-01

    Disordered 2D system with Josephson interactions is considered. Disordered XY-model describes the granular films, Josephson arrays etc. Two types of disorder are analyzed: (1) randomly diluted system: Josephson coupling constants J ij are equal to J with probability p or zero (bond percolation problem); (2) coupling constants J ij are positive and distributed randomly and uniformly in some interval either including the vicinity of zero or apart from it. These systems are simulated by Monte Carlo method. Behaviour of potential energy, specific heat, phase correlation function and helicity modulus are analyzed. The phase diagram of the diluted system in T c-p plane is obtained.

  3. Mesonic effects in nuclear physics

    International Nuclear Information System (INIS)

    Johnson, M.

    1978-01-01

    The relation between mesons and nucleons and the properties of nuclear matter, as presently understood, is considered in these lectures. Feynman diagrams, meson theoretical nucleon-nucleon interactions, mesonic components in nuclear wave functions, direct observation of mesonic components in NN scattering above the pion production threshold, nuclear matter theory, and pion condensation are treated. 120 references

  4. A semiconductor nanowire Josephson junction microwave laser

    Science.gov (United States)

    Cassidy, Maja; Uilhoorn, Willemijn; Kroll, James; de Jong, Damaz; van Woerkom, David; Nygard, Jesper; Krogstrup, Peter; Kouwenhoven, Leo

    We present measurements of microwave lasing from a single Al/InAs/Al nanowire Josephson junction strongly coupled to a high quality factor superconducting cavity. Application of a DC bias voltage to the Josephson junction results in photon emission into the cavity when the bias voltage is equal to a multiple of the cavity frequency. At large voltage biases, the strong non-linearity of the circuit allows for efficient down conversion of high frequency microwave photons down to multiple photons at the fundamental frequency of the cavity. In this regime, the emission linewidth narrows significantly below the bare cavity linewidth to 50%. The junction-cavity coupling and laser emission can be tuned rapidly via an external gate, making it suitable to be integrated into a scalable qubit architecture as a versatile source of coherent microwave radiation. This work has been supported by the Netherlands Organisation for Scientific Research (NWO/OCW), Foundation for Fundamental Research on Matter (FOM), European Research Council (ERC), and Microsoft Corporation Station Q.

  5. Modeling Bloch oscillations in nanoscale Josephson junctions

    Science.gov (United States)

    Vora, Heli; Kautz, R. L.; Nam, S. W.; Aumentado, J.

    2018-01-01

    Bloch oscillations in nanoscale Josephson junctions with a Coulomb charging energy comparable to the Josephson coupling energy are explored within the context of a model previously considered by Geigenmüller and Schön that includes Zener tunneling and treats quasiparticle tunneling as an explicit shot-noise process. The dynamics of the junction quasicharge are investigated numerically using both Monte Carlo and ensemble approaches to calculate voltage-current characteristics in the presence of microwaves. We examine in detail the origin of harmonic and subharmonic Bloch steps at dc biases I = (n/m)2ef induced by microwaves of frequency f and consider the optimum parameters for the observation of harmonic (m = 1) steps. We also demonstrate that the GS model allows a detailed semiquantitative fit to experimental voltage-current characteristics previously obtained at the Chalmers University of Technology, confirming and strengthening the interpretation of the observed microwave-induced steps in terms of Bloch oscillations. PMID:29577106

  6. Josephson current in ballistic graphene Corbino disk

    Science.gov (United States)

    Abdollahipour, Babak; Mohammadkhani, Ramin; Khalilzadeh, Mina

    2018-06-01

    We solve Dirac-Bogoliubov-De-Gennes (DBdG) equation in a superconductor-normal graphene-superconductor (SGS) junction with Corbino disk structure to investigate the Josephson current through this junction. We find that the critical current Ic has a nonzero value at Dirac point in which the concentration of the carriers is zero. We show this nonzero critical current depends on the system geometry and it decreases monotonically to zero by decreasing the ratio of the inner to outer radii of the Corbino disk (R1 /R2), while in the limit of R1 /R2 → 1 it scales like a diffusive Corbino disk. The product of the critical current and the normal-state resistance IcRN increases by increasing R1 /R2 and attains the same value for the wide and short rectangular structure at the limit of R1 /R2 → 1 at zero doping. These results reveals the pseudodiffusive behavior of the graphene Corbino Josephson junction similar to the rectangular structure at the zero doping.

  7. Vortex dynamics in Josephson junctions arrays

    International Nuclear Information System (INIS)

    Shalom, Diego Edgar

    2005-01-01

    In this work we study the dynamics of vortices in two-dimensional overdamped Josephson Junctions Arrays (JJA) driven by dc current in a wide range of conditions varying magnetic field and temperature using experiments, numerical simulations and analytic studies.We develop the Fixed Phase method, a variation of numeric relaxation techniques in which we fix and control the phase of some islands, adjacent to the vortex center, while allowing all other phases in the system to relax.In this way we are able to pull and push the vortex uphill, as we are forcing the center of rotation of the vortex currents to be in a defined location, allowing us to calculate the potential energy of a vortex located in any arbitrary position.We use this method to study the potential energy of a vortex in a variety of situations in homogeneous and non-homogeneous JJA, such as arrays with defects, channel arrays and ratchets.We study the finite size effects in JJA by means of analytic and numerical tools.We implement the rings model, in which we replace the two-dimensional square array by a series of square, concentric, uncoupled rings. This is equivalent to disregarding the radial junctions that couple consecutive rings.In spite of its extreme simplicity, this model holds the main ingredients of the magnetic dependence of the energy.We combine this model with other terms that take into account the dependence in the position of the vortex to obtain a general expression for the potential energy of a vortex in a finite JJA with applied magnetic field.We also present an expression for the first critical field, corresponding to the value of the magnetic field in which the entrance of the first vortex becomes energetically favorable.We build and study JJA modulated to form periodic and asymmetrical potentials for the vortices, named ratchet potentials.The experimental results clearly show the existence of a rectification in the motion of vortices in these potentials.Under certain conditions we

  8. Turbulence, chaos and thermal noise in globally coupled Josephson junction arrays

    International Nuclear Information System (INIS)

    Dominguez, D.

    1995-03-01

    We discuss the effects of thermal noise in underdamped Josephson junction series arrays that are globally coupled through a resistive load and driven by an rf current. We study the breakdown of the law of large numbers in the turbulent phase of the Josephson arrays. This corresponds to a saturation of the broad band noise S 0 for a large number N of junctions. We find that this phenomenon is stable against thermal fluctuations below a critical temperature T cl . The behaviour of S 0 vs. T, for large N, shows three different regimes. For 0 cl , S 0 decreases when increasing T, and there is turbulence and the breakdown of the law of large numbers. For T cl c2 , S 0 is constant and the dynamics is dominated by the chaos of the individual junctions. Finally for T > T c2 , S 0 in mainly due to thermal fluctuations, since it increases linearly with T. (author). 23 refs, 6 figs

  9. Energy scales in YBaCuO grain boundary biepitaxial Josephson junctions

    Energy Technology Data Exchange (ETDEWEB)

    Tafuri, F., E-mail: tafuri@na.infn.it [Dip. Ingegneria dell' Informazione, Seconda Universita di Napoli, 81031 Aversa (CE) (Italy); CNR-SPIN, UOS Napoli, Monte S. Angelo via Cinthia, 80126 Napoli (Italy); Dip. Scienze Fisiche, Universita di Napoli Federico II, Monte S. Angelo via Cinthia, 80126 Napoli (Italy); Stornaiuolo, D. [DPMC, University of Geneva, 24 Quai Ernest-Ansermet, 1211 Geneva 4 (Switzerland); CNR-SPIN, UOS Napoli, Monte S. Angelo via Cinthia, 80126 Napoli (Italy); Lucignano, P. [CNR-ISC, sede di Tor Vergata, Via del Fosso del Cavaliere 100, 00133 Roma (Italy); Dip. Scienze Fisiche, Universita di Napoli Federico II, Monte S. Angelo via Cinthia, 80126 Napoli (Italy); Galletti, L. [Dip. Scienze Fisiche, Universita di Napoli Federico II, Monte S. Angelo via Cinthia, 80126 Napoli (Italy); Longobardi, L. [Dip. Ingegneria dell' Informazione, Seconda Universita di Napoli, 81031 Aversa (CE) (Italy); Massarotti, D. [Dip. Scienze Fisiche, Universita di Napoli Federico II, Monte S. Angelo via Cinthia, 80126 Napoli (Italy); CNR-SPIN, UOS Napoli, Monte S. Angelo via Cinthia, 80126 Napoli (Italy); Montemurro, D. [NEST and Scuola Normale Superiore, Piazza San Silvestro 12, I-56127 Pisa (Italy); Papari, G. [INPAC - Institute for Nanoscale Physics and Chemistry, Nanoscale Superconductivity and Magnetism Pulsed Fields Group, K.U. Leuven, Celestijnenlaan 200 D, B-3001 Leuven (Belgium); Dip. Scienze Fisiche, Universita di Napoli Federico II, Monte S. Angelo via Cinthia, 80126 Napoli (Italy); Barone, A.; Tagliacozzo, A. [Dip. Scienze Fisiche, Universita di Napoli Federico II, Monte S. Angelo via Cinthia, 80126 Napoli (Italy); CNR-SPIN, UOS Napoli, Monte S. Angelo via Cinthia, 80126 Napoli (Italy)

    2012-09-15

    Self-assembled nanoscale channels may naturally arise in the growth process of grain boundaries (GBs) in high critical temperature superconductor (HTS) systems, and deeply influence the transport properties of the GB Josephson junctions (JJs). By isolating nano-channels in YBCO biepitaxial JJs and studying their properties, we sort out specific fingerprints of the mesoscopic nature of the contacts. The size of the channels combined to the characteristic properties of HTS favors a special regime of the proximity effect, where normal state coherence prevails on the superconducting coherence in the barrier region. Resistance oscillations from the current-voltage characteristic encode mesoscopic information on the junction and more specifically on the minigap induced in the barrier. Thouless energy emerges as a characteristic energy of these types of Josephson junctions. Possible implications on the understanding of coherent transport of quasiparticles in HTS and of the dissipation mechanisms are discussed, along with elements to take into account when designing HTS nanostructures.

  10. Properties on niobium-based Josephson tunneling elements in junction microstructures

    International Nuclear Information System (INIS)

    Albrecht, G.; Richter, J.; Weber, P.

    1982-01-01

    We describe the fabrication and electrical characteristics of niobium oxide-barrier tunnel junctions with counterelectrodes of lead/lead alloy. Primary attention is directed to the experimental conditions necessary to obtain high-quality tunnel barriers as well as studies on characterizing the atomic structure of the barrier region. In order to study the tunnel barrier homogeneity in the tunneling region the magnetic field dependence of the critical Josephson current is investigated. The I--V characteristics and dependence of the critical Josephson current on temperature are analyzed quantitatively by using a proximity effect model. Finally, we discuss experimental results on the improvement of junction quality by including traces of carbon in the rf argon plasma during the sputter cleaning of niobium base electrodes

  11. Asymmetric current-phase relation due to spin-orbit interaction in semiconductor nanowire Josephson junction

    Energy Technology Data Exchange (ETDEWEB)

    Yokoyama, Tomohiro; Eto, Mikio [Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522 (Japan); Nazarov, Yuli V. [Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands (Netherlands)

    2013-12-04

    We theoretically study the current-phase relation in semiconductor nanowire Josephson junction in the presence of spin-orbit interaction. In the nanowire, the impurity scattering with strong SO interaction is taken into account using the random matrix theory. In the absence of magnetic field, the Josephson current I and phase difference φ between the superconductors satisfy the relation of I(φ) = –I(–φ). In the presence of magnetic field along the nanowire, the interplay between the SO interaction and Zeeman effect breaks the current-phase relation of I(φ) = –I(–φ). In this case, we show that the critical current depends on the current direction, which qualitatively agrees with recent experimental findings.

  12. Nuclear threshold effects and neutron strength function

    International Nuclear Information System (INIS)

    Hategan, Cornel; Comisel, Horia

    2003-01-01

    One proves that a Nuclear Threshold Effect is dependent, via Neutron Strength Function, on Spectroscopy of Ancestral Neutron Threshold State. The magnitude of the Nuclear Threshold Effect is proportional to the Neutron Strength Function. Evidence for relation of Nuclear Threshold Effects to Neutron Strength Functions is obtained from Isotopic Threshold Effect and Deuteron Stripping Threshold Anomaly. The empirical and computational analysis of the Isotopic Threshold Effect and of the Deuteron Stripping Threshold Anomaly demonstrate their close relationship to Neutron Strength Functions. It was established that the Nuclear Threshold Effects depend, in addition to genuine Nuclear Reaction Mechanisms, on Spectroscopy of (Ancestral) Neutron Threshold State. The magnitude of the effect is proportional to the Neutron Strength Function, in their dependence on mass number. This result constitutes also a proof that the origins of these threshold effects are Neutron Single Particle States at zero energy. (author)

  13. Coupled Josephson local oscillator and detector experiments in the terahertz regime

    International Nuclear Information System (INIS)

    Robertazzi, R.P.; Hallen, H.D.; Buhrman, R.A.

    1988-01-01

    Recent coupled Josephson junction experiments in the authors' laboratory have demonstrated that high critical current density tunnel junctions can serve as effective local oscillators at frequencies up to and in excess of the gap sum frequency of the junction, i.e. well above 1 Terahertz for a niobium or niobium compound tunnel junction. While the details of the behavior of such a THz. oscillator were found not to be in accord with the predictions of the accepted theory of the A.C. Josephson effect in the gap region significant radiation could be capacitively coupled from the oscillator junction to an adjacent junction, sufficient for SIS mixer experiments at Terahertz frequencies. Research efforts are now under way to further extend and expand these studies. A high critical current density all NbN tunnel junction system is now under development for Terahertz applications and a new set of coupled Josephson oscillator - SIS detector experiments is being initiated using NbN tunnel junctions. In this paper the authors review the original coupled junction high frequency experiments and report on the recent progress of the current NbN tunnel junction experiments

  14. Fragmentation of Fast Josephson Vortices and Breakdown of Ordered States by Moving Topological Defects.

    Science.gov (United States)

    Sheikhzada, Ahmad; Gurevich, Alex

    2015-12-07

    Topological defects such as vortices, dislocations or domain walls define many important effects in superconductivity, superfluidity, magnetism, liquid crystals, and plasticity of solids. Here we address the breakdown of the topologically-protected stability of such defects driven by strong external forces. We focus on Josephson vortices that appear at planar weak links of suppressed superconductivity which have attracted much attention for electronic applications, new sources of THz radiation, and low-dissipative computing. Our numerical simulations show that a rapidly moving vortex driven by a constant current becomes unstable with respect to generation of vortex-antivortex pairs caused by Cherenkov radiation. As a result, vortices and antivortices become spatially separated and accumulate continuously on the opposite sides of an expanding dissipative domain. This effect is most pronounced in thin film edge Josephson junctions at low temperatures where a single vortex can switch the whole junction into a resistive state at currents well below the Josephson critical current. Our work gives a new insight into instability of a moving topological defect which destroys global long-range order in a way that is remarkably similar to the crack propagation in solids.

  15. Coherent Josephson radiation from an array of two Dayem bridges

    International Nuclear Information System (INIS)

    Lidelof, P.E.; Hansen, J.B.; Mygind, J.; Pedersen, N.F.; Soerensen, O.H.

    1977-01-01

    Phase-locking of two independently baised thin-film microbridge (Josephson)-oscillators separated by a short length of superconductor has been observed experimentally using a broad band microwave coupling of the bridges to the receiver. (Auth.)

  16. Fluxons in long and annular intrinsic Josephson junction stacks

    CERN Document Server

    Clauss, T; Moessle, M; Müller, A; Weber, A; Kölle, D; Kleiner, R

    2002-01-01

    A promising approach towards a THz oscillator based on intrinsic Josephson junctions in high-temperature superconductors is based on the collective motion of Josephson fluxons, which are predicted to form various configurations ranging from a triangular to a quadratic lattice. Not only for this reason, but certainly also for the sake of basic physics, several experimental and theoretical investigations have been done on the subject of collective fluxon dynamics in stacked intrinsic Josephson junctions. In this paper we will present some experimental results on the fluxon dynamics of long intrinsic Josephson junction stacks made of Bi sub 2 Sr sub 2 CaCu sub 2 O sub 8. The stacks were formed either in an open or in an annular geometry, and clear resonant fluxon modes were observed. Experiments discussed include measurements of current-voltage characteristics in external magnetic fields and in external microwave fields.

  17. Visualizing supercurrents in 0-{pi} ferromagnetic Josephson tunnel junctions

    Energy Technology Data Exchange (ETDEWEB)

    Goldobin, Edward; Guerlich, Christian; Gaber, Tobias; Koelle, Dieter; Kleiner, Reinhold [Physikalisches Institut and Center for Collective Quantum Phenomena, Universitaet Tuebingen (Germany); Weides, Martin; Kohlstedt, Hermann [Institute of Solid State Physics, Reserch Center Juelich (Germany)

    2009-07-01

    So-called 0 and {pi} Josephson junctions can be treated as having positive and negative critical currents. This implies that the same phase shift applied to a Josephson junction causes counterflow of supercurrents in 0 and in {pi} junctions connected in parallel provided they are short in comparison with Josephson penetration depth {lambda}{sub J}. We have fabricated several 0, {pi}, 0-{pi}, 0-{pi}-0 and 20 x (0-{pi}-) planar superconductor-insulator-ferromagnet-superconductor Josephson junctions and studied the spatial supercurrent density distribution j{sub s}(x,y) across the junction area using low temperature scanning electron microscopy. At zero magnetic field we clearly see counterflow of the supercurrents in 0 and {pi} regions. The picture also changes consistently in the applied magnetic field.

  18. Power spectrum of an injection-locked Josephson oscillator

    International Nuclear Information System (INIS)

    Stancampiano, C.V.; Shapiro, S.

    1975-01-01

    Experiments have shown that a Josephson oscillator, exposed to a weak narrow-band input signal, exhibits behavior characteristic of an injection-locked oscillator. When in lock, Adler's theory of injection locking describes the experimental observations reasonably well. The range of applicability of the theory is extended to the out-of-lock regime where a spectrum of output frequencies is observed. Obtaining the theoretical output power spectrum requires solving a differential equation having the same form as the equation describing the resistively shunted junction model of Stewart and of McCumber. Experimental measurements of the output spectrum of a nearly locked Josephson oscillator are shown to be in reasonable agreement with the theory. Additional results discussed briefly include the observation of a frequency dependence of the locked Josephson oscillator output and experiments in which a Josephson oscillator-mixer was injection locked by a weak signal at the rf

  19. Nuclear reaction inputs based on effective interactions

    Energy Technology Data Exchange (ETDEWEB)

    Hilaire, S.; Peru, S.; Dubray, N.; Dupuis, M.; Bauge, E. [CEA, DAM, DIF, Arpajon (France); Goriely, S. [Universite Libre de Bruxelles, Institut d' Astronomie et d' Astrophysique, CP-226, Brussels (Belgium)

    2016-11-15

    Extensive nuclear structure studies have been performed for decades using effective interactions as sole input. They have shown a remarkable ability to describe rather accurately many types of nuclear properties. In the early 2000 s, a major effort has been engaged to produce nuclear reaction input data out of the Gogny interaction, in order to challenge its quality also with respect to nuclear reaction observables. The status of this project, well advanced today thanks to the use of modern computers as well as modern nuclear reaction codes, is reviewed and future developments are discussed. (orig.)

  20. Resonator coupled Josephson junctions; parametric excitations and mutual locking

    DEFF Research Database (Denmark)

    Jensen, H. Dalsgaard; Larsen, A.; Mygind, Jesper

    1991-01-01

    Self-pumped parametric excitations and mutual locking in systems of Josephson tunnel junctions coupled to multimode resonators are reported. For the very large values of the coupling parameter, obtained with small Nb-Al2O3-Nb junctions integrated in superconducting microstrip resonators, the DC I......-V characteristic shows an equidistant series of current steps generated by subharmonic pumping of the fundamental resonator mode. This is confirmed by measurement of frequency and linewidth of the emitted Josephson radiation...

  1. Critical current fluctuation in a microwave-driven Josephson junction

    International Nuclear Information System (INIS)

    Dong Ning; Sun Guozhu; Wang Yiwen; Cao Junyu; Yu Yang; Chen Jian; Kang Lin; Xu Weiwei; Han Siyuan; Wu Peiheng

    2007-01-01

    Josephson junction devices are good candidates for quantum computation. A large energy splitting was observed in the spectroscopy of a superconducting Josephson junction. The presence of the critical current fluctuation near the energy splitting indicated coupling between the junction and a two-level system. Furthermore, we find that this fluctuation is microwave dependent. It only appears at certain microwave frequency. This relation suggested that the decoherence of qubits is influenced by the necessary computing operations

  2. Effects of nuclear electromagnetic pulse (EMP) on nuclear power plants

    International Nuclear Information System (INIS)

    Barnes, P.R.; Manweiler, R.W.; Davis, R.R.

    1977-09-01

    The electromagnetic pulse (EMP) from a high-altitude nuclear detonation consists of a transient pulse of high intensity electromagnetic fields. These intense fields induce current and voltage transients in electrical conductors. Although most nuclear power plant cables are not directly exposed to these fields, the attenuated EMP fields that propagate into the plant will couple some EMP energy to these cables. The report predicts the probable effects of the EMP transients that could be induced in critical circuits of safety-related systems. It was found that the most likely consequence of EMP for nuclear plants is an unscheduled shutdown. EMP could prolong the shutdown period by the unnecessary actuation of certain safety systems. In general, EMP could be a nuisance to nuclear power plants, but it is not considered a serious threat to plant safety

  3. Interaction between fractional Josephson vortices in multi-gap superconductor tunnel junctions

    Science.gov (United States)

    Kim, Ju H.

    In a long Josephson junction (LJJ) with two-band superconductors, fractionalization of Josephson vortices (fluxons) can occur in the broken time reversal symmetry state when spatial phase textures (i-solitons) are excited. Excitation of i-solitons in each superconductor layer of the junction, arising due to the presence of two condensates and the interband Josephson effect, leads to spatial variation of the critical current density between the superconductor layers. Similar to the situation in a YBa2 Cu3O7 - x superconductor film grain boundary, this spatial dependence of the crtitical current density can self-generate magnetic flux in the insulator layer, resulting in fractional fluxons with large and small fraction of flux quantum. Similar to fluxons in one-band superconductor LJJ, these fractional fluxons are found to interact with each other. The interaction between large and small fractional fluxons determines the size of a fluxon which includes two (one large and one small) fractional fluxons. We discuss the nature of interaction between fractional fluxons and suggest that i-soliton excitations in multi-gap superconductor LJJs may be probed by using magnetic flux measurements.

  4. Josephson scanning tunneling microscopy -- a local and direct probe of the superconducting order parameter

    Energy Technology Data Exchange (ETDEWEB)

    Kimura, Hikari; Dynes, Robert; Barber Jr., Richard. P.; Ono, S.; Ando, Y.

    2009-09-01

    Direct measurements of the superconducting superfluid on the surface of vacuum-cleaved Bi2Sr2CaCu2O8+delta (BSCCO) samples are reported. These measurements are accomplished via Josephson tunneling into the sample using a novel scanning tunneling microscope (STM) equipped with a superconducting tip. The spatial resolution of the STM of lateral distances less than the superconducting coherence length allows it to reveal local inhomogeneities in the pair wavefunction of the BSCCO. Instrument performance is demonstrated first with Josephson measurements of Pb films followed by the layered superconductor NbSe2. The relevant measurement parameter, the Josephson ICRN product, is discussed within the context of both BCS superconductors and the high transition temperature superconductors. The local relationship between the ICRN product and the quasiparticle density of states (DOS) gap are presented within the context of phase diagrams for BSCCO. Excessive current densities can be produced with these measurements and have been found to alter the local DOS in the BSCCO. Systematic studies of this effect were performed to determine the practical measurement limits for these experiments. Alternative methods for preparation of the BSCCO surface are also discussed.

  5. Managing for nuclear operational effectiveness

    International Nuclear Information System (INIS)

    Nevins, P.A.; Kasperski, D.C.

    1990-01-01

    The nuclear energy industry worldwide is changing, with significant implications for nuclear utility managers. While the UK and US nuclear industries have many differences, a number of the lessons learned in the US have direct applicability to the UK. Just as the physics behind nuclear power transcends political boundaries, so do many of the management techniques that are necessary to run an efficient and sound operation. The US nuclear industry is no longer a construction-based industry, as it has been for years. As nuclear construction slows or stops in many parts of the world and nuclear power comes under increased scrutiny everywhere, the industry is shifting away from a construction emphasis and towards an operations and maintenance emphasis. In North America more than one-half of nuclear executives believe that plant operating and maintenance costs, and not construction-related problems, are their number one concern. Furthermore, when asked what actions they would expect to take as a result of this concern, the majority indicated that the actions would be management-related for the most part, and included items such as: emphasize operating improvements, emphasize management improvements, upgrade outage management and maintenance management programs, increase senior management involvement and set management performance criteria. (author)

  6. The Characteristics of an Effective Nuclear Regulator

    International Nuclear Information System (INIS)

    Cheok, Michael; Wertelaers, An; Lojk, Robert; Santini, Miguel; Alm-Lytz, Kirsi; Rigail, Anne-Cecile; Weidenbruck, Kai-Jochen; Stoppa, Gisela; Rainieri, Roberto; Aoki, Masahiro; Gonzalez-Mercado; Miroshnichenko, Mikhail; Kuznetsov, Nikolay; Kudryavtsev, Evgeny; Cid, Rafael; Franzen, Anna; Skanberg, Lars; Gibson, Steve; Golshan, Mina; Cheok, Michael; Nicic, Adriana; Salgado, Nancy; Creswell, Len

    2014-01-01

    Both national and international organisations agree that the fundamental objective of all nuclear safety regulatory bodies - the regulator's prime purpose - is to ensure that nuclear licensees operate their facilities at all times in a safe manner. Much has been written about ways to improve regulatory processes or to improve the effectiveness of a regulatory body, including in previous OECD/NEA regulatory guidance booklets. But until now, none have focused on the characteristics of an effective nuclear safety regulator. Effective organisations are those that have good leadership and are able to transform strategic direction into operational programmes. Effectiveness is about how well the organisation is achieving its fundamental purpose - in the case of a nuclear safety regulator, ensuring that licensees operate their facilities and discharge their obligations in a safe manner. This regulatory guidance booklet describes the characteristics of an effective nuclear safety regulator in terms of roles and responsibilities, principles and attributes. Each of the characteristics discussed in this report is a necessary feature of an effective nuclear safety regulator but no one characteristic is sufficient on its own. It is the combination of these characteristics that leads to the effectiveness of a nuclear regulatory body. The report provides a unique resource to countries with existing, mature regulators and can be used for benchmarking as well as training and developing staff. It will also be useful for new entrant countries in the process of developing and maintaining an effective nuclear safety regulator. (authors)

  7. Vortices trapped in discrete Josephson rings

    International Nuclear Information System (INIS)

    Van der Zanta, H.S.J.; Orlando, T.P.; Watanabe, Shinya; Strogatz, S.H.

    1994-01-01

    We report the first measurements of current- (I-V) characteristics of discrete rings of Josephson junctions. As I is increased, resonant steps appear in the I-V curve, due to phase-locking between a propagating, trapped vortex and the linear waves excited in its wake. Unexpectedly, the phase velocity of the linear waves, not the group velocity, is the physically important quantity and mode numbers outside the Brillouin zone are relevant. Our measurements show that away from the resonant steps, a single vortex can move in an environment with very little damping, making the discrete one-dimensional ring a well-defined model system for the study of ballistic and quantum vortex experiments. ((orig.))

  8. Vortices trapped in discrete Josephson rings

    Energy Technology Data Exchange (ETDEWEB)

    Van der Zanta, H.S.J. [Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Orlando, T.P. [Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Watanabe, Shinya [Department of Mathematics, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Strogatz, S.H. [Department of Mathematics, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)

    1994-12-01

    We report the first measurements of current- (I-V) characteristics of discrete rings of Josephson junctions. As I is increased, resonant steps appear in the I-V curve, due to phase-locking between a propagating, trapped vortex and the linear waves excited in its wake. Unexpectedly, the phase velocity of the linear waves, not the group velocity, is the physically important quantity and mode numbers outside the Brillouin zone are relevant. Our measurements show that away from the resonant steps, a single vortex can move in an environment with very little damping, making the discrete one-dimensional ring a well-defined model system for the study of ballistic and quantum vortex experiments. ((orig.)).

  9. Simplifying the circuit of Josephson parametric converters

    Science.gov (United States)

    Abdo, Baleegh; Brink, Markus; Chavez-Garcia, Jose; Keefe, George

    Josephson parametric converters (JPCs) are quantum-limited three-wave mixing devices that can play various important roles in quantum information processing in the microwave domain, including amplification of quantum signals, transduction of quantum information, remote entanglement of qubits, nonreciprocal amplification, and circulation of signals. However, the input-output and biasing circuit of a state-of-the-art JPC consists of bulky components, i.e. two commercial off-chip broadband 180-degree hybrids, four phase-matched short coax cables, and one superconducting magnetic coil. Such bulky hardware significantly hinders the integration of JPCs in scalable quantum computing architectures. In my talk, I will present ideas on how to simplify the JPC circuit and show preliminary experimental results

  10. Fabrication of Josephson Junction without shadow evaporation

    Science.gov (United States)

    Wu, Xian; Ku, Hsiangsheng; Long, Junling; Pappas, David

    We developed a new method of fabricating Josephson Junction (Al/AlOX/Al) without shadow evaporation. Statistics from room temperature junction resistance and measurement of qubits are presented. Unlike the traditional ``Dolan Bridge'' technique, this method requires two individual lithographies and straight evaporations of Al. Argon RF plasma is used to remove native AlOX after the first evaporation, followed by oxidation and second Al evaporation. Junction resistance measured at room temperature shows linear dependence on Pox (oxidation pressure), √{tox} (oxidation time), and inverse proportional to junction area. We have seen 100% yield of qubits made with this method. This method is promising because it eliminates angle dependence during Junction fabrication, facilitates large scale qubits fabrication.

  11. Josephson junction arrays and superconducting wire networks

    International Nuclear Information System (INIS)

    Lobb, C.J.

    1992-01-01

    Techniques used to fabricate integrated circuits make it possible to construct superconducting networks containing as many as 10 6 wires or Josephson junctions. Such networks undergo phase transitions from resistive high-temperature states to ordered low-resistance low-temperature states. The nature of the phase transition depends strongly on controllable parameters such as the strength of the superconductivity in each wire or junction and the external magnetic field. This paper will review the physics of these phase transitions, starting with the simplest zero-magnetic field case. This leads to a Kosterlitz-Thouless transition when the junctions or wires are weak, and a simple mean-field fransition when the junctions or wires are strong. Rich behavior, resulting from frustration, occurs in the presence of a magnetic field. (orig.)

  12. Josephson tunnel junctions with ferromagnetic interlayer

    International Nuclear Information System (INIS)

    Weides, M.P.

    2006-01-01

    Superconductivity and ferromagnetism are well-known physical properties of solid states that have been widely studied and long thought about as antagonistic phenomena due to difference in spin ordering. It turns out that the combination of both superconductor and ferromagnet leads to a very rich and interesting physics. One particular example, the phase oscillations of the superconducting order parameter inside the ferromagnet, will play a major role for the devices discussed in this work. In this thesis, I present Josephson junctions with a thin Al 2 O 3 tunnel barrier and a ferromagnetic interlayer, i.e. superconductor-insulator-ferromagnet-superconductor (SIFS) stacks. The fabrication of junctions was optimized regarding the insulation of electrodes and the homogeneity of the current transport. The junctions were either in the 0 or π coupled ground state, depending on the thickness of the ferromagnetic layer and on temperature. The influence of ferromagnetic layer thickness on the transport properties and the coupling (0, π) of SIFS tunnel junctions was studied. Furthermore, using a stepped ferromagnetic layer with well-chosen thicknesses, I obtained the so-called 0-π Josephson junction. At a certain temperature this 0-π junction can be made perfectly symmetric. In this case the ground state corresponds to a vortex of supercurrent creating a magnetic flux which is a fraction of the magnetic flux quantum Φ 0 . Such structures allow to study the physics of fractional vortices and to build various electronic circuits based on them. The SIFS junctions presented here have an exponentially vanishing damping at T → 0. The SIFS technology developed within the framework of this work may be used to construct classical and quantum devices such as oscillators, memory cells and qubits. (orig.)

  13. Josephson tunnel junctions with ferromagnetic interlayer

    Energy Technology Data Exchange (ETDEWEB)

    Weides, M.P.

    2006-07-01

    Superconductivity and ferromagnetism are well-known physical properties of solid states that have been widely studied and long thought about as antagonistic phenomena due to difference in spin ordering. It turns out that the combination of both superconductor and ferromagnet leads to a very rich and interesting physics. One particular example, the phase oscillations of the superconducting order parameter inside the ferromagnet, will play a major role for the devices discussed in this work. In this thesis, I present Josephson junctions with a thin Al{sub 2}O{sub 3} tunnel barrier and a ferromagnetic interlayer, i.e. superconductor-insulator-ferromagnet-superconductor (SIFS) stacks. The fabrication of junctions was optimized regarding the insulation of electrodes and the homogeneity of the current transport. The junctions were either in the 0 or {pi} coupled ground state, depending on the thickness of the ferromagnetic layer and on temperature. The influence of ferromagnetic layer thickness on the transport properties and the coupling (0, {pi}) of SIFS tunnel junctions was studied. Furthermore, using a stepped ferromagnetic layer with well-chosen thicknesses, I obtained the so-called 0-{pi} Josephson junction. At a certain temperature this 0-{pi} junction can be made perfectly symmetric. In this case the ground state corresponds to a vortex of supercurrent creating a magnetic flux which is a fraction of the magnetic flux quantum {phi}{sub 0}. Such structures allow to study the physics of fractional vortices and to build various electronic circuits based on them. The SIFS junctions presented here have an exponentially vanishing damping at T {yields} 0. The SIFS technology developed within the framework of this work may be used to construct classical and quantum devices such as oscillators, memory cells and qubits. (orig.)

  14. High Tc Josephson Junctions, SQUIDs and magnetometers

    International Nuclear Information System (INIS)

    Clarke, J.

    1991-01-01

    There has recently been considerable progress in the state-of-the-art of high-T c magnetometers based on dc SQUIDs (Superconducting Quantum Interference Devices). This progress is due partly to the development of more manufacturable Josephson junctions, making SQUIDs easier to fabricate, and partly to the development of multiturn flux transformers that convert the high sensitivity of SQUIDs to magnetic flux to a correspondingly high sensitivity to magnetic field. Needless to say, today's high-T c SQUIDs are still considerably less sensitive than their low-T c counterparts, particularly at low frequencies (f) where their level of 1/f noise remains high. Nonetheless, the performance of the high-T c devices has now reached the point where they are adequate for a number of the less demanding applications; furthermore, as we shall see, at least modest improvements in performance are expected in the near future. In this article, the author outlines these various developments. This is far from a comprehensive review of the field, however, and, apart from Sec. 2, he describes largely his own work. He begins in Sec. 2 with an overview of the various types of Josephson junctions that have been investigated, and in Sec. 3, he describes some of the SQUIDs that have been tested, and assess their performance. Section 4 discuss the development of the multilayer structures essential for an interconnect technology, and, in particular, for crossovers and vias. Section 5 shows how this technology enables one to fabricate multiturn flux transformers which, in turn, can be coupled to SQUIDs to make magnetometers. The performance and possible future improvements in these magnetometers are assessed, and some applications mentioned

  15. Long-range spin-singlet proximity effect for a Josephson system with a single-crystal ferromagnet due to its band-structure features

    Science.gov (United States)

    Avdeev, M. V.; Proshin, Yu. N.

    2018-03-01

    A possible explanation for the long-range proximity effect observed in single-crystalline cobalt nanowires sandwiched between two tungsten superconducting electrodes [Nat. Phys. 6, 389 (2010), 10.1038/nphys1621] is proposed. The theoretical model uses properties of a ferromagnet band structure. Specifically, to connect the exchange field with the momentum of quasiparticles the distinction between the effective masses in majority and minority spin subbands and the Fermi-surface anisotropy are considered. The derived Eilenberger-like equations allowed us to obtain a renormalized exchange interaction that is completely compensated for some crystallographic directions under certain conditions. The proposed theoretical model is compared with previous approaches.

  16. Effective citizen advocacy of beneficial nuclear technologies

    International Nuclear Information System (INIS)

    McKibben, J. Malvyn; Wood, Susan

    2007-01-01

    In 1991, a small group of citizens from communities near the Savannah River Site (SRS) formed a pro-nuclear education and advocacy group, Citizens for Nuclear Technology Awareness (CNTA). Their purpose was to: (1) counter nuclear misinformation that dominated the nation's news outlets, (2) provide education on nuclear subjects to area citizens, students, elected officials, and (3) provide informed citizen support for potential new missions for SRS when needed. To effectively accomplish these objectives it is also essential to establish and maintain good relations with community leaders and reporters that cover energy and nuclear subjects. The organization has grown considerably since its inception and has expanded its sphere of influence. We believe that our experiences over these fifteen years are a good model for effectively communicating nuclear subjects with the public. This paper describes the structure, operation and some of the results of CNTA. (authors)

  17. The greenhouse effect and nuclear energy

    International Nuclear Information System (INIS)

    Coulter, J.

    1988-01-01

    The author argues that nuclear power will do little to mitigate the problem of the greenhouse effect and is likely to exacerbate it. Changes since the mid 1970s illustrate the close linking of nuclear and economic growth with the associated growth of fossil fill consumption, the inability of nuclear power to substitute for fossil either technically or economically, and the greater contribution that can be made to energy availability and to reduction of carbon dioxide release by conservation

  18. Laser induced nuclear orientation effects

    International Nuclear Information System (INIS)

    Burns, M.; Pappas, P.; Feld, M.S.; Murnick, D.E.

    1977-01-01

    Resonant laser radiation can orient metastable nuclei, resulting in spatially anisotropic emission of β or γ radiation. This technique can be used to obtain isomer shifts and nuclear moments and can lead to isomer separation. (Auth.)

  19. Widespread after-effects of nuclear war

    International Nuclear Information System (INIS)

    Teller, E.

    1984-01-01

    Radioactive fallout and depletion of the ozone layer, once believed catastrophic consequences of nuclear war, are now proved unimportant in comparison to immediate war damage. Today, ''nuclear winter'' is claimed to have apocalyptic effects. Uncertainties in massive smoke production and in meteorological phenomena give reason to doubt this conclusion. (author)

  20. Health and environmental effects of nuclear weapons

    International Nuclear Information System (INIS)

    1995-08-01

    Since 1981 WHO has been studying and reporting on the effects of nuclear war on health and health services. This report provides information on the subject and refers to earlier related work of WHO. It forms the basis for a request from WHO to the International Court of Justice regarding the legality of the use of nuclear weapons. 15 refs

  1. Effect of hotspot on THz radiation from Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} intrinsic Josephson junctions

    Energy Technology Data Exchange (ETDEWEB)

    Iranmehr, Masoud; Mohamadian, Ali; Faez, Rahim [Sharif University of Technology, Tehran (Iran, Islamic Republic of)

    2017-08-15

    We investigate hot spot effects on increasing THz emission of the frequency modes in a square mesa structure with constant hot spot size in different positions, without applying magnetic field. We show that in the presence of hot spot at any position, the average of emitted power intensity level is increased. The frequency modes that the position of their field concentration is more matched with hot spot position are more excited. Accordingly, in the case with hot spot located at center of a-axis or b-axis, frequency modes TM(m,n) with even indices m or n is more excited and in the case in which hot spot is located at the corner of a-axis or b-axis, frequency modes TM(m,n) with odd indices m or n is more excited. We also show that in the presence of hot spot, the excited frequencies are independent of hot spot temperature and critical current attenuation ratio. Increase of the emission intensity of excited modes and average power intensity has a little dependency on critical current density attenuation ratio of hot spot region. (orig.)

  2. Magnetic properties of strip-like Josephson-junction arrays

    International Nuclear Information System (INIS)

    Chen, D.-X; Moreno, J.J.; Hernando, A.; Sanchez, A.

    2000-01-01

    Zero-field-cooled (ZFC) and field-cooled (FC) magnetic properties of strip-like Josephson-junction (JJ) arrays with very strong demagnetizing effects are calculated from basic laws. Similar to slab-like JJ arrays without considering demagnetizing effects, a vortex state evolves to a critical state (CS) with increasing maximum JJ currents in the ZFC case, and a vortex state always remains with a negative low-field susceptibility in the FC case. However, the strong demagnetizing effects cause qualitative changes in the CS, where the overall feature of the field and current profiles turns out to be similar to that in type-II superconducting strips, but not like the ordinary Bean CS in slab-like JJ arrays, the CS current profile is never flat and the critical current is no longer a step function of the maximum JJ current as in slab-like JJ arrays. The calculated results of different types of JJ arrays indicate that although the intergranular CS in granular superconductors may have a common origin, the discovered paramagnetic Meissner effect in them is still difficult to explain. (author)

  3. The environmental effects of nuclear war

    International Nuclear Information System (INIS)

    MacCracken, M.C.

    1988-09-01

    Substantial environmental disruption will significantly add to the disastrous consequences caused by the direct thermal, blast, and radiological effects brought on by a major nuclear war. Local fallout could cover several percent of the Northern Hemisphere with potentially lethal doses. Smoke from post-nuclear fires could darken the skies and induce temperature decreases of tens of degrees in continental interiors. Stratospheric ozone could be significantly reduced due to nitric oxide injections and smoke-induced circulation changes. The environmental effects spread the consequences of a nuclear war to the world population, adding to the potentially large disruptive effects a further reason to avoid such a catastrophe. 27 refs., 4 figs

  4. Effect of nuclear education on public attitude

    International Nuclear Information System (INIS)

    Ohnishi, Teruaki

    1995-01-01

    A method is proposed to assess the effect of nuclear education. In this method, the nuclear education is treated as a part of the activities for public acceptance (PA), and a unit PA activity is assumed to give the same effect on the public, in essence, as a unit of nuclear information given by the newsmedia. Moreover, the change of attitude to nuclear energy is assumed to originate from enhanced understanding which, in turn, is brought by the stimulus given by the nuclear education. With the values of constants determined by using the data in Japan, example calculations were made for the educational time b 0 and the infiltration rate of education into minors B as parameters. It became clear from this calculation that the attitude to nuclear energy formed in the age of school children plays an essential role in shaping future public opinion since it is held in individuals without any notable modification for a long time after its formation, and that the effect of nuclear education to minors emerges depending on the variables b 0 and B in a highly non-linear manner. It was also found that there exists an optimum condition for nuclear education to attain the maximum amelioration of public opinion under a given condition of man-power for educational workers. (author)

  5. Suppression and enhancement of decoherence in an atomic Josephson junction

    Science.gov (United States)

    Japha, Yonathan; Zhou, Shuyu; Keil, Mark; Folman, Ron; Henkel, Carsten; Vardi, Amichay

    2016-05-01

    We investigate the role of interatomic interactions when a Bose gas, in a double-well potential with a finite tunneling probability (a ‘Bose-Josephson junction’), is exposed to external noise. We examine the rate of decoherence of a system initially in its ground state with equal probability amplitudes in both sites. The noise may induce two kinds of effects: firstly, random shifts in the relative phase or number difference between the two wells and secondly, loss of atoms from the trap. The effects of induced phase fluctuations are mitigated by atom-atom interactions and tunneling, such that the dephasing rate may be suppressed by half its single-atom value. Random fluctuations may also be induced in the population difference between the wells, in which case atom-atom interactions considerably enhance the decoherence rate. A similar scenario is predicted for the case of atom loss, even if the loss rates from the two sites are equal. We find that if the initial state is number-squeezed due to interactions, then the loss process induces population fluctuations that reduce the coherence across the junction. We examine the parameters relevant for these effects in a typical atom chip device, using a simple model of the trapping potential, experimental data, and the theory of magnetic field fluctuations near metallic conductors. These results provide a framework for mapping the dynamical range of barriers engineered for specific applications and set the stage for more complex atom circuits (‘atomtronics’).

  6. Versatile multi-layer Josephson junction process for vortex molecules

    Energy Technology Data Exchange (ETDEWEB)

    Meckbach, Johannes Maximilian; Buehler, Simon; Merker, Michael; Il' in, Konstantin; Siegel, Michael [Institut fuer Mikro- und Nanoelektronische Systeme, KIT (Germany); Buckenmaier, Kai; Gaber, Tobias; Kienzle, Uta; Neumaier, Benjamin; Goldobin, Edward; Kleiner, Reinhold; Koelle, Dieter [Physikalisches Institut - Experimentalphysik II, Universitaet Tuebingen (Germany)

    2012-07-01

    In long Josephson junctions magnetic flux may penetrate the barrier resulting in a so-called Josephson-Vortex carrying one flux quantum Φ{sub 0}. In recent years a new type of Josephson-Vortex became available, which carries any arbitrary fraction Φ = -Φ{sub 0}κ/2π of magnetic flux. These fractional vortices (p-vortices) spontaneously appear at discontinuities of the Josephson phase along the junction, which in turn are created using a pair of current injectors. We present a new Nb/Al-AlO{sub x}/Nb process for the fabrication of Josephson junctions of very high quality. Placing two injector pairs along the strongly underdamped long junctions allows the investigation of fractional vortex molecules. The topological charge of each vortex and their interaction can be altered even during experiment by changing the individual injector currents. Vortex molecule states have been measured using asymmetric DC-SQUIDs coupled to the vortices by overlying pick-up loops. To uphold the p-vortices we use persistent currents, which can be altered using heat switches. Fractional vortex molecules are promising candidates for a new type of qubits.

  7. The critical current of point symmetric Josephson tunnel junctions

    International Nuclear Information System (INIS)

    Monaco, Roberto

    2016-01-01

    Highlights: • We disclose some geometrical properties of the critical current field dependence that apply to a large class of Josephson junctions characterized by a point symmetric shape. • The developed theory is valid for any orientation of the applied magnetic field, therefore it allows the determine the consequences of field misalignment in the experimental setups. • We also address that the threshold curves of Josephson tunnel junctions with complex shapes can be expressed as a linear combination of the threshold curves of junctions with simpler point symmetric shapes. - Abstract: The physics of Josephson tunnel junctions drastically depends on their geometrical configurations. The shape of the junction determines the specific form of the magnetic-field dependence of its Josephson current. Here we address the magnetic diffraction patterns of specially shaped planar Josephson tunnel junctions in the presence of an in-plane magnetic field of arbitrary orientations. We focus on a wide ensemble of junctions whose shape is invariant under point reflection. We analyze the implications of this type of isometry and derive the threshold curves of junctions whose shape is the union or the relative complement of two point symmetric plane figures.

  8. Proposed differential-frequency-readout system by hysteretic Josephson junctions

    International Nuclear Information System (INIS)

    Wang, L.Z.; Duncan, R.V.

    1992-01-01

    The Josephson relation V=nhν/2e has been verified experimentally to 3 parts in 10 19 [A. K. Jain, J. E. Lukens, and J.-S. Tsai, Phys. Rev. Lett. 58, 1165 (1987)]. Motivated by this result, we propose a differential-frequency-readout system by two sets of hysteretic Josephson junctions rf biased at millimeter wavelengths. Because of the Josephson relation, the proposed differential-frequency-readout system is not limited by photon fluctuation, which limits most photon-detection schemes. In the context of the Stewart-McCumber model [W. C. Stewart, Appl. Phys. Lett. 12, 277 (1968); D. E. McCumber, J. Appl. Phys. 39, 3113 (1968)] of Josephson junctions, we show theoretically that the differential frequency of the two milliwave biases can be read out by the proposed system to unprecedented accuracy. The stability of the readout scheme is also discussed. The measurement uncertainty of the readout system resulting from the intrinsic thermal noise in the hysteretic junctions is shown to be insignificant. The study of two single junctions can be extended to two sets of Josephson junctions connected in series (series array) in this measurement scheme provided that junctions are separated by at least 10 μm [D. W. Jillie, J. E. Lukens, and Y. H. Kao, Phys. Rev. Lett. 38, 915 (1977)]. The sensitivity for the differential frequency detection may be increased by biasing both series arrays to a higher constant-voltage step

  9. Atmospheric effects of a nuclear war

    International Nuclear Information System (INIS)

    Birks, J.W.

    1983-01-01

    The subject is discussed under the headings: nuclear war scenario (assumptions of size and place of explosions); fires; urban and forest fires; smoke and soot; darkness; meteorological and climatic effects; photochemical smog; ozone shield depletion; conclusions. (U.K.)

  10. Phase dynamics of a Josephson junction ladder driven by modulated currents

    International Nuclear Information System (INIS)

    Kawaguchi, T.

    2011-01-01

    Phase dynamics of disordered Josephson junction ladders (JJLs) driven by external currents which are spatially and temporally modulated is studied using a numerical simulation based on a random field XY model. This model is considered theoretically as an effective model of JJLs with structural disorder in a magnetic field. The spatiotemporal modulation of external currents causes peculiar dynamical effects of phases in the system under certain conditions, such as the directed motion of phases and the mode-locking in the absence of dc currents. We clarify the details of effects of the spatiotemporal modulation on the phase dynamics.

  11. The nuclear energy and the greenhouse effect

    International Nuclear Information System (INIS)

    Marignac, Y.; Legrand, V.

    2003-01-01

    This article tackles the problem of greenhouse effect and asks the question to know if the development of nuclear energy constitutes the answer to this problem. It appears that the nuclear energy cannot solve in itself the problem of greenhouse effect. Others actions on energy demand, on transport ( that is a big consumer of petroleum and that represents 25% of world emissions) have to studied and need a real policy will. (N.C.)

  12. Nuclear effects in neutrino oscillation experiments

    International Nuclear Information System (INIS)

    Chauhan, S.; Athar, M. Sajjad; Singh, S. K.

    2011-01-01

    We have studied the nuclear medium effects in the neutrino(antineutrino) induced interactions in nuclei which are relevant for present neutrino oscillation experiments in the few GeV energy region. The study is specially focused on calculating the cross sections and the event rates for atmospheric and accelerator neutrino experiments. The nuclear effects are found to be important for the quasielastic lepton production and the charged current incoherent and coherent pion production processes.

  13. Nuclear energy and the greenhouse effect

    International Nuclear Information System (INIS)

    Weinberg, A.M.

    1990-01-01

    The extent and nature of the greenhouse effect are examined and placed in an environmental and historical context. The effect of energy policies on the greenhouse effect are discussed and the offending countries are identified. What energy policies would mitigate the greenhouse effect, and yet make good sense whether or not the effect proves to be real? Conservation is a desirable though not completely understood strategy. Conservation may not be a better bet in every instance than is increase in supply. If the greenhouse effect turns out to be real, nuclear energy can be one of the supply options that we turn to. If the greenhouse effect turns out to be false, and acceptable, economic nuclear option is surely better than one that does nothing but create strife and dissension. Let us remember that nuclear energy is the only large-scale non-fossil source other than hydropower that has been demonstrated to be practical. (author)

  14. Stochastic Effects; Application in Nuclear Physics

    International Nuclear Information System (INIS)

    Mazonka, O.

    2000-04-01

    Stochastic effects in nuclear physics refer to the study of the dynamics of nuclear systems evolving under stochastic equations of motion. In this dissertation we restrict our attention to classical scattering models. We begin with introduction of the model of nuclear dynamics and deterministic equations of evolution. We apply a Langevin approach - an additional property of the model, which reflect the statistical nature of low energy nuclear behaviour. We than concentrate our attention on the problem of calculating tails of distribution functions, which actually is the problem of calculating probabilities of rare outcomes. Two general strategies are proposed. Result and discussion follow. Finally in the appendix we consider stochastic effects in nonequilibrium systems. A few exactly solvable models are presented. For one model we show explicitly that stochastic behaviour in a microscopic description can lead to ordered collective effects on the macroscopic scale. Two others are solved to confirm the predictions of the fluctuation theorem. (author)

  15. Quantum logical states and operators for Josephson-like systems

    International Nuclear Information System (INIS)

    Faoro, Lara; Raffa, Francesco A; Rasetti, Mario

    2006-01-01

    We give a formal algebraic description of Josephson-type quantum dynamical systems, i.e., Hamiltonian systems with a cos θ-like potential term. The two-boson Heisenberg algebra plays for such systems the role that the h(1) algebra does for the harmonic oscillator. A single Josephson junction is selected as a representative of Josephson systems. We construct both logical states (codewords) and logical (gate) operators in the superconductive regime. The codewords are the even and odd coherent states of the two-boson algebra: they are shift-resistant and robust, due to squeezing. The logical operators acting on the qubit codewords are expressed in terms of operators in the enveloping of the two-boson algebra. Such a scheme appears to be relevant for quantum information applications. (letter to the editor)

  16. High-quality planar high-Tc Josephson junctions

    International Nuclear Information System (INIS)

    Bergeal, N.; Grison, X.; Lesueur, J.; Faini, G.; Aprili, M.; Contour, J.P.

    2005-01-01

    Reproducible high-T c Josephson junctions have been made in a rather simple two-step process using ion irradiation. A microbridge (1 to 5 μm wide) is firstly designed by ion irradiating a c-axis-oriented YBa 2 Cu 3 O 7-δ film through a gold mask such as the nonprotected part becomes insulating. A lower T c part is then defined within the bridge by irradiating with a much lower fluence through a narrow slit (20 nm) opened in a standard electronic photoresist. These planar junctions, whose settings can be finely tuned, exhibit reproducible and nearly ideal Josephson characteristics. This process can be used to produce complex Josephson circuits

  17. A fully operational 1-kb variable threshold Josephson RAM

    International Nuclear Information System (INIS)

    Kurosawa, I.; Nakagawa, H.; Aoyagi, M.; Kosaks, S.; Takada, S.

    1991-01-01

    This paper describes the first fully operational Josephson RAM in LSI level integration. The chip was designed as a 4-b x 256-word data RAM unit for a 4-b Josephson computer, The variable threshold memory cell and the relating memory architecture were used. They are so simple in structure that the fabrication is satisfied by the current Josephson junction technology. A directly coupled driver gate for a resistive bit line applies an accurate and stable driving current to the memory cell array. The RAM chip was fabricated with a 3-μm Nb/Al-oxide/Nb junction technology. For obtaining reliable RAM chips, a plasma-enhanced CVD silicon dioxide layer was introduced for insulation between the ground plane and the base electrode. The thermal uniformity of the wafer was improved during the oxidation process for making a tunnel barrier in this work

  18. Quantum dynamics of a strongly driven Josephson Junction

    Energy Technology Data Exchange (ETDEWEB)

    Gosner, Jennifer; Kubala, Bjoern; Ankerhold, Joachim [Institute for Complex Quantum Systems, University of Ulm (Germany)

    2015-07-01

    A Josephson Junction embedded in a dissipative circuit can be driven to exhibit non-linear oscillations. Classically the non-linear oscillator shows under sufficient strong driving and weak damping dynamical bifurcations and a bistable region similar to the conventional Duffing-oscillator. These features depend sensitively on initial conditions and parameters. The sensitivity of this circuit, called Josephson Bifurcation Amplifier, can be used to amplify an incoming signal, to form a sensing device or even for measuring a quantum system. The quantum dynamics can be described by a dissipative Lindblad master equation. Signatures of the classical bifurcation phenomena appear in the Wigner representation, used to characterize and visualize the resulting behaviour. In order to compare this quantum dynamics to that of the conventional Duffing-oscillator, the complete cosine-nonlinearity of the Josephson Junction is kept for the quantum description while going into a rotating frame.

  19. Towards quantum signatures in a swept-bias Josephson junction

    Energy Technology Data Exchange (ETDEWEB)

    Losert, Harald; Vogel, Karl; Schleich, Wolfgang P. [Institut fuer Quantenphysik and Center for Integrated Quantum Science and Technology (IQST), Universitaet Ulm, D-89069 Ulm (Germany)

    2016-07-01

    Josephson junctions are one of the best examples for the observation of macroscopic quantum tunneling. The phase difference in a current-biased Josephson junction behaves like the position of a particle in a tilted washboard potential. The escape of this phase-particle corresponds to the voltage switching of the associated junction. Quantum mechanically, the escape from the washboard potential can be explained as tunneling from the ground state, or an excited state. However, it has been shown, that in the case of periodic driving the experimental data for quantum mechanical key features, e.g. Rabi oscillations or energy level quantization, can be reproduced by a completely classical description. Motivated by this discussion, we investigate a swept-bias Josephson junction in the case of a large critical current. In particular, we contrast the switching current distributions resulting from a quantum mechanical and classical description of the time evolution.

  20. Terahertz Josephson spectral analysis and its applications

    Science.gov (United States)

    Snezhko, A. V.; Gundareva, I. I.; Lyatti, M. V.; Volkov, O. Y.; Pavlovskiy, V. V.; Poppe, U.; Divin, Y. Y.

    2017-04-01

    Principles of Hilbert-transform spectral analysis (HTSA) are presented and advantages of the technique in the terahertz (THz) frequency range are discussed. THz HTSA requires Josephson junctions with high values of characteristic voltages I c R n and dynamics described by a simple resistively shunted junction (RSJ) model. To meet these requirements, [001]- and [100]-tilt YBa2Cu3O7-x bicrystal junctions with deviations from the RSJ model less than 1% have been developed. Demonstrators of Hilbert-transform spectrum analyzers with various cryogenic environments, including integration into Stirling coolers, are described. Spectrum analyzers have been characterized in the spectral range from 50 GHz to 3 THz. Inside a power dynamic range of five orders, an instrumental function of the analyzers has been found to have a Lorentz form around a single frequency of 1.48 THz with a spectral resolution as low as 0.9 GHz. Spectra of THz radiation from optically pumped gas lasers and semiconductor frequency multipliers have been studied with these spectrum analyzers and the regimes of these radiation sources were optimized for a single-frequency operation. Future applications of HTSA will be related with quick and precise spectral characterization of new radiation sources and identification of substances in the THz frequency range.

  1. Perturbation treatment of mixing in Josephson junctions

    International Nuclear Information System (INIS)

    Levinsen, M.T.; Ulrich, B.T.

    1975-01-01

    A current biased, resistively shunted Josephson Junction irradiated at two frequencies is considered. The perturbation technique introduced by Aslamasov and Larkin is used in the calculations, and both signals are treated as perturbations. The second order calculation yields the size of the mixing steps at V/sub +-/ = h(ω 1 +- ω 2 )/2e. As in the case of a single frequency, subharmonic mixing steps are absent. The amplitude of the voltage oscillation at the difference and sum frequencies is shown to be non-zero at all voltages. The microwave resistance is calculated for one frequency ω 2 to third order in the perturbation. There are negative resistance regions near V/sub +-/ (as well as near V 2 = hω 2 /2e). Near V/sub -/, the negative resistance region appears for bias voltage V just above V/sub -/, while near V the region appears for V just below V/sub +/. This means that when an incident frequency mixes with a cavity mode, the mixing step at V/sub -/ will be inverted compared to the cavity step itself

  2. Josephson tunneling in bilayer quantum Hall system

    International Nuclear Information System (INIS)

    Ezawa, Z.F.; Tsitsishvili, G.; Sawada, A.

    2012-01-01

    A Bose–Einstein condensation is formed by composite bosons in the quantum Hall state. A composite boson carries the fundamental charge (−e). We investigate Josephson tunneling of such charges in the bilayer quantum Hall system at the total filling ν=1. We show the existence of the critical current for the tunneling current to be coherent and dissipationless. Our results explain recent experiments due to [L. Tiemann, Y. Yoon, W. Dietsche, K. von Klitzing, W. Wegscheider, Phys. Rev. B 80 (2009) 165120] and due to [Y. Yoon, L. Tiemann, S. Schmult, W. Dietsche, K. von Klitzing, Phys. Rev. Lett. 104 (2010) 116802]. We predict also how the critical current changes as the sample is tilted in the magnetic field. -- Highlights: ► Composite bosons undergo Bose–Einstein condensation to form the bilayer quantum Hall state. ► A composite boson is a single electron bound to a flux quantum and carries one unit charge. ► Quantum coherence develops due to the condensation. ► Quantum coherence drives the supercurrent in each layer and the tunneling current. ► There exists the critical input current so that the tunneling current is coherent and dissipationless.

  3. Soliton excitations in Josephson tunnel junctions

    DEFF Research Database (Denmark)

    Lomdahl, P. S.; Sørensen, O. H.; Christiansen, Peter Leth

    1982-01-01

    A detailed numerical study of a sine-Gordon model of the Josephson tunnel junction is compared with experimental measurements on junctions with different L / λJ ratios. The soliton picture is found to apply well on both relatively long (L / λJ=6) and intermediate (L / λJ=2) junctions. We find good...... agreement for the current-voltage characteristics, power output, and for the shape and height of the zero-field steps (ZFS). Two distinct modes of soliton oscillations are observed: (i) a bunched or congealed mode giving rise to the fundamental frequency f1 on all ZFS's and (ii) a "symmetric" mode which...... on the Nth ZFS yields the frequency Nf1 Coexistence of two adjacent frequencies is found on the third ZFS of the longer junction (L / λJ=6) in a narrow range of bias current as also found in the experiments. Small asymmetries in the experimental environment, a weak magnetic field, e.g., is introduced via...

  4. Spin transport in diffusive ferromagnetic Josephson junctions with noncollinear magnetization

    Energy Technology Data Exchange (ETDEWEB)

    Shomali, Zahra; Zareyan, Malek [Institute for Advanced Studies in Basic Sciences (IASBS), Zanjan 45195 (Iran, Islamic Republic of); Belzig, Wolfgang [Fachbereich Physik, Universitaet Konstanz, D-78457 Konstanz (Germany)

    2011-07-01

    We numerically study the Josephson coupling of two s-wave superconductors which are connected through a diffusive contact made of two ferromagnetic domains with the magnetization vectors misoriented by an angle {theta}. The assumed superconducting leads are conventional s-wave type with the phase difference of {phi}. Using the quantum circuit theory, we find that in addition to the charge supercurrent, which shows a 0-{pi} transition relative to the angle {theta}, the spin supercurrent with a spin polarization normal to the magnetization vectors will flow through the contact. Our results present a 0-{pi} quantum phase transition as a function of the wave vector, Q{xi}. Finally, we investigate the spin supercurrent in an extended magnetic texture with multiple domain walls. We find the behavior of spin supercurrent is highly sensitive to the barrier. When asymmetric barriers don't change the value of the spin supercurrent, the symmetric ones decrease the value of it notably. We also investigate some other interesting effects for these systems. In addition, we present when Q{xi} is the even multiple of {pi}, the spin-current which is penetrated into the nonhomogeneous ferromagnets is nearly zero, how ever the odd ones show the large amount of penetrated spin supercurrent.

  5. Coherent current states in mesoscopic four-terminal Josephson junction

    International Nuclear Information System (INIS)

    Zareyan, M.; Omelyanchouk, A.N.

    1999-01-01

    A theory is offered for the ballistic 4-terminal Josephson junction. The studied system consist of a mesoscopic two-dimensional normal rectangular layer which is attached on each side to the bulk superconducting banks (terminals). A relation is obtained between the currents through the different terminals, that is valid for arbitrary temperatures and junction sizes. The nonlocal coupling of the supercurrent leads to a new effect, specific for the mesoscopic weak link between two superconducting rings; an applied magnetic flux through one of the rings produces a magnetic flux in the other ring even in the absence of an external flux through the other one. The phase dependent distributions of the local density of Andreev states, of the supercurrents and of the induced order parameter are obtained. The 'interference pattern' for the anomalous average inside the two-dimensional region cam be regulated by the applied magnetic fluxes or the transport currents. For some values of the phase differences between the terminals, the current vortex state and two-dimensional phase slip center appear

  6. Josephson frequency meter for millimeter and submillimeter wavelengths

    International Nuclear Information System (INIS)

    Anischenko, S.E.; Larkin, S.Y.; Chaikovsky, V.I.

    1994-01-01

    Frequency measurements of electromagnetic oscillations of millimeter and submillimeter wavebands with frequency growth due to a number of reasons become more and more difficult. First, these frequencies are considered to be cutoff for semiconductor converting devices and one has to use optical measurement methods instead of traditional ones with frequency transfer. Second, resonance measurement methods are characterized by using relatively narrow bands and optical ones are limited in frequency and time resolution due to the limited range and velocity of movement of their mechanical elements as well as the efficiency of these optical techniques decreases with the increase of wavelength due to diffraction losses. That requires the apriori information on the radiation frequency band of the source involved. Method of measuring frequency of harmonic microwave signals in millimeter and submillimeter wavebands based on the ac Josephson effect in superconducting contacts is devoid of all the above drawbacks. This approach offers a number of major advantages over the more traditional measurement methods, that is the one based on frequency conversion, resonance and interferrometric techniques. It can be characterized by high potential accuracy, wide range of frequencies measured, prompt measurement and the opportunity to obtain panoramic display of the results as well as full automation of the measuring process

  7. Josephson frequency meter for millimeter and submillimeter wavelengths

    Energy Technology Data Exchange (ETDEWEB)

    Anischenko, S.E.; Larkin, S.Y.; Chaikovsky, V.I. [State Research Center, Kiev (Ukraine)] [and others

    1994-12-31

    Frequency measurements of electromagnetic oscillations of millimeter and submillimeter wavebands with frequency growth due to a number of reasons become more and more difficult. First, these frequencies are considered to be cutoff for semiconductor converting devices and one has to use optical measurement methods instead of traditional ones with frequency transfer. Second, resonance measurement methods are characterized by using relatively narrow bands and optical ones are limited in frequency and time resolution due to the limited range and velocity of movement of their mechanical elements as well as the efficiency of these optical techniques decreases with the increase of wavelength due to diffraction losses. That requires the apriori information on the radiation frequency band of the source involved. Method of measuring frequency of harmonic microwave signals in millimeter and submillimeter wavebands based on the ac Josephson effect in superconducting contacts is devoid of all the above drawbacks. This approach offers a number of major advantages over the more traditional measurement methods, that is the one based on frequency conversion, resonance and interferrometric techniques. It can be characterized by high potential accuracy, wide range of frequencies measured, prompt measurement and the opportunity to obtain panoramic display of the results as well as full automation of the measuring process.

  8. Experiments on phase retrapping in φ Josephson junctions

    Energy Technology Data Exchange (ETDEWEB)

    Goldobin, Edward; Menditto, Rosina; Koelle, Dieter; Kleiner, Reinhold [University of Tuebingen, Tuebingen (Germany); Weides, Martin [KIT, Karlsruhe (Germany)

    2015-07-01

    We experimentally study retrapping of the phase in φ Josephson junctions (JJs) based on superconductor-insulator-ferromagnet-superconductor (SIFS) 0-π heterostructures. Such φ JJs have a doubly degenerate ground state (two potential energy wells) with the phases ±φ (0 < φ < π). We study in which of these two wells the phase is trapped upon return of the JJ to the zero voltage state. We find that for T>T* ∼ 2.4 K (large damping) the phase is always trapped in the +φ state. However, for lower T (small damping) the trapping result is a statistical mixture of the +φ and the -φ states due to the presence of noise in the system. The probability for retrapping to the -φ state increases and oscillates as T is decreasing below T*, reaching a saturation value of ∝ 30% for Teffect in the limit of low damping.

  9. Radioactive and Other Effects of Nuclear Explosion

    International Nuclear Information System (INIS)

    Ilijas, B.; Cizmek, A.; Prah, M.; Medakovic, S.

    2008-01-01

    As a result of long lasting efforts of international community to definitely ban all test nuclear explosions, the Comprehensive Nuclear-Test-Ban Treaty (CTBT) was opened for signature in New York on 24 September 1996, when it was signed by 71 states, including Croatia. The State Office for Nuclear Safety (SONS) which, as an independent state regulatory authority has a responsibility for activities relating to nuclear safety, including the national authority over this Treaty, is actively engaged in CTBTO activities. The nuclear explosion causes a lot of effects (blast, thermal, radioactive, electromagnetic) which differs a lot in its nature, reach, lasting and other. The longest lasting aftermath is from the radioactive effects that cause a radioactive fallout and a lot of radioactive elements in the environment, created by the influence of a primary beam of radiation. Fission and fusion are the main source of radionuclide created by the nuclear explosion, and the longest lasting aftermaths are by the fission products, namely their offspring in natural disintegration chains. This can make contaminated areas inappropriate for life for very long periods. Even in the case of underground nuclear explosion (when underground cavity is formed with no effects on the surface), a leakage of radioactive gases through cracks is possible. A number of radionuclide is created by the neutron activation of elements naturally present in an environment, because a very strong neutron radiation appears in the moment of nuclear explosion. The abundance of particular radionuclide is a very much dependent of a place of performing nuclear explosion and a composition of soil or water in the vicinity.(author)

  10. Isospin effects on collective nuclear dynamics

    CERN Document Server

    Di Toro, M; Baran, V; Larionov, A B

    1999-01-01

    We suggest several ways to study properties of the symmetry term in the nuclear equation of state, EOS, from collective modes in beta-unstable nuclei. After a general discussion on compressibility and saturation density in asymmetric nuclear matter we show some predictions on the collective response based on the solution of generalized Landau dispersion relations. Isoscalar-isovector coupling, disappearance of collectivity and possibility of new instabilities in low and high density regions are discussed with accent on their relation to the symmetry term of effective forces. The onset of chemical plus mechanical instabilities in a dilute asymmetric nuclear matter is discussed with reference to new features in fragmentation reactions.

  11. THz detectors using surface Josephson plasma waves in layered superconductors

    International Nuclear Information System (INIS)

    Savel'ev, Sergey; Yampol'skii, Valery; Nori, Franco

    2006-01-01

    We describe a proposal for THz detectors based on the excitation of surface waves, in layered superconductors, at frequencies lower than the Josephson plasma frequency ω J . These waves propagate along the vacuum-superconductor interface and are attenuated in both transverse directions out of the surface (i.e., towards the superconductor and towards the vacuum). The surface Josephson plasma waves are also important for the complete suppression of the specular reflection from a sample (Wood's anomalies, used for gratings) and produce a huge enhancement of the wave absorption, which can be used for the detection of THz waves

  12. Spectrum of resonant plasma oscillations in long Josephson junctions

    International Nuclear Information System (INIS)

    Holst, T.

    1996-01-01

    An analysis is presented for the amplitude of the plasma oscillations in the zero-voltage state of a long and narrow Josephson tunnel junction. The calculation is valid for arbitrary normalized junction length and arbitrary bias current. The spectrum of the plasma resonance is found numerically as solutions to an analytical equation. The low-frequency part of the spectrum contains a single resonance, which is known to exist also in the limit of a short and narrow junction. Above a certain cutoff frequency, a series of high-frequency standing wave plasma resonances is excited, a special feature of long Josephson junctions. copyright 1996 The American Physical Society

  13. Fluctuation Dominated Josephson Tunneling with a Scanning Tunneling Microscope

    International Nuclear Information System (INIS)

    Naaman, O.; Teizer, W.; Dynes, R. C.

    2001-01-01

    We demonstrate Josephson tunneling in vacuum tunnel junctions formed between a superconducting scanning tunneling microscope tip and a Pb film, for junction resistances in the range 50--300 k Omega. We show that the superconducting phase dynamics is dominated by thermal fluctuations, and that the Josephson current appears as a peak centered at small finite voltage. In the presence of microwave fields (f=15.0 GHz) the peak decreases in magnitude and shifts to higher voltages with increasing rf power, in agreement with theory

  14. Phase-locked flux-flow Josephson oscillator

    DEFF Research Database (Denmark)

    Ustinov, A. V.; Mygind, Jesper; Oboznov, V. A.

    1992-01-01

    We report on the observation of large rf induced steps due to phase-locking of unidirectional flux-flow motion in long quasi-one-dimensional Josephson junctions. The external microwave irradiation in the frequency range 62–77 GHz was applied from the edge of the junction at which the fluxons enter....... The dependence of the amplitude of the phase-locked step on external magnetic field and microwave power has been measured. The observed zero-crossing steps have potential application in Josephson voltage standards. A simple model for the flux-flow as determined by the microwave driven boundary gate at the edge...

  15. Josephson soliton oscillators in a superconducting thin film resonator

    DEFF Research Database (Denmark)

    Holm, J.; Mygind, Jesper; Pedersen, Niels Falsig

    1993-01-01

    Josephson soliton oscillators integrated in a resonator consisting of two closely spaced coplanar superconducting microstrips have been investigated experimentally. Pairs of long 1-D Josephson junctions with a current density of about 1000 A/cm2 were made using the Nb-AlOx-Nb trilayer technique....... Different modes of half-wave resonances in the thin-film structure impose different magnetic field configurations at the boundaries of the junctions. The DC I-V characteristic shows zero-field steps with a number of resonator-induced steps. These structures are compared to RF-induced steps generated...

  16. Josephson junction analog and quasiparticle-pair current

    DEFF Research Database (Denmark)

    Bak, Christen Kjeldahl; Pedersen, Niels Falsig

    1973-01-01

    A close analogy exists between a Josephson junction and a phase-locked loop. A new type of electrical analog based on this principle is presented. It is shown that the inclusion in this analog of a low-pass filter gives rise to a current of the same form as the Josephson quasiparticle-pair current....... A simple picture of the quasiparticle-pair current, which gives the right dependences, is obtained by assuming a junction cutoff frequency to be at the energy gap. ©1973 American Institute of Physics...

  17. Superconducting Coset Topological Fluids in Josephson Junction Arrays

    CERN Document Server

    Diamantini, M C; Trugenberger, C A; Sodano, Pasquale; Trugenberger, Carlo A.

    2006-01-01

    We show that the superconducting ground state of planar Josephson junction arrays is a P- and T-invariant coset topological quantum fluid whose topological order is characterized by the degeneracy 2 on the torus. This new mechanism for planar superconductivity is the P- and T-invariant analogue of Laughlin's quantum Hall fluids. The T=0 insulator-superconductor quantum transition is a quantum critical point characterized by gauge fields and deconfined degrees of freedom. Experiments on toroidal Josephson junction arrays could provide the first direct evidence for topological order and superconducting quantum fluids.

  18. Terahertz Responses of Intrinsic Josephson Junctions in High TC Superconductors

    International Nuclear Information System (INIS)

    Wang, H. B.; Wu, P. H.; Yamashita, T.

    2001-01-01

    High frequency responses of intrinsic Josephson junctions up to 2.5THz, including the observation of Shapiro steps under various conditions, are reported and discussed in this Letter. The sample was an array of intrinsic Josephson junctions singled out from inside a high T C superconducting Bi 2 Sr 2 CaCu 2 O 8+x single crystal, with a bow-tie antenna integrated to it. The number of junctions in the array was controllable, the junctions were homogeneous, the distribution of applied irradiation among the junctions was even, and the junctions could synchronously respond to high frequency irradiation

  19. Microwave phase locking of Josephson-junction fluxon oscillators

    DEFF Research Database (Denmark)

    Salerno, M.; Samuelsen, Mogens Rugholm; Filatrella, G.

    1990-01-01

    Application of the classic McLaughlin-Scott soliton perturbation theory to a Josephson-junction fluxon subjected to a microwave field that interacts with the fluxon only at the junction boundaries reduces the problem of phase locking of the fluxon oscillation to the study of a two-dimensional fun......Application of the classic McLaughlin-Scott soliton perturbation theory to a Josephson-junction fluxon subjected to a microwave field that interacts with the fluxon only at the junction boundaries reduces the problem of phase locking of the fluxon oscillation to the study of a two...

  20. Long Josephson tunnel junctions with doubly connected electrodes

    DEFF Research Database (Denmark)

    Monaco, R.; Mygind, J.; Koshelets, V. P.

    2012-01-01

    of such experiments, the number of magnetic flux quanta spontaneously trapped in a superconducting loop was measured by means of a long Josephson tunnel junction built on top of the loop itself. We have analyzed this system and found a number of interesting features not occurring in the conventional case with simply...... connected electrodes. In particular, the fluxoid quantization results in a frustration of the Josephson phase, which, in turn, reduces the junction critical current. Further, the possible stable states of the system are obtained by a self-consistent application of the principle of minimum energy...

  1. Low frequency noise in resonant Josephson soliton oscillators

    DEFF Research Database (Denmark)

    Hansen, Jørn Bindslev; Holst, T.; Wellstood, Frederick C.

    1991-01-01

    The noise in the resonant soliton mode of long and narrow Josephson tunnel junctions (Josephson transmission lines or JTLs) have been measured in the frequency range from 0.1 Hz to 25 kHz by means of a DC SQUID. The measured white noise was found, to within a factor of two, to be equal...... to the Nyquist voltage noise in a resistance equal to the dynamic resistance RD of the current-voltage characteristic of the bias point. In contrast, measurements of the linewidth of the microwave radiation from the same JTL showed that the spectral density of the underlying noise voltage scaled as R D2/RS where...

  2. Neutron albedo effects of underground nuclear explosion

    International Nuclear Information System (INIS)

    Yang Bo; Ying Yangjun; Li Jinhong; Bai Yun

    2013-01-01

    The neutron field distribution is affected by the surrounding medium in the underground nuclear explosion. It will influence the radiation chemical diagnosis. By Monte Carlo simulation, the fuel burnup induced by device and neutron albedo was calculated. The analysis method of albedo effect on radiation chemical diagnosis result under special environment was proposed. Neutron albedo should be considered when capture reaction burnup fraction is used, and then correct analysis can be carried out on the nuclear device.The neutron field distribution is affected by the surrounding medium in the underground nuclear explosion. It will influence the radiation chemical diagnosis. By Monte Carlo simulation, the fuel burnup induced by device and neutron albedo was calculated. The analysis method of albedo effect on radiation chemical diagnosis result under special environment was proposed. Neutron albedo should be considered when capture reaction burnup fraction is used, and then correct analysis can be carried out on the nuclear device. (authors)

  3. Radiation Effects in Nuclear Waste Materials

    International Nuclear Information System (INIS)

    Weber, William J.

    2005-01-01

    The objective of this project is to develop a fundamental understanding of radiation effects in glasses and ceramics, as well as the influence of solid-state radiation effects on aqueous dissolution kinetics, which may impact the performance of nuclear waste forms and stabilized nuclear materials. This work provides the underpinning science to develop improved glass and ceramic waste forms for the immobilization and disposition of high-level tank waste, excess plutonium, plutonium residues and scrap, other actinides, and other nuclear waste streams. Furthermore, this work is developing develop predictive models for the performance of nuclear waste forms and stabilized nuclear materials. Thus, the research performed under this project has significant implications for the immobilization of High-Level Waste (HLW) and Nuclear Materials, two mission areas within the Office of Environmental Management (EM). With regard to the HLW mission, this research will lead to improved understanding of radiation-induced degradation mechanisms and their effects on dissolution kinetics, as well as development of predictive models for waste form performance. In the Nuclear Materials mission, this research will lead to improvements in the understanding of radiation effects on the chemical and structural properties of materials for the stabilization and long-term storage of plutonium, highly-enriched uranium, and other actinides. The research uses plutonium incorporation, ion-beam irradiation, and electron-beam irradiation to simulate the effects of alpha decay and beta decay on relevant glasses and ceramics. The research under this project has the potential to result in improved glass and ceramic materials for the stabilization and immobilization of high-level tank waste, plutonium residues and scraps, surplus weapons plutonium, highly-enriched uranium, other actinides, and other radioactive materials

  4. Radiation Effects in Nuclear Waste Materials

    International Nuclear Information System (INIS)

    Weber, William J.; Wang, Lumin; Hess, Nancy J.; Icenhower, Jonathan P.; Thevuthasan, Suntharampillai

    2003-01-01

    The objective of this project is to develop a fundamental understanding of radiation effects in glasses and ceramics, as well as the influence of solid-state radiation effects on aqueous dissolution kinetics, which may impact the performance of nuclear waste forms and stabilized nuclear materials. This work provides the underpinning science to develop improved glass and ceramic waste forms for the immobilization and disposition of high-level tank waste, excess plutonium, plutonium residues and scrap, other actinides, and other nuclear waste streams. Furthermore, this work is developing develop predictive models for the performance of nuclear waste forms and stabilized nuclear materials. Thus, the research performed under this project has significant implications for the immobilization of High-Level Waste (HLW) and Nuclear Materials, two mission areas within the Office of Environmental Management (EM). With regard to the HLW mission, this research will lead to improved understanding of radiation-induced degradation mechanisms and their effects on dissolution kinetics, as well as development of predictive models for waste form performance. In the Nuclear Materials mission, this research will lead to improvements in the understanding of radiation effects on the chemical and structural properties of materials for the stabilization and long-term storage of plutonium, highly-enriched uranium, and other actinides. The research uses plutonium incorporation, ion-beam irradiation, and electron-beam irradiation to simulate the effects of alpha decay and beta decay on relevant glasses and ceramics. The research under this project has the potential to result in improved glass and ceramic materials for the stabilization and immobilization of high-level tank waste, plutonium residues and scraps, surplus weapons plutonium, highly-enriched uranium, other actinides, and other radioactive materials

  5. Geometric dependence of Nb-Bi2Te3-Nb topological Josephson junction transport parameters

    International Nuclear Information System (INIS)

    Molenaar, C G; Leusink, D P; Brinkman, A; Wang, X L

    2014-01-01

    Superconductor-topological insulator–superconductor Josephson junctions have been fabricated in order to study the width dependence of the critical current, normal state resistance and flux periodicity of the critical current modulation in an external field. Previous literature reports suggest anomalous scaling in topological junctions due to the presence of Majorana bound states. However, for most realized devices, one would expect that trivial 2π-periodic Andreev levels dominate transport. We also observe anomalous scaling behaviour of junction parameters, but the scaling can be well explained by mere geometric effects, such as the parallel bulk conductivity shunt and flux focusing. (paper)

  6. Dynamic current susceptibility as a probe of Majorana bound states in nanowire-based Josephson junctions

    Science.gov (United States)

    Trif, Mircea; Dmytruk, Olesia; Bouchiat, Hélène; Aguado, Ramón; Simon, Pascal

    2018-02-01

    We theoretically study a Josephson junction based on a semiconducting nanowire subject to a time-dependent flux bias. We establish a general density-matrix approach for the dynamical response of the Majorana junction and calculate the resulting flux-dependent susceptibility using both microscopic and effective low-energy descriptions for the nanowire. We find that the diagonal component of the susceptibility, associated with the dynamics of the Majorana state populations, dominates over the standard Kubo contribution for a wide range of experimentally relevant parameters. The diagonal term, explored, in this Rapid Communication, in the context of Majorana physics, allows probing accurately the presence of Majorana bound states in the junction.

  7. Controlling chaos in RCL-shunted Josephson junction by delayed linear feedback

    International Nuclear Information System (INIS)

    Feng Yuling; Shen Ke

    2008-01-01

    The resistively-capacitively-inductively-shunted (RCL-shunted) Josephson junction (RCLSJJ) shows chaotic behaviour under some parameter conditions. Here a scheme for controlling chaos in the RCLSJJ is presented based on the linear feedback theory. Numerical simulations show that this scheme can be effectively used to control chaotic states in this junction into stable periodic states. Moreover, the different stable period states with different period numbers can be obtained by appropriately adjusting the feedback intensity and delay time without any pre-knowledge of this system required

  8. Quantum dynamics of a Josephson junction driven cavity mode system in the presence of voltage bias noise

    Science.gov (United States)

    Wang, Hui; Blencowe, M. P.; Armour, A. D.; Rimberg, A. J.

    2017-09-01

    We give a semiclassical analysis of the average photon number as well as photon number variance (Fano factor F ) for a Josephson junction (JJ) embedded microwave cavity system, where the JJ is subject to a fluctuating (i.e., noisy) bias voltage with finite dc average. Through the ac Josephson effect, the dc voltage bias drives the effectively nonlinear microwave cavity mode into an amplitude squeezed state (F Armour et al., Phys. Rev. Lett. 111, 247001 (2013), 10.1103/PhysRevLett.111.247001], but bias noise acts to degrade this squeezing. We find that the sensitivity of the Fano factor to bias voltage noise depends qualitatively on which stable fixed point regime the system is in for the corresponding classical nonlinear steady-state dynamics. Furthermore, we show that the impact of voltage bias noise is most significant when the cavity is excited to states with large average photon number.

  9. An Effective Method For Nuclear Technology Transfer

    International Nuclear Information System (INIS)

    Jeon, Jan Pung

    1987-01-01

    Three basic entities involved in the implementation of nuclear projects are the Owner, Regulatory Authority and Nuclear Industry. Their ultimate objective is to secure the safe, reliable and economical nuclear energy. For s successful nuclear power program, the owner should maintain a good relationship with the other entities and pursue an optimization of the objectives. On the other hand, he should manage projects along the well - planned paths in order to effectively learn the nuclear technology. One of the problems in the nuclear projects of developing countries was the absence of long - term technology development program, a limited local participation and the technical incapability. For the effective technology transfer, a motivation of the technology supplier and a readiness of the recipient to accommodate such technologies are required. Advanced technology is usually developed at considerable expense with the expectation that the developer will use it in furthering his own business. Therefore, he tends to be reluctant to transfer it to the others, particularly, to the potential competitors. There is a disinclination against further technology transfer beyond the minimum contractual obligation or the requirements by Government Regulatory. So, an additional commercial incentive must be provided to the developer

  10. Deregulation and Nuclear Training: Cost Effective Alternatives

    International Nuclear Information System (INIS)

    Richard P. Coe; Patricia A. Lake

    2000-01-01

    Training is crucial to the success of any organization. It is also expensive, with some estimates exceeding $50 billion annually spent on training by U.S. corporations. Nuclear training, like that of many other highly technical organizations, is both crucial and costly. It is unlikely that the amount of training can be significantly reduced. If anything, current trends indicate that training needs will probably increase as the industry and workforce ages and changes. With the advent of energy deregulation in the United States, greater pressures will surface to make the costs of energy more cost-competitive. This in turn will drive businesses to more closely examine existing costs and find ways to do things in a more cost-effective way. The commercial nuclear industry will be no exception, and nuclear training will be equally affected. It is time for nuclear training and indeed the entire nuclear industry to begin using more aggressive techniques to reduce costs. This includes the need for nuclear training to find alternatives to traditional methods for the delivery of cost-effective high-quality training that meets regulatory requirements and produces well-qualified personnel capable of working in an efficient and safe manner. Computer-based and/or Web-based training are leading emerging technologies

  11. Shell effects in the nuclear deformation energy

    International Nuclear Information System (INIS)

    Ross, C.K.

    1973-01-01

    A new approach to shell effects in the Strutinsky method for calculating nuclear deformation energy is evaluated and the suggestion of non-conservation of angular momentum in the same method is resolved. Shell effects on the deformation energy in rotational bands of deformed nuclei are discussed. (B.F.G.)

  12. Effectiveness of Existing International Nuclear Liability Regime

    International Nuclear Information System (INIS)

    Al-Doais, Salwa; Kessel, Daivd

    2015-01-01

    The first convention was the Paris Convention on Third Party Liability in the Field of Nuclear Energy (the Paris Convention) had been adopted on 29 July 1960 under the auspices of the OECD, and entered into force on 1 April 1968. In 1963,the Brussels Convention - supplementary to the Paris Convention- was adopted in to provide additional funds to compensate damage as a result of a nuclear incident where Paris Convention funds proved to be insufficient. The IAEA's first convention was the Vienna Convention on Civil Liability for Nuclear Damage (the Vienna Convention) which adopted on 21 May 1963,and entered into force in 1977. Both the Paris Convention and the Vienna Convention laid down very similar nuclear liability rules based on the same general principles. The broad principles in these conventions can be summarized as follows: 1- The no-fault liability principle (strict liability) 2- Liability is channeled exclusively to the operator of the nuclear installation (legal channeling) 3- Only courts of the state in which the nuclear accident occurs would have jurisdiction (exclusive jurisdiction) 4- Limitation of the amount of liability and the time frame for claiming damages (limited liability) 5- The operator is required to have adequate insurance or financial guarantees to the extent of its liability amount (liability must be financially secured). 6- Liability is limited in time. Compensation rights are extinguished after specific time. 7- Non-discrimination of victims on the grounds of nationality, domicile or residence. Nuclear liability conventions objective is to provide adequate compensation payments to victims of a nuclear accident. Procedures for receiving these compensation are controlled by some rules such as exclusive jurisdiction, that rule need a further amendment to ensure the effectiveness of the exiting nuclear liability regime . Membership of the Conventions is a critical issue, because the existence of the conventions without being party to

  13. Effectiveness of Existing International Nuclear Liability Regime

    Energy Technology Data Exchange (ETDEWEB)

    Al-Doais, Salwa; Kessel, Daivd [KEPCO International Nuclear Graduate School, Daejeon (Korea, Republic of)

    2015-10-15

    The first convention was the Paris Convention on Third Party Liability in the Field of Nuclear Energy (the Paris Convention) had been adopted on 29 July 1960 under the auspices of the OECD, and entered into force on 1 April 1968. In 1963,the Brussels Convention - supplementary to the Paris Convention- was adopted in to provide additional funds to compensate damage as a result of a nuclear incident where Paris Convention funds proved to be insufficient. The IAEA's first convention was the Vienna Convention on Civil Liability for Nuclear Damage (the Vienna Convention) which adopted on 21 May 1963,and entered into force in 1977. Both the Paris Convention and the Vienna Convention laid down very similar nuclear liability rules based on the same general principles. The broad principles in these conventions can be summarized as follows: 1- The no-fault liability principle (strict liability) 2- Liability is channeled exclusively to the operator of the nuclear installation (legal channeling) 3- Only courts of the state in which the nuclear accident occurs would have jurisdiction (exclusive jurisdiction) 4- Limitation of the amount of liability and the time frame for claiming damages (limited liability) 5- The operator is required to have adequate insurance or financial guarantees to the extent of its liability amount (liability must be financially secured). 6- Liability is limited in time. Compensation rights are extinguished after specific time. 7- Non-discrimination of victims on the grounds of nationality, domicile or residence. Nuclear liability conventions objective is to provide adequate compensation payments to victims of a nuclear accident. Procedures for receiving these compensation are controlled by some rules such as exclusive jurisdiction, that rule need a further amendment to ensure the effectiveness of the exiting nuclear liability regime . Membership of the Conventions is a critical issue, because the existence of the conventions without being party to

  14. Josephson junctions in high-T/sub c/ superconductors

    Science.gov (United States)

    Falco, C.M.; Lee, T.W.

    1981-01-14

    The invention includes a high T/sub c/ Josephson sperconducting junction as well as the method and apparatus which provides the junction by application of a closely controlled and monitored electrical discharge to a microbridge region connecting two portions of a superconducting film.

  15. Flux flow in high-Tc Josephson junctions

    DEFF Research Database (Denmark)

    Filatrella, G.; Pedersen, Niels Falsig

    1993-01-01

    The possibility of achieving fluxon nucleation in nonhysteretic high-T(c) Josephson junctions due to the presence of inhomogeneities is investigated numerically. For a large range of parameters the I- V characteristics in presence of such discontinuities show a strong similarity with those obtain...

  16. Aspects of stochastic resonance in Josephson junction, bimodal

    Indian Academy of Sciences (India)

    We present the results of extensive numerical studies on stochastic resonance and its characteristic features in three model systems, namely, a model for Josephson tunnel junctions, the bistable cubic map and a coupled map lattice formed by coupling the cubic maps. Some interesting features regarding the mechanism ...

  17. The two Josephson junction flux qubit with large tunneling amplitude

    International Nuclear Information System (INIS)

    Shnurkov, V.I.; Soroka, A.A.; Mel'nik, S.I.

    2008-01-01

    In this paper we discuss solid-state nanoelectronic realizations of Josephson flux qubits with large tunneling amplitude between the two macroscopic states. The latter can be controlled via the height and form of the potential barrier, which is determined by quantum-state engineering of the flux qubit circuit. The simplest circuit of the flux qubit is a superconducting loop interrupted by a Josephson nanoscale tunnel junction. The tunneling amplitude between two macroscopically different states can be increased substantially by engineering of the qubit circuit if the tunnel junction is replaced by a ScS contact. However, only Josephson tunnel junctions are particularly suitable for large-scale integration circuits and quantum detectors with present-day technology. To overcome this difficulty we consider here a flux qubit with high energy-level separation between the 'ground' and 'excited' states, consisting of a superconducting loop with two low-capacitance Josephson tunnel junctions in series. We demonstrate that for real parameters of resonant superposition between the two macroscopic states the tunneling amplitude can reach values greater than 1 K. Analytical results for the tunneling amplitude obtained within the semiclassical approximation by the instanton technique show good correlation with a numerical solution

  18. Magnetic Field Dependence and Q of the Josephson Plasma Resonance

    DEFF Research Database (Denmark)

    Pedersen, Niels Falsig; Finnegan, T. F.; Langenberg, D. N.

    1972-01-01

    of supercurrent density which is not observed in conventional measurements of the field-dependent critical current. The frequency and field dependence of the plasma-resonance linewidth are interpreted as evidence that the previously unobserved quasiparticle-pair-interference tunnel current predicted by Josephson...

  19. Negative differential resistance in Josephson junctions coupled to a cavity

    DEFF Research Database (Denmark)

    Pedersen, Niels Falsig; Filatrella, G.; Pierro, V.

    2014-01-01

    or external – is often used. A cavity may also induce a negative differential resistance region at the lower side of the resonance frequency. We investigate the dynamics of Josephson junctions with a negative differential resistance in the quasi particle tunnel current, i.e. in the McCumber curve. We find...

  20. Vortex dynamics in Josephson ladders with II-junctions

    DEFF Research Database (Denmark)

    Kornev, Victor K.; Klenov, N. V.; Oboznov, V.A.

    2004-01-01

    Both experimental and numerical studies of a self-frustrated triangular array of pi-junctions are reported. The array of SFS Josephson junctions shows a transition to the pi-state and self-frustration with a decrease in temperature. This manifests itself in a half-period shift of the bias critica...

  1. Josephson flux-flow oscillators in nonuniform microwave fields

    DEFF Research Database (Denmark)

    Salerno, Mario; Samuelsen, Mogens Rugholm

    2000-01-01

    We present a simple theory for Josephson flux-flow oscillators in the presence of nonuniform microwave fields. In particular we derive an analytical expression for the I-V characteristic of the oscillator from which we show that satellite steps are spaced around the main flux-flow resonance by only...

  2. Breathers in Josephson junction ladders: Resonances and electromagnetic wave spectroscopy

    DEFF Research Database (Denmark)

    Miroshnichenko, A. E.; Flach, S.; Fistul, M.

    2001-01-01

    We present a theoretical study of the resonant interaction between dynamical localized states (discrete breathers) and linear electromagnetic excitations (EE's) in Josephson junction ladders. By making use of direct numerical simulations we find that such an interaction manifests itself by resonant...

  3. Switching between dynamic states in intermediate-length Josephson junctions

    DEFF Research Database (Denmark)

    Pagano, S.; Sørensen, Mads Peter; Parmentier, R. D.

    1986-01-01

    The appearance of zero-field steps (ZFS’s) in the current-voltage characteristics of intermediate-length overlap-geometry Josephson tunnel junctions described by a perturbed sine-Gordon equation (PSGE) is associated with the growth of parametrically excited instabilities of the McCumber backgroun...

  4. Aspects of stochastic resonance in Josephson junction, bimodal ...

    Indian Academy of Sciences (India)

    Abstract. We present the results of extensive numerical studies on stochastic resonance and its characteristic features in three model systems, namely, a model for Josephson tunnel junctions, the bistable cubic map and a coupled map lattice formed by coupling the cubic maps. Some interesting features regarding the ...

  5. Phenomenological approach to bistable behavior of Josephson junctions

    International Nuclear Information System (INIS)

    Nishi, K.; Nara, S.; Hamanaka, K.

    1985-01-01

    The interaction of unbiased Josephson junction with external electromagnetic field in the presence of externally applied uniform magnetic field is theoretically examined by means of phenomenological treatment. It is proposed that an irradiated junction with suitably chosen parameters shows a bistable behavior of voltage across the junction as a function of the radiation intensity

  6. Josephson tunnel junctions in a magnetic field gradient

    DEFF Research Database (Denmark)

    Monaco, R.; Mygind, Jesper; Koshelets, V.P.

    2011-01-01

    We measured the magnetic field dependence of the critical current of high-quality Nb-based planar Josephson tunnel junctions in the presence of a controllable nonuniform field distribution. We found skewed and slowly changing magnetic diffraction patterns quite dissimilar from the Fraunhofer...

  7. Josephson current through a molecular transistor in a dissipative environment

    DEFF Research Database (Denmark)

    Novotny, T; Rossini, Gianpaolo; Flensberg, Karsten

    2005-01-01

    We study the Josephson coupling between two superconductors through a single correlated molecular level, including Coulomb interaction on the level and coupling to a bosonic environment. All calculations are done to the lowest, i.e., the fourth, order in the tunneling coupling and we find...

  8. The climatic effects of nuclear war

    Science.gov (United States)

    Turco, R. P.; Toon, O. B.; Ackerman, T. P.; Pollack, J. B.; Sagan, C.

    1984-01-01

    The effects of various US-USSR nuclear-exchange scenarios on global climate are investigated by means of computer simulations, summarizing the results of Turco et al. (1983) and follow-up studies using 3D global-circulation models. A nuclear-scenario model is used to determine the amounts of dust, smoke, radioactivity, and pyrotoxins generated by a particular type of nuclear exchange (such as a general 5,000-Mt exchange, a 1,000-Mt limited exchange, a 5,000-Mt hard-target counterforce attack, and a 100-Mt attack on cities only): a particle-microphysics model predicts the evolution of the dust and smoke particles; and a radiative-convective climate model estimates the effects of the dust and smoke clouds on the global radiation budget. The findings are presented in graphs, diagrams, and a table. Thick clouds blocking most sunlight over the Northern Hemisphere midlatitudes for weeks or months and producing ground-temperature reductions of 20-40 C, disruption of global circulation patterns, and rapid spread of clouds to the Southern Hemisphere are among the 'nuclear-winter' effects predicted for the 5,000-Mt baseline case. The catastrophic consequences for plant, animal, and human populations are considered, and the revision of superpower nuclear strategies is urged.

  9. Biological effects of nuclear radiation

    International Nuclear Information System (INIS)

    Hotz, G.

    1975-01-01

    After a brief survey about the main radiobiological effects caused by ionizing radiation, human symptoms after irradiation and incorporation are shown. The special radiotoxic effect of radionuclides which are chemically associated with metabolism-specific elements such as calcium and potassium is shown and methods of treatment are indicated. (ORU) [de

  10. Realistic effective interactions for nuclear systems

    International Nuclear Information System (INIS)

    Hjort-Jensen, M.; Osnes, E.; Kuo, T.T.S.

    1994-09-01

    A review of perturbative many-body descriptions of several nuclear systems is presented. Symmetric and asymmetric nuclear matter and finite nuclei with few valence particles are examples of systems considered. The many-body description starts with the most recent meson-exchange potential models for the nucleon-nucleon interaction, an interaction which in turn is used in perturbative schemes to evaluate the effective interaction for finite nuclei and infinite nuclear matter. A unified perturbative approach based on time-dependent perturbation theory is elaborated. For finite nuclei new results are presented for the effective interaction and the energy spectra in the mass areas of oxygen, calcium and tin. 166 refs., 83 refs., 21 tabs

  11. Engineering effects of underground nuclear explosions

    Energy Technology Data Exchange (ETDEWEB)

    Boardman, Charles R [CER Geonuclear Corporation, Las Vegas, NV (United States)

    1970-05-01

    Useful effects of contained underground nuclear explosions are discussed in light of today's most promising potential applications. Relevant data obtained through exploration of explosion environments of nine U.S. tests in competent rock are summarized and presented as a practical basis for estimating magnitudes of effects. Effects discussed include chimney configuration, permeability, and volume as well as rubble particle size distributions and extents of permeability change in the chimney wall rock. Explosion mediums include shale, granite, dolomite, and salt. (author)

  12. Animal Effects from Soviet Atmospheric Nuclear Tests

    Science.gov (United States)

    2008-03-01

    describes the effect on animal models of atmospheric nuclear weapons tests performed by the Soviet Union at the Semipalatinsk Test Site . Part I describes...understand the pathogenic mechanisms of injury and the likelihood of efficacy of proposed treatment measures. 15. SUBJECT TERMS Semipalatinsk Test Site ...the Semipalatinsk Test Site . Part 1 describes the air blast and thermal radiation effects. Part 2 covers the effects of primary (prompt) radiation and

  13. Engineering effects of underground nuclear explosions

    International Nuclear Information System (INIS)

    Boardman, Charles R.

    1970-01-01

    Useful effects of contained underground nuclear explosions are discussed in light of today's most promising potential applications. Relevant data obtained through exploration of explosion environments of nine U.S. tests in competent rock are summarized and presented as a practical basis for estimating magnitudes of effects. Effects discussed include chimney configuration, permeability, and volume as well as rubble particle size distributions and extents of permeability change in the chimney wall rock. Explosion mediums include shale, granite, dolomite, and salt. (author)

  14. Effective Methods of Nuclear Power Technology Transfer

    International Nuclear Information System (INIS)

    Shave, D. F.; Kent, G. F.; Giambusso, A.

    1987-01-01

    An effective technology transfer program is a necessary and significant step towards independence in nuclear power technology. Attaining success in the conduct of such a program is a result of a) the donor and recipient jointly understanding the fundamental concepts of the learning process, b) sharing a mutual philosophy involving a partnership relationship, c) joint and careful planning, d) rigorous adherence to proven project management techniques, and e) presence of adequate feedback to assure continuing success as the program proceeds. Several years ago, KEPCO President Park, Jung-KI presented a paper on technology in which he stated, 'Nuclear technology is an integration of many unit disciplines, and thus requires extensive investment and training in order to establish the base for efficient absorption of transferred technology.' This paper addresses President Park's observations by discussing the philosophy, approach, and mechanisms that are necessary to support an efficient and effective process of nuclear power technology transfer. All technical content and presentation methods discussed are based on a technology transfer program developed by Stone and Webster, as an Engineer/Constructor for nuclear power plants, and are designed and implemented to promote the primary program goal - the ability of the trainees and the organization to perform specific nuclear power related multi-discipline function independently and competitively

  15. Multiwall carbon nanotube Josephson junctions with niobium contacts

    International Nuclear Information System (INIS)

    Pallecchi, Emiliano

    2009-01-01

    The main goal of this thesis is the investigation of dissipationless supercurrent in multiwall carbon nanotubes embedded in a controlled environment. The experimental observation of a dissipationless supercurrent in gated carbon nanotubes remains challenging because of its extreme sensitivity to the environment and to noise fluctuations. We address these issues by choosing niobium as a superconductor and by designing an optimized on chip electromagnetic environment. The environment is meant to reduce the suppression of the supercurrent and allows to disentangle the effects of thermal fluctuations from the intrinsic behavior of the junction. This is crucial for the extraction of the value critical current from the measured data. When the transparency of the contacts is high enough we observed a fully developed supercurrent and we found that it depends on the gate voltage in a resonant manner. In average the critical current increases when the gate is tuned more negative, reflecting the increase of the transparency of the contacts, while the resonant behavior is due to quantum interference effects. We measured the temperature dependence of the switching current and we analyzed the data with an extended RCSJ model that allow to extract the critical current from the experimental data. The measured critical currents are very high with respect to previous reports on gated devices. At positive gate voltage the contacts transparency is lowered and Coulomb blockade is observed. This allows to use Coulomb blockade measurements to further characterize the nanotube and to study the physics of a quantum dot coupled to superconducting leads. The last part of this thesis is dedicated to the measurements of a carbon nanotube Josephson junction in the Coulomb blockade regime. (orig.)

  16. Multiwall carbon nanotube Josephson junctions with niobium contacts

    Energy Technology Data Exchange (ETDEWEB)

    Pallecchi, Emiliano

    2009-02-17

    The main goal of this thesis is the investigation of dissipationless supercurrent in multiwall carbon nanotubes embedded in a controlled environment. The experimental observation of a dissipationless supercurrent in gated carbon nanotubes remains challenging because of its extreme sensitivity to the environment and to noise fluctuations. We address these issues by choosing niobium as a superconductor and by designing an optimized on chip electromagnetic environment. The environment is meant to reduce the suppression of the supercurrent and allows to disentangle the effects of thermal fluctuations from the intrinsic behavior of the junction. This is crucial for the extraction of the value critical current from the measured data. When the transparency of the contacts is high enough we observed a fully developed supercurrent and we found that it depends on the gate voltage in a resonant manner. In average the critical current increases when the gate is tuned more negative, reflecting the increase of the transparency of the contacts, while the resonant behavior is due to quantum interference effects. We measured the temperature dependence of the switching current and we analyzed the data with an extended RCSJ model that allow to extract the critical current from the experimental data. The measured critical currents are very high with respect to previous reports on gated devices. At positive gate voltage the contacts transparency is lowered and Coulomb blockade is observed. This allows to use Coulomb blockade measurements to further characterize the nanotube and to study the physics of a quantum dot coupled to superconducting leads. The last part of this thesis is dedicated to the measurements of a carbon nanotube Josephson junction in the Coulomb blockade regime. (orig.)

  17. Memory effects in nuclear fragmentation?

    International Nuclear Information System (INIS)

    Colonna, M.; Di Toro, M.; Guarnera, A.

    1994-01-01

    A general procedure to identify instability regions which lead to multifragmentation events is presented. The dominant mode at the instability point is determined from the knowledge of the mean properties (density and temperature) of the system at that point. For spinodal instabilities the dependence of fragment structures on the dynamical conditions is studied changing the beam energy and the considered equation of state. An important competition between two dynamical effects, expansion of the system and growth of fluctuations, is revealed. It is shown that in heavy-ion central collisions at medium energies memory effects of the configuration formed at the instability time could be observed in the final fragmentation pattern. Some hints towards a fully dynamical picture of fragmentation processes are finally suggested. ((orig.))

  18. Surface effects of underground nuclear explosions

    Energy Technology Data Exchange (ETDEWEB)

    Allen, B.M.; Drellack, S.L. Jr.; Townsend, M.J.

    1997-06-01

    The effects of nuclear explosions have been observed and studied since the first nuclear test (code named Trinity) on July 16, 1945. Since that first detonation, 1,053 nuclear tests have been conducted by the US, most of which were sited underground at the Nevada Test Site (NTS). The effects of underground nuclear explosions (UNEs) on their surroundings have long been the object of much interest and study, especially for containment, engineering, and treaty verification purposes. One aspect of these explosion-induced phenomena is the disruption or alteration of the near-surface environment, also known as surface effects. This report was prepared at the request of the Los Alamos National Laboratory (LANL), to bring together, correlate, and preserve information and techniques used in the recognition and documentation of surface effects of UNEs. This report has several main sections, including pertinent background information (Section 2.0), descriptions of the different types of surface effects (Section 3.0), discussion of their application and limitations (Section 4.0), an extensive bibliography and glossary (Section 6.0 and Appendix A), and procedures used to document geologic surface effects at the NTS (Appendix C). Because a majority of US surface-effects experience is from the NTS, an overview of pertinent NTS-specific information also is provided in Appendix B. It is not within the scope of this report to explore new relationships among test parameters, physiographic setting, and the types or degree of manifestation of surface effects, but rather to compile, summarize, and capture surface-effects observations and interpretations, as well as documentation procedures and the rationale behind them.

  19. Recommendable Practices for Effective Nuclear Crisis Communication

    International Nuclear Information System (INIS)

    Lee, Chang Ju; Hah, Yeon Hee

    2011-01-01

    'Crisis communication' refers one of the activities done by the Nuclear Regulatory Organizations (NROs) in order to protect the public and the environment from the possible harmful effects. As denoted by the BMU, German NRO, crisis communication is not only 'public information' or 'information for the public', but also communication between authorities in order to guarantee that public information is consistent. This study proposes some recommendable practices for developing a guideline of well-prepared nuclear crisis communication system, including its management framework, and for introducing good insights, based on the study of international aspects provided by relevant OECD/NEA WPGC (Working Group on Public Communication for Nuclear Regulatory Organizations)i working group

  20. Climatic Effects of Regional Nuclear War

    Science.gov (United States)

    Oman, Luke D.

    2011-01-01

    We use a modern climate model and new estimates of smoke generated by fires in contemporary cities to calculate the response of the climate system to a regional nuclear war between emerging third world nuclear powers using 100 Hiroshima-size bombs (less than 0.03% of the explosive yield of the current global nuclear arsenal) on cities in the subtropics. We find significant cooling and reductions of precipitation lasting years, which would impact the global food supply. The climate changes are large and longlasting because the fuel loadings in modern cities are quite high and the subtropical solar insolation heats the resulting smoke cloud and lofts it into the high stratosphere, where removal mechanisms are slow. While the climate changes are less dramatic than found in previous "nuclear winter" simulations of a massive nuclear exchange between the superpowers, because less smoke is emitted, the changes seem to be more persistent because of improvements in representing aerosol processes and microphysical/dynamical interactions, including radiative heating effects, in newer global climate system models. The assumptions and calculations that go into these conclusions will be described.

  1. Nuclear power and the greenhouse effect

    International Nuclear Information System (INIS)

    1989-01-01

    Carbon dioxide from fossil fuel combustion accounts for about 40% of the global warming due to the 'greenhouse effect'. Thus national energy policies of the fuels used to generate electricity can have a significant effect on the levels of gas emissions which contribute to the 'greenhouse effect'. The more efficient use of energy is the first way of controlling the increase in gas emissions. The use of natural gas instead of coal or oil would also be beneficial but the reserves of natural gas are limited. The use of nuclear-generated electricity has already reduced the level of global warming by 3% but could have a greater effect in the future. Ways in which the government could reduce 'greenhouse' gas emissions are listed. These include the more extensive use of nuclear power for generating electricity not only for domestic but industrial uses. (U.K.)

  2. Spatiotemporal chaos in rf-driven Josephson junction series arrays

    International Nuclear Information System (INIS)

    Dominguez, D.; Cerdeira, H.A.

    1995-01-01

    We study underdamped Josephson junction series arrays that are globally coupled through a resistive shunting load and driven by an rf bias current. They can be an experimental realization of many phenomena currently studied in globally coupled logistic maps. We study their spatiotemporal dynamics and we find coherent, ordered, partially ordered, turbulent, and quasiperiodic phases. The ordered phase corresponds to giant Shapiro steps in the IV characteristics. In the turbulent phase there is a saturation of the broad-band noise for a large number of junctions. This corresponds to a breakdown of the law of large numbers as seen in globally coupled maps. Coexisting with this phenomenon, we find an emergence of pseudosteps in the IV characteristics. This effect can be experimentally distinguished from the true Shapiro steps, which do not have broad-band noise emission. We study the stability of the breakdown of the law of large numbers against thermal fluctuations. We find that it is stable below a critical temperature T c1 . A measurement of the broad-band noise as a function of temperature T will show three different regimes: below T c1 the broad-band noise decreases when increasing T, and there is turbulence and the breakdown of the law of large numbers. Between T c1 and a second critical temperature T c2 the broad-band noise is constant and the dynamics is dominated by the chaos of the individual junctions. Finally above T c2 all the broad-band noise is due to thermal fluctuations, since it increases linearly with T

  3. Complex dynamics in Josephson system with two external forcing terms

    International Nuclear Information System (INIS)

    Yang Jianping; Feng Wei; Jing Zhujun

    2006-01-01

    Josephson system with two external forcing terms is investigated. By applying Melnikov method, we prove that criterion of existence of chaos under periodic perturbation. By second-order averaging method and Melnikov method, we obtain the criterion of existence of chaos in averaged system under quasi-periodic perturbation for ω 2 =ω 1 +εν, and cannot prove the criterion of existence of chaos in averaged system under quasi-periodic perturbation for ω 2 =nω 1 +εν (n>=2 and n-bar N), where ν is not rational to ω 1 . We also study the effects of the parameters of system on dynamical behaviors by using numerical simulation. The numerical simulations, including bifurcation diagram of fixed points, bifurcation diagram of system in three- and two-dimensional space, homoclinic and heteroclinic bifurcation surface, Maximum Lyapunov exponent, phase portraits, Poincare map, are also plotted to illustrate theoretical analysis, and to expose the complex dynamical behaviors, including the period-n (n=1,2,5,7) orbits in different chaotic regions, cascades of period-doubling bifurcation from period-1, 2 and 5 orbits, reverse period-doubling bifurcation, onset of chaos which occurs more than once for two given external frequencies and chaos suddenly converting to periodic orbits, transient chaos with complex periodic windows and crisis, reverse period-5 bubble, non-attracting chaotic set and nice attracting chaotic set. In particular, we observe that the system can leave chaotic region to periodic motion by adjusting damping α, amplitude f 1 and frequency ω 2 of external forcing which can be considered as a control strategy

  4. Flux-flow drag in coupled Josephson junctions

    International Nuclear Information System (INIS)

    Parmentier, R.D.; Barbara, P.; Costabile, G.; DAnna, A.; Malomed, B.A.; Soriano, C.

    1997-01-01

    We present a detailed analysis of the interaction between two fluxon chains in parallel magnetically coupled long Josephson junctions, one of which is biased (open-quotes generatorclose quotes) while another is unbiased (open-quotes detectorclose quotes). The main effect is that the driven fluxon chain in the generator may drag the chain in the detector. We note that five different regimes of the interaction are possible: both chains may be pinned by the external magnetic field; both may move in a locked state, inducing the same dc voltage in both junctions; in an unlocked state they may move at different velocities; the chain in the detector may remain pinned while the one in the generator is moving; and, finally, in a limited range of parameters the mean detector voltage may be negative, which implies that the detector chain is moving in the direction opposite to that of the chain in the generator. We consider a simplified model based on the assumptions that the fluxon chains are dense and rigid, and that their motion is nonrelativistic. In this model, each chain is represented by a single degree of freedom (its coordinate). Numerical and analytical consideration of the simplified model demonstrates that it is able to reproduce correctly all the dynamical regimes except for the negative-voltage one. To explain the existence of the latter regime, we introduce another model, suggested by the simulations, which is based on the presence of two fluxons and one antifluxon in the generator, and a single fluxon in the detector. The negative voltage is produced by motion of the antifluxon in a bound state with the detector close-quote s fluxon. The existence region of this state is limited by its collisions with free fluxons in the generator. copyright 1997 The American Physical Society

  5. 0 - π Quantum transition in a carbon nanotube Josephson junction: Universal phase dependence and orbital degeneracy

    Science.gov (United States)

    Delagrange, R.; Weil, R.; Kasumov, A.; Ferrier, M.; Bouchiat, H.; Deblock, R.

    2018-05-01

    In a quantum dot hybrid superconducting junction, the behavior of the supercurrent is dominated by Coulomb blockade physics, which determines the magnetic state of the dot. In particular, in a single level quantum dot singly occupied, the sign of the supercurrent can be reversed, giving rise to a π-junction. This 0 - π transition, corresponding to a singlet-doublet transition, is then driven by the gate voltage or by the superconducting phase in the case of strong competition between the superconducting proximity effect and Kondo correlations. In a two-level quantum dot, such as a clean carbon nanotube, 0- π transitions exist as well but, because more cotunneling processes are allowed, are not necessarily associated to a magnetic state transition of the dot. In this proceeding, after a review of 0- π transitions in Josephson junctions, we present measurements of current-phase relation in a clean carbon nanotube quantum dot, in the single and two-level regimes. In the single level regime, close to orbital degeneracy and in a regime of strong competition between local electronic correlations and superconducting proximity effect, we find that the phase diagram of the phase-dependent transition is a universal characteristic of a discontinuous level-crossing quantum transition at zero temperature. In the case where the two levels are involved, the nanotube Josephson current exhibits a continuous 0 - π transition, independent of the superconducting phase, revealing a different physical mechanism of the transition.

  6. Repulsive fluxons in a stack of Josephson junctions perturbed by a cavity

    DEFF Research Database (Denmark)

    Madsen, Søren; Pedersen, Niels Falsig; Christiansen, Peter Leth

    2008-01-01

    The BSCCO type intrinsic Josephson junction has been modeled as a stack of inductively coupled long Josephson junctions, which were described by a system of coupled sine-Gordon equations. In a system of 10 long Josephson junctions coupled to a linear cavity, we numerically investigate how...... of the inductive coupling strength, we investigate the cavity current, fluxon phase difference, and current–voltage characteristic. The stack-cavity system with in-phase fluxon motion may be utilized as a THz oscillator....

  7. Non-equilibrium properties of Josephson critical current in Nb-based three terminal superconducting tunnel devices

    International Nuclear Information System (INIS)

    Ammendola, G.; Parlato, L.; Peluso, G.; Pepe, G.

    1998-01-01

    Tunnel quasi-particle injection into a superconducting film provides useful information on the non-equilibrium state inside the perturbed superconductor as well as on the potential application to electronic devices. Three terminal injector-detector superconducting devices have a long history in non-equilibrium superconductivity. In the recent past non-equilibrium phenomena have attracted again considerable attention because of many superconducting based detectors involve processes substantially non-equilibrium in nature. The possibility of using a stacked double tunnel junction to study the influence of non-equilibrium superconductivity on the Josephson critical current is now considered. An experimental study of the effect of quasi-particle injection on the Josephson current both in steady-state and pulsed experiments down to T=1.2 K is presented using 3 terminal Nb-based stacked double tunnel devices. The feasibility of a new class of particle detectors based on the direct measurement of the change in the Josephson current following the absorption of a X-ray quantum is also discussed in terms of non-equilibrium theories. (orig.)

  8. Radiation effects, nuclear energy and comparative risks

    International Nuclear Information System (INIS)

    Gopinath, D.V.

    2007-01-01

    Nuclear energy had a promising start as an unlimited, inexpensive and environmentally benign source of energy for electricity generation. However, over the decades its growth was severely retarded due to concerns about its possible detrimental effects on the well-being of mankind and the environment. Since such concerns are essentially due to the gigantic magnitude of radioactivity and ionizing radiations associated with nuclear energy, this article starts with a comprehensive account of effects of the ionizing radiation on living systems. Quantitative description of types of radiation exposure and their varied effects is given. The origin, type and magnitude of mutagenic effects of radiation are described. The concept of radiation risk factors, basis for their evaluation and their currently accepted values are presented. With this background, origin and magnitude of radioactivity and associated ionizing radiations in nuclear reactors are presented and the elaborate measures to contain them are described. It is recognized that notwithstanding all the measures taken in the nuclear industry, certain amount of radiation exposure, however small, is inevitable and the values, based on the experience world over, are presented. Estimated health risk due to such exposures is evaluated. For a comparative analysis, risks in other options of electricity generation such as hydel and fossil-fuelled plants are described. It is seen that on an overall basis, the nuclear option is no more risky than the other commonly employed options, and is in fact, significantly less. Lastly, since every option of electricity generation entails some risk, the case of 'no addition of electricity, and its impact on the society are considered. Based on the analysis of extensive data provided by UNDP on the human development parameters for different countries in the world, it is shown that at least for developing countries, any option of addition of electricity would be far more desirable than the

  9. The persistent current and energy spectrum on a driven mesoscopic LC-circuit with Josephson junction

    Science.gov (United States)

    Pahlavanias, Hassan

    2018-03-01

    The quantum theory for a mesoscopic electric circuit including a Josephson junction with charge discreteness is studied. By considering coupling energy of the mesoscopic capacitor in Josephson junction device, a Hamiltonian describing the dynamics of a quantum mesoscopic electric LC-circuit with charge discreteness is introduced. We first calculate the persistent current on a quantum driven ring including Josephson junction. Then we obtain the persistent current and energy spectrum of a quantum mesoscopic electrical circuit which includes capacitor, inductor, time-dependent external source and Josephson junction.

  10. Phase transition in one Josephson junction with a side-coupled magnetic impurity

    Science.gov (United States)

    Zhi, Li-Ming; Wang, Xiao-Qi; Jiang, Cui; Yi, Guang-Yu; Gong, Wei-Jiang

    2018-04-01

    This work focuses on one Josephson junction with a side-coupled magnetic impurity. And then, the Josephson phase transition is theoretically investigated, with the help of the exact diagonalization approach. It is found that even in the absence of intradot Coulomb interaction, the magnetic impurity can efficiently induce the phenomenon of Josephson phase transition, which is tightly related to the spin correlation manners (i.e., ferromagnetic or antiferromagnetic) between the impurity and the junction. Moreover, the impurity plays different roles when it couples to the dot and superconductor, respectively. This work can be helpful in describing the influence of one magnetic impurity on the supercurrent through the Josephson junction.

  11. Critical current of the nonuniform Josephson transition at intergranular boundary with random dislocation distribution

    International Nuclear Information System (INIS)

    Mejlikhov, E.Z.; Farzetdinova, R.M.

    1997-01-01

    Critical current of inhomogeneous intergranular Josephson transition is calculated in the assumption concerning superconductivity suppression by local strains of boundary dislocations with random distribution

  12. Effective masses and the nuclear mean field

    International Nuclear Information System (INIS)

    Mahaux, C.; Sartor, R.

    1985-01-01

    The effective mass characterizes the energy dependence of the empirical average nuclear potential. This energy dependence has two different sources, namely the nonlocality in space of the microscopic mean field on the one hand, and its true energy dependence on the other hand. Correspondingly it is convenient to divide the effective mass into two components, the k-mass and the ω-mass. The latter is responsible for the existence of a peak in the energy dependence of the effective mass. This peak is located near the Fermi energy in nuclear matter and in nuclei, as well as in the electron gas, the hard sphere Fermi gas and liquid helium 3. A related phenomenon is the existence of a low energy anomaly in the energy dependence of the optical model potential between two heavy ions. (orig.)

  13. Nuclear compression effects on pion production in nuclear collisions

    International Nuclear Information System (INIS)

    Sano, M.; Gyulassy, M.; Wakai, M.; Kitazoe, Y.

    1984-11-01

    The pion multiplicity produced in nuclear collisions between 0.2 and 2 AGeV is calculated assuming shock formation. We also correct the procedure of extracting the nuclear equation of state as proposed by Stock et al. The nuclear equation of state would have to be extremely stiff for this model to reproduce the observed multiplicities. The assumptions of this model are critically analyzed. (author)

  14. Strengthened International Nuclear Safeguards; burdens and Effects on Nuclear Technology Development

    International Nuclear Information System (INIS)

    Badawy, I.

    2000-01-01

    The present paper deals with the recent direction of strengthening the international nuclear safeguards and the effects on the development of nuclear technology for peaceful applications. The new basic principles for strengthening the international nuclear control in the direction of undeclared nuclear activities are elaborated, and the national obligations are indicated. The burdens on the development of nuclear technology are discussed. Approaches are proposed in this work for coping with the present and future situations

  15. Time-dependent photon heat transport through a mesoscopic Josephson device

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Wen-Ting; Zhao, Hong-Kang, E-mail: zhaohonk@bit.edu.cn

    2017-02-15

    The time-oscillating photon heat current through a dc voltage biased mesoscopic Josephson Junction (MJJ) has been investigated by employing the nonequilibrium Green’s function approach. The Landauer-like formula of photon heat current has been derived in both of the Fourier space and its time-oscillating versions, where Coulomb interaction, self inductance, and magnetic flux take effective roles. Nonlinear behaviors are exhibited in the photon heat current due to the quantum nature of MJJ and applied external dc voltage. The magnitude of heat current decreases with increasing the external bias voltage, and subtle oscillation structures appear as the superposition of different photon heat branches. The overall period of heat current with respect to time is not affected by Coulomb interaction, however, the magnitude and phase of it vary considerably by changing the Coulomb interaction. - Highlights: • The time-oscillating photon heat current through a mesoscopic Josephson Junction has been investigated. • The Landauer-like formula of photon heat current has been derived by the nonequilibrium Green’s function approach. • Nonlinear behaviors are exhibited in the photon heat current resulting from the self inductance and Coulomb interaction. • The oscillation structure of heat current is composed of the superposition of oscillations with different periods.

  16. Critical temperatures Tc estimated by Josephson-junction array model of layered high Tc superconductors

    International Nuclear Information System (INIS)

    Kawabata, C.; Shenoy, S.R.; Bishop, A.R.

    1994-11-01

    We model high T c superconductors (HTS) by quantum capacitive Josephson junction arrays (JJA), with Angstrom-scale parameters, to obtain an estimate of Tc trends. The basic idea is as follows. Number (or change) and phase are conjugate variables, with the uncertainty products obeying ΔN · Δ Θ > 1. Thus, in HTS, global phase coherence is opposed by charging-energy induced quantum phase fluctuations, especially across Josephson-coupled CuO 2 planes. These have separation d 1 and effective interplanar dielectric constant ε, e.g. from Y atoms in YBaCuO. Decreasing the interplane charging energy E 0 perpendicular to ∼ d 1 /ε, raises Tc. In Section 1, we motivate a modelling of HTS phase excitations by a quantum capacitive 3D JJA model, with XY planar phases. Section 2 gives a physical picture of the HTS transition, relating the complex layered HTS structure to a simpler ''intermediate level'' quantum 3D JJA/XY model. Section 3 sets up a path integral (3+1)D model that reduces to a previously studied anisotropic 3D XY/JJA model, with constants renormalized in some way, by the capacitance. Postponing a detailed analysis to elsewhere, we make a heuristic estimate for the reduction of the previous Tc, by the charging energy. (author). 30 refs, 8 figs

  17. Nanoscale phase engineering of thermal transport with a Josephson heat modulator

    Science.gov (United States)

    Fornieri, Antonio; Blanc, Christophe; Bosisio, Riccardo; D'Ambrosio, Sophie; Giazotto, Francesco

    2016-03-01

    Macroscopic quantum phase coherence has one of its pivotal expressions in the Josephson effect, which manifests itself both in charge and energy transport. The ability to master the amount of heat transferred through two tunnel-coupled superconductors by tuning their phase difference is the core of coherent caloritronics, and is expected to be a key tool in a number of nanoscience fields, including solid-state cooling, thermal isolation, radiation detection, quantum information and thermal logic. Here, we show the realization of the first balanced Josephson heat modulator designed to offer full control at the nanoscale over the phase-coherent component of thermal currents. Our device provides magnetic-flux-dependent temperature modulations up to 40 mK in amplitude with a maximum of the flux-to-temperature transfer coefficient reaching 200 mK per flux quantum at a bath temperature of 25 mK. Foremost, it demonstrates the exact correspondence in the phase engineering of charge and heat currents, breaking ground for advanced caloritronic nanodevices such as thermal splitters, heat pumps and time-dependent electronic engines.

  18. Josephson junction between two high Tc superconductors with arbitrary transparency of interface

    Directory of Open Access Journals (Sweden)

    GhR Rashedi

    2010-03-01

    Full Text Available In this paper, a dc Josephson junction between two singlet superconductors (d-wave and s-wave with arbitrary reflection coefficient has been investigated theoretically. For the case of high Tc superconductors, the c-axes are parallel to an interface with finite transparency and their ab-planes have a mis-orientation. The physics of potential barrier will be demonstrated by a transparency coefficient via which the tunneling will occur. We have solved the nonlocal Eilenberger equations and obtained the corresponding and suitable Green functions analytically. Then, using the obtained Green functions, the current-phase diagrams have been calculated. The effect of the potential barrier and mis-orientation on the currents is studied analytically and numerically. It is observed that, the current phase relations are totally different from the case of ideal transparent Josephson junctions between d-wave superconductors and two s-wave superconductors. This apparatus can be used to demonstrate d-wave order parameter in high Tc superconductors.

  19. Magnetic field oscillations of the critical current in long ballistic graphene Josephson junctions

    Science.gov (United States)

    Rakyta, Péter; Kormányos, Andor; Cserti, József

    2016-06-01

    We study the Josephson current in long ballistic superconductor-monolayer graphene-superconductor junctions. As a first step, we have developed an efficient computational approach to calculate the Josephson current in tight-binding systems. This approach can be particularly useful in the long-junction limit, which has hitherto attracted less theoretical interest but has recently become experimentally relevant. We use this computational approach to study the dependence of the critical current on the junction geometry, doping level, and an applied perpendicular magnetic field B . In zero magnetic field we find a good qualitative agreement with the recent experiment of M. Ben Shalom et al. [Nat. Phys. 12, 318 (2016), 10.1038/nphys3592] for the length dependence of the critical current. For highly doped samples our numerical calculations show a broad agreement with the results of the quasiclassical formalism. In this case the critical current exhibits Fraunhofer-like oscillations as a function of B . However, for lower doping levels, where the cyclotron orbit becomes comparable to the characteristic geometrical length scales of the system, deviations from the results of the quasiclassical formalism appear. We argue that due to the exceptional tunability and long mean free path of graphene systems a new regime can be explored where geometrical and dynamical effects are equally important to understand the magnetic field dependence of the critical current.

  20. Capacitance measurement of Josephson tunnel junctions with microwave-induced dc quasiparticle tunneling currents

    International Nuclear Information System (INIS)

    Hamasaki, K.; Yoshida, K.; Irie, F.; Enpuku, K.

    1982-01-01

    The microwave response of the dc quasiparticle tunneling current in Josephson tunnel junctions, where the Josephson current is suppressed by an external magnetic field, has been studied quantitatively in order to clarify its characteristics as a probe for the measurement of the junction capacitance. Extensive experiments for both small and long junctions are carried out for distinguishing between microwave behaviors of lumped and distributed constant junctions. It is shown that the observed voltage dependence of the dc quasiparticle tunneling current modified by an applied rf field is in good agreement with a theoretical result which takes into account the influence of the microwave circuit connected to the junction. The comparison between theory and experiment gives the magnitude of the internal rf field in the junction. Together with the applied rf field, this internal rf field leads to the junction rf impedance which is dominated by the junction capacitance in our experimental condition. In the case of lumped junctions, this experimental rf impedance is in reasonable agreement with the theoretical one with the junction capacitance estimated from the Fiske step of the distributed junction fabricated on the same substrate; the obtained ratio of the experimental impedance to the theoretical one is approximately 0.6--1.7. In the case of distributed junctions, however, experimental values of their characteristic impedances are approximately 0.2--0.3 of theoretical values calculated by assuming the one-dimensional junction model and taking account of the standing-wave effect in the junction

  1. Time-dependent photon heat transport through a mesoscopic Josephson device

    International Nuclear Information System (INIS)

    Lu, Wen-Ting; Zhao, Hong-Kang

    2017-01-01

    The time-oscillating photon heat current through a dc voltage biased mesoscopic Josephson Junction (MJJ) has been investigated by employing the nonequilibrium Green’s function approach. The Landauer-like formula of photon heat current has been derived in both of the Fourier space and its time-oscillating versions, where Coulomb interaction, self inductance, and magnetic flux take effective roles. Nonlinear behaviors are exhibited in the photon heat current due to the quantum nature of MJJ and applied external dc voltage. The magnitude of heat current decreases with increasing the external bias voltage, and subtle oscillation structures appear as the superposition of different photon heat branches. The overall period of heat current with respect to time is not affected by Coulomb interaction, however, the magnitude and phase of it vary considerably by changing the Coulomb interaction. - Highlights: • The time-oscillating photon heat current through a mesoscopic Josephson Junction has been investigated. • The Landauer-like formula of photon heat current has been derived by the nonequilibrium Green’s function approach. • Nonlinear behaviors are exhibited in the photon heat current resulting from the self inductance and Coulomb interaction. • The oscillation structure of heat current is composed of the superposition of oscillations with different periods.

  2. RADIATION EFFECTS IN NUCLEAR WASTE MATERIALS

    International Nuclear Information System (INIS)

    Weber, William J.

    2000-01-01

    The objective of this research was to develop fundamental understanding and predictive models of radiation effects in glasses and ceramics at the atomic, microscopic, and macroscopic levels, as well as an understanding of the effects of these radiation-induced solid-state changes on dissolution kinetics (i.e., radionuclide release). The research performed during the duration of this project has addressed many of the scientific issues identified in the reports of two DOE panels [1,2], particularly those related to radiation effects on the structure of glasses and ceramics. The research approach taken by this project integrated experimental studies and computer simulations to develop comprehensive fundamental understanding and capabilities for predictive modeling of radiation effects and dissolution kinetics in both glasses and ceramics designed for the stabilization and immobilization of high-level tank waste (HLW), plutonium residues and scraps, surplus weapons plutonium, other actinides, and other highly radioactive waste streams. Such fundamental understanding is necessary in the development of predictive models because all experimental irradiation studies on nuclear waste materials are ''accelerated tests'' that add a great deal of uncertainty to predicted behavior because the damage rates are orders of magnitude higher than the actual damage rates expected in nuclear waste materials. Degradation and dissolution processes will change with damage rate and temperature. Only a fundamental understanding of the kinetics of all the physical and chemical processes induced or affected by radiation will lead to truly predictive models of long-term behavior and performance for nuclear waste materials. Predictive models of performance of nuclear waste materials must be scientifically based and address both radiation effects on structure (i.e., solid-state effects) and the effects of these solid-state structural changes on dissolution kinetics. The ultimate goal of this

  3. The effects of nuclear war. 2. rev. enl. ed.

    International Nuclear Information System (INIS)

    Rodejohann, J.

    1982-01-01

    Possible and probable effects of a nuclear war in Europe are described on the basis of a study by the Office of Technology Assessment, US Kongress ('The effects of nuclear war', Wash. D.C. 1979). (HP) [de

  4. Effect of the Fukushima nuclear disaster on global public acceptance of nuclear energy

    International Nuclear Information System (INIS)

    Kim, Younghwan; Kim, Minki; Kim, Wonjoon

    2013-01-01

    The Fukushima nuclear disaster has significantly changed public attitudes toward nuclear energy. It is important to understand how this change has occurred in different countries before the global community revises existing nuclear policies. This study examines the effect of the Fukushima disaster on public acceptance of nuclear energy in 42 countries. We find that the operational experience of nuclear power generation which has significantly affected positive public opinion about nuclear energy became considerably negative after the disaster, suggesting fundamental changes in public acceptance regardless of the level of acceptance before the disaster. In addition, contrary to our expectation, the proportion of nuclear power generation is positively and significantly related to public acceptance of nuclear energy after the Fukushima accident and government pressure on media content led to a greater decrease in the level of public acceptance after the accident. Nuclear energy policymakers should consider the varied factors affecting public acceptance of nuclear energy in each country depending on its historical, environmental, and geographical circumstances before they revise nuclear policy in response to the Fukushima accident. - Highlights: • Fukushima accident has negatively changed public attitudes toward nuclear energy. • Effect of operational experience became considerably negative after the accident. • Effect of proportion of nuclear power generation is positive after the accident. • Effect of government pressure on media content became negative after the accident. • Country specific policy responses on nuclear public acceptance are required

  5. Preface: Special Topic on Nuclear Quantum Effects.

    Science.gov (United States)

    Tuckerman, Mark; Ceperley, David

    2018-03-14

    Although the observable universe strictly obeys the laws of quantum mechanics, in many instances, a classical description that either ignores quantum effects entirely or accounts for them at a very crude level is sufficient to describe a wide variety of phenomena. However, when this approximation breaks down, as is often the case for processes involving light nuclei, a full quantum treatment becomes indispensable. This Special Topic in The Journal of Chemical Physics showcases recent advances in our understanding of nuclear quantum effects in condensed phases as well as novel algorithmic developments and applications that have enhanced the capability to study these effects.

  6. Preface: Special Topic on Nuclear Quantum Effects

    Science.gov (United States)

    Tuckerman, Mark; Ceperley, David

    2018-03-01

    Although the observable universe strictly obeys the laws of quantum mechanics, in many instances, a classical description that either ignores quantum effects entirely or accounts for them at a very crude level is sufficient to describe a wide variety of phenomena. However, when this approximation breaks down, as is often the case for processes involving light nuclei, a full quantum treatment becomes indispensable. This Special Topic in The Journal of Chemical Physics showcases recent advances in our understanding of nuclear quantum effects in condensed phases as well as novel algorithmic developments and applications that have enhanced the capability to study these effects.

  7. The deterrent effect of nuclear forensics: The case of Hungary

    International Nuclear Information System (INIS)

    Gil, Laura

    2016-01-01

    A State capable of identifying the origin and history of intercepted nuclear or radioactive material can have a deterrent effect. This is why nuclear forensics — the examination of nuclear and other radioactive material as part of criminal or nuclear security investigations — is an important tool.

  8. Effets Josephson generalises entre antiferroaimants et entre supraconducteurs antiferromagnetiques

    Science.gov (United States)

    Chasse, Dominique

    L'effet Josephson est generalement presente comme le resultat de l'effet tunnel coherent de paires de Cooper a travers une jonction tunnel entre deux supraconducteurs, mais il est possible de l'expliquer dans un contexte plus general. Par exemple, Esposito & al. ont recemment demontre que l'effet Josephson DC peut etre decrit a l'aide du boson pseudo-Goldstone de deux systemes couples brisant chacun la symetrie abelienne U(1). Puisque cette description se generalise de facon naturelle a des brisures de symetries continues non-abeliennes, l'equivalent de l'effet Josephson devrait donc exister pour des types d'ordre a longue portee differents de la supraconductivite. Le cas de deux ferroaimants itinerants (brisure de symetrie 0(3)) couples a travers une jonction tunnel a deja ete traite dans la litterature Afin de mettre en evidence la generalite du phenomene et dans le but de faire des predictions a partir d'un modele realiste, nous etudions le cas d'une jonction tunnel entre deux antiferroaimants itinerants. En adoptant une approche Similaire a celle d'Ambegaokar & Baratoff pour une jonction Josephson, nous trouvons un courant d'aimantation alternee a travers la jonction qui est proportionnel a sG x sD ou fG et sD sont les vecteurs de Neel de part et d'autre de la jonction. La fonction sinus caracteristique du courant Josephson standard est donc remplacee.ici par un produit vectoriel. Nous montrons que, d'un point de vue microscopique, ce phenomene resulte de l'effet tunnel coherent de paires particule-trou de spin 1 et de vecteur d'onde net egal au vecteur d'onde antiferromagnetique Q. Nous trouvons egalement la dependance en temperature de l'analogue du courant critique. En presence d'un champ magnetique externe, nous obtenons l'analogue de l'effet Josephson AC et la description complete que nous en donnons s'applique aussi au cas d'une jonction tunnel entre ferroaimants (dans ce dernier cas, les traitements anterieurs de cet effet AC s'averent incomplets). Nous

  9. Anisotropic Josephson-vortex dynamics in layered organic superconductors

    International Nuclear Information System (INIS)

    Yasuzuka, S.; Uji, S.; Satsukawa, H.; Kimata, M.; Terashima, T.; Koga, H.; Yamamura, Y.; Saito, K.; Akutsu, H.; Yamada, J.

    2010-01-01

    To study the anisotropic Josephson-vortex dynamics in the d-wave superconductors, the interplane resistance has been measured on layered organic superconductors κ-(ET) 2 Cu(NCS) 2 and β-(BDA-TTP) 2 SbF 6 under magnetic fields precisely parallel to the conducting planes. For κ-(ET) 2 Cu(NCS) 2 , in-plane angular dependence of the Josephson-vortex flow resistance is mainly described by the fourfold symmetry and dip structures appear when the magnetic field is applied parallel to the b- and c-axes. The obtained results have a relation to the d-wave superconducting gap symmetry. However, the absence of in-plane fourfold anisotropy was found for β-(BDA-TTP) 2 SbF 6 . The different anisotropic behavior is discussed in terms of the interlayer coupling strength.

  10. Anisotropic Josephson-vortex dynamics in layered organic superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Yasuzuka, S., E-mail: yasuzuka@chem.tsukuba.ac.j [Department of Chemistry, Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571 (Japan); Uji, S.; Satsukawa, H.; Kimata, M.; Terashima, T. [National Institute for Materials Science (NIMS), Tsukuba, Ibaraki 305-0003 (Japan); Koga, H.; Yamamura, Y.; Saito, K. [Department of Chemistry, Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571 (Japan); Akutsu, H.; Yamada, J. [Department of Material Science, Graduate School of Material Science, University of Hyogo, Ako-gun, Hyogo 678-1297 (Japan)

    2010-06-01

    To study the anisotropic Josephson-vortex dynamics in the d-wave superconductors, the interplane resistance has been measured on layered organic superconductors {kappa}-(ET){sub 2}Cu(NCS){sub 2} and {beta}-(BDA-TTP){sub 2}SbF{sub 6} under magnetic fields precisely parallel to the conducting planes. For {kappa}-(ET){sub 2}Cu(NCS){sub 2}, in-plane angular dependence of the Josephson-vortex flow resistance is mainly described by the fourfold symmetry and dip structures appear when the magnetic field is applied parallel to the b- and c-axes. The obtained results have a relation to the d-wave superconducting gap symmetry. However, the absence of in-plane fourfold anisotropy was found for {beta}-(BDA-TTP){sub 2}SbF{sub 6}. The different anisotropic behavior is discussed in terms of the interlayer coupling strength.

  11. Thin film hybrid Josephson junctions with Co doped Ba-122

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, Stefan; Doering, Sebastian; Schmidl, Frank; Tympel, Volker; Grosse, Veit; Seidel, Paul [Friedrich-Schiller-Universitaet Jena, Institut fuer Festkoerperphysik, Helmholtzweg 5, 07743 Jena (Germany); Haindl, Silvia; Iida, Kazumasa; Kurth, Fritz; Holzapfel, Bernhard [IFW Dresden, Institut fuer Metallische Werkstoffe, Helmholtzstrasse 20, 01069 Dresden (Germany); Moench, Ingolf [IFW Dresden, Institut fuer Integrative Nanowissenschaften, Helmholtzstrasse 20, 01069 Dresden (Germany)

    2011-07-01

    Josephson junctions are a strong tool to investigate fundamental superconducting properties, such as gap behaviour, dependencies from external fields and the order parameter symmetry. Finding secure values enables the possibility of theoretical descriptions to understand the physical processes within the new iron-based superconductors. Based on Co-doped BaFe{sub 2}As{sub 2} (Ba-122) layers produced via pulsed laser deposition (PLD) on (La,Sr)(Al,Ta)O{sub 3} substrates, we manufactured superconductor-normal conductor-superconductor (S-N-S) junctions structures by using photolithography, ion beam etching as well as insulating SiO{sub 2} layers. We present working Ba-122/Au/PbIn thin film Josephson junctions with different contact areas and barrier thicknesses, their temperature dependence and response to microwave irradiation. The calculated I{sub c}R{sub N} product is in the range of a couple of microvolts.

  12. Spatially resolved detection of mutually locked Josephson junctions in arrays

    International Nuclear Information System (INIS)

    Keck, M.; Doderer, T.; Huebener, R.P.; Traeuble, T.; Dolata, R.; Weimann, T.; Niemeyer, J.

    1997-01-01

    Mutual locking due to the internal coupling in two-dimensional arrays of Josephson junctions was investigated. The appearance of Shapiro steps in the current versus voltage curve of a coupled on-chip detector junction is used to indicate coherent oscillations in the array. A highly coherent state is observed for some range of the array bias current. By scanning the array with a low-power electron beam, mutually locked junctions remain locked while the unlocked junctions generate a beam-induced additional voltage drop at the array. This imaging technique allows the detection of the nonlocked or weakly locked Josephson junctions in a (partially) locked array state. copyright 1997 American Institute of Physics

  13. Lightning effects on electrical and nuclear equipment

    International Nuclear Information System (INIS)

    Gary, C.

    1986-01-01

    This paper gives the physical bases on which lightning protection of buildings and other erections such as nuclear power stations depend. To this end it first examines the impact phenomena of lightning, the operating systems of lightning conductors and methods of protection using metal mesh. It then describes various secondary effects of lightning, particularly those which occur inside buildings as a result of the potential rise in earthing systems and electromagnetic induction phenomena. 18 refs [fr

  14. The effectiveness and development trend of nuclear third party liability insurance in the nuclear risk management

    International Nuclear Information System (INIS)

    Wang Pei

    2010-01-01

    Nuclear power considerably benefited mankind since it was utilized peaceably. The cleanness, safety and high efficiency of nuclear power were gradually known and recognized by the public. However at the same time, nuclear power had produced significant accident and consequently caused severe aftereffects during its utilization. Therefore, effective management of nuclear risk and reducing its accident probability are the social responsibilities of every nuclear nation. From the insurance point of view, this document analyzes the validity and development trends of nuclear third party insurance in nuclear risk management. It also introduces effectual experience in this field from nuclear insurance developed countries. This document discusses the necessity of consummating nuclear third party insurance under the aggressive development situation of nuclear power in our country. (author)

  15. Shunted-Josephson-junction model. I. The autonomous case

    DEFF Research Database (Denmark)

    Belykh, V. N.; Pedersen, Niels Falsig; Sørensen, O. H.

    1977-01-01

    The shunted-Josephson-junction model: the parallel combination of a capacitance, a phase-dependent conductance, and an ideal junction element biased by a constant current, is discussed for arbitrary values of the junction parameters. The main objective is to provide a qualitative understanding...... current-voltage curves are presented. The case with a time-dependent monochromatic bias current is treated in a similar fashion in the companion paper....

  16. Onset of chaos in Josephson junctions with intermediate damping

    International Nuclear Information System (INIS)

    Yao, X.; Wu, J.Z.; Ting, C.S.

    1990-01-01

    By use of the analytical solution of the Stewart-McCumber equation including quadratic damping and dc bias, the Melnikov method has been extended to the parameter regions of intermediate damping and dc bias for the Josephson junctions with quadratic damping and with linear damping and cosφ term. The comparison between the thresholds predicted by the Melnikov method and that derived from numerical simulation has been studied. In addition, the validity conditions for the Melnikov threshold are also discussed

  17. Memory states in small arrays of Josephson junctions

    Energy Technology Data Exchange (ETDEWEB)

    Braiman, Yehuda [ORNLOak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Computer Science and Mathematics Division, Computing and Computational Science Directorate; Univ. of Tennessee, Knoxville, TN (United States). Dept. of Mechanical, Aerospace, and Biomedical Engineering; Neschke, Brendan [ORNLOak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Computer Science and Mathematics Division, Computing and Computational Science Directorate; Univ. of Tennessee, Knoxville, TN (United States). Dept. of Mechanical, Aerospace, and Biomedical Engineering; Nair, Niketh S. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Computer Science and Mathematics Division, Computing and Computational Science Directorate; Univ. of Tennessee, Knoxville, TN (United States). Dept. of Mechanical, Aerospace, and Biomedical Engineering; Imam, Neena [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Computing and Computational Science Directorat; Glowinski, R. [Univ. of Houston, TX (United States). Dept. of Mathematics

    2017-11-30

    Here, we study memory states of a circuit consisting of a small inductively coupled Josephson junction array and introduce basic (write, read, and reset) memory operations logics of the circuit. The presented memory operation paradigm is fundamentally different from conventional single quantum flux operation logics. We calculate stability diagrams of the zero-voltage states and outline memory states of the circuit. We also calculate access times and access energies for basic memory operations.

  18. Multiple frequency generation by bunched solitons in Josephson tunnel junctions

    DEFF Research Database (Denmark)

    Lomdahl, P. S.; Sørensen, O. H.; Christiansen, Peter Leth

    1981-01-01

    A detailed numerical study of a long Josephson tunnel junction modeled by a perturbed sine-Gordon equation demonstrates the existence of a variety of bunched soliton configurations. Thus, on the third zero-field step of the V-I characteristic, two simultaneous adjacent frequencies are generated...... in a narrow bias current range. The analysis of the soliton modes provides an explanation of recent experimental observations....

  19. Political aspects of nuclear test effects at Semipalatinsk nuclear test site

    International Nuclear Information System (INIS)

    Sydykov, E.B.; Panin, M.S.

    2003-01-01

    The paper describes tense struggle of Kazakhstan people for closure of the Semipalatinsk Nuclear Test Site. It reveals major foreign policy aspects and nuclear test effects for both Kazakhstan and the world community. (author)

  20. Quantum Nuclear Extension of Electron Nuclear Dynamics on Folded Effective-Potential Surfaces

    DEFF Research Database (Denmark)

    Hall, B.; Deumens, E.; Ohrn, Y.

    2014-01-01

    A perennial problem in quantum scattering calculations is accurate theoretical treatment of low energy collisions. We propose a method of extracting a folded, nonadiabatic, effective potential energy surface from electron nuclear dynamics (END) trajectories; we then perform nuclear wave packet...

  1. Search for a correlation between Josephson junctions and gravity

    International Nuclear Information System (INIS)

    Robertson, Glen A.

    2000-01-01

    Woodward's transient mass shift (TMS) formula has commonality with Modanese's anomalous coupling theory (ACT) and Woodward's capacitor experiment has commonality with Podkletnov's layered superconductor disk experiment. The TMS formula derives a mass fluctuation from a time-varying energy density. The ACT suggests that the essential ingredient for the gravity phenomenon is the presence of strong variations or fluctuations of the Cooper pair density (a time-varying energy density). Woodward's experiment used a small array of capacitors whose energy density was varied by an applied 11 kHz signal. Podkletnov's superconductor disk contained many Josephson junctions (small capacitive like interfaces), which were radiated with a 3-4 MHz signal. This paper formulates a TMS for superconductor Josephson junctions. The equation was compared to the 2% mass change claimed by Podkletnov in his gravity shielding experiments. The TMS is calculated to be 2% for a 2-kg superconductor with an induced total power to the multiple Josephson junctions of about 3.3-watts. A percent mass change equation is then formulated based on the Cavendish balance equation where the superconductor TMS is used for the delta change in mass. An experiment using a Cavendish balance is then discussed

  2. Effective inventory management for nuclear power plants

    International Nuclear Information System (INIS)

    MacFarlane, I.S.

    1985-01-01

    Effective inventory management plays a major role at nuclear power plants toward achieving a high level of availability in a cost-effective manner. It enables maintenance personnel to obtain the correct parts easily, when needed, and in satisfactory condition to perform as intended. In addition, appropriate controls and documentation ensure parts are being used in the correct equipment application. The following elements of inventory management will help achieve plant availability goals: (1) appropriate inventory levels, (2) preapproved procurement requirements, (3) storage maintenance, (4) documentation of parts, and (5) control of computer data base

  3. Nuclear parity violation in effective field theory

    International Nuclear Information System (INIS)

    Zhu Shilin; Maekawa, C.M.; Holstein, B.R.; Ramsey-Musolf, M.J.; Kolck, U. van

    2005-01-01

    We reformulate the analysis of nuclear parity violation (PV) within the framework of effective field theory (EFT). To O(Q), the PV nucleon-nucleon (NN) interaction depends on five a priori unknown constants that parameterize the leading-order, short-range four-nucleon operators. When pions are included as explicit degrees of freedom, the potential contains additional medium- and long-range components parameterized by PV πNN coupling. We derive the form of the corresponding one- and two-pion-exchange potentials. We apply these considerations to a set of existing and prospective PV few-body measurements that may be used to determine the five independent low-energy constants relevant to the pionless EFT and the additional constants associated with dynamical pions. We also discuss the relationship between the conventional meson-exchange framework and the EFT formulation, and argue that the latter provides a more general and systematic basis for analyzing nuclear PV

  4. Nuclear compression effects on pion production in nuclear collisions

    International Nuclear Information System (INIS)

    Sano, M.; Gyulassy, M.; Wakai, M.; Kitazoe, Y.

    1985-01-01

    We show that the method of analyzing the pion excitation function proposed by Stock et al. may determine only a part of the nuclear matter equation of state. With the addition of missing kinetic energy terms the implied high density nuclear equation of state would be much stiffer than expected from conventional theory. A stiff equation of state would also follow if shock dynamics with early chemical freeze out were valid. (orig.)

  5. High-Tc SNS Junctions: A New Generation of Proximity-Coupled Josephson Devices

    Science.gov (United States)

    Kleinsasser, A. W.

    1997-01-01

    This paper reviews this evolution of proximity - coupled Josephson jucntion from the early investigations on low temperature superconductor-normal -superconductor junctions through the introduction of hybrid superconductor-semiconductor devices and the resulting interest in mesoscopic Josephson junctions, to the recent development of high temperature devices.

  6. Collective modes and radiation from gliding Josephson vortex lattice in layered superconductors

    International Nuclear Information System (INIS)

    Artemenko, S.N.; Remizov, S.V.

    1999-01-01

    We found that stability of moving lattice of Josephson vortices driven by the transport current is limited by the critical velocity which agrees with the maximum velocity observed in BSCCO in the flux-flow regime. We also predict a peak of the radiation at Josephson plasma frequency which may be observed in high magnetic field. (orig.)

  7. Bifurcation and chaos in a dc-driven long annular Josephson junction

    DEFF Research Database (Denmark)

    Grnbech-Jensen, N.; Lomdahl, Peter S.; Samuelsen, Mogens Rugholm

    1991-01-01

    Simulations of long annular Josephson junctions in a static magnetic field show that in large regions of bias current the system can exhibit a period-doubling bifurcation route to chaos. This is in contrast to previously studied Josephson-junction systems where chaotic behavior has primarily been...

  8. Direct detection of the parametrically generated half-harmonic voltage in a Josephson tunnel junction

    DEFF Research Database (Denmark)

    Mygind, Jesper; Pedersen, Niels Falsig; Sørensen, O. H.

    1976-01-01

    The first direct observation of the parametrically generated half-harmonic voltage in a Josephson tunnel junction is reported. A microwave signal at f=17.25 GHz is applied to the junction dc current biased at zero voltage such that the Josephson plasma resonance fp=f/2. Under these conditions...

  9. Nonadiabatic effects in electronic and nuclear dynamics

    Directory of Open Access Journals (Sweden)

    Martin P. Bircher

    2017-11-01

    Full Text Available Due to their very nature, ultrafast phenomena are often accompanied by the occurrence of nonadiabatic effects. From a theoretical perspective, the treatment of nonadiabatic processes makes it necessary to go beyond the (quasi static picture provided by the time-independent Schrödinger equation within the Born-Oppenheimer approximation and to find ways to tackle instead the full time-dependent electronic and nuclear quantum problem. In this review, we give an overview of different nonadiabatic processes that manifest themselves in electronic and nuclear dynamics ranging from the nonadiabatic phenomena taking place during tunnel ionization of atoms in strong laser fields to the radiationless relaxation through conical intersections and the nonadiabatic coupling of vibrational modes and discuss the computational approaches that have been developed to describe such phenomena. These methods range from the full solution of the combined nuclear-electronic quantum problem to a hierarchy of semiclassical approaches and even purely classical frameworks. The power of these simulation tools is illustrated by representative applications and the direct confrontation with experimental measurements performed in the National Centre of Competence for Molecular Ultrafast Science and Technology.

  10. Nuclear Winter: Uncertainties Surround the Long-Term Effects of Nuclear War. Report to the Congress.

    Science.gov (United States)

    General Accounting Office, Washington, DC.

    Nuclear winter, a term used to describe potential long-term climate and environmental effects of nuclear war, has been a subject of debate and controversy. This report examines and presents scientific and policy implications of nuclear winter. Contents include: (1) an executive summary (highlighting previous and current studies on the topic); (2)…

  11. Potential effects of nuclear war on agricultural productivity

    International Nuclear Information System (INIS)

    Harwell, M.A.; Cropper, W.P. Jr.

    1985-01-01

    The authors examine the vulnerabilities of agricultural systems to nuclear war-induced climatic perturbations and to other, indirect effects of nuclear war. Discussion is included of the dependency of agricultural production on technological inputs and the effects of loss or reduction of these inputs in a post-nuclear war world

  12. Nuclear Forces from Effective Field Theory

    International Nuclear Information System (INIS)

    Krebs, H.

    2011-01-01

    Chiral effective field theory allows for a systematic and model-independent derivation of the forces between nucleons in harmony with the symmetries of the quantum chromodynamics. After a brief review on the current status in the development of the chiral nuclear forces I will focus on the role of the Δ-resonance contributions in the nuclear dynamics.We find improvement in the convergence of the chiral expansion of the nuclear forces if we explicitly take into account the Δ-resonance degrees of freedom. The overall results for two-nucleon forces with and without explicit Δ-resonance degrees of freedom are remarkably similar. We discussed the long- and shorter-range N 3 LO contributions to chiral three-nucleon forces. No additional free parameters appear at this order. There are five different topology classes which contribute to the forces. Three of them describe long-range contributions which constitute the first systematic corrections to the leading 2π exchange that appear at N 2 LO. Another two contributions are of a shorter range and include, additionally to an exchange of pions, also one short-range contact interaction and all corresponding 1/m corrections. The requirement of renormalizability leads to unique expressions for N 3 LO contributions to the three-nucleon force (except for 1/m-corrections). We presented the complete N 2 LO analysis of the nuclear forces with explicit Δ-isobar degrees of freedom. Although the overall results in the isospin-conserving case are very similar in the Δ-less and Δ-full theories, we found a much better convergence in all peripheral partial waves once Δ-resonance is explicitly taken into account. The leading CSB contributions to nuclear forces are proportional to nucleon- and Δ-mass splittings. There appear strong cancellations between the two contributions which at leading order yield weaker V III potentials. This effect is, however, entirely compensated at subleading order such that the results in the theories

  13. Aging and its circumvention in rf-plasma oxidized Pb-alloy Josephson junctions

    International Nuclear Information System (INIS)

    Wada, M.; Nakano, J.

    1987-01-01

    The aging phenomenon of Pb-alloy Josephson junctions is investigated and an effective method of circumventing it is presented. Junctions consist of Pb-alloy electrodes and a tunneling barrier formed by rf-plasma oxidation of the Pb-alloy. First, aging and annealing-driven change in normal tunneling resistance are compared to verify the usage of annealing as an experimental method for simulation and acceleration of aging. Next, process variables affecting the annealing change in junction characteristics are examined and their influence is described. The importance of the oxide-base electrode interface is confirmed and that of the counterelectrode-oxide interface is experimentally shown. Furthermore, possible changes in the oxide itself are discussed. Finally, on the basis of these studies, rf-plasma oxidation in a CO 2 atmosphere is employed and proven to be an effective method for circumventing the annealing change in the junction characteristics

  14. Effect of pairing on nuclear dynamics

    International Nuclear Information System (INIS)

    Scamps, Guillaume

    2014-01-01

    Pairing correlations is an essential component for the description of the atomic nuclei. The effects of pairing on static property of nuclei are now well known. In this thesis, the effect of pairing on nuclear dynamics is investigated. Theories that includes pairing are benchmarked in a model case. The TDHF+BCS theory turns out to be a good compromise between the physics taken into account and the numerical cost. This TDHF+BCS theory was retained for realistic calculations. Nevertheless, the application of pairing in the BCS approximation may induce new problems due to (1) the particle number symmetry breaking, (2) the non-conservation of the continuity equation. These difficulties are analysed in detail and solutions are proposed. In this thesis, a 3 dimensional TDHF+BCS code is developed to simulate the nuclear dynamic. Applications to giant resonances show that pairing modify only the low lying peaks. The high lying collective components are only affected by the initial conditions. An exhaustive study of the giant quadrupole resonances with the TDHF+BCS theory is performed on more than 700 spherical or deformed nuclei. Is is shown that the TDHF+BCS theory reproduces well the collective energy of the resonance. After validation on the small amplitude limit problem, the approach was applied to study nucleon transfer in heavy ion reactions. A new method to extract transfer probabilities is introduced. It is demonstrated that pairing significantly increases the two-nucleon transfer probability. (author) [fr

  15. Josephson current and Andreev level dynamics in nanoscale superconducting weak links

    Energy Technology Data Exchange (ETDEWEB)

    Brunetti, Aldo

    2014-11-15

    In this thesis we focus on the interplay between proximity induced superconducting correlations and Coulomb interactions in a Josephson junction: i.e., in a system where two superconductors modeled as two s-wave superconductors at a phase difference φ are contacted by means of a weak link, in our case a quantum dot located in the contact. In the first part we study the Josephson current-phase relation for a multi-level quantum dot tunnel-contacted by two conventional s-waves superconductors. We determine in detail the conditions for observing a finite anomalous Josephson current, i.e. a supercurrent flowing at zero phase difference in a two-level dot with spin-orbit interactions, a weak magnetic (Zeeman) field, and in the presence of Coulomb interactions. This leads to an onset behavior I{sub a}∝sgn(B), interpreted as the sign of an incipient spontaneous breakdown of time-reversal symmetry. Moreover, we will provide conditions for realizing spatially separated - but topologically unprotected - Majorana bound states, whose signature in the system will be detectable via the current-phase relation. In the second part of the thesis, we address the Andreev bound state population dynamics in superconducting weak links (a superconducting 'atomic contact'), in which a poisoning mechanism due to the trapping of single quasiparticles can occur. Our motivation is that quantum coherent superconducting circuits are the most promising candidates for future large-scale quantum information processing devices. Moreover, quasiparticle poisoning has recently been observed in devices which contain a short superconducting weak link with few transport channels. We discuss a novel charge imbalance effect in the continuum quasiparticle population, which is due to phase fluctuations of the environment weakly coupled to the superconducting contact. This coupling enters the system as a transition rate connecting continuum quasiparticles and the Andreev bound state system. The

  16. Effects of nuclear war on health and health services

    International Nuclear Information System (INIS)

    1990-01-01

    This report reviews the findings since 1987 in the field of research related to the possible impact of nuclear war and nuclear explosions on health and health services. An annex contains the finding and conclusions of a 1989 United Nations study on the climatic and other effects of nuclear war. 1 tab

  17. Coherent and dissipative transport in a Josephson junction between fermionic superfluids of 6Li atoms

    Science.gov (United States)

    Neri, Elettra; Scazza, Francesco; Roati, Giacomo

    2018-04-01

    Quantum systems out of equilibrium offer the possibility of understanding intriguing and challenging problems in modern physics. Studying transport properties is not only valuable to unveil fundamental properties of quantum matter but it is also an excellent tool for developing new quantum devices which inherently employ quantum-mechanical effects. In this contribution, we present our experimental studies on quantum transport using ultracold Fermi gases of 6Li atoms. We realize the analogous of a Josephson junction by bisecting fermionic superfluids by a thin optical barrier. We observe coherent dynamics in both the population and in the relative phase between the two reservoirs. For critical parameters, the superfluid dynamics exhibits both coherent and resistive flow due to phase-slippage events manifesting as vortices propagating into the bulk. We uncover also a regime of strong dissipation where the junction operation is irreversibly affected by vortex proliferation. Our studies open new directions for investigating dissipation and superfluid transport in strongly correlated fermionic systems.

  18. Charge solitons and their dynamical mass in one-dimensional arrays of Josephson junctions

    International Nuclear Information System (INIS)

    Homfeld, Jens; Protopopov, Ivan; Rachel, Stephan; Shnirman, Alexander

    2011-01-01

    We investigate charge transport in one-dimensional arrays of Josephson junctions. In the interesting regime of ''small charge solitons'' (polarons), ΛE J >E C >E J , where Λ is the (electrostatic) screening length, the charge dynamics are strongly influenced by the polaronic effects (i.e., by dressing of a Cooper pair by charge dipoles). In particular, the soliton's mass in this regime scales approximately as E J -2 . We employ two theoretical techniques: the many-body tight-binding approach and the mean-field approach, and the results of the two approaches agree in the regime of ''small charge solitons.'' Renormalization of the soliton's mass could be observed; for example, as enhancement of the persistent current in a ring-shaped array.

  19. Break down of the law of large numbers in Josephson junction series arrays

    International Nuclear Information System (INIS)

    Dominguez, D.; Cerdeira, H.A.

    1995-01-01

    We study underdamped Josephson junction series arrays that are globally coupled through a resistive shunting load and driven by an rf bias current. We find that they can be an experimental realization of many phenomena currently studied in globally coupled logistic maps. We find coherent, ordered, partially ordered and turbulent phases in the IV characteristics of the array. The ordered phase corresponds to giant Shapiro steps. In the turbulent phase there is a saturation of the broad band noise for a large number of junctions. This corresponds to a break down of the law of large numbers as seen in globally coupled maps. Coexisting with this, we find an emergence of novel pseudo-steps in the IV characteristics. This effect can be experimentally distinguished from the true Shapiro steps, which do not have broad band noise emission. (author). 21 refs, 5 figs

  20. Breakdown of the law of large numbers in Josephson junction series arrays

    International Nuclear Information System (INIS)

    Dominguez, D.; Cerdeira, H.A.

    1994-01-01

    We study underdamped Josephson junction series arrays that are globally coupled through a resistive shunting load and driven by an rf bias current. We find that they can be an experimental realization of many phenomena currently studied in globally coupled logistic maps. We find coherent, ordered, partially ordered and turbulent phases in the IV characteristics of the array. The ordered phase corresponds to giant Shapiro steps. In the turbulent phase there is a saturation of the broad band noise for a large number of junctions. This corresponds to a break down of the law of large numbers as seen in the globally coupled maps. Coexisting with this, we find an emergence of novel pseudo-steps in the IV characteristics. This effect can be experimentally distinguished from the Shapiro steps, which do not have broad band noise emission. (author). 21 refs, 5 figs

  1. A model of magnetic impurities within the Josephson junction of a phase qubit

    Energy Technology Data Exchange (ETDEWEB)

    Erickson, R P; Pappas, D P [National Institute of Standards and Technology, Boulder, CO 80305 (United States)

    2010-02-15

    We consider a superconducting phase qubit consisting of a monocrystalline sapphire Josephson junction with its symmetry axis perpendicular to the junction interfaces. Via the London gauge, we present a theoretical model of Fe{sup 3+} magnetic impurities within the junction that describes the effect of a low concentration of such impurities on the operation of the qubit. Specifically, we derive an interaction Hamiltonian expressed in terms of angular momentum states of magnetic impurities and low-lying oscillator states of a current-biased phase qubit. We discuss the coupling between the qubit and impurities within the model near resonance. When the junction is biased at an optimal point for acting as a phase qubit, with a phase difference of {pi}/2 and impurity concentration no greater than 0.05%, we find only a slight decrease in the Q factor of less than 0.01%.

  2. Rectification of harmonically oscillating magnetic fields in quarter circular Josephson junctions

    International Nuclear Information System (INIS)

    Shaju, P.D.; Kuriakose, V.C.

    2003-01-01

    A novel method for rectifying harmonically varying magnetic fields is demonstrated using fluxons in quarter circular Josephson junctions (JJs). A JJ with a quarter circular geometry terminated with a load resistor at one end is found to be capable of rectifying alternating fields when biased with a constant dc current. An external magnetic field applied parallel to the dielectric barrier of the junction interacts with the edges of the junction and make asymmetric boundary conditions. These asymmetric boundary conditions facilitate fluxon penetration under a dc bias from one end of the junction in alternate half cycles of the applied field. Thus effective rectification of the field can be achieved using quarter circular JJs. This unique phenomenon is specific to this geometry and can be exploited for making superconducting magnetic field rectifiers. This proposed device is expected to have important applications in millimeter and sub-millimeter radio wave astronomy

  3. Self-positioned thin Pb-alloy base electrode Josephson junction

    International Nuclear Information System (INIS)

    Kuroda, K.; Sato, K.

    1986-01-01

    A self-positioned thin (SPOT) Pb-alloy base electrode Josephson junction is developed. In this junction, a 50-nm thick Pb-alloy base electrode is restricted within the junction region on an Nb underlayer using a self-alignment technique. The grain size reduction and the base electrode area restriction greatly improve thermal cycling stability, where the thermal cycling tests of 4000 proposed junctions (5 x 5 μm 2 ) showed no failures after 4000 cycles. In addition, the elimination of insulator layer stress on the Pb-alloy base electrode rectifies the problem of size effect on current density. The Nb underlayers also serve to isolate the Pb-alloy base electrodes from the resistors

  4. Tunneling conductance in superconductor-hybrid double quantum dots Josephson junction

    Science.gov (United States)

    Chamoli, Tanuj; Ajay

    2018-05-01

    The present work deals with the theoretical model study to analyse the tunneling conductance across a superconductor hybrid double quantum dots tunnel junction (S-DQD-S). Recently, there are many experimental works where the Josephson current across such nanoscopic junction is found to be dependent on nature of the superconducting electrodes, coupling of the hybrid double quantum dot's electronic states with the electronic states of the superconductors and nature of electronic structure of the coupled dots. For this, we have attempted a theoretical model containing contributions of BCS superconducting leads, magnetic coupled quantum dot states and coupling of superconducting leads with QDs. In order to include magnetic coupled QDs the contributions of competitive Kondo and Ruderman-Kittel- Kasuya-Yosida (RKKY) interaction terms are also introduced through many body effects in the model Hamiltonian at low temperatures (where Kondo temperature TK tunnel junctions. Tunneling conductance is proportional to DOS, hence we can analyse it's behaviour with the help of DOS.

  5. Chaotic Dynamics of a Josephson Junction with a Ratchet Potential and Current-Modulating Damping

    Science.gov (United States)

    Li, Fei; Li, Wenwu; Xu, Lan

    2018-04-01

    The chaotic dynamics of a Josephson junction with a ratchet potential and current-modulating damping are studied. Under the first-order approximation, we construct the general solution of the first-order equation whose boundedness condition contains the famous Melnikov chaotic criterion. Based on the general solution, the incomputability and unpredictability of the system's chaotic behavior are discussed. For the case beyond perturbation conditions, the evolution of stroboscopic Poincaré sections shows that the system undergoes a quasi-periodic transition to chaos with an increasing intensity of the rf-current. Through a suitable feedback controlling strategy, the chaos can be effectively suppressed and the intensity of the controller can vary in a large range. It is also found that the current between the two separated superconductors increases monotonously in some specific parameter spaces.

  6. Internal resonances in periodically modulated long Josephson junctions

    DEFF Research Database (Denmark)

    Larsen, Britt Hvolbæk; Mygind, Jesper; Ustinov, Alexey V.

    1995-01-01

    Current-voltage (I-V) characteristics of long Josephson junctions with a periodic lattice of localized inhomogeneities are studied. The interaction between the moving fluxons and the inhomogeneities causes resonant steps in the IV-curve. Some of these steps are due to a synchronization to resonant...... Fiske modes in the sub-junctions formed between the inhomogeneities. The voltage positions of the resonant steps oscillate as function of the applied magnetic field with a period corresponding to the inclusion of one magnetic flux quantum, Φ0=h/2e, per sub-junction. A qualitative explanation that takes...

  7. Images of interlayer Josephson vortices in single-layer cuprates

    International Nuclear Information System (INIS)

    Moler, K. A.; Kirtley, J. R.; Liang, R.; Bonn, D. A.; Hardy, W. N.; Williams, J. M.; Schlueter, J. A.; Hinks, D.; Villard, G.; Maignan, A.; Nohara, M.; Takagi, H.

    2000-01-01

    The interlayer penetration depth in layered superconductors may be determined from scanning Superconducting QUantum Interference Device (SQUID) microscope images of interlayer Josephson vortices. The authors compare their findings at 4 K for single crystals of the organic superconductor κ-(BEDT-TTF) 2 Cu(NCS) 2 and three near-optimally doped cuprate superconductors: La 2-x Sr x CuO 4 , (Hg, Cu)Ba 2 CuO 4+δ , and Tl 2 Ba 2 CuO 6+δ

  8. A novel ternary logic circuit using Josephson junction

    International Nuclear Information System (INIS)

    Morisue, M.; Oochi, K.; Nishizawa, M.

    1989-01-01

    This paper describes a novel Josephson complementary ternary logic circuit named as JCTL. This fundamental circuit is constructed by combination of two SQUIDs, one of which is switched in the positive direction and the other in the negative direction. The JCTL can perform the fundamental operations of AND, OR, NOT and Double NOT in ternary form. The principle of the operation and design criteria are described in detail. The results of the simulation show that the reliable operations of these circuits can be achieved with a high performance

  9. Measurements of a vortex transitional ndro Josephson memory cell

    International Nuclear Information System (INIS)

    Tahara, S.; Ishida, I.; Hidaka, M.; Nagasawa, S.; Ajisawa, Y.; Wada, Y.

    1988-01-01

    A novel vortex transitional NDRO Jospehson memory cell has been successfully fabricated and tested. The memory cell consists of two superconducting loops and a two-junction interferometer gate as a sense gate. The superconducting loop contains one Josephson junction and inductances, and stores single flux quantum. The memory cell employs vortex transitions in the superconducting loops for writing and reading data. The memory cell chips have been fabricated using niobium planarization process. The +-21 percent address signal current margin and the +-33 percent sense gate current margin have been obtained experimentally. The memory operation of the cell driven by the two-junction interferometer gates has been accurately demonstrated

  10. Double-well potential in annular Josephson junction

    International Nuclear Information System (INIS)

    Shaju, P.D.; Kuriakose, V.C.

    2004-01-01

    A double-well potential suitable for quantum-coherent vortex tunnelling can be created in an annular Josephson junction by inserting a microshort in the junction and by applying an in-plane dc magnetic field. Analysis shows that the intensity of the magnetic field determines the depth of the potential well and the strength of the microshort controls the potential barrier height while a dc bias across the junction tilts the potential well. At milli-Kelvin temperatures, the system is expected to behave as a quantum two-level system and may be useful in designing vortex qubits

  11. Several alternative approaches to the manufacturing of HTS Josephson junctions

    OpenAIRE

    Villegier , J.; Boucher , H.; Ghis , A.; Levis , M.; Méchin , Laurence; Moriceau , H.; Pourtier , F.; Vabre , M.; Nicoletti , S.; Correra , L.

    1994-01-01

    In this work we describe comparatively the fabrication and the characterization of various types of HTS Josephson junctions manufactured using different processes : grain boundary junctions have been studied both by the way of junctions on bicrystal substrates and of bi-epitaxial junctions. Ramp-edge types have been elaborated and characterized using mainly N-YBaCuO thin film as a barrier while the trilayer approach has been investigated through a-axis structures. YBaCuO or GdBaCuO supercondu...

  12. Fluoride barriers in Nb/Pb Josephson junctions

    Science.gov (United States)

    Asano, H.; Tanabe, K.; Michikami, O.; Igarashi, M.; Beasley, M. R.

    1985-03-01

    Josephson tunnel junctions are fabricated using a new class of artificial barriers, metal fluorides (Al fluoride and Zr fluoride). These fluoride barriers are deposited on the surface of a Nb base electrode, which are previously cleaned using a CF4 cleaning process, and covered by a Pb counterelectrode. The junctions with both Al fluoride and Zr fluoride barriers exhibit good tunneling characteristics and have low specific capacitance. In the case of Zr fluoride, it is observed that reasonable resistances are obtained even at thickness greater than 100 A. This phenomenon might be explained by tunneling via localized states in Zr fluoride.

  13. Transition behaviours in two coupled Josephson junction equations

    International Nuclear Information System (INIS)

    Wang Jiazeng; Zhang Xuejuan; You Gongqiang; Zhou Fengyan

    2007-01-01

    The dynamics of two coupled Josephson junction equations are investigated via mathematical reasoning and numerical simulations. We show that for a fixed coupling K, the whole parameter space can be comparted into three regions: a quenching region, a synchronized running periodic region and a region where these two states coexist. It is further shown that with the increase of the coupling K, the system may transit from a synchronizing state to a quenching state. The characteristic of the critical line K*(b) which separates these two states is mathematically analysed

  14. Displacement of microwave squeezed states with Josephson parametric amplifiers

    Energy Technology Data Exchange (ETDEWEB)

    Zhong, Ling; Baust, Alexander; Xie, Edwar; Schwarz, Manuel; Gross, Rudolf [Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, Garching (Germany); Physik-Department, TU Muenchen, Garching (Germany); Nanosystems Initiative Munich (NIM), Muenchen (Germany); Fedorov, Kirill; Menzel, Edwin; Marx, Achim [Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, Garching (Germany); Betzenbichler, Martin; Pogorzalek, Stefan; Haeberlein, Max; Eder, Peter; Goetz, Jan; Wulschner, Karl Friedrich; Huebl, Hans; Deppe, Frank [Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, Garching (Germany); Physik-Department, TU Muenchen, Garching (Germany)

    2015-07-01

    Propagating quantum microwaves are promising building blocks for quantum communication. Interestingly, such itinerant quantum microwaves can be generated in the form of squeezed photon states by Josephson parametric amplifiers (JPA). We employ a specific ''dual-path'' setup for both state reconstruction and JPA characterization. Displacement operations are performed by using a directional coupler after the squeezing. We compare our results with theory predictions. In particular, we discuss our experiments in the context of remote state preparation and quantum teleportation with propagating microwaves.

  15. Dynamical behavior of RF-biased Josephson junctions (I)

    Energy Technology Data Exchange (ETDEWEB)

    Zi-Dan, Wang; Xi-Xian, Yao

    1985-09-01

    A lot of numerical investigation of equations of RF-biased Josephson junctions is carried out, in which the interference term is included in current-phase relation. Chaotic behavior, sequence of period-doubling bifurcations, inverse sequence of chaotic band and intermittent chaos are found separately in various parameter regions. The convergent factor delta n of 2/sup /P sequence and the ratio Phi(k)/Phi(k+1) are calculated, where Phi(k) is the average height of the peaks corresponding to 2/sup k/P in the power spectrum. We also study the symmetry possessed by period solutions and its relation to the nature of approach to chaos.

  16. High-Tc superconducting Josephson mixers for terahertz heterodyne detection

    International Nuclear Information System (INIS)

    Malnou, M.; Feuillet-Palma, C.; Olanier, L.; Lesueur, J.; Bergeal, N.; Ulysse, C.; Faini, G.; Febvre, P.; Sirena, M.

    2014-01-01

    We report on an experimental and theoretical study of the high-frequency mixing properties of ion-irradiated YBa 2 Cu 3 O 7 Josephson junctions embedded in THz antennas. We investigated the influence of the local oscillator power and frequency on the device performances. The experimental data are compared with theoretical predictions of the general three-port model for mixers in which the junction is described by the resistively shunted junction model. A good agreement is obtained for the conversion efficiency in different frequency ranges, spanning above and below the characteristic frequencies f c of the junctions

  17. Relaxation towards phase-locked dynamics in long Josephson junctions

    DEFF Research Database (Denmark)

    Salerno, M.; Grønbech-Jensen, Niels; Samuelsen, Mogens Rugholm

    1995-01-01

    We study the relaxation phenomenon towards phase-locked dynamics in long Josephson junctions. In particular the dependence of the relaxation frequency for the equal time of flight solution on the junction parameters is derived. The analysis is based on a phase-locked map and is compared with direct...... numerical experiments performed both on the map and on the perturbed sine-Gordon equation. As an interesting result we find that very close to a bifurcation the relaxation frequency is exactly equal to the half of the step frequency, i.e., the frequency characterizing the period-one solution....

  18. Laminar phase flow for an exponentially tapered Josephson oscillator

    DEFF Research Database (Denmark)

    Benabdallah, A.; Caputo, J. G.; Scott, Alwyn C.

    2000-01-01

    Exponential tapering and inhomogeneous current feed were recently proposed as means to improve the performance of a Josephson flux flow oscillator. Extensive numerical results backed up by analysis are presented here that support this claim and demonstrate that exponential tapering reduces...... the small current instability region and leads to a laminar flow regime where the voltage wave form is periodic giving the oscillator minimal spectral width. Tapering also leads to an increased output power. Since exponential tapering is not expected to increase the difficulty of fabricating a flux flow...

  19. Strong environmental coupling in a Josephson parametric amplifier

    International Nuclear Information System (INIS)

    Mutus, J. Y.; White, T. C.; Barends, R.; Chen, Yu; Chen, Z.; Chiaro, B.; Dunsworth, A.; Jeffrey, E.; Kelly, J.; Neill, C.; O'Malley, P. J. J.; Roushan, P.; Sank, D.; Vainsencher, A.; Wenner, J.; Cleland, A. N.; Martinis, John M.; Megrant, A.; Sundqvist, K. M.

    2014-01-01

    We present a lumped-element Josephson parametric amplifier designed to operate with strong coupling to the environment. In this regime, we observe broadband frequency dependent amplification with multi-peaked gain profiles. We account for this behavior using the “pumpistor” model which allows for frequency dependent variation of the external impedance. Using this understanding, we demonstrate control over the complexity of gain profiles through added variation in the environment impedance at a given frequency. With strong coupling to a suitable external impedance, we observe a significant increase in dynamic range, and large amplification bandwidth up to 700 MHz giving near quantum-limited performance.

  20. Optimal Operation of a Josephson Parametric Amplifier for Vacuum Squeezing

    Science.gov (United States)

    Malnou, M.; Palken, D. A.; Vale, Leila R.; Hilton, Gene C.; Lehnert, K. W.

    2018-04-01

    A Josephson parametric amplifier (JPA) can create squeezed states of microwave light, lowering the noise associated with certain quantum measurements. We experimentally study how the JPA's pump influences the phase-sensitive amplification and deamplification of a coherent tone's amplitude when that amplitude is commensurate with vacuum fluctuations. We predict and demonstrate that, by operating the JPA with a single current pump whose power is greater than the value that maximizes gain, the amplifier distortion is reduced and, consequently, squeezing is improved. Optimizing the singly pumped JPA's operation in this fashion, we directly observe 3.87 ±0.03 dB of vacuum squeezing over a bandwidth of 30 MHz.

  1. Graphene-Based Josephson-Junction Single-Photon Detector

    Science.gov (United States)

    Walsh, Evan D.; Efetov, Dmitri K.; Lee, Gil-Ho; Heuck, Mikkel; Crossno, Jesse; Ohki, Thomas A.; Kim, Philip; Englund, Dirk; Fong, Kin Chung

    2017-08-01

    We propose to use graphene-based Josephson junctions (GJJs) to detect single photons in a wide electromagnetic spectrum from visible to radio frequencies. Our approach takes advantage of the exceptionally low electronic heat capacity of monolayer graphene and its constricted thermal conductance to its phonon degrees of freedom. Such a system could provide high-sensitivity photon detection required for research areas including quantum information processing and radio astronomy. As an example, we present our device concepts for GJJ single-photon detectors in both the microwave and infrared regimes. The dark count rate and intrinsic quantum efficiency are computed based on parameters from a measured GJJ, demonstrating feasibility within existing technologies.

  2. Effect of pairing in nuclear level density at low temperatures

    International Nuclear Information System (INIS)

    Rhine Kumar, A.K.; Modi, Swati; Arumugam, P.

    2013-01-01

    The nuclear level density (NLD) has been an interesting topic for researchers, due its importance in many aspects of nuclear physics, nuclear astrophysics, nuclear medicine, and other applied areas. The calculation of NLD helps us to understand the energy distribution of the excited levels of nuclei, entropy, specific heat, reaction cross sections etc. In this work the effect of temperature and pairing on level-density of the nucleus 116 Sn has been studied

  3. Kyoto: nuclear power against greenhouse effect

    International Nuclear Information System (INIS)

    Anon.

    1997-01-01

    Among the different possibilities to slow down the increase of greenhouse gas emissions, several participants of the Kyoto conference (December 11, 1997) held the nuclear power resort in a good position. This short paper reports on some extracts of talks given during the conference by participants who take a definite position in favour of the development of nuclear power: FORATOM (European Atomic Forum), Nuclear Energy Institute (US), Japan Atomic Industrial Forum, the Uranium Institute, WONUC (World Council of Nuclear Workers) and SFEN (French Society of Nuclear Energy). (J.S.)

  4. Numerical simulation of the self-pumped long Josephson junction using a modified sine-Gordon model

    DEFF Research Database (Denmark)

    Sobolev, A.; Pankratov, A.; Mygind, Jesper

    2006-01-01

    We have numerically investigated the dynamics of a long Josephson junction (flux-flow oscillator) biased by a DC current in the presence of magnetic field. The study is performed in the frame of the modified sine-Gordon model, which includes the surface losses, RC-load at both FFO ends and the self-pumping...... effect. In our model the dumping parameter depends both on the spatial coordinate and the amplitude of the AC voltage. In order to find the DC FFO voltage the damping parameter has to be calculated by successive approximations and time integration of the perturbed sine-Gordon equation. The modified model...

  5. Adolescents' knowledge of nuclear issues and the effects of nuclear war

    International Nuclear Information System (INIS)

    Roscoe, B.; Goodwin, M.P.

    1987-01-01

    Three hundred fifty-seven college students were surveyed to assess later adolescents' awareness of the status of nuclear arms development and possible effects of a nuclear war on people and the environment. Chi-square analyses were performed to determine whether the frequency of correct responses differed with regard to participants' sex, political orientation, and position toward the United States' possession of nuclear weapons. Results suggest that later adolescents are extremely uninformed regarding the current status of nuclear issues and the consequences of a nuclear war. These data, coupled with findings from previous studies reporting children's and adolescents' concerns and fears about nuclear war, indicate that there is a strong need to educate young people concerning nuclear issues

  6. Nuclear spectroscopy with density dependent effective interactions

    International Nuclear Information System (INIS)

    Krewald, S.

    1976-07-01

    The paper investigates excited nuclear states with density-dependent effective interactions. In the first part of the paper, the structure and the width of the multipole giant resonances discovered in 1972 are derived microscopically. Because of their high excitation energy, these giant resonances are unstable to particle emission and thus often have a considerable decay width. Due to their collective structure, the giant resonances can be described by RPA in good approximation. In this paper, the continuum RPA is applied to the spherical nuclei 16 O, 40 Ca, 90 Zr and 208 Pb. The experimental centroid energy are in very good agreement with the calculations performed in the paper. (orig./WL) [de

  7. Nuclear power and the greenhouse effect

    International Nuclear Information System (INIS)

    Donaldson, D; Tolland, H.; Grimston, M.

    1990-01-01

    The greenhouse effect is first explained. The evidence is shown in global warming and changing weather patterns which are generally believed to be due to the emission of greenhouse gases, including carbon dioxide. Serious consequences are predicted if emission of the greenhouse gases is not reduced. Sources of these gases are identified - agriculture, carbon fluorocarbons, coal-fired power stations, vehicle exhausts. The need is to use energy more efficiently but such measures as combined heat and power stations, more fuel efficient cars and better thermal insulation in homes is advocated. The expansion of renewable energy sources such as wind and water power is also suggested. Nuclear power is promoted as it reduces the carbon dioxide emissions and in both the short and long-term will reduce the emission of greenhouse gases. (author)

  8. Psychotherapist countertransference in the nuclear age: Effects on therapeutic interventions

    International Nuclear Information System (INIS)

    Oderberg, N.A.

    1991-01-01

    Since the early 1980s, there has been considerable attention in the psychology literature to mental health problems related to living in a world threatened by nuclear destruction. Questionnaires were mailed to 630 psychotherapists from the Colorado Psychological Association, California Psychotherapists for Social Responsibility, California Psychologists for Social Responsibility, the US Army, and the APA Division of Military Psychology; 174 questionnaires were returned. It was hypothesized that liberalism, nuclear weapons opposition, nuclear concern, nuclear awareness, and anti-nuclear activism in psychotherapists would facilitate perception of, and openness to working with, a client's nuclear concerns and thus, would be positively correlated with intentions to discuss nuclear issues with clients in three different clinical vignettes. Results indicated that when controlling for subject group, psychotherapy orientation, age, sex, and income, all five independent variables were positively correlated with responses to all three clinical vignettes, with nuclear concern having the strongest unique effect in accounting for variance in responses to the vignettes

  9. Non-equilibrium coherent vortex states and subharmonic giant Shapiro steps in Josephson junction arrays

    International Nuclear Information System (INIS)

    Dominguez, D.; Jose, J.V.; Northeastern Univ., Boston, MA

    1994-01-01

    This is a review of recent work on the dynamic response of Josephson junction arrays driven by dc and ac currents. The arrays are modeled by the resistively shunted Josephson junction model, appropriate for proximity effect junctions, including self-induced magnetic fields as well as disorder. The relevance of the self-induced fields is measured as a function of a parameter κ = λ L /a, with λ L the London penetration depth of the arrays, and a the lattice spacing. The transition from Type II (κ > 1) to Type I (κ < 1) behavior is studied in detail. The authors compare the results for models with self, self + nearest-neighbor, and full inductance matrices. In the κ = ∞ limit, they find that when the initial state has at least one vortex-antivortex pair, after a characteristic transient time these vortices unbind and radiate other vortices. These radiated vortices settle into a parity-broken, time-periodic, axisymmetric coherent vortex state (ACVS), characterized by alternate rows of positive and negative vortices lying along a tilted axis. The ACVS produces subharmonic steps in the current voltage (IV) characteristics, typical of giant Shapiro steps. For finite κ they find that the IV's show subharmonic giant Shapiro steps, even at zero external magnetic field. They find that these subharmonic steps are produced by a whole family of coherent vortex oscillating patterns, with their structure changing as a function of κ. In general, they find that these patterns are due to a breakdown of translational invariance produced, for example, by disorder of antisymmetric edge-fields. The zero field case results are in good qualitative agreement with experiments in Nb-Au-Nb arrays

  10. Logic delays of 5-μm resistor coupled Josephson logic

    International Nuclear Information System (INIS)

    Sone, J.; Yoshida, T.; Tahara, S.; Abe, H.

    1982-01-01

    Logic delays of resistor coupled Josephson logic (RCJL) have been investigated. An experimental circuit with a cascade chain of ten RCJL OR gates was fabricated using Pb-alloy Josephson IC technology with 5-μm minimum linewidth. Logic delay was measured to be as low as 10.8 ps with power dissipation of 11.7 μW. This demonstrates a switching operation faster than those reported for other Josephson gate designs. Comparison with computer-simulation results is also presented

  11. Berry's phase, Josephson's equation, and the dynamics of weak link superconductors and their vortices

    International Nuclear Information System (INIS)

    Gaitan, F.; Shenoy, S.R.

    1995-05-01

    We examine the dynamical consequences of Berry's phase for Josephson junctions, junction arrays, and their vortices. Josephson's equation and the related phase slip voltages are shown to be unaffected by Berry's phase. In an annular Josephson junction, Berry's phase is seen to generate a new current drive on a vortex. In the continuum limit, vortex is expected in a 2D array is shown to map onto that of a 2D film. A Hall sing anomaly is expected arrays; and the merits of arrays for studies of disorder on vortex motion is discussed. (author). 12 refs

  12. Static properties of small Josephson tunnel junctions in a transverse magnetic field

    DEFF Research Database (Denmark)

    Monaco, R.; Aarøe, Morten; Mygind, Jesper

    2008-01-01

    The magnetic field distribution in the barrier of small planar Josephson tunnel junctions is numerically simulated in the case when an external magnetic field is applied perpendicular to the barrier plane. The simulations allow for heuristic analytical solutions for the Josephson static phase...... profile from which the dependence of the maximum Josephson current on the applied field amplitude is derived. The most common geometrical configurations are considered and, when possible, the theoretical findings are compared with the experimental data. ©2008 American Institute of Physics...

  13. Effectiveness of the Convention on Nuclear Safety

    International Nuclear Information System (INIS)

    Schwarz, G.

    2016-01-01

    The Convention on Nuclear Safety (CNS) has been established after the Chernobyl accident with the primary objective of achieving and maintaining a high level of nuclear safety worldwide, through the enhancement of national measures and international cooperation. The CNS is an incentive convention. It defines the basic safety standard which shall be met by the Contracting Parties. The verification of compliance is based on a self-assessment by the Countries and a Peer Review by the other Contracting Parties. As of July 2015, there are 78 Contracting Parties. Among the Contracting Parties of the Convention are all countries operating nuclear power plants except the Islamic Republic of Iran and Taiwan, all countries constructing nuclear power plants, all countries having nuclear power plants in long term shutdown and all countries having signed contracts for the construction of nuclear power plants. The National Reports under the CNS therefore cover almost all nuclear power plants of the world. The peer review of reports, questions and answers that are exchanged in connection with the Review Meetings provided a unique overview of nuclear safety provisions and issues in countries planning or operating nuclear power plants. This is especially important for neighbouring countries to those operating nuclear power plants.

  14. Two-Volt Josephson Arbitrary Waveform Synthesizer Using Wilkinson Dividers

    Science.gov (United States)

    Flowers-Jacobs, Nathan E.; Fox, Anna E.; Dresselhaus, Paul D.; Schwall, Robert E.; Benz, Samuel P.

    2016-01-01

    The root-mean-square (rms) output voltage of the NIST Josephson arbitrary waveform synthesizer (JAWS) has been doubled from 1 V to a record 2 V by combining two new 1 V chips on a cryocooler. This higher voltage will improve calibrations of ac thermal voltage converters and precision voltage measurements that require state-of-the-art quantum accuracy, stability, and signal-to-noise ratio. We achieved this increase in output voltage by using four on-chip Wilkinson dividers and eight inner-outer dc blocks, which enable biasing of eight Josephson junction (JJ) arrays with high-speed inputs from only four high-speed pulse generator channels. This approach halves the number of pulse generator channels required in future JAWS systems. We also implemented on-chip superconducting interconnects between JJ arrays, which reduces systematic errors and enables a new modular chip package. Finally, we demonstrate a new technique for measuring and visualizing the operating current range that reduces the measurement time by almost two orders of magnitude and reveals the relationship between distortion in the output spectrum and output pulse sequence errors. PMID:27453676

  15. Ultralow power artificial synapses using nanotextured magnetic Josephson junctions

    Science.gov (United States)

    Schneider, Michael L.; Donnelly, Christine A.; Russek, Stephen E.; Baek, Burm; Pufall, Matthew R.; Hopkins, Peter F.; Dresselhaus, Paul D.; Benz, Samuel P.; Rippard, William H.

    2018-01-01

    Neuromorphic computing promises to markedly improve the efficiency of certain computational tasks, such as perception and decision-making. Although software and specialized hardware implementations of neural networks have made tremendous accomplishments, both implementations are still many orders of magnitude less energy efficient than the human brain. We demonstrate a new form of artificial synapse based on dynamically reconfigurable superconducting Josephson junctions with magnetic nanoclusters in the barrier. The spiking energy per pulse varies with the magnetic configuration, but in our demonstration devices, the spiking energy is always less than 1 aJ. This compares very favorably with the roughly 10 fJ per synaptic event in the human brain. Each artificial synapse is composed of a Si barrier containing Mn nanoclusters with superconducting Nb electrodes. The critical current of each synapse junction, which is analogous to the synaptic weight, can be tuned using input voltage spikes that change the spin alignment of Mn nanoclusters. We demonstrate synaptic weight training with electrical pulses as small as 3 aJ. Further, the Josephson plasma frequencies of the devices, which determine the dynamical time scales, all exceed 100 GHz. These new artificial synapses provide a significant step toward a neuromorphic platform that is faster, more energy-efficient, and thus can attain far greater complexity than has been demonstrated with other technologies. PMID:29387787

  16. What happens in Josephson junctions at high critical current densities

    Science.gov (United States)

    Massarotti, D.; Stornaiuolo, D.; Lucignano, P.; Caruso, R.; Galletti, L.; Montemurro, D.; Jouault, B.; Campagnano, G.; Arani, H. F.; Longobardi, L.; Parlato, L.; Pepe, G. P.; Rotoli, G.; Tagliacozzo, A.; Lombardi, F.; Tafuri, F.

    2017-07-01

    The impressive advances in material science and nanotechnology are more and more promoting the use of exotic barriers and/or superconductors, thus paving the way to new families of Josephson junctions. Semiconducting, ferromagnetic, topological insulator and graphene barriers are leading to unconventional and anomalous aspects of the Josephson coupling, which might be useful to respond to some issues on key problems of solid state physics. However, the complexity of the layout and of the competing physical processes occurring in the junctions is posing novel questions on the interpretation of their phenomenology. We classify some significant behaviors of hybrid and unconventional junctions in terms of their first imprinting, i.e., current-voltage curves, and propose a phenomenological approach to describe some features of junctions characterized by relatively high critical current densities Jc. Accurate arguments on the distribution of switching currents will provide quantitative criteria to understand physical processes occurring in high-Jc junctions. These notions are universal and apply to all kinds of junctions.

  17. Long Josephson tunnel junctions with doubly connected electrodes

    Science.gov (United States)

    Monaco, R.; Mygind, J.; Koshelets, V. P.

    2012-03-01

    In order to mimic the phase changes in the primordial Big Bang, several cosmological solid-state experiments have been conceived, during the last decade, to investigate the spontaneous symmetry breaking in superconductors and superfluids cooled through their transition temperature. In one of such experiments, the number of magnetic flux quanta spontaneously trapped in a superconducting loop was measured by means of a long Josephson tunnel junction built on top of the loop itself. We have analyzed this system and found a number of interesting features not occurring in the conventional case with simply connected electrodes. In particular, the fluxoid quantization results in a frustration of the Josephson phase, which, in turn, reduces the junction critical current. Further, the possible stable states of the system are obtained by a self-consistent application of the principle of minimum energy. The theoretical findings are supported by measurements on a number of samples having different geometrical configuration. The experiments demonstrate that a very large signal-to-noise ratio can be achieved in the flux quanta detection.

  18. Spin-triplet supercurrent in Co-based Josephson junctions

    International Nuclear Information System (INIS)

    Khasawneh, Mazin A; Khaire, Trupti S; Klose, Carolin; Pratt, William P Jr; Birge, Norman O

    2011-01-01

    In the past year several groups have reported experimental evidence for spin-triplet supercurrents in Josephson junctions containing strong ferromagnetic materials. In this paper we present several new experimental results that follow up on our previous work. We study Josephson junctions of the form S/X/N/SAF/N/X/S, where S is a superconductor (Nb), N is a normal metal, SAF is a synthetic antiferromagnet of the form Co/Ru/Co and X is an ferromagnetic layer necessary to induce spin-triplet correlations in the structure. Our work is distinguished by the fact that the generation of spin-triplet correlations is tuned by the type and thickness of the X layers. The most important new result reported here is the discovery that a conventional, strong ferromagnetic material, Ni, performs well as the X layer, if it is sufficiently thin. This discovery rules out our earlier hypothesis that out-of-plane magnetocrystalline anisotropy is an important attribute of the X layers. These results suggest that the spin-triplet correlations are most likely induced by noncollinear magnetization between the X layers and adjacent Co layers.

  19. Two Superconducting Charge Qubits Coupled by a Josephson Inductance

    Science.gov (United States)

    Watanabe, Michio; Yamamoto, Tsuyoshi; Pashkin, Yuri A.; Astafiev, Oleg; Nakamura, Yasunobu; Tsai, Jaw-Shen

    2007-03-01

    When the quantum oscillations [Pashkin et al., Nature 421, 823 (2003)] and the conditional gate operation [Yamamoto et al., Nature 425, 941 (2003)] were demonstrated using superconducting charge qubits, the charge qubits were coupled capacitively, where the coupling was always on and the coupling strength was not tunable. This fixed coupling, however, is not ideal because for example, it makes unconditional gate operations difficult. In this work, we aimed to tunably couple two charge qubits. We fabricated circuits based on the theoretical proposal by You, Tsai, and Nori [PRB 68, 024510 (2003)], where the inductance of a Josephson junction, which has a much larger junction area than the qubit junctions, couples the qubits and the coupling strength is controlled by the external magnetic flux. We confirmed by spectroscopy that the large Josephson junction was indeed coupled to the qubits and that the coupling was turned on and off by the external magnetic flux. In the talk, we will also discuss the quantum oscillations in the circuits.

  20. Thermal and quantum escape of fractional Josephson vortices

    Energy Technology Data Exchange (ETDEWEB)

    Poehler, Hanna; Kienzle, Uta; Buckenmaier, Kai; Gaber, Tobias; Koelle, Dieter; Kleiner, Reinhold; Goldobin, Edward [Physikalisches Institut, Center for Collective Quantum Phenomena, Universitaet Tuebingen (Germany); Siegel, Michael [Institut fuer Mikro- und Nanoelektronische Systeme, Universitaet Karlsruhe (Germany)

    2009-07-01

    By using a pair of tiny current injectors one can create an arbitrary {kappa} discontinuity of the phase in a long Josephson junction (LJJ) and a fractional Josephson vortex (FJV), carrying a fraction {phi}/{phi}{sub 0}={kappa}/2{pi}{<=}1 of the magnetic flux quantum {phi}{sub 0}{approx}2.07 .10{sup -15} Wb, which is pinned at the discontinuity. If a bias current I, exceeds the critical value I{sub c}({kappa}), an integer fluxon is torn off the discontinuity and the LJJ switches to the voltage state. Due to thermal or quantum fluctuations this escape event may occur at I

  1. Phase dynamics of low critical current density YBCO Josephson junctions

    Energy Technology Data Exchange (ETDEWEB)

    Massarotti, D., E-mail: dmassarotti@na.infn.it [Dipartimento di Fisica, Università degli Studi di Napoli Federico II, Via Cinthia, 80126 Napoli (Italy); CNR-SPIN UOS Napoli, Complesso Universitario di Monte Sant’Angelo, Via Cinthia, 80126 Napoli (Italy); Stornaiuolo, D. [Dipartimento di Fisica, Università degli Studi di Napoli Federico II, Via Cinthia, 80126 Napoli (Italy); Rotoli, G. [Dipartimento di Ingegneria Industriale e dell’Informazione, Seconda Università di Napoli, Via Roma 29, 81031 Aversa (CE) (Italy); Carillo, F. [Nest, Scuola Normale Superiore, Piazza San Silvestro 12, 56126 Pisa (Italy); Galletti, L. [Dipartimento di Fisica, Università degli Studi di Napoli Federico II, Via Cinthia, 80126 Napoli (Italy); CNR-SPIN UOS Napoli, Complesso Universitario di Monte Sant’Angelo, Via Cinthia, 80126 Napoli (Italy); Longobardi, L. [Dipartimento di Ingegneria Industriale e dell’Informazione, Seconda Università di Napoli, Via Roma 29, 81031 Aversa (CE) (Italy); American Physical Society, 1 Research Road, Ridge, NY 11961 (United States); Beltram, F. [Nest, Scuola Normale Superiore, Piazza San Silvestro 12, 56126 Pisa (Italy); Tafuri, F. [CNR-SPIN UOS Napoli, Complesso Universitario di Monte Sant’Angelo, Via Cinthia, 80126 Napoli (Italy); Dipartimento di Ingegneria Industriale e dell’Informazione, Seconda Università di Napoli, Via Roma 29, 81031 Aversa (CE) (Italy)

    2014-08-15

    Highlights: • We study the phase dynamics of YBaCuO Josephson junctions using various tools. • We derive information on the dissipation in a wide range of transport parameters. • Dissipation in such devices can be described by a frequency dependent damping model. • The use of different substrates allows us to tune the shell circuit. - Abstract: High critical temperature superconductors (HTS) based devices can have impact in the study of the phase dynamics of Josephson junctions (JJs) thanks to the wide range of junction parameters they offer and to their unconventional properties. Measurements of current–voltage characteristics and of switching current distributions constitute a direct way to classify different regimes of the phase dynamics and of the transport, also in nontrivial case of the moderately damped regime (MDR). MDR is going to be more and more common in JJs with advances in nanopatterning superconductors and synthesizing novel hybrid systems. Distinctive signatures of macroscopic quantum tunneling and of thermal activation in presence of different tunable levels of dissipation have been detected in YBCO grain boundary JJs. Experimental data are supported by Monte Carlo simulations of the phase dynamics, in a wide range of temperatures and dissipation levels. This allows us to quantify dissipation in the MDR and partially reconstruct a phase diagram as guideline for a wide range of moderately damped systems.

  2. Dynamics of fractional vortices in long Josephson junctions

    International Nuclear Information System (INIS)

    Gaber, Tobias

    2007-01-01

    In this thesis static and dynamic properties of fractional vortices in long Josephson junctions are investigated. Fractional vortices are circulating supercurrents similar to the well-known Josephson fluxons. Yet, they show the distinguishing property of carrying only a fraction of the magnetic flux quantum. Fractional vortices are interesting non-linear objects. They spontaneously appear and are pinned at the phase discontinuity points of so called 0-κ junctions but can be bend or flipped by external forces like bias currents or magnetic fields. 0-κ junctions and fractional vortices are generalizations of the well-known 0-π junctions and semifluxons, where not only phase jumps of pi but arbitrary values denoted by kappa are considered. By using so-called artificial 0-κ junctions that are based on standard Nb-AlO x -Nb technology the classical dynamics of fractional vortices has been investigated experimentally for the very first time. Here, half-integer zero field steps could be observed. These voltage steps on the junction's current-voltage characteristics correspond to the periodic flipping/hopping of fractional vortices. In addition, the oscillatory eigenmodes of fractional vortices were investigated. In contrast to fluxons fractional vortices have an oscillatory eigenmode with a frequency within the plasma gap. Using resonance spectroscopy the dependence of the eigenmode frequency on the flux carried by the vortex and an applied bias current was determined. (orig.)

  3. Majorana zero modes in Dirac semimetal Josephson junctions

    Science.gov (United States)

    Li, Chuan; de Boer, Jorrit; de Ronde, Bob; Huang, Yingkai; Golden, Mark; Brinkman, Alexander

    We have realized proximity-induced superconductivity in a Dirac semimetal and revealed the topological nature of the superconductivity by the observation of Majorana zero modes. As a Dirac semimetal, Bi0.97Sb0.03 is used, where a three-dimensional Dirac cone exists in the bulk due to an accidental touching between conduction and valence bands. Electronic transport measurements on Hall-bars fabricated out of Bi0.97Sb0.03 flakes consistently show negative magnetoresistance for magnetic fields parallel to the current, which is associated with the chiral anomaly. In perpendicular magnetic fields, we see Shubnikov-de Haas oscillations that indicate very low carrier densities. The low Fermi energy and protection against backscattering in our Dirac semimetal Josephson junctions provide favorable conditions for a large contribution of Majorana zero modes to the supercurrent. In radiofrequency irradiation experiments, we indeed observe these Majorana zero modes in Nb-Bi0.97Sb0.03-Nb Josephson junctions as a 4 π periodic contribution to the current-phase relation.

  4. Manipulating Josephson junctions in thin-films by nearby vortices

    International Nuclear Information System (INIS)

    Kogan, V.G.; Mints, R.G.

    2014-01-01

    Highlights: • Vortex located in a bank of a planar Josephson junction changes its character. • Vortex located at some discreet positions in thin strip bank suppresses to zero the zero-field current. • The number of these positions is equal to the number of vortices trapped. • Critical current-field patterns are strongly affected by the vortex position. - Abstract: It is shown that a vortex trapped in one of the banks of a planar edge-type Josephson junction in a narrow thin-film superconducting strip can change drastically the dependence of the junction critical current on the applied field, I c (H). When the vortex is placed at certain discrete positions in the strip middle, the pattern I c (H) has zero at H=0 instead of the traditional maximum of ‘0-type’ junctions. The number of these positions is equal to the number of vortices trapped at the same location. When the junction–vortex separation exceeds ∼W, the strip width, I c (H) is no longer sensitive to the vortex presence. The same is true for any separation if the vortex approaches the strip edges

  5. Thermalization of a quenched Bose-Josephson junction

    Energy Technology Data Exchange (ETDEWEB)

    Posazhennikova, Anna [Royal Holloway, University of London (United Kingdom); Trujillo-Martinez, Mauricio; Kroha, Johann [Universitaet Bonn (Germany)

    2015-07-01

    The experimental realization and control of quantum systems isolated from the environment, in ultracold atomic gases relaunched the interest in the fundamental non-equilibrium problem of how a finite system approaches thermal equilibrium. Despite intensive research there is still no conclusive answer to this question. We investigate theoretically how a quenched Bose-Josephson junction, where the Josephson coupling is switched on instantaneously, approaches its stationary state. We use the field theoretical approach for bosons out of equilibrium in a trap with discrete levels, developed by us previously. In this approach the operators for Bose-Einstein condensate (BEC) particles are treated on mean-field level, while excitations of the Bose gas in higher trap levels are treated fully quantum-mechanically. This leads to coupled equations of motion for the BEC amplitudes (Gross-Pitaevskii equation) and the quasiparticle propagators. The inelastic quasiparticle collisions responsible for the system relaxation during the time-dependent evolution are described within self-consistent second-order approximation.

  6. Nuclear power and the greenhouse effect

    International Nuclear Information System (INIS)

    Donaldson, D.M.; Tolland, H.G.

    1989-05-01

    Global levels of the ''Greenhouse'' gases - carbon dioxide, the chlorofluorocarbons (CFCs), methane, nitrous oxide and tropospheric ozone are increasing as a result of man's activities. This increase is widely expected to bring about a rise in global temperature with concomitant environmental impacts. Global warming has been observed over the last century, and the last decade has seen seven of the warmest years on record. There has also been increased variability in the weather (an expected consequence of global warming). However, these possible manifestations of the Greenhouse Effect are within natural variations and proof must await more definitive indications. A brief outline of current views on the Greenhouse Effect is given. This report addresses the energy sector using CO 2 emissions as a measure of its ''Greenhouse'' contribution. This approach understates the energy sector contribution. However, the difference is within the error band. It seems likely that the warming effect of non-energy related emissions will remain the same and there will be more pressure to reduce the emissions from the energy sector. To assess policy options the pattern of future energy demand is estimated. Two scenarios have been adopted to provide alternative frameworks. Both assume low energy growth projections based on increased energy efficiency. The role of nuclear power in reducing carbon dioxide emissions is considered. (author)

  7. Will Iran Nuclear Deal Be Effectively Implemented?

    Institute of Scientific and Technical Information of China (English)

    Li Guofu

    2016-01-01

    The fourth Nuclear Security Summit is convened in Washington DC of the US on March 31st,2016.The development and utilization of nuclear energy has brought new power for the development of human society and significantly enhanced human capability of knowing and transforming the world.However,it also brought about nuclear security risks and challenge.Particularly in today’s international political struggle,some states are making use

  8. Nuclear shell effects at high temperatures

    International Nuclear Information System (INIS)

    Davidson, N.J.; Miller, H.G.

    1993-01-01

    In discussing the disappearance of nuclear shell effects at high temperatures, it is important to distinguish between the ''smearing out'' of the single-particle spectrum with increasing temperature and the vanishing of shell related structures in many-body quantities such as the excitation energy per nucleon. We propose a semiempirical method to obtain an upper bound on the temperature required to smooth the single-particle spectrum, and point out that shell effects in many-body parameters may persist above this temperature. We find that the temperature required to smear out the single-particle spectrum is approximately 1 MeV for heavy nuclei (A approx-gt 150) and about 3--4 MeV for light nuclei (A approx-lt 50), in reasonable agreement with the estimate of 41/πA 1/3 obtained from calculations with harmonic oscillator potentials. These temperatures correspond to many-body excitation energies of approximately 20 and 60 MeV, respectively

  9. Nuclear power's effects on electric rate making

    International Nuclear Information System (INIS)

    Smith, D.S.; Lancaster, A.A.

    1978-01-01

    Government and the electric utility industry are re-evaluating nuclear power's contribution to the total U.S. energy supplies. This article addresses how the recently increased nuclear plant construction and operation costs are translated into the prices that consumers pay for electricity. The electric rates that consumers pay must reflect the costs of producing electricity, as well as the costs of transmission, distribution, metering, and billing. The use of nuclear power for electric production is anticipated to grow rapidly so as to meet a larger portion of our country's electricity needs through the end of the century; so nuclear power costs are expected to be an even larger portion of the total electricity price. There are certain rate-making issues that are actively being discussed in public forums and before state and Federal regulatory bodies. These issues are not unique to nuclear power, but take on added significance when nuclear power is used by utilities to produce electricity because of the technology required and because of the type, timing, and magnitude of the costs involved. These are: (1) inclusion of construction work in progress in the rate base; (2) fuel adjustment clauses and treatment of nuclear fuel cycle costs; (3) treatment of certain taxes under the rate-making method called normalization or deferral accounting (sometimes referred to as ''phantom taxes''); and (4) rate treatment for particular nuclear expense items reflecting costs of delays, plant cancellations, and operational slowdowns

  10. Chaos synchronization in a Josephson junction system via active sliding mode control

    International Nuclear Information System (INIS)

    Zhao Yang; Wang Wei

    2009-01-01

    In this letter, two types of active siding control methods are proposed and applied to achieve chaotic synchronization in a Josephson junction system. Numerical simulations are used to verify the proposed control techniques.

  11. Experimental relationship between damping and stability of Sine-Gordon solitons in Josephson junctions

    International Nuclear Information System (INIS)

    Davidson, A.; Pedersen, N.F.; Dueholm, B.

    1985-01-01

    We show some experimental results which suggest that total damping, including surface loss, plays a fundamental role in limiting the stability of high-velocity Sine-Gordon solitons in real Josephson tunnel junctions

  12. Pinning of Josephson vortex chain in periodically heterogeneous junctions: theory and experiment

    International Nuclear Information System (INIS)

    Malomed, B.A.; Ustinov, A.V.

    1989-01-01

    Critical values of the density of extrinsic current of rigid Josephson vortex chain depinning in a long Josephson junction are calculated in terms of the perturbation theory. The dynamics of the chain is considered. In particular, a minimum value of the current density is estimated which permits the chain free motion through the transition on dissipation. The dependence of critical current, Jc, on external magnetic field H is measured for long Josephson junctions Nb-NbO x -Pb with artificial spatially periodic heterogeneities of dielectric barrier. For multiple values of H, the curve Jc(H) is found to display some peaks which, by the theory, are responsible for by an increase in the force of Josephson vortex chain and the heterogeneity lattice are commensurate

  13. Coordinate transformation in the model of long Josephson contacts: geometrically equivalent contacts

    International Nuclear Information System (INIS)

    Semerdzhieva, E.G.; Boyadzhiev, T.L.; ); Shukrinov, Yu.M.; Physical Technical Institute Dushanbe, 734063

    2005-01-01

    The transition from model of long Josephson variable-width contact to the contact model with coordinate-dependent Josephson current amplitude is realized by transforming the coordinates. This sets up a correspondence between Josephson contacts of variable width and quasi-one-dimensional contacts of variable thickness barrier layer. It is shown, that for contacts of exponentially varying width the barrier layer of the corresponding quasi-one-dimensional contact contains the distributed resistive inhomogeneity which is an attractor to magnetic flux vortices. With numerical experiments, a 'critical current-magnetic field' dependence for a resistive microinhomogeneity Josephson contact was plotted, and its comparison with the critical curve for a contact of exponentially varying width was made. Thus, this demonstrates that the distributed inhomogeneity may be replaced by a local one at the JC end what technologically, may offer definite advantages

  14. Economic effect of applied nuclear-agricultural science in China

    International Nuclear Information System (INIS)

    Ji Xiaobing; Zhou Zhihong; Zhao Shoufeng

    1998-01-01

    The economic effect of applied nuclear-agricultural science for 40 years in China have been summarized, analyzed and appraised. The economic regularity and features which are followed by research-development-production in the field of applied nuclear agricultural science in China are explored according to the essential characteristics of economics for input-output ratio and the itself-features of nuclear agricultural science. Some propositions for promoting the development and the economic effect of the applied nuclear-agricultural science in China are also given

  15. Negative Differential Resistance due to Nonlinearities in Single and Stacked Josephson Junctions

    DEFF Research Database (Denmark)

    Filatrella, Giovanni; Pierro, Vincenzo; Pedersen, Niels Falsig

    2014-01-01

    Josephson junction systems with a negative differential resistance (NDR) play an essential role for applications. As a well-known example, long Josephson junctions of the BSCCO type have been considered as a source of terahertz radiation in recent experiments. Numerical results for the dynamics...... shapes of NDR region are considered, and we found that it is essential to distinguish between current bias and voltage bias....

  16. Instanton glass generated by noise in a Josephson-junction array.

    Science.gov (United States)

    Chudnovsky, E M

    2009-09-25

    We compute the correlation function of a superconducting order parameter in a continuous model of a two-dimensional Josephson-junction array in the presence of a weak Gaussian noise. When the Josephson coupling is large compared to the charging energy, the correlations in the Euclidian space decay exponentially at low temperatures regardless of the strength of the noise. We interpret such a state as a collective Cooper-pair insulator and argue that it resembles properties of disordered superconducting films.

  17. Observation of nonresonant vortex motion in a long Josephson tunnel junction

    International Nuclear Information System (INIS)

    Rajeevakumar, T.V.; Przybysz, J.X.; Chen, J.T.; Langenberg, D.N.

    1980-01-01

    We have observed resistive branches in the I-V characteristics of long Josephson junctions which can be simply understood in terms of the motion of individual Josephson fluxoids with reflection as antifluxoids at the junction edges. The characteristics of these resistive branches differ qualitatively from those of the current singularities previously reported by Chen et al. and by Fulton and Dynes. Our results indicate that the current singularities are not simply related to the motion of individual fluxoids

  18. Quantum resonances in a single plaquette of Josephson junctions: excitations of Rabi oscillations

    OpenAIRE

    Fistul, M. V.

    2001-01-01

    We present a theoretical study of a quantum regime of the resistive (whirling) state of dc driven anisotropic single plaquette containing three small Josephson junctions. The current-voltage characteristics of such a system display resonant steps that are due to the resonant interaction between the time dependent Josephson current and the excited electromagnetic oscillations (EOs). The voltage positions of the resonances are determined by the quantum interband transitions of EOs. We show that...

  19. Experimental relationship between damping and stability of sine-Gordon solitons in Josephson junctions

    DEFF Research Database (Denmark)

    Davidson, A.; Pedersen, Niels Falsig; Dueholm, B.

    1985-01-01

    We show some experimental results which suggest that total damping, including surface loss, plays a fundamental role in limiting the stability of high-velocity sine-Gordon solitons in real Josephson tunnel junctions.......We show some experimental results which suggest that total damping, including surface loss, plays a fundamental role in limiting the stability of high-velocity sine-Gordon solitons in real Josephson tunnel junctions....

  20. Pumping $ac$ Josephson current in the Single Molecular Magnets by spin nutation

    OpenAIRE

    Abdollahipour, B.; Abouie, J.; Rostami, A. A.

    2012-01-01

    We demonstrate that an {\\it ac} Josephson current is pumped through the Single Molecular Magnets (SMM) by the spin nutation. The spin nutation is generated by applying a time dependent magnetic field to the SMM. We obtain the flowing charge current through the junction by working in the tunneling limit and employing Green's function technique. At the resonance conditions some discontinuities and divergencies are appeared in the normal and Josephson currents, respectively. Such discontinuities...