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.)
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.)
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, SiO_{2}/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 Ta_{x}N barriers are controlled by adjusting the nitrogen flow during sputtering. This technology offers a scalable alternative to the more traditional junctions based on AlO_{x} barriers for low - power, high - performance computing.
Crespi, Vincent Henry; Cohen, Marvin Lou; Louie, Steven Gwon Sheng; Zettl, Alexander Karlwalter
2003-01-01
The present invention comprises a new nanoscale metal-semiconductor, semiconductor-semiconductor, or metal-metal junction, designed by introducing topological or chemical defects in the atomic structure of the nanotube. Nanotubes comprising adjacent sections having differing electrical properties are described. These nanotubes can be constructed from combinations of carbon, boron, nitrogen and other elements. The nanotube can be designed having different indices on either side of a junction point in a continuous tube so that the electrical properties on either side of the junction vary in a useful fashion. For example, the inventive nanotube may be electrically conducting on one side of a junction and semiconducting on the other side. An example of a semiconductor-metal junction is a Schottky barrier. Alternatively, the nanotube may exhibit different semiconductor properties on either side of the junction. Nanotubes containing heterojunctions, Schottky barriers, and metal-metal junctions are useful for microcircuitry.
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.
Terahertz pulse driven Josephson junctions
Energy Technology Data Exchange (ETDEWEB)
Camerlingo, Carlo, E-mail: c.camerlingo@cib.na.cnr.it [CNR - Consiglio Nazionale delle Ricerche, Istituto di Cibernetica ' E. Caianiello' , Via Campi Flegrei 34, I-80078 Pozzuoli (Italy)
2011-09-15
Theoretical model of the ac Josephson effect in pulsed current driven junctions. Evaluation of the voltage response of a THz pulsed radiation driven Josephson junction. The pulsed current bias induces steps in the junction I/V characteristics for voltages depending on the pulse rate. Working principles of a fast response detector for THz pulsed radiation. The voltage response of a Josephson junction to a pulsed terahertz current is evaluated in the limit of a negligible junction capacitance (overdamped limit). The time-dependent superconductor phase difference across the junction is calculated in the framework of the standard resistive shunted junction model by using a perturbative method. The pulsed current bias affects the time average value of the voltage across the junction and current steps are induced in the current-voltage characteristics for voltage values depending on the pulse repetition rate. The current step height is proportional to the square of the pulse time width ({tau}) to the period (T) ratio. A fast response detector for pulsed Terahertz radiation is proposed, with an expected responsivity of the order of 0.1 V/W and an equivalent noise power of about 3 x 10{sup -10} W/Hz{sup 1/2}.
Squeezed States in Josephson Junctions.
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.
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.
Josephson junctions and dark energy
Jetzer, Philippe; Straumann, Norbert
2006-08-01
In a recent paper Beck and Mackey [C. Beck, M.C. Mackey, astro-ph/0603397] argue that the argument we gave in our paper [Ph. Jetzer, N. Straumann, Phys. Lett. B 606 (2005) 77, astro-ph/0411034] to disprove their claim that dark energy can be discovered in the Lab through noise measurements of Josephson junctions is incorrect. In particular, they emphasize that the measured noise spectrum in Josephson junctions is a consequence of the fluctuation dissipation theorem, while our argument was based on equilibrium statistical mechanics. In this note we show that the fluctuation dissipation relation does not depend upon any shift of vacuum (zero-point) energies, and therefore, as already concluded in our previous paper, dark energy has nothing to do with the proposed measurements.
Josephson junctions and dark energy
International Nuclear Information System (INIS)
Jetzer, Philippe; Straumann, Norbert
2006-01-01
In a recent paper Beck and Mackey [C. Beck, M.C. Mackey, astro-ph/0603397] argue that the argument we gave in our paper [Ph. Jetzer, N. Straumann, Phys. Lett. B 606 (2005) 77, astro-ph/0411034] to disprove their claim that dark energy can be discovered in the Lab through noise measurements of Josephson junctions is incorrect. In particular, they emphasize that the measured noise spectrum in Josephson junctions is a consequence of the fluctuation dissipation theorem, while our argument was based on equilibrium statistical mechanics. In this note we show that the fluctuation dissipation relation does not depend upon any shift of vacuum (zero-point) energies, and therefore, as already concluded in our previous paper, dark energy has nothing to do with the proposed measurements
Josephson junctions and dark energy
Energy Technology Data Exchange (ETDEWEB)
Jetzer, Philippe [Institute for Theoretical Physics, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich (Switzerland)]. E-mail: jetzer@physik.unizh.ch; Straumann, Norbert [Institute for Theoretical Physics, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich (Switzerland)
2006-08-03
In a recent paper Beck and Mackey [C. Beck, M.C. Mackey, astro-ph/0603397] argue that the argument we gave in our paper [Ph. Jetzer, N. Straumann, Phys. Lett. B 606 (2005) 77, astro-ph/0411034] to disprove their claim that dark energy can be discovered in the Lab through noise measurements of Josephson junctions is incorrect. In particular, they emphasize that the measured noise spectrum in Josephson junctions is a consequence of the fluctuation dissipation theorem, while our argument was based on equilibrium statistical mechanics. In this note we show that the fluctuation dissipation relation does not depend upon any shift of vacuum (zero-point) energies, and therefore, as already concluded in our previous paper, dark energy hathing to do with the proposed measurements.
Josephson junctions as heterodyne detectors
International Nuclear Information System (INIS)
Taur, Y.; Claassen, J.H.; Richards, P.L.
Heterodyne detection with a point-contact Josephson junction has been investigated both experimentally and theoretically. The measured performance of the device at 36 GHz is in good agreement with the theory. By operating vanadium point contacts at 1.4 K, the authors have achieved a single-sideband (SSB) mixer noise temperature of 54 K with a conversion gain of 1.35 and a signal bandwidth on the order of 1 GHz. A potentially impressive performance for these devices at submillimeter wavelengths can be extrapolated from the results
Josephson junctions as heterodyne detectors
International Nuclear Information System (INIS)
Taur, Y.; Claassen, J.H.; Richards, P.L.
1974-01-01
Heterodyne detection with a point-contact Josephson junction has been investigated both experimentally and theoretically. The measured performance of the device at 36 GHz is in good agreement with the theory. By operating vanadium point contacts at 1.4 K, a single-sideband (SSB) mixer noise temperature of 54 K with a conversion gain of 1.35 and a signal bandwidth on the order of 1 GHz has been achieved. From the results one can extrapolate a potentially impressive performance for these devices at submillimeter wavelengths
Graphene Josephson Junction Microwave Detector
Fong, Kin Chung; Walsh, Evan; Lee, Gil-Ho; Efetov, Dmitri; Crossno, Jesse; Ranzani, Leonardo; Ohki, Thomas; Kim, Philip; Englund, Dirk
Modern readout schemes for superconducting qubits have predominately relied on weak microwave signal detection and discrimination. Most schemes are based on heterodyne or homodyne receiver systems and only a few have demonstrated direct detection of microwave photons. The challenges of direct detection stem from the low energy of microwave photons and existing detector efficiency. We have designed, fabricated, and measured a graphene-based Josephson junction (gJJ) microwave detector. Exploiting its low electronic thermal conductivity and specific heat, an electron temperature rise on the order of 0.1 K due to a time average of about 10 photons in the graphene thermal photodetector is readout via a Josephson junction embedded in an 8 GHz microwave cavity. We will estimate the quantum efficiency and dark count probability of the gJJ microwave single photon detectors. This document does not contain technology or technical data controlled under either the U.S. International Traffic in Arms Regulations or the U.S. Export Administration Regulations.
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....
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)
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...... integrated submillimeter receiver circuit which comprises a flux-flow oscillator (FFO) as local oscillator, a superconducting variable attenuator, and a microwave SIS detector with tuned-out capacitance is also reported....
Modelling and Analysis of Long Josephson Junctions
Visser, T.P.P.
2002-01-01
For various reasons people have been interested in Josephson junctions. Ranging from "understanding nature" to building quantum computers. In this thesis we focus on a special type of junction (the long junction) and to a special type of problem fluxon dynamics.
Soliton bunching in annular Josephson junctions
DEFF Research Database (Denmark)
Vernik, I.V; Lazarides, Nickos; Sørensen, Mads Peter
1996-01-01
By studying soliton (fluxon) motion in long annular Josephson junctions it is possible to avoid the influence of the boundaries and soliton-soliton collisions present in linear junctions. A new experimental design consisting of a niobium coil placed on top of an annular junction has been used...
Strong Josephson Coupling in Planar Graphene Junctions
Park, Jinho; Lee, Gil-Ho; Lee, Jae Hyeong; Takane, Yositake; Imura, Ken-Ichiro; Taniguchi, Takashi; Watanabe, Kenji; Lee, Hu-Jong
A recent breakthrough of processing graphene, employing encapsulation by hexagonal boron nitride layers (BGB structure), allows realizing the ballistic carrier transport in graphene. Thereafter, ballistic Josephson coupling has been studied by closely edge-contacted BGB structure with two superconducting electrodes. Here, we report on the strong Josephson coupling with planar graphene junction in truly short and ballistic regime. Our device showed high transmission probability and the junction critical current (IC) oscillating for sweeping the gate voltage along with the normal conductance oscillation (Fabry-Perot oscillations), providing a direct evidence for the ballistic nature of the junction pair current. We also observed the convex-upward shape of decreasing critical currents with increasing temperature, canonical properties of the short Josephson coupling. By fitting these curves into theoretical models, we demonstrate the strong Josephson coupling in our devices, which is also supported by the exceptionally large value of ICRN ( 2 Δ / e RNis the normal resistance).
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...... that the detailed behavior of a solitonic mode (fluxon dynamics) in the junction is different from the results of the conventional perturbed sine-Gordon model....
Ballistic Josephson junctions based on CVD graphene
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.
Fast thermometry with a proximity Josephson junction
Wang, L. B.; Saira, O.-P.; Pekola, J. P.
2018-01-01
We couple a proximity Josephson junction to a Joule-heated normal metal film and measure its electron temperature under steady state and nonequilibrium conditions. With a timed sequence of heating and temperature probing pulses, we are able to monitor its electron temperature in nonequilibrium with effectively zero back-action from the temperature measurement in the form of additional dissipation or thermal conductance. The experiments demonstrate the possibility of using a fast proximity Josephson junction thermometer for studying thermal transport in mesoscopic systems and for calorimetry.
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)
Generalized Eck peak in inhomogeneous Josephson junctions
Fistul, Mikhail V.; Giuliani, Gabriele F.
1997-02-01
In inhomogeneous Josephson junctions the Eck peak characterizing the current-voltage characteristics is predicted to be replaced by a rather different yet prominent feature whose location and shape strongly depend on the strength of the applied magnetic field and the spatial correlations of the associated distorted Abrikosov flux lattice.
Phase-dependent noise in Josephson junctions
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.
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...
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...
Intrinsically shunted Josephson junctions for electronics applications
Belogolovskii, M.; Zhitlukhina, E.; Lacquaniti, V.; De Leo, N.; Fretto, M.; Sosso, A.
2017-07-01
Conventional Josephson metal-insulator-metal devices are inherently underdamped and exhibit hysteretic current-voltage response due to a very high subgap resistance compared to that in the normal state. At the same time, overdamped junctions with single-valued characteristics are needed for most superconducting digital applications. The usual way to overcome the hysteretic behavior is to place an external low-resistance normal-metal shunt in parallel with each junction. Unfortunately, such solution results in a considerable complication of the circuitry design and introduces parasitic inductance through the junction. This paper provides a concise overview of some generic approaches that have been proposed in order to realize internal shunting in Josephson heterostructures with a barrier that itself contains the desired resistive component. The main attention is paid to self-shunted devices with local weak-link transmission probabilities that are so strongly disordered in the interface plane that transmission probabilities are tiny for the main part of the transition region between two super-conducting electrodes, while a small part of the interface is well transparent. We discuss the possibility of realizing a universal bimodal distribution function and emphasize advantages of such junctions that can be considered as a new class of self-shunted Josephson devices promising for practical applications in superconducting electronics operating at 4.2 K.
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
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...... measurements were carried out within frequency bands of 1-2 GHz and 0.3-300 kHz. At bias voltages 10 less than or equal to V less than or equal to 60 mV a linear voltage dependence of noise power has been registered, while at V less than or equal to 5 mV a noticeable noise rise has been observed. The latter...
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
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
Internal dynamics of long Josephson junction oscillators
DEFF Research Database (Denmark)
Christiansen, Peter Leth; Lomdahl, P. S.; Scott, Alwyn C.
1981-01-01
Numerical computations on a sine-Gordon model of the Josephson junction fluxon oscillator are compared with experimental measurements. Good agreement is found for the voltage current characteristic, oscillator power output, and range of current bias over which oscillation is observed. Our numeric...... results imply a ''bunched-fluxon'' mode of oscillation at larger values of bias current. Applied Physics Letters is copyrighted by The American Institute of Physics....
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....
Magnetic remanence of Josephson junction arrays
Passos, W. A. C.; Araujo-Moreira, F. M.; Ortiz, W. A.
1999-01-01
In this work we study the magnetic remanence exhibited by Josephson junction arrays in response to an excitation with an AC magnetic field. The effect, predicted by numerical simulations to occur in a range of temperatures, is clearly seen in our tridimensional disordered arrays. We also discuss the influence of the critical current distribution on the temperature interval within which the array develops a magnetic remanence. This effect can be used to determine the critical current distribut...
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
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
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.)
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.)
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.
Ferromagnetic resonance with long Josephson junction
Golovchanskiy, I. A.; Abramov, N. N.; Stolyarov, V. S.; Emelyanova, O. V.; Golubov, A. A.; Ustinov, A. V.; Ryazanov, V. V.
2017-05-01
In this work we propose a hybrid device based on a long Josephson junction (JJ) coupled inductively to an external ferromagnetic (FM) layer. The long JJ in a zero-field operation mode induces a localized AC magnetic field in the FM layer and enables a synchronized magnetostatic standing wave. The magnetostatic wave induces additional dissipation for soliton propagation in the junction and also enables a phase locking (resonant soliton synchronization) at a frequency of natural ferromagnetic resonance. The later manifests itself as an additional constant voltage step on the current-voltage characteristics at the corresponding voltage. The proposed device allows to study magnetization dynamics of individual micro-scaled FM samples using just DC technique, and also it provides additional phase locking frequency in the junction, determined exclusively by characteristics of the ferromagnet.
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
Dissipation and traversal time in Josephson junctions
International Nuclear Information System (INIS)
Cacciari, Ilaria; Ranfagni, Anedio; Moretti, Paolo
2010-01-01
The various ways of evaluating dissipative effects in macroscopic quantum tunneling are re-examined. The results obtained by using functional integration, while confirming those of previously given treatments, enable a comparison with available experimental results relative to Josephson junctions. A criterion based on the shortening of the semiclassical traversal time τ of the barrier with regard to dissipation can be established, according to which Δτ/τ > or approx. N/Q, where Q is the quality factor of the junction and N is a numerical constant of order unity. The best agreement with the experiments is obtained for N=1.11, as it results from a semiempirical analysis based on an increase in the potential barrier caused by dissipative effects.
Spectral Flow in Josephson Junctions and Effective Magnus Force
Makhlin, Yu. G.; Volovik, G. E.
1995-01-01
Momentum production during the phase slip process in SNS Josephson junction is discussed. It is caused by the spectral flow of bound states of fermions localized within the junction. This effectively reduces the Magnus force acting on vortices which provides an explanation for the experimental observation of the negligible Magnus force in 2D Josephson junction arrays. The flow of the fermionic levels is similar to that in sphalerons in particle physics, where it gives rise to the baryogenesis.
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
Simulation of Collective Excitations in Long Josephson Junction Stacks
Rahmonov, Ilhom; Shukrinov, Yury; Atanasova, Pavlina; Zemlyanaya, Elena; Streltsova, Oksana; Zuev, Maxim; Plecenik, Andrej; Irie, Akinobu
2018-02-01
The phase dynamics of a stack of long Josephson junctions has been studied. Both inductive and capacitive couplings between Josephson junctions have been taken into account in the calculations. The IV-curve, the dependence on the bias current of the radiation power and dynamics of each JJs of the stack have been investigated. The coexistence of the charge traveling wave and fluxon states has been observed. This state can be considered as a new collective excitation in the system of coupled Josephson junctions. We demonstrate that the observed collective excitation leads to the decrease of radiation power from the system.
Planar Josephson tunnel junctions in a transverse magnetic field
DEFF Research Database (Denmark)
Monacoa, R.; Aarøe, Morten; Mygind, Jesper
2007-01-01
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...... 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...... magnetic field rather than an in-plane field. The conditions under which this occurs are discussed....
RF assisted switching in magnetic Josephson junctions
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.
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
Negative differential resistance in Josephson junctions coupled to a cavity
DEFF Research Database (Denmark)
Pedersen, Niels Falsig; Filatrella, G.; Pierro, V.
2014-01-01
Regions with negative differential resistance can arise in the IV curve of Josephson junctions and this phenomenon plays an essential role for applications, in particular for THz radiation emission. For the measurement of high frequency radiation from Josephson junctions, a cavity – either internal...... 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...... that very complicated and unexpected interactions take place. This may be useful for the interpretation of experimental measurements of THz radiation from intrinsic Josephson junctions....
Microwave parametric amplifiers using externally pumped Josephson junctions
DEFF Research Database (Denmark)
Sørensen, O. H.; Mygind, Jesper; Pedersen, Niels Falsig
1978-01-01
Externally pumped parametric amplifiers are discussed. Theory and experiments on the singly degenerate parametric amplifier based on a Josephson junction are presented. Advantages and limitations of the singly degenerate and doubly degenerate parametric amplifiers are discussed. Some plans and pr...
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
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...
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
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
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
Negative differential resistance in Josephson junctions coupled to a cavity
Energy Technology Data Exchange (ETDEWEB)
Pedersen, N.F. [Department of Applied Mathematics and Computer Science, Technical University of Denmark, 2800 Kgs. Lyngby (Denmark); Filatrella, G., E-mail: filatrella@unisannio.it [Department of Science and Technology, University of Sannio (Italy); Pierro, V. [Department of Engineering, University of Sannio (Italy); Sørensen, M.P. [Department of Applied Mathematics and Computer Science, Technical University of Denmark, 2800 Kgs. Lyngby (Denmark)
2014-08-15
Highlights: • A simple model for the negative differential resistance observed in JJ arrays. • The N- and S-shape differential resistances are included in JJ models. • A single junction model mimics the behavior of stacks of Josephson junctions. • A peak in the power is linked to the negative differential resistance. • Relevant to model emission in millimeter wave device, e.g. circuits and antennas. - Abstract: Regions with negative differential resistance can arise in the IV curve of Josephson junctions and this phenomenon plays an essential role for applications, in particular for THz radiation emission. For the measurement of high frequency radiation from Josephson junctions, a cavity – either internal 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 that very complicated and unexpected interactions take place. This may be useful for the interpretation of experimental measurements of THz radiation from intrinsic Josephson junctions.
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.
Phase locked fluxon-antifluxon states in stacked Josephson junctions
DEFF Research Database (Denmark)
Carapella, Giovanni; Constabile, Giovanni; Petraglia, Antonio
1996-01-01
Measurements were made on a two-stack long Josephson junction with very similar parameters and electrical access to the thin middle electrode. Mutually phase-locked fluxon-antifluxon states were observed. The observed propagation velocity is in agreement with the theoretical prediction. The I-V c...... in the junctions coexist with fluxons. (C) 1996 American Institute of Physics....
Parametric excitation of plasma oscillations in a Josephson tunnel junction
DEFF Research Database (Denmark)
Bak, Christen Kjeldahl; Kofoed, Bent; Pedersen, Niels Falsig
1975-01-01
Experimental evidence for subharmonic parametric excitation of plasma oscillations in Josephson tunnel junctions is presented. The experiments described are performed by measuring the microwave power necessary to switch a Josephson−tunnel junction biased in the zero−voltage state to a finite−volt......−voltage state. Journal of Applied Physics is copyrighted by The American Institute of Physics....
Processing of Superconductor-Normal-Superconductor Josephson Edge Junctions
Kleinsasser, A. W.; Barner, J. B.
1997-01-01
The electrical behavior of epitaxial superconductor-normal-superconductor (SNS) Josephson edge junctions is strongly affected by processing conditions. Ex-situ processes, utilizing photoresist and polyimide/photoresist mask layers, are employed for ion milling edges for junctions with Yttrium-Barium-Copper-Oxide (YBCO) electrodes and primarily Co-doped YBCO interlayers.
Frequency Windows of Absolute Negative Conductance in Josephson Junctions
Machura, L.; Kostur, M.; Talkner, P.; Hanggi, P.; Luczka, J.
2007-01-01
We report on anomalous conductance in a resistively and capacitively shunted Josephson junction which is simultaneously driven by ac and dc currents. The dependence of the voltage across the junction on the frequency of the ac current shows windows of absolute negative conductance regimes, i.e. for a positive (negative) dc current, the voltage is negative (positive).
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...... numerical simulations, we are able to clearly distinguish between triangular and square vortex lattices and to identify the parameters leading to an in-phase vortex configuration....
Superconducting Coset Topological Fluids in Josephson Junction Arrays
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.
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 curren....... 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...
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
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.
Parametric excitation of plasma oscillations in Josephson Junctions
DEFF Research Database (Denmark)
Pedersen, Niels Falsig; Samuelsen, Mogens Rugholm; Særmark, Knud
1973-01-01
A theory is presented for parametric excitation of plasma oscillations in a Josephson junction biased in the zero voltage mode. A threshold curve for the onset of the parametric excitation is deduced via the stability properties of a Mathieu differential equation obtained by a self...
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...
Self-field effects in Josephson junction arrays
DEFF Research Database (Denmark)
Petraglia, Antonio; Filatrella, G.; Rotoli, G.
1996-01-01
The purpose of this work is to compare the dynamics of arrays of Josephson junctions in the presence of a magnetic field in two different frameworks: the so-called XY frustrated model with no self-inductance and an approach that takes into account the self-field generated by the screening currents...
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 ...
Theory of the singly quasidegenerate Josephson junction parametric amplifier
DEFF Research Database (Denmark)
Sørensen, O.H.; Dueholm, B.; Mygind, Jesper
1980-01-01
A comprehensive account of the theory of the singly quasidegenerate Josephson junction parametric amplifier is given. In this mode the signal and idler frequencies are both approximately equal to half the pump frequency, and hence the signal and idler channels have a common termination. It is shown...
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
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 plays...... the dominant role in determining the shape and stability of the soliton at high velocity. Applied Physics Letters is copyrighted by The American Institute of Physics....
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
Josephson radiation and shot noise of a semiconductor nanowire junction
van Woerkom, David J.; Proutski, Alex; van Gulik, Ruben J. J.; Kriváchy, Tamás; Car, Diana; Plissard, Sébastian R.; Bakkers, Erik P. A. M.; Kouwenhoven, Leo P.; Geresdi, Attila
2017-09-01
We measured the Josephson radiation emitted by an InSb semiconductor nanowire junction utilizing photon-assisted quasiparticle tunneling in an ac-coupled superconducting tunnel junction. We quantify the action of the local microwave environment by evaluating the frequency dependence of the inelastic Cooper-pair tunneling of the nanowire junction and find the zero-frequency impedance Z (0 )=492 Ω with a cutoff frequency of f0=33.1 GHz . We extract a circuit coupling efficiency of η ≈0.1 and a detector quantum efficiency approaching unity in the high-frequency limit. In addition to the Josephson radiation, we identify a shot noise contribution with a Fano factor F ≈1 , consistently with the presence of single electron states in the nanowire channel.
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
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...
Externally pumped millimeter-wave Josephson-junction parametric amplifier
DEFF Research Database (Denmark)
Levinsen, M.T; Pedersen, Niels Falsig; Sørensen, Ole
1980-01-01
A unified theory of the singly and doubly degenerate Josephson-junction parametric amplifier is presented. Experiments with single junctions on both amplifier modes at frequencies 10, 35, and 70 GHz are discussed. Low-noise temperature (∼100 K, single sideband (SSB)) and reasonable gain (∼8 d......B) were obtained at 35 GHz in the singly degenerate mode. On the basis of the theory and experiments, a general procedure for optimizing junction parameters is discussed and illustrated by the specific design of a 100-GHz amplifier....
Fluxon propagation and Fiske steps in long Josephson tunnel junctions
DEFF Research Database (Denmark)
Erné, S. N.; Ferrigno, A.; Parmentier, R. D.
1983-01-01
The dynamical behavior of fluxons propagating in the presence of an applied magnetic field on an overlap-geometry Josephson tunnel junction of length 5λJ having a McCumber βc=5π is studied by numerical integration of the circuit equations of a 50-section lumped RSJ-type (resistive shunted junction......) model. Resonant propagating configurations corresponding to the first and third Fiske steps are found. The fundamental frequencies and power levels of the radiation emitted from one end when the junction is biased on the first and third Fiske steps and on the first zero-field step are comparable...
Measurement of Quantum Phase-Slips in Josephson Junction Chains
Guichard, Wiebke
2011-03-01
Quantum phase-slip dynamics in Josephson junction chains could provide the basis for the realization of a new type of topologically protected qubit or for the implementation of a new current standard. I will present measurements of the effect of quantum phase-slips on the ground state of a Josephson junction chain. We can tune in situ the strength of the phase-slips. These phase-slips are the result of fluctuations induced by the finite charging energy of each junction in the chain. Our measurements demonstrate that a Josephson junction chain under phase bias constraint behaves in a collective way. I will also show evidence of coherent phase-slip interference, the so called Aharonov-Casher effect. This phenomenon is the dual of the well known Aharonov-Bohm interference. In collaboration with I.M. Pop, Institut Neel, C.N.R.S. and Universite Joseph Fourier, BP 166, 38042 Grenoble, France; I. Protopopov, L. D. Landau Institute for Theoretical Physics, Kosygin str. 2, Moscow 119334, Russia and Institut fuer Nanotechnologie, Karlsruher Institut fuer Technologie, 76021 Karlsruhe, Germany; and F. Lecocq, Z. Peng, B. Pannetier, O. Buisson, Institut Neel, C.N.R.S. and Universite Joseph Fourier. European STREP MIDAS, ANR QUANTJO.
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.
Shunted-Josephson-junction model. II. The nonautonomous case
DEFF Research Database (Denmark)
Belykh, V. N.; Pedersen, Niels Falsig; Sørensen, O. H.
1977-01-01
The shunted-Josephson-junction model with a monochromatic ac current drive is discussed employing the qualitative methods of the theory of nonlinear oscillations. As in the preceding paper dealing with the autonomous junction, the model includes a phase-dependent conductance and a shunt capacitance....... The mathematical discussion makes use of the phase-space representation of the solutions to the differential equation. The behavior of the trajectories in phase space is described for different characteristic regions in parameter space and the associated features of the junction IV curve to be expected are pointed...... out. The main objective is to provide a qualitative understanding of the junction behavior, to clarify which kinds of properties may be derived from the shunted-junction model, and to specify the relative arrangement of the important domains in the parameter-space decomposition....
Variability metrics in Josephson Junction fabrication for Quantum Computing circuits
Rosenblatt, Sami; Hertzberg, Jared; Brink, Markus; Chow, Jerry; Gambetta, Jay; Leng, Zhaoqi; Houck, Andrew; Nelson, J. J.; Plourde, Britton; Wu, Xian; Lake, Russell; Shainline, Jeff; Pappas, David; Patel, Umeshkumar; McDermott, Robert
Multi-qubit gates depend on the relative frequencies of the qubits. To reliably build multi-qubit devices therefore requires careful fabrication of Josephson junctions in order to precisely set their critical currents. The Ambegaokar-Baratoff relation between tunnel conductance and critical current implies a correlation between qubit frequency spread and tunnel junction resistance spread. Here we discuss measurement of large numbers of tunnel junctions to assess these resistance spreads, which can exceed 5% of mean resistance. With the goal of minimizing these spreads, we investigate process parameters such as lithographic junction area, evaporation and masking scheme, oxidation conditions, and substrate choice, as well as test environment, design and setup. In addition, trends of junction resistance with temperature are compared with theoretical models for further insights into process and test variability.
Magnetic field behavior of current steps in long Josephson junctions
International Nuclear Information System (INIS)
Costabile, G.; Cucolo, A.M.; Pace, S.; Parmentier, R.D.; Savo, B.; Vaglio, R.
1980-01-01
The zero-field steps, or dc current singularities, in the current-voltage characteristics of long Josephson tunnel junctions, first reported by Chen et al., continue to attract research interest both because their study can provide fundamental information on the dynamics of fluxons in such junctions and because they are accompanied by the emission of microwave radiation from the junction, which may be exploitable in practical oscillator applications. The purpose of this paper is to report some experimental observations of the magnetic field behavior of the steps in junctions fabricated in our Laboratory and to offer a qualitative explanation for this behavior. Measurements have been made both for very long (L >> lambdasub(J)) and for slightly long (L approx. >= lambdasub(J)) junctions with a view toward comparing our results with those of other workers. (orig./WRI)
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.)
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....
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.
0-π phase-controllable thermal Josephson junction
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| 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.
The persistent current and energy spectrum on a driven mesoscopic LC-circuit with Josephson junction
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.
Phase transition in a modified square Josephson-junction array
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.
Charging effects in the inductively shunted Josephson junction.
Koch, Jens; Manucharyan, V; Devoret, M H; Glazman, L I
2009-11-20
The choice of impedance used to shunt a Josephson junction determines if the charge transferred through the circuit is quantized: a capacitive shunt renders the charge discrete, whereas an inductive shunt gives continuous charge. This discrepancy leads to a paradox in the limit of large inductances L. We show that while the energy spectra of the capacitively and inductively shunted junction are vastly different, their high-frequency responses become identical for large L. Inductive shunting thus opens the possibility to observe charging effects unimpeded by charge noise.
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
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)
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
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.
Phase transition in one Josephson junction with a side-coupled magnetic impurity
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.
Theory of the Josephson effect in unconventional superconducting junctions with diffusive barriers
Yokoyama, T.; Tanaka, Y.; Golubov, Alexandre Avraamovitch
2007-01-01
We study theoretically the Josephson effect in junctions based on unconventional superconductors with diffusive barriers, using the quasiclassical Green's function formalism. Generalized boundary conditions at junction interfaces applicable to unconventional superconductors are derived by
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 o...
Josephson spin current in triplet superconductor junctions
Asano, Yasuhiro
2006-01-01
This paper theoretically discusses the spin current in spin-triplet superconductor / insulator / spin-triplet superconductor junctions. At low temperatures, a midgap Andreev resonant state anomalously enhances not only the charge current but also the spin current. The coupling between the Cooper pairs and the electromagnetic fields leads to the Frounhofer pattern in the direct current spin flow in magnetic fields and the alternative spin current under applied bias-voltages.
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......-like ones typical of a homogeneous field. Our findings can be well interpreted in terms of recent theoretical predictions [R. Monaco, J. Appl. Phys. 108, 033906 (2010)] for a uniform magnetic field gradient, leading to Fresnel-like magnetic diffraction patterns. We also show that Fiske resonances can...... be suppressed by an asymmetric magnetic field profile. © 2011 American Institute of Physics....
Noise induced transition in Josephson junction with second harmonic
Bhadra, Nivedita
2018-01-01
We show a noise induced transition in Josephson junction with fundamental as well as second harmonic. A periodically modulated multiplicative colored noise can stabilize an unstable configuration in such a system. The stabilization of the unstable configuration has been captured in the effective potential of the system obtained by integrating out the high frequency components of the noise. This is a classical approach to understand the stability of an unstable configuration due to the presence of such stochasticity in the system and our numerical analysis confirms the prediction from the analytical calculation.
Crises in a driven Josephson junction studied by cell mapping
DEFF Research Database (Denmark)
Sørensen, Mads Peter; Davidson, A.; Pedersen, Niels Falsig
1988-01-01
We use the method of cell-to-cell mapping to locate attractors, basins, and saddle nodes in the phase plane of a driven Josephson junction. The cell-mapping method is discussed in some detail, emphasizing its ability to provide a global view of the phase plane. Our computations confirm...... the existence of a previously reported interior crisis. In addition, we observe a boundary crisis for a small shift in one parameter. The cell-mapping method allows us to show both crises explicitly in the phase plane, at low computational cost....
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...... steps and various sharp switchings (voltage jumps) in the current-voltage characteristics. Moreover, the power of ac oscillations away from the breather center (the breather tail) displays singularities as the externally applied dc bias decreases. All these features may be mapped to the spectrum of EE...
Theoretical Analysis of Josephson Junction Systems and Superconducting Superlattices.
Edis, Taner
Superconducting superlattices and Josephson junction networks provide a context for investigation of various problems related to superconductivity. Aspects of the layered nature of high-T_{c} materials, the statistical mechanics of Josephson junction systems, and the response of granular systems in the presence of a magnetic field are explored. Experiments on superlattices with a structure of alternating layers of superconducting { rm YBa_2Cu_3O}_{7-x } and insulating {rm PrBa _2Cu_3O}_{7-x} exhibit a suppression of the resistive transition temperature T_{c}, depending on layer thicknesses. This behavior can be explained by reduction of the bulk T_{c} through charge redistribution into insulating layers, and a further reduction through the Kosterlitz-Thouless nature of the transition, taking place in the effectively two-dimensional superconducting layers. The statistical mechanics of Josephson junction systems must account for their macroscopic quantum nature, and the "unusual constraints" arising from knowledge of superconducting wave function magnitudes in a steady state. Working with the maximum entropy formulation of statistical mechanics, the equivalence of state-probability level and density matrix quantum information entropy maximization is demonstrated; a state-level approach is then used to enforce the unusual constraint, providing an extension of the standard formalism. A novel physical result is predicted, where in equilibrium, the temperature dependence becomes modified from the usual 1/kT factor. Magnetically Modulated Resistance (MMR) techniques are effective in experimentally determining the quality of superconducting samples, in particular when weak links are present in granular materials. The weak link component of the MMR response can be explained using numerical studies of a disordered network of non-ideal Josephson junctions, where the non-linear oscillations in the macroscopic grain phases is simulated, in order to obtain the voltage across the
Crises in a driven Josephson junction studied by cell mapping
International Nuclear Information System (INIS)
Soerensen, M.P.; Davidson, A.; Pedersen, N.F.; Pagano, S.
1988-01-01
We use the method of cell-to-cell mapping to locate attractors, basins, and saddle nodes in the phase plane of a driven Josephson junction. The cell-mapping method is discussed in some detail, emphasizing its ability to provide a global view of the phase plane. Our computations confirm the existence of a previously reported interior crisis. In addition, we observe a boundary crisis for a small shift in one parameter. The cell-mapping method allows us to show both crises explicitly in the phase plane, at low computational cost
Electron-beam damaged high-temperature superconductor Josephson junctions
International Nuclear Information System (INIS)
Pauza, A.J.; Booij, W.E.; Herrmann, K.; Moore, D.F.; Blamire, M.G.; Rudman, D.A.; Vale, L.R.
1997-01-01
Results are presented on the fabrication and characterization of high critical temperature Josephson junctions in thin films of YBa 2 Cu 3 O 7-δ produced by the process of focused electron-beam irradiation using 350 keV electrons. The junctions so produced have uniform spatial current densities, can be described in terms of the resistive shunted junction model, and their current densities can be tailored for a given operating temperature. The physical properties of the damaged barrier can be described as a superconducting material of either reduced or zero critical temperature (T c ), which has a length of ∼15nm. The T c reduction is caused primarily by oxygen Frenkel defects in the Cu - O planes. The large beam currents used in the fabrication of the junctions mean that the extent of the barrier is limited by the incident electron-beam diameter, rather than by scattering within the film. The properties of the barrier can be calculated using a superconductor/normal/superconductor (SNS) junction model with no boundary resistance. From the SNS model, we can predict the scaling of the critical current resistance (I c R n ) product and gain insight into the factors controlling the junction properties, T c , and reproducibility. From the measured I c R n scaling data, we can predict the I c R n product of a junction at a given operating temperature with a given current density. I c R n products of ∼2mV can be achieved at 4.2 K. The reproducibility of several junctions in a number of samples can be characterized by the ratio of the maximum-to-minimum critical currents on the same substrate of less than 1.4. Stability over several months has been demonstrated at room and refrigerator temperatures (297 and 281 K) for junctions that have been initially over damaged and then annealed at temperatures ∼380K. (Abstract Truncated)
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
Experiments on soliton motion in annular Josephson junctions
DEFF Research Database (Denmark)
Davidson, A.; Dueholm, B.; Pedersen, Niels Falsig
1986-01-01
We report here the results of an extensive experimental investigation of soliton dynamics in Josephson junctions of different annular geometries. The annular geometry is unique in that it allows for the study of undisturbed soliton motion as well as soliton–antisoliton collisons, since...... there are no boundary effects. We have successfully trapped a single soliton in an annular junction and found good agreement with perturbation theory at low soliton velocity, and evidence of departure from perturbation theory at higher velocity. We also discuss the observation of fine structure on the I-V curve...... for a single trapped soliton, and evidence linking the stability of the soliton to surface damping. Journal of Applied Physics is copyrighted by The American Institute of Physics....
Doubled Shapiro steps in a topological Josephson junction
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.
Ultralow power artificial synapses using nanotextured magnetic Josephson junctions
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
Chaos and related nonlinear noise phenomena in Josephson tunnel junctions
International Nuclear Information System (INIS)
Miracky, R.F.
1984-07-01
The nonlinear dynamics of Josephson tunnel junctions shunted by a resistance with substantial self-inductance have been thoroughly investigated. The current-voltage characteristics of these devices exhibit stable regions of negative differential resistance. Very large increases in the low-frequency voltage noise with equivalent noise temperatures of 10 6 K or more, observed in the vicinity of these regions, arise from switching, or hopping, between subharmonic modes. Moderate increases in the noise, with temperatures of about 10 3 K, arise from chaotic behavior. Analog and digital simulations indicate that under somewhat rarer circumstances the same junction system can sustain a purely deterministic hopping between two unstable subharmonic modes, accompanied by excess low-frequency noise. Unlike the noise-induced case, this chaotic process occurs over a much narrower range in bias current and is destroyed by the addition of thermal noise. The differential equation describing the junction system can be reduced to a one-dimensional mapping in the vicinity of one of the unstable modes. A general analytical calculation of switching processes for a class of mappings yields the frequency dependence of the noise spectrum in terms of the parameters of the mapping. Finally, the concepts of noise-induced hopping near bifurcation thresholds are applied to the problem of the three-photon Josephson parametric amplifier. Analog simulations indicate that the noise rise observed in experimental devices arises from occasional hopping between a mode at the pump frequency ω/sub p/ and a mode at the half harmonic ω/sub p//2. The hopping is induced by thermal noise associated with the shunt resistance. 71 references
DEFF Research Database (Denmark)
Krasnov, V.M.; Oboznov, V.A.; Pedersen, Niels Falsig
1997-01-01
self-energy (from the cold to the hot end of the junction). A phenomenon, the ''zero crossing flux flow step'' (ZCFFS) with a nonzero voltage at a zero applied current, was observed in nonuniform long Josephson junctions. The phenomenon is due to the existence of a preferential direction...... for the Josephson vortex motion. ZCFFS's were observed at certain magnetic fields when the critical current in one direction but not the other becomes zero. Possible applications of nonuniform Josephson junctions in flux flow oscillators and as a superconducting diode are discussed....
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
Proximity effect Nb/Al,AlOxide, Al/Nb Josephson tunnel junctions
Houwman, Evert Pieter; Gijsbertsen, J.G.; Gijsbertsen, Hans; Flokstra, Jakob; Rogalla, Horst; Le grand, J.B.; de Korte, P.A.J.; Golubov, Alexandre Avraamovitch
1993-01-01
Regions with reduced energy gap induced by the proximity effect give rise to quasi-particle loss in Josephson-junction X-ray detectors, but may also be used advantageously for quasi-particle collection. The influence of the thickness of the Al proximity layers in Nb/Al1 , AlOx, Al2/Nb Josephson
Search for the in-phase Flux Flow mode in stacked Josephson junctions
DEFF Research Database (Denmark)
Pedersen, Niels Falsig; Madsen, Søren Peder
2006-01-01
Josephson vortex flux flow states in stacked Josephson junctions are investigated numerically. The aim of the work is to understand the mechanisms behind the formation of triangular (anti-phase) and square (in-phase) vortex lattices, and is motivated by recent experiments on layered BSCCO type hi...
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.
Short Ballistic Josephson Coupling in Planar Graphene Junctions with Inhomogeneous Carrier Doping
Park, Jinho; Lee, Jae Hyeong; Lee, Gil-Ho; Takane, Yositake; Imura, Ken-Ichiro; Taniguchi, Takashi; Watanabe, Kenji; Lee, Hu-Jong
2018-02-01
We report on short ballistic (SB) Josephson coupling in junctions embedded in a planar heterostructure of graphene. Ballistic Josephson coupling is confirmed by the Fabry-Perot-type interference of the junction critical current Ic . The product of Ic and the normal-state junction resistance RN , normalized by the zero-temperature gap energy Δ0 of the superconducting electrodes, turns out to be exceptionally large close to 2, an indication of strong Josephson coupling in the SB junction limit. However, Ic shows a temperature dependence that is inconsistent with the conventional short-junction-like behavior based on the standard Kulik-Omel'yanchuk prediction. We argue that this feature stems from the effects of inhomogeneous carrier doping in graphene near the superconducting contacts, although the junction is in fact in the short-junction limit.
Fabrication of high-quality Josephson junctions for applications as particle detectors
International Nuclear Information System (INIS)
Cristiano, R.; Frunzio, L.; Pagano, S.; Spina, G.
1997-01-01
The use of Josephson junctions as particle detectors requires, besides high quality of the tunnel characteristics, special geometrical configurations, and fabrication processes. A new fabrication process for Josephson junctions is presented. 'Island' geometry junctions with rhomboid shape (in order to minimize the magnetic field necessary to suppress the critical current) have been fabricated with a special Si O 'bridge' that minimized the overlap area between the insulating layer and the junction. The measured junctions exhibit high levels of tunneling quality (V m = 91 mV at T = 4.2 K)
High-performance passive microwave survey on Josephson junctions
International Nuclear Information System (INIS)
Denisov, A.G.; Radzikhovsky, V.N.; Kudeliya, A.M.
1994-01-01
The quasi-optical generations of image of objects with their internal structure in millimeter (MM) and submillimeter (SMM) bands is one of the prime problems of modern radioelectronics. The main advantage of passive MM imaging systems in comparison with visible and infrared (IR) systems is small attenuation of signals in fog, cloud, smoke, dust and other obscurants. However at a panoramic scanning of space the observation time lengthens and thereby the information processing rate becomes restricted. So that single-channel system cannot image in real time. Therefore we must use many radiometers in parallel to reduce the observation time. Such system must contain receiving sensors as pixels in multibeam antenna. The use of Josephson Junctions (JJ) for this purpose together with the cryoelectronic devices like GaAs FET or SQUIDS for signal amplifications after JJ is of particular interest in this case
A supersymmetric phase transition in Josephson-tunnel-junction arrays
International Nuclear Information System (INIS)
Foda, O.
1988-01-01
The fully frustrated XY model in two dimensions exhibits a vortex-unbinding as well as an Ising transition. If the Ising transition overlaps with the critical line that ends on the vortex transition: T I ≤T V , then the model is equivalent, at the overlap temperature, to a free massless field theory of 1 boson and 1 Majorana fermion, which is a superconformal field theory, of central charge c=3/2. The model is experimentally realized in terms of an array of Josephson-tunnel junctions in a transverse magnetic field. The experiment reveals a phase transition consistent with T I =T V . Thus, at the critical temperature, the array provides a physical realization of a supersymmetric quantum field theory. (orig.)
Supersymmetric phase transition in Josephson-tunnel-junction arrays
Energy Technology Data Exchange (ETDEWEB)
Foda, O.
1988-08-31
The fully frustrated XY model in two dimensions exhibits a vortex-unbinding as well as an Ising transition. If the Ising transition overlaps with the critical line that ends on the vortex transition: T/sub I/less than or equal toT/sub V/, then the model is equivalent, at the overlap temperature, to a free massless field theory of 1 boson and 1 Majorana fermion, which is a superconformal field theory, of central charge c=3/2. The model is experimentally realized in terms of an array of Josephson-tunnel junctions in a transverse magnetic field. The experiment reveals a phase transition consistent with T/sub I/=T/sub V/. Thus, at the critical temperature, the array provides a physical realization of a supersymmetric quantum field theory.
Positional disorder in a Josephson-junction array
International Nuclear Information System (INIS)
Choi, M.Y.; Chung, J.S.; Stroud, D.
1987-01-01
The effects of positional disorder on the critical behavior of a two-dimensional Josephson-junction array in a magnetic field are investigated both analytically and numerically. The standard replica method is used to analyze this disordered system, which is a physical realization of the two-dimensional gauge glass. It is shown that in the fully frustrated case, weak positional disorder does not change the critical behavior of the pure system although the critical temperature is lowered. Numerical simulations show that the sharpness of the transition is indeed preserved under weak positional disorder. For sufficiently strong disorder, evidence of the transition disappears from the Monte Carlo simulations. Evidence for or against a reentrant transition at low temperature is inconclusive
Determination of the dissipation in superconducting Josephson junctions
Energy Technology Data Exchange (ETDEWEB)
Mugnai, D., E-mail: d.mugnai@ifac.cnr.it; Ranfagni, A.; Cacciari, I. [“Nello Carrara” Institute of Applied Physics, CNR Florence Research Area, Via Madonna del Piano 10, 50019 Sesto Fiorentino, Florence (Italy)
2015-02-07
The results relative to macroscopic quantum tunneling rate, out of the metastable state of Josephson junctions, are examined in view of determining the effect of dissipation. We adopt a simple criterion in accordance to which the effect of dissipation can be evaluated by analyzing the shortening of the semiclassical traversal time of the barrier. In almost all the considered cases, especially those with relatively large capacitance values, the relative time shortening turns out to be about 20% and with a corresponding quality factor Q ≃ 5.5. However, beyond the specific cases here considered, still in the regime of moderate dissipation, the method is applicable also to different situations with different values of the quality factor. The method allows, within the error limits, for a reliable determination of the load resistance R{sub L}, the less accessible quantity in the framework of the resistively and capacitively shunted junction model, provided that the characteristics of the junction (intrinsic capacitance, critical current, and the ratio of the bias current to the critical one) are known with sufficient accuracy.
Resonant tunneling in small current-biased Josephson Junctions
Energy Technology Data Exchange (ETDEWEB)
Schmidt, John Mark [Univ. of California, Berkeley, CA (United States)
1994-05-01
Effects of resonant tunneling between bound quantum states of a current-biased Josephson tunnel junction is studied both theoretically and experimentally. Several effects are predicted to arise from resonant tunneling, including a series of voltage peaks along the supercurrent branch of the current-voltage characteristic, and enhanced rate of escape from zero voltage state to voltage state at particular values of bias current. A model is developed to estimate magnitude and duration of voltage peaks, and to estimate enhancement of the escape rate, which appears as peaks in the rate as a function of bias current. An experimental investigation was carried out in an attempt to observe these predicted peaks in the escape rate distribution in a current-biased DC SQUID, which is shown to be dynamically equivalent to a Josephson junction with adjustable critical current. Electrical contact to each SQUID (fabricated from aluminium) was made through high resistance thin film leads located on the substrate. These resistors provided a high impedance at the plasma frequency which is for the isolation of the SQUID from its electromagnetic environment. Measurements were carried out on a dilution refrigerator at temperatures as low as 19 mK. No evidence was found for resonant tunneling; this is attributed to effective temperatures of hundreds of millikelvin. The behavior is well explained by a heating model where the high effective temperatures are generated by ohmic heating of the electron gas of the isolation resistors, which decouples from the phonon system (hot electron effect). The prospects for further theoretical and experimental research are discussed.
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 a l...... a large-amplitude microwave signal is emitted at fp provided the input power exceeds a threshold value. The results are compared to existing theory. Applied Physics Letters is copyrighted by The American Institute of Physics.......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...
Maximum supercurrent in two Josephson-junction stacks: Theory and experiment
DEFF Research Database (Denmark)
Carapella, G; Costabile, G; Sakai, S
1998-01-01
The interaction between two long Josephson junctions in a stack is investigated experimentally in the absence of applied magnetic field. Mutual interaction is observed when both junctions or only one junction in the stack is in the zero voltage state. To account for the observed phenomena we...... propose a model that takes into account the nonuniform self-fields generated by the bias currents....
Mutual Phase Locking of Fluxons in Stacked Long Josephson Junctions: Simulations and Experiment
DEFF Research Database (Denmark)
Carapella, Giovanni; Costabile, Giovanni; Filatrella, Giovanni
1997-01-01
We report on the experimental observation of reciprocal phase-locking in stacked $Nb-AlO_x-Nb$ Josephson junctions having overlap geometry. When the junctions are independently biased in zero external magnetic field, they each exhibit several Zero Field Steps. Biasing both the junctions on the Ze...
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
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 might...... be as low as the physical temperature in the temperature range investigated. This makes it possible to use the resistively shunted junction (RSJ) model with thermal fluctuations to get a limiting performance of high-T c devices utilizing the AC Josephson effect. The lowest value of the linewidth of 72 GHz...
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
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.)
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
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.
Is there a relationship between curvature and inductance in the Josephson junction?
Dobrowolski, T.; Jarmoliński, A.
2018-03-01
A Josephson junction is a device made of two superconducting electrodes separated by a very thin layer of isolator or normal metal. This relatively simple device has found a variety of technical applications in the form of Superconducting Quantum Interference Devices (SQUIDs) and Single Electron Transistors (SETs). One can expect that in the near future the Josephson junction will find applications in digital electronics technology RSFQ (Rapid Single Flux Quantum) and in the more distant future in construction of quantum computers. Here we concentrate on the relation of the curvature of the Josephson junction with its inductance. We apply a simple Capacitively Shunted Junction (CSJ) model in order to find condition which guarantees consistency of this model with prediction based on the Maxwell and London equations with Landau-Ginzburg current of Cooper pairs. This condition can find direct experimental verification.
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 Am...
Static semifluxons in a long Josephson junction with π-discontinuity points
Susanto, H.; van Gils, Stephanus A.; Visser, T.P.P.; Ariando, A.; Smilde, H.J.H.; Hilgenkamp, Johannes W.M.
2003-01-01
We investigate analytically a long Josephson junction with several $\\pi$-discontinuity points characterized by a jump of $\\pi$ in the phase difference of the junction. The system is described by a perturbed-combined sine-Gordon equation. Via phase-portrait analysis, it is shown how the existence of
Energy Technology Data Exchange (ETDEWEB)
Wendt, J.R.; Tigges, C.P.; Hietala, V.M.; Plut, T.A. [Sandia National Labs., Albuquerque, NM (United States); Martens, J.S.; Char, K.; Johansson, M.E. [Conductus, Inc., Sunnyvale, CA (United States)
1994-03-01
A well-controlled, high-yield Josephson junction process in high temperature superconductors (HTS) is necessary for the demonstration of ultra-high-speed devices and circuits which exceed the capabilities of conventional electronics. The authors developed nanobridge Josephson junctions in high quality thin-film YBaCuO with dimensions below 100 nm fabricated using electron-beam nanolithography. They characterized this Josephson junction technology for process yield, junction parameter uniformity, and overall applicability for use in high-performance circuits. To facilitate the determination of junction parameters, they developed a measurement technique based on spectral analysis in the range of 90--160 GHz of phase-locked, oscillating arrays of up to 2,450 Josephson junctions. Because of the excellent yield and uniformity of the nanobridge junctions, they successfully applied the junction technology to a wide variety of circuits. These circuits included transmission-line pulse formers and 32 and 64-bit shift registers. The 32-bit shift register was shown to operate at clock speeds near 100 GHz and is believed to be one of the faster and more complex digital circuit demonstrated to date using high temperature superconductor technology.
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...
Experimental Evidence for Phase-Locked States in Stacked Long Josephson Junctions
DEFF Research Database (Denmark)
Carapella, Giovanni; Costabile, Giovanni; Mancher, Martin
1997-01-01
We fabricated and tested samples consisteing of two long stacked Josephson junctions with direct access to the intermediate electrode, whose thickness is smaller than the London penetration depth $\\lambda _L$. The electrodes are patterned so that the junctions can be idependently biased in the ov...
Oxide superconductor Josephson junction and fabrication method therefor
Energy Technology Data Exchange (ETDEWEB)
Enomoto, Y.; Inamura, T.; Inukai, T.; Murakami, T.; Suzuki, M.
1982-02-23
A tunneling Josephson junction is disclosed in which first and second superposed superconducting electrode layers are formed of thin films of oxide superconducting materials having a perovskite structure of bapb1-xbixo3. A barrier layer interposed between these superconducting electrode layers is a thin film of long service life which is stable and breakdown free under heat cycles from room temperature to ultra low temperatures. This film is made of an oxide with perovskite structure which has the same crystal structure and thermal expansion coefficient as those of the first and second superconducting layers for functioning as an insulator or a semiconductor. The oxide with perovskite structure may be BAsNo3, BA1-YSrYPb1-XBiXo3 (Wherein 0 < or = X < or = 0.3, y>0.3) or BaPb1-X(A1-YBiY)o3 (Wherein a is at least one member selected from the group consisting of V, Nb, Ta and Sb; 0.1 < or = X < or = 0.3; and 0 < or = Y < or = 0.5).
Fluxons in a triangular set of coupled long Josephson junctions
Energy Technology Data Exchange (ETDEWEB)
Yukon, Stanford P., E-mail: yukon@alum.mit.edu [Air Force Research Laboratory (United States); Malomed, Boris A. [Department of Physical Electronics, School of Electrical Engineering, Faculty of Engineering, Tel Aviv University, Tel Aviv 69978 (Israel)
2015-09-15
We report results of an analysis of the dynamics of magnetic flux solitons in the system of three long Josephson junctions between three bulk superconductors that form a prism. The system is modeled by coupled sine-Gordon equations for the phases of the junctions. The Aharonov-Bohm constraint takes into account the axial magnetic flux enclosed by the prism and reduces the system from three independent phases to two. The equations of motion for the phases include dissipative terms, and a control parameter δ which accounts for the deviation of the enclosed flux from half a quantum. Analyzing the effective potential of the coupled equations, we identify different species of topological and non-topological phase solitons (fluxons) in this system. In particular, subkinks with fractional topological charges ±1/3 and ±2/3, confined inside integer-charge fluxons, may be mapped onto the root diagrams for mesons and baryons in the original quark model of hadrons. Solutions for straight-line kinks and for two types of non-topological solitons are obtained in an explicit analytical form. Numerical tests demonstrate that the former species is unstable against breakup into pairs of separating single-fluxon kinks. The non-topological kinks feature metastability, eventually breaking up into fluxon-antifluxon pairs. Free fractional-fluxon kinks, that connect different potential minima and are, accordingly, pulled by the potential difference, are also considered. Using the momentum-balance method, we predict the velocity at which these kinks should move in the presence of the dissipation. Numerical tests demonstrate that the analysis predicts the velocity quite closely. Higher-energy static solutions for all of the stable kink types mentioned above, as well as kinks connecting false vacua, are found by means of the shooting method. Inelastic collisions among the stable fractional and single-fluxon kinks are investigated numerically.
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
Instanton glass generated by noise in a Josephson-junction array.
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.
Experimental study of macroscopic quantum tunnelling in Bi2212 intrinsic Josephson junctions
International Nuclear Information System (INIS)
Matsumoto, Tetsuro; Kashiwaya, Hiromi; Shibata, Hajime; Kashiwaya, Satoshi; Kawabata, Shiro; Eisaki, Hiroshi; Yoshida, Yoshiyuki; Tanaka, Yukio
2007-01-01
The quantum dynamics of Bi 2 Sr 2 CaCu 2 O 8+δ intrinsic Josephson junctions (IJJs) is studied based on escape rate measurements. The saturations observed in the escape temperature and in the width of the switching current below 0.5 K (= T * ) indicate the transition of the switching mechanism from thermal activation to macroscopic quantum tunnelling. It is shown that the switching properties are consistently explained in terms of the underdamped Josephson junction with a quality factor of 70 ± 20 in spite of possible damping due to the nodal quasiparticles of d-wave superconductivity. The present result gives the upper limit of the damping of IJJs
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
Nanometer-scale patterning of high-Tc superconductors for Josephson junction-based digital circuits
International Nuclear Information System (INIS)
Wendt, J.R.; Plut, T.A.; Corless, R.F.; Martens, J.S.; Berkowitz, S.; Char, K.; Johansson, M.; Hou, S.Y.; Phillips, J.M.
1994-01-01
A straightforward method for nanometer-scale patterning of high-T c superconductor thin films is discussed. The technique combines direct-write electron beam lithography with well-controlled aqueous etches and is applied to the fabrication of Josephson junction nanobridges in high-quality, epitaxial thin-film YBa 2 Cu 3 O 7 . We present the results of our studies of the dimensions, yield, uniformity, and mechanism of the junctions along with the performance of a representative digital circuit based on these junctions. Direct current junction parameter statistics measured at 77 K show critical currents of 27.5 μA±13% for a sample set of 220 junctions. The Josephson behavior of the nanobridge is believed to arise from the aggregation of oxygen vacancies in the nanometer-scale bridge
Characterization of Nb/AlOx-Al/Nb Josephson junctions by anodization profiles
International Nuclear Information System (INIS)
Imamura, T.; Hasuo, S.
1989-01-01
The thin tunneling barrier in a Nb/AlO x -Al/Nb Josephson junction was characterized by anodization profiles. Our studies focused on Nb/AlO x and Al/Nb interfaces in Nb/AlO x -Al/Nb junctions made by varying certain process parameters. The interface quality was checked by the anodization profiles and was greatly affected by film thickness, layer sequence, annealing treatment, and the existence of a thin oxide. By comparing the profiles with the junction characteristics measured at 4.2 K, we confirmed that the interface sharpness in the profiles is related to the junction quality. The anodization profile is a useful tool to diagnose the tunneling barrier interfaces in Nb/AlO x -Al/Nb Josephson junctions, especially at room temperature during fabrication
International Nuclear Information System (INIS)
Abal'osheva, I.; Lewandowski, S.J.
2004-01-01
It is shown that the inclusion of junctions characterized by non-sinusoidal current - phase relationship in the systems composed of multiple Josephson junctions - results in the appearance of additional system phase states. Numerical simulations and stability considerations confirm that those phase states can be realized in practice. Moreover, spontaneous formation of the grain boundary junctions in high-T c superconductors with non-trivial current-phase relations due to the d-wave symmetry of the order parameter is probable. Switching between the phase states of multiple grain boundary junction systems can lead to additional 1/f noise in high-T c superconductors. (author)
Stability analysis of pi-kinks in a 0-pi Josephson junction
G. Derks (Gianne); A. Doelman (Arjen); S.A. van Gils; H. Susanto
2006-01-01
textabstractWe consider a spatially non-autonomous discrete sine-Gordon equation with constant forcing and its continuum limit(s) to model a 0-pi Josephson junction with an applied bias current. The continuum limits correspond to the strong coupling limit of the discrete system. The non-autonomous
Stability Analysis of pi-Kinks in a 0-pi Josephson Junction
Derks, G.; Doelman, A.; van Gils, S.A.; Susanto, H.
2007-01-01
Abstract We consider a spatially nonautonomous discrete sine-Gordon equation with constant forcing and its continuum limit(s) to model a 0-pi Josephson junction with an applied bias current. The continuum limits correspond to the strong coupling limit of the discrete system. The nonautonomous
Criteria for fluxon generation in long Josephson junctions by current pulses
DEFF Research Database (Denmark)
Sakai, S.; Samuelsen, Mogens Rugholm
1987-01-01
In recent measurements in the time domain on the fluxon shape in long Josephson junctions the fluxons were generated by a current pulse injected into one end. We present here a perturbation treatment of the fluxon generation which we compare with numerical experiments. The agreement turns out to ...... to be excellent. Applied Physics Letters is copyrighted by The American Institute of Physics....
Subharmonic generation in Josephson junction fluxon oscillators biased on Fiske steps
DEFF Research Database (Denmark)
Sørensen, Mads Peter; Christiansen, Peter Leth; Parmentier, R. D.
1983-01-01
Numerical integration of the perturbed sine-Gordon equation describing a long overlap-geometry Josephson junction in a magnetic field indicates a branched structure of the first Fiske step. The major portion of the step corresponds to a simply periodic fluxon oscillation whereas the branches are ...... are characterized by subharmonic generation. Applied Physics Letters is copyrighted by The American Institute of Physics....
Study of correlation and autocorrelation of supercurrent and charge in stacked Josephson junctions
Directory of Open Access Journals (Sweden)
M Hamdipour
2010-09-01
Full Text Available Charge creation in superconductor layers affects current–voltage characteristics (CVC of the Josephson junction array and creates a breakpoint region in CVC. This charge may oscillate in the form of longitudinal plasma wave, (LPW, or nonregularity. In this paper we intend to distinguish the region with LPW from the nonregular region.
Parameter dependence of homoclinic solutions in a single long Josephson junction
van den Berg, J.B.; van Gils, Stephanus A.; Visser, T.P.P.
2003-01-01
For a model of the long Josephson junction one can calculate for which parameter values there exists a homoclinic solution (fluxon solution). These parameter values appear to lie on a spiral. We show that this is a consequence of the presence of a heteroclinic solution, which lies at the centre of
Van Heck, B.; Mi, S.; Akhmerov, A.R.
2014-01-01
We show how the superconducting phase difference in a Josephson junction may be used to split the Kramers degeneracy of its energy levels and to remove all the properties associated with time-reversal symmetry. The superconducting phase difference is known to be ineffective in two-terminal short
DEFF Research Database (Denmark)
Filatrella, G; Pedersen, Niels Falsig
1999-01-01
We have numerically investigated the behavior of stacks of long Josephson junctions considering a nonuniform bias profile. In the presence of a microwave field the nonuniform bias, which favors the formation of fluxons, can give rise to a change of the sequence of radio-frequency induced steps...
Prediction of chaos in a Josephson junction by the Melnikov-function technique
DEFF Research Database (Denmark)
Bartuccelli, M.; Christiansen, Peter Leth; Pedersen, Niels Falsig
1986-01-01
The Melnikov function for prediction of Smale horseshoe chaos is applied to the rf-driven Josephson junction. Linear and quadratic damping resistors are considered. In the latter case the analytic solution including damping and dc bias is used to obtain an improved threshold curve for the onset...
Phase transitions of Josephson-tunnel-junction arrays at zero and full frustration
Wees, B.J. van; Zant, H.S.J. van der; Mooij, J.E.
1987-01-01
We have fabricated and studied square two-dimensional arrays of Josephson oxide tunnel junctions. Remarkable structure is observed in the longitudinal and transverse resistance as a function of a perpendicular magnetic field. The linear and nonlinear resistance have been measured for f=0 and f=½,
Dependence of fluxon dynamics on loaded terminations in long overlap Josephson junctions
DEFF Research Database (Denmark)
Olsen, O.H.; Samuelsen, Mogens Rugholm
1983-01-01
Fluxon motion in long overlap-geometry Josephson junctions influenced by loaded terminations is investigated. The combination of results from a perturbation method with an approximate expression for the emitted power yields equations describing the fluxon dynamics. The form of the first zero fiel...
Kink propagation and trapping in a two-dimensional curved Josephson junction
DEFF Research Database (Denmark)
Gorria, Carlos; Gaididei, Yuri Borisovich; Sørensen, Mads Peter
2004-01-01
for Josephson junctions of overlap type. A collective variable approach based on the kink position and the kink width depending on the transversal coordinate is developed. The latter allows to take into account both longitudinal and centrifugal forces which act on the nonlinear excitation moving in a region...
International Nuclear Information System (INIS)
Vdovichev, S.N.; Gribkov, B.A.; Gusev, S.A.; Il'ichev, E.; Nozdrin, Yu.N.; Pakhomov, G.L.; Samokhvalov, A.V.; Stolz, R.; Fraerman, A.A.
2006-01-01
The effect of an array of ferromagnetic nanoparticles on the field-dependent critical current of the short overlap Josephson junction is experimentally studied. Large reversible variations of the maximum critical current are observed depending on the magnetic state of the particles. The pronounced commensurability effects are detected which are proved by the additional peaks of magnetic field induced diffraction pattern
High-Q cavity-induced fluxon bunching in inductively coupled Josephson junctions
DEFF Research Database (Denmark)
Madsen, S.; Grønbech-Jensen, Niels; Pedersen, Niels Falsig
2008-01-01
We consider fluxon dynamics in a stack of inductively coupled long Josephson junctions connected capacitively to a common resonant cavity at one of the boundaries. We study, through theoretical and numerical analyses, the possibility for the cavity to induce a transition from the energetically...
Microwave oscillator based on an intrinsic BSCCO-type Josephson junction
DEFF Research Database (Denmark)
Pedersen, Niels Falsig; Madsen, Søren Peder
2005-01-01
The electrical behavior of anisotropic BSCCO single crystals is modeled by mutually coupled long Josephson junctions. For the basic fluxon modes with one fluxon per layer, the fluxons will arrange themselves in an anti phase configuration (triangular lattice) because of the mutual repulsion. We a...
Noise properties of dc-SQUID with quasiplanar YBa2Cu3O7 Josephson junctions
Faley, M.I.; Poppe, U.; Urban, K.; Hilgenkamp, Johannes W.M.; Hemmes, Herman K.; Aarnink, W.A.M.; Aarnink, W.; Flokstra, Jakob; Rogalla, Horst
1995-01-01
We describe the noise performance of dc SQUIDs fabricated with quasiplanar ramp‐type Josephson junctions on the basis of c‐axis‐oriented YBa2Cu3O7/PrBa2Cu3O7 thin‐film heterostructures. The noise spectrum of the dc SQUIDs was measured with dc‐ and ac‐bias schemes at different temperatures and showed
Testing the kibble-zurek scenario with annular josephson tunnel junctions
Kavoussanaki; Monaco; Rivers
2000-10-16
In parallel with Kibble's description of the onset of phase transitions in the early Universe, Zurek has provided a simple picture for the onset of phase transitions in condensed matter systems, supported by agreement with experiments in 3He and superconductors. We show how experiments with annular Josephson tunnel junctions can, and do, provide further support for this scenario.
Storage and detection of a single flux quantum in Josephson junction devices
International Nuclear Information System (INIS)
Gueret, P.
1975-01-01
It is shown both by computer simulations and experimentally that a single Josephson junction has memory and can therefore be used for information storage. Means of reading-out the information content of such a memory element are demonstrated. Finally, memory operation, writing and reading, is described as a direct application of these concepts
Quench-induced trapping of magnetic flux in annular Josephson junctions
DEFF Research Database (Denmark)
Aarøe, Morten; Monaco, R.; Rivers, R.
2008-01-01
The aim of the project is to investigate spontaneous symmetry breaking in non-adiabatic phase transitions (Kibble-Zurek processes). A long and narrow annular Josephson tunnel junction is subjected to repeated thermal quenches through the normal-superconducting transition. The quench rate is varied...
Static and dynamic properties of fluxons in a zig-zag 0-π Josephson junction
Susanto, H.; Darminto, D.; Darminto, [Unknown; van Gils, Stephanus A.
2007-01-01
We consider a long Josephson junction with alternating 0- and $\\pi$-facets with different facet lengths between the 0- and the $\\pi$-parts. Depending on the combinations between the 0- and the $\\pi$-facet lengths, an antiferromagnetically ordered semifluxons array can be the ground state of the
Stability analysis of π-kinks in a 0-π Josephson junction
Derks, G.; Doelman, A.; van Gils, Stephanus A.; Susanto, H.
2007-01-01
We consider a spatially nonautonomous discrete sine-Gordon equation with constant forcing and its continuum limit(s) to model a 0-$\\pi$ Josephson junction with an applied bias current. The continuum limits correspond to the strong coupling limit of the discrete system. The nonautonomous character is
Fluxon motion in long overlap and in-line Josephson junctions
DEFF Research Database (Denmark)
Levring, O. A.; Pedersen, Niels Falsig; Samuelsen, Mogens Rugholm
1982-01-01
The motion of a single fluxon in long Josephson junctions of the overlap and inline geometries is investigated. It is concluded that if the junction is long and the damping is not too large then zero-field steps exist also in the inline junction. Thee zero-field steps are found to be mathematical...... identical to those of the overlap junctions in spite of the fact that the fluxon dynamics are quite different in the two cases. Applied Physics Letters is copyrighted by The American Institute of Physics....
Urushadze, G. I.
1986-03-01
A study has been carried out on the nonlinear nature of Anderson plasma excitations in narrow Josephson junctions in case of a longitudinal ultrasonic wave propagating normal to the tunnel barrier plane with a frequency resonant to the plasma oscillation frequency in the junction. A high frequency current associated with a sound-induced displacement of Anderson plasma energy levels was shown to be excited across the junction. The problem of sound wave attenuation and amplification is discussed and an attempt is made to predict the effect of amplification of ultrasonic waves passing through the junction.
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
Carbon nanotube junctions and devices
Postma, H.W.Ch.
2001-01-01
In this thesis Postma presents transport experiments performed on individual single-wall carbon nanotubes. Carbon nanotubes are molecules entirely made of carbon atoms. The electronic properties are determined by the exact symmetry of the nanotube lattice, resulting in either metallic or
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)
Low temperature properties of spin filter NbN/GdN/NbN Josephson junctions
Energy Technology Data Exchange (ETDEWEB)
Massarotti, D., E-mail: dmassarotti@na.infn.it [Dipartimento di Ingegneria Industriale e dell’Informazione, Seconda Università di Napoli, via Roma 29, 81031 Aversa (CE) (Italy); CNR-SPIN UOS Napoli, Complesso Universitario di Monte Sant’Angelo, via Cinthia, 80126 Napoli (Italy); Caruso, R. [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); Pal, A. [Department of Materials Science and Metallurgy, University of Cambridge, Cambridge CB3 0FS (United Kingdom); Rotoli, G. [Dipartimento di Ingegneria Industriale e dell’Informazione, Seconda Università di Napoli, via Roma 29, 81031 Aversa (CE) (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, New York 11961 (United States); Pepe, G.P. [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); Blamire, M.G. [Department of Materials Science and Metallurgy, University of Cambridge, Cambridge CB3 0FS (United Kingdom); Tafuri, F. [Dipartimento di Ingegneria Industriale e dell’Informazione, Seconda Università di Napoli, via Roma 29, 81031 Aversa (CE) (Italy); CNR-SPIN UOS Napoli, Complesso Universitario di Monte Sant’Angelo, via Cinthia, 80126 Napoli (Italy)
2017-02-15
Highlights: • We study the phase dynamics of ferromagnetic NbN/GdN/NbN Josephson junctions. • The ferromagnetic insulator GdN barrier generates spin-filtering properties. • Spin filter junctions fall in the underdamped regime. • MQT occurs with the same phenomenology as in conventional Josephson junctions. • Dissipation is studied in a wide range of critical current density values. - Abstract: A ferromagnetic Josephson junction (JJ) represents a special class of hybrid system where different ordered phases meet and generate novel physics. In this work we report on the transport measurements of underdamped ferromagnetic NbN/GdN/NbN JJs at low temperatures. In these junctions the ferromagnetic insulator gadolinium nitride barrier generates spin-filtering properties and a dominant second harmonic component in the current-phase relation. These features make spin filter junctions quite interesting also in terms of fundamental studies on phase dynamics and dissipation. We discuss the fingerprints of spin filter JJs, through complementary transport measurements, and their implications on the phase dynamics, through standard measurements of switching current distributions. NbN/GdN/NbN JJs, where spin filter properties can be controllably tuned along with the critical current density (J{sub c}), turn to be a very relevant term of reference to understand phase dynamics and dissipation in an enlarged class of JJs, not necessarily falling in the standard tunnel limit characterized by low J{sub c} values.
Energy Technology Data Exchange (ETDEWEB)
Blackburn, James A. [Physics & Computer Science, Wilfrid Laurier University, Waterloo, Ontario (Canada); Cirillo, Matteo, E-mail: cirillo@roma2.infn.it [Dipartimento di Fisica and MINAS-Lab, Università di Roma “Tor Vergata”, I-00133 Roma (Italy); Grønbech-Jensen, Niels [Department of Mathematics, University of California, Davis, CA 95616 (United States); Department of Mechanical and Aerospace Engineering, University of California, Davis, CA 95616 (United States)
2016-02-05
For decades following its introduction in 1968, the resistively and capacitively shunted junction (RCSJ) model, sometimes referred to as the Stewart–McCumber model, was successfully applied to study the dynamics of Josephson junctions embedded in a variety of superconducting circuits. In 1980 a theoretical conjecture by A.J. Leggett suggested a possible new and quite different behavior for Josephson junctions at very low temperatures. A number of experiments seemed to confirm this prediction and soon it was taken as given that junctions at tens of millikelvins should be regarded as macroscopic quantum entities. As such, they would possess discrete levels in their effective potential wells, and would escape from those wells (with the appearance of a finite junction voltage) via a macroscopic quantum tunneling process. A zeal to pursue this new physics led to a virtual abandonment of the RCSJ model in this low temperature regime. In this paper we consider a selection of essentially prototypical experiments that were carried out with the intention of confirming aspects of anticipated macroscopic quantum behavior in Josephson junctions. We address two questions: (1) How successful is the non-quantum theory (RCSJ model) in replicating those experiments? (2) How strong is the evidence that data from these same experiments does indeed reflect macroscopic quantum behavior?.
Low-Tc ramp-type superconductor-insulator-superconductor Josephson junctions
International Nuclear Information System (INIS)
Podt, M; Flokstra, J; Rogalla, H
2003-01-01
Superconductor-insulator-superconductor Josephson junctions with an area smaller than 1 μm 2 are increasingly used for many applications because of their low capacitances and short switching times. The characteristics of analogue and digital SQUIDs, for example, can be improved using small-area Josephson junctions. We have developed Nb/Al, AlO x /Al/Nb junctions based on an edge geometry. These low-T c ramp-type junctions allow sub-μm 2 junction areas using micrometre resolution photolithography. The experimental I-V characteristics of the ramp-type junctions showed non-hysteretic behaviour. Using these ramp-type junctions, the first series of dc SQUIDs have been successfully developed. The characteristics of the ramp-type junctions and the dc SQUIDs have been investigated both experimentally and by using numerical simulations. The white flux noise level of a dc SQUID based on ramp-type junctions with an area of 0.2 μm x 12 μm was measured to be √S φ = 1.2μΦ 0 Hz -1/2
Anomalous Josephson Effect in Junctions with Rashba Spin-Orbit Coupling
Nesterov, Konstantin; Houzet, Manuel; Meyer, Julia
2015-03-01
We study two-dimensional double-barrier SINIS Josephson junctions in which the inversion symmetry in the normal part is broken by Rashba spin-orbit coupling. In the presence of a suitably oriented Zeeman field in the normal part, the system displays the anomalous Josephson effect: the current is nonzero even at zero phase difference between two superconductors. We investigate this effect by means of the Ginzburg-Landau formalism and microscopic Green's functions approach in the clean limit. This work was supported in part by the Grants No. ANR-12-BS04-0016-03 and an EU-FP7 Marie Curie IRG.
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
Self-induced steps in a small Josephson junction strongly coupled to a multimode resonator
DEFF Research Database (Denmark)
Larsen, A.; Jensen, H. Dalsgaard; Mygind, Jesper
1991-01-01
coupled systems. Based on a single-resonator model, we explain the exceptional size of the steps by the large content of higher harmonics of the Josephson oscillation sustained by the multiple modes of the resonator. The parameters of the junction and the loaded resonator—measured in situ by using......An equally spaced series of very large and nearly constant-voltage self-induced singularities has been observed in the dc I-V characteristics of a small Josephson tunnel junction strongly coupled to a resonant section of a superconducting transmission line. The system allows extremely high values...... of the coupling parameter. The current steps are due to subharmonic parametric excitation of the fundamental mode of the resonator loaded by the junction admittance. Using an applied magnetic field to vary the coupling parameter, we traced out half-integer steps as well as the mode steps known from more weakly...
National Research Council Canada - National Science Library
Wu, Judy
2000-01-01
..., in the fabrication of electron beam modified planar Hg-1212 Josephson junctions. The results indicate that for beam energy less than about 80 keV the changes in the superconducting properties of Hg-1212 thin films are temporary...
Paik, Hanhee; Schuster, D. I.; Bishop, Lev S.; Kirchmair, G.; Catelani, G.; Sears, A. P.; Johnson, B. R.; Reagor, M. J.; Frunzio, L.; Glazman, L. I.; Girvin, S. M.; Devoret, M. H.; Schoelkopf, R. J.
2011-12-01
Superconducting quantum circuits based on Josephson junctions have made rapid progress in demonstrating quantum behavior and scalability. However, the future prospects ultimately depend upon the intrinsic coherence of Josephson junctions, and whether superconducting qubits can be adequately isolated from their environment. We introduce a new architecture for superconducting quantum circuits employing a three-dimensional resonator that suppresses qubit decoherence while maintaining sufficient coupling to the control signal. With the new architecture, we demonstrate that Josephson junction qubits are highly coherent, with T2˜10 to 20μs without the use of spin echo, and highly stable, showing no evidence for 1/f critical current noise. These results suggest that the overall quality of Josephson junctions in these qubits will allow error rates of a few 10-4, approaching the error correction threshold.
Energy Technology Data Exchange (ETDEWEB)
Leppaekangas, Juha; Thuneberg, Erkki [Department of Physical Sciences, University of Oulu, FI-90014 (Finland)], E-mail: juha.leppakangas@oulu.fi
2009-02-01
We analyze how the dynamics in a current-biased mesoscopic Josephson junction can be probed by an additional smaller Josephson junction (probe). The probe is connected to a small island in between the Josephson junction and a resistor R >> R{sub Q} = h/4e{sup 2}. The current through the resistor results in an effective current bias to the larger JJ. We model the steady state properties of the system under thermal and quantum fluctuations of the feed current. We use a density matrix approach based on the Born-Markov equations treating the current fluctuations perturbatively. The probe is also treated perturbatively assuming the regime of incoherent Cooper-pair tunneling. We find that the I - V characteristics across the probe shows traces of energy bands, Bloch oscillations and Zener tunneling in the current-biased Josephson junction.
Chemically etched edges of YBa2Cu3O7 films for interconnects, crossovers and Josephson junctions
International Nuclear Information System (INIS)
Poppe, U.; Faley, M.I.; Urban, K.; Soltner, H.
1993-01-01
To produce damage-free edges is one of the main problems during the preparation of Josephson edge-type junctions and interconnects in multilayer structures including high temperature superconductors. The inherently short and anisotropic coherence length in high temperature superconductors makes it also difficult to fabricate Josephson junctions from these materials. One promising technique which helps to overcome such problems using a nonaqueous chemical etching with a Br-ethanol solution was first presented in a recent publication. Here we report results obtained with the use of this method: test of insulation properties of PrBa 2 Cu 3 O 7 , PrBa 2 Cu 2.85 Ga 0.15 O 7 , and SrTiO 3 used for crossovers and Josephson junctions. Some features of interconnects and Josephson junctions, prepared on the basis of the chemical technique are also discussed. (orig.)
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.
Stability of fluxon motion in long Josephson junctions at high bias
DEFF Research Database (Denmark)
Pagano, S.; Sørensen, Mads Peter; Christiansen, Peter Leth
1988-01-01
In long Josephson junctions the motion of fluxons is revealed by the existence of current steps, zero-field steps, in the current-voltage characteristics. In this paper we investigate the stability of the fluxon motion when high values of the current bias are involved. The investigation is carried...... dissipations and of the junction length on the switching-current value is investigated. A simple boundary model is able to describe, for junctions of overlap geometry, the qualitative dependence of the switching current on the system parameters....
Fluxon propagation in long Josephson junctions with external magnetic field
DEFF Research Database (Denmark)
Olsen, O.H.; Samuelsen, Mogens Rugholm
1981-01-01
The reflection of a single fluxon propagating in a Josephson line cavity influenced by an external magnetic field is examined numerically. We find a single reflected fluxon, an antifluxon, collapse of the incident fluxon, fission into a higher number of antifluxons or fluxons, and formation...... of breather-like waves depending on the velocity of the incident fluxon and the magnitude of the external magnetic field. Approximations based on energy analysis describing the border lines between regions of different processes are presented. Journal of Applied Physics is copyrighted by The American...
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
DEFF Research Database (Denmark)
Holm, Jesper; Mygind, Jesper
1995-01-01
The first local oscillators based on moving magnetic flux quanta in long Josephson junctions are being developed for superconducting integrated quasi-optical SIS receivers. In order to further refine these oscillators one has to understand the complex dynamics of these devices. Since the local...... on measurements on different oscillator samples, performed with a novel Cryogenic Scanning Laser Microscope (CSLM) having a spatial resolution of less than ±2.5 μm over a 500 μm×50 μm wide scanning area in the temperature range 2 K-300 K. Even though the dynamical states are extremely sensitive to external noise...... this microscope enables us to make stable in-situ measurements on operating Josephson junctions. Recent results are presented and discussed....
Resonance modes in one-dimensional parallel arrays of Josephson junctions
International Nuclear Information System (INIS)
Van der Zant, H.S.J.; Delin, K.A.; Bock, R.D.; Berman, D.; Phillips, J.R.; Orlando, T.P.
1994-01-01
We investigate both experimentally and numerically the dynamics of discrete one-dimensional parallel arrays of underdamped Josephson junctions. In a magnetic field, measurements show steps in the current-voltage characteristics which are the discrete analogs of Fiske steps in a long Josephson junction. From the position of the steps, one can construct a plot of the dispersion relation ω(k). We observe a sine--dependence in the dispersion relation due to the discrete nature of our arrays. We also observe an additional, smaller gap at a k-value determined by the periodicity of the vortex lattice. Our measurements are supported by numerical simulations of the full dynamics. The Fiske steps provide an experimental method to measure the self-inductance of 1D parallel arrays. (orig.)
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
Static properties of small Josephson tunnel junctions in an oblique magnetic field
DEFF Research Database (Denmark)
Monaco, Roberto; Aarøe, Morten; Mygind, Jesper
2009-01-01
We have carried out a detailed experimental investigation of the static properties of planar Josephson tunnel junctions in presence of a uniform external magnetic field applied in an arbitrary orientation with respect to the barrier plane. We considered annular junctions, as well as rectangular...... junctions (having both overlap and cross-type geometries) with different barrier aspect ratios. It is shown how most of the experimental findings in an oblique field can be reproduced invoking the superposition principle to combine the classical behavior of electrically small junctions in an in-plane field...... together with the small junction behavior in a transverse field that we recently published [R. Monaco , J. Appl. Phys. 104, 023906 (2008)]. We show that the presence of a transverse field may have important consequences, which could be either voluntarily exploited in applications or present an unwanted...
An ion-beam-assisted process for high-Tc Josephson junctions
International Nuclear Information System (INIS)
Huang, M.Q.; Chen, L.; Zhao, Z.X.; Yang, T.; Nie, J.C.; Wu, P.J.; Xiong, X.M.
1997-01-01
We have developed a non-ion-etching ion-beam-assisted-deposition (IBAD) process for fabricating high critical-temperature (T c ) grain boundary Josephson junctions through a photoresist liftoff mask. The YBa 2 Cu 3 O 7 (YBCO) junctions fabricated through this process exhibited the resistively-shunted-junction (RSJ)-like I - V characteristics. The well-defined Shapiro steps have been seen on the I - V curves under microwave radiation. The magnetic modulation of critical current of a 4 μm width YBCO junction tallied with the prior simulated Fraunhofer diffraction pattern of a Josephson junction with a spatially homogeneous critical current density. The maximum peak-to-peak modulation voltage across the dc superconducting quantum interference device (SQUID) fabricated by using these junctions reached up to 32 μV at 77 K. The magnetic modulation of the SQUID exhibited periodic behavior with the observed modulation period of 5.0x10 -4 G. copyright 1997 American Institute of Physics
Energy Technology Data Exchange (ETDEWEB)
Gaber, Tobias
2007-07-01
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-{kappa} junctions but can be bend or flipped by external forces like bias currents or magnetic fields. 0-{kappa} junctions and fractional vortices are generalizations of the well-known 0-{pi} junctions and semifluxons, where not only phase jumps of pi but arbitrary values denoted by kappa are considered. By using so-called artificial 0-{kappa} junctions that are based on standard Nb-AlO{sub 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.)
X-band singly degenerate parametric amplification in a Josephson tunnel junction
DEFF Research Database (Denmark)
Mygind, Jesper; Pedersen, Niels Falsig; Sørensen, O. H.
1978-01-01
Preliminary measurements on a (quasi-) degenerate parametric amplifier using a single Josephson tunnel junction as the active element is reported. The pump frequency is at 18 GHz and the signal and idler frequencies are both at about 9 GHz. A power gain of 16 dB in a 4-MHz 3-dB bandwidth is achie...... is achieved at the top of the cryostat. Applied Physics Letters is copyrighted by The American Institute of Physics....
Critical current of a high Tc Josephson grain boundary junction in high magnetic field
Däumling, M.; Sarnelli, E.; Chaudhari, P.; Gupta, A.; Lacey, J.
1992-09-01
The critical current (Ic) of YBa2Cu3O7-δ grain boundary Josephson junctions was measured up to magnetic fields of 5 T. Magnetic field history dependent Ic values were observed even after correction for self-field effects stemming from hysteretic shielding currents in the grain adjacent to the boundary. A novel feature observed is an anomalous increase in Ic in high magnetic fields of several Telsa.
DEFF Research Database (Denmark)
Levring, O. A.; Pedersen, Niels Falsig; Samuelsen, Mogens Rugholm
1983-01-01
The motion of a single fluxon in long Josephson-junctions of overlap and inline geometries is investigated in the presence of an applied external magnetic field. The form of the first zero-field step for various parameters is given in closed analytic forms in both cases, and the differences...... and similarities between the two geometries are emphasized. Journal of Applied Physics is copyrighted by The American Institute of Physics....
Chaos synchronization in RCL-shunted Josephson junction via active control
International Nuclear Information System (INIS)
Ucar, Ahmet; Lonngren, Karl E.; Bai, E.-W.
2007-01-01
This paper investigates the synchronization of coupled RCL-shunted Josephson junction that is of interest in high-frequency applications. A nonlinear controller is developed in order to achieve the desired behavior. The synchronization is obtained using the slave-master technique and the controller ensures that the states of the controlled chaotic slave system exponentially synchronize with the state of the master system. Numerical simulations are illustrate and verify the proposed method
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.)
Effects of intrinsic inelastic scattering on the critical current of a Josephson junction
Ranjan, S.; Fistul, M. V.; Giuliani, G. F.
1997-07-01
It is shown that inelastic scattering suffered by tunneling electrons in the barrier of an S-I-S Josephson junction can lead to a remarkable nonmonotonic temperature dependence of the critical current of the structure. The understanding of this effect rests on the fact that under suitable conditions the inevitable loss of coherence can be more than compensated by a temperature-dependent exponential enhancement of the pair tunneling probability.
Millimetre and sub-mm wavelength radiation sources based on discrete Josephson junction arrays
International Nuclear Information System (INIS)
Darula, M.; Beuven, S.; Doderer, T.
1999-01-01
This paper reviews the present status and future perspectives of discrete Josephson junction arrays for applications as sub-mm wavelength radiation sources. It is intended to cover the whole field, i.e. theory, fabrication and experimental results. The theoretical part reviews the fundamental aspects of Josephson junctions for oscillator applications and introduces the different possible array types. The recent results of analytical as well as numerical investigations are discussed. After the description of the fabrication of both low-T c as well as high-T c superconductor Josephson junctions and arrays, methods to investigate the array dynamics experimentally are mentioned. Finally, the recent experimental results are reviewed. This topic is divided into two parts, the first dealing with low-T c arrays, the second with high-T c arrays. The different possibilities to design arrays and to include them in practical applications are discussed and compared, with special emphasis on those experiments where radiation was generated successfully. The article is completed with a discussion of the most important experimental results. (author)
Low-energy states in a chain of inductively coupled Josephson junctions
Meier, Hendrik; Brierley, Richard T.; Kou, Angela; Girvin, Steven M.; Glazman, Leonid I.
2015-03-01
We investigate a long chain of inductively coupled Josephson junctions penetrated by an external magnetic field. In the limit of infinite junction capacitances, we determine the classical ground state and find that the competition between Josephson and inductive forces leads to a rich phase phase diagram as a function of magnetic flux per plaquette ϕe and the ratio l2 =EJ /EL of Josephson (EJ) and inductive (EL) energies. At large l, kinks in the superconducting phase set in as a function of ϕe similarly to vortices in type-II superconductors. Upon further increasing ϕe, the interplay between kink-kink interaction and pinning on the lattice leads to a Frenkel-Kontorova-type (devil's) staircase of phases distinguished by different rational kink densities. At ϕe equal to half a flux quantum, the system bears similarity to a classical Ising antiferromagnet, possibly with a long-ranged exchange. Inclusion of a finite junction capacitances is similar to placing the Ising chain in a transverse magnetic field (the quantum Ising model). Using this similarity, we investigate the quantum dynamics of a chain of fluxonium qubits.
Band-gaps in long Josephson junctions with periodic phase-shifts
Energy Technology Data Exchange (ETDEWEB)
Ahmad, Saeed, E-mail: saeedahmad@uom.edu.pk [Department of Mathematics, University of Malakand Chakdara, Dir(L), Pakhtunkhwa (Pakistan); Susanto, Hadi, E-mail: hsusanto@essex.ac.uk [Department of Mathematical Sciences, University of Essex, Colchester CO4 3SQ (United Kingdom); Wattis, Jonathan A.D. [School of Mathematical Sciences, University of Nottingham, University Park, Nottingham NG7 2RD (United Kingdom)
2017-04-04
We investigate analytically and numerically a long Josephson junction on an infinite domain, having arbitrary periodic phase shift of κ, that is, the so-called 0–κ long Josephson junction. The system is described by a one-dimensional sine-Gordon equation and has relatively recently been proposed as artificial atom lattices. We discuss the existence of periodic solutions of the system and investigate their stability both in the absence and presence of an applied bias current. We find critical values of the phase-discontinuity and the applied bias current beyond which static periodic solutions cease to exist. Due to the periodic discontinuity in the phase, the system admits regions of allowed and forbidden bands. We perturbatively investigate the Arnold tongues that separate the region of allowed and forbidden bands, and discuss the effect of an applied bias current on the band-gap structure. We present numerical simulations to support our analytical results. - Highlights: • A long Josephson junction on an infinite domain having arbitrary periodic phase shift has been proposed as artificial atom lattices recently. • We compute the band-gaps of the system asymptotically. • We show that the phase-shift and applied bias current can be used to control the band structures.
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)
Temporal stability of Y Ba Cu O nano Josephson junctions from ion irradiation
Energy Technology Data Exchange (ETDEWEB)
Cybart, Shane A.; Roediger, Peter; Chen, Ke; Parker, J. M.; Cho, Ethan Y.; Wong, Travis J.; Dynes, R. C.
2012-11-29
We investigate the temporal stability of YBa2Cu3O7 Josephson junctions created by ion irradiation through a nano-scale implant mask fabricated using electron beam lithography and reactive ion etching. A comparison of current-voltage characteristics measured for junctions after fabrication and eight years of storage at room temperature show a slight decrease in critical current and increase in normal state resistance consistent with broadening of the weaklink from diffusion of defects. Shapiro step measurements performed 8 years after fabrication reveal that device uniformity is maintained and is strong evidence that these devices have excellent temporal stability for applications.
Vortex trapping in Pb-alloy Josephson junctions induced by strong sputtering of the base electrode
International Nuclear Information System (INIS)
Wada, M.; Nakano, J.; Yanagawa, F.
1985-01-01
It is observed that strong rf sputtering of the Pb-alloy base electrodes causes the junctions to trap magnetic vortices and thus induces Josephson current (I/sub J/) suppression. Trapping begins to occur when the rf sputtering that removes the native thermal oxide on the base electrode is carried out prior to rf plasma oxidation. Observed large I/sub J/ suppression is presumably induced by the concentration of vortices into the sputtered area upon cooling the sample below the transition temperature. This suggests a new method of the circumvention of the vortex trapping by strongly rf sputtering the areas of the electrode other than the junction areas
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...... analyses show that for rf frequencies larger than a certain threshold value no hysteresis is expected. This is verified in numerical simulations where the frequency and length of the junction have been varied....
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
Development of High Temperature Superconducting Josephson Junction Device Technology
National Research Council Canada - National Science Library
Myers, Kirsten
1998-01-01
The DuPont program was successful in generating useful knowledge about thallium cuprate materials, photoresist reflow processing, and radiant heater technology though it did not lead to a new junction technology...
High Density Planar High Temperature Superconducting Josephson Junctions Arrays
National Research Council Canada - National Science Library
Dynes, Robert C; Cybart, Shane
2006-01-01
.... We have found that a circuit fabrication technique pioneered in our lab during previous AFOSR funding periods can be used to fabricate arrays of junctions as well as superconducting interference devices...
Dynamical Properties of Two-Dimensional Josephson Junction Arrays
1990-05-01
current, i,0 , simply by Ic. = Mico , where M = 1000 is the number of junctions in parallel across the width of the array perpendicular to the current...identical junctions or some other form of disorder, the motion may be more complex , including effects such as vortex lattice shear. At higher temperatures...with the rf drive current as proposed in the vortex motion model. We have found interesting and complex dynamical behavior in the simulations that
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
Terahertz frequency metrology based on high-T sub c Josephson junctions
Chen, J; Wang, H B; Nakajima, K; Yamashita, T; Wu, P H
2002-01-01
Using YBa sub 2 Cu sub 3 O sub 7 /MgO bicrystal Josephson junctions operating between 6-77 K, we have studied their responses to monochromatic electromagnetic radiation from 50 GHz to 4.25 THz. We have obtained direct detections for radiation at 70 K from 50 GHz to 760 GHz and at 40 K from 300 GHz to 3.1 THz. This indicates that fast detectors can be realized to cover the 10:1 frequency band at one operation temperature, and about 100:1 can be covered by operating only one junction at two different temperatures. Both the highest response frequency and the maximum value of the normalized response are shown to be proportional to the I sub C R sub N product of the junction, where I sub C and R sub N are the critical current and the normal resistance of the junction, respectively.
Phase Locking and Chaos in a Josephson Junction Array Shunted by a Common Resistance
International Nuclear Information System (INIS)
Tie-Ge, Zhou; Jing, Mao; Ting-Shu, Liu; Yue, Lai; Shao-Lin, Yan
2009-01-01
The dynamics of a Josephson junction array shunted by a common resistance are investigated by using numerical methods. Coexistence of phase locking and chaos is observed in the system when the resistively and capacitively shunted junction model is adopted. The corresponding parameter ranges for phase locking and chaos are presented. When there are three resistively shunted junctions in the array, chaos is found for the first time and the parameter range for chaos is also presented. According to the theory of Chernikov and Schmidt, when there are four or more junctions in the array, the system exhibits chaotic behavior. Our results indicate that the theory of Chernikov and Schmidt is not exactly appropriate. (condensed matter: electronicstructure, electrical, magnetic, and opticalproperties)
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
Model studies of long Josephson junction arrays coupled to a high-Q resonator
DEFF Research Database (Denmark)
Filatrella, G.; Rotoli, G.; Grønbech-Jensen, N.
1992-01-01
Series-biased arrays of long Josephson junction fluxon oscillators can be phase locked by mutual coupling to a high-Q, linear distributed resonator. A simplified model of such a device, consisting of junctions described by the particle-map perturbation theory approach which are capacitively coupled...... of the simplified model. In the particle-map model, the locking range in junction bias current increases linearly with the coupling capacitance; in the partial differential equation (p.d.e.) model, this holds up to a certain maximum value of the capacitance, after which a saturation of the locking range is observed....... In both models, for a given spread of junction lengths, the existence of a minimum value of the capacitance for locking to a tank with a given resonant frequency is evidenced. Journal of Applied Physics is copyrighted by The American Institute of Physics....
Elliptic annular Josephson tunnel junctions in an external magnetic field: the statics
DEFF Research Database (Denmark)
Monaco, Roberto; Granata, Carmine; Vettoliere, Antonio
2015-01-01
or in the perpendicular direction. We report a detailed study of both short and long elliptic annular junctions having different eccentricities. For junctions having a normalized perimeter less than one the threshold curves are derived and computed even in the case with one trapped Josephson vortex. For longer junctions...... a numerical analysis is carried out after the derivation of the appropriate perturbed sine-Gordon equation. For a given applied field we find that a number of different phase profiles exist which differ according to the number of fluxon-antifluxon pairs. We demonstrate that in samples made by specularly...... symmetric electrodes a transverse magnetic field is equivalent to an in-plane field applied in the direction of the current flow. Varying the ellipse eccentricity we reproduce all known results for linear and ring-shaped JTJs. Experimental data on high-quality Nb/Al-AlOx/Nb elliptic annular junctions...
Directory of Open Access Journals (Sweden)
Fernando Gimeno Bellver
Full Text Available In this paper, we explore the chaotic behavior of resistively and capacitively shunted Josephson junctions via the so-called Network Simulation Method. Such a numerical approach establishes a formal equivalence among physical transport processes and electrical networks, and hence, it can be applied to efficiently deal with a wide range of differential systems.The generality underlying that electrical equivalence allows to apply the circuit theory to several scientific and technological problems. In this work, the Fast Fourier Transform has been applied for chaos detection purposes and the calculations have been carried out in PSpice, an electrical circuit software.Overall, it holds that such a numerical approach leads to quickly computationally solve Josephson differential models. An empirical application regarding the study of the Josephson model completes the paper. Keywords: Electrical analogy, Network Simulation Method, Josephson junction, Chaos indicator, Fast Fourier Transform
Noise characteristics of an ideal shunted Josephson Junction
International Nuclear Information System (INIS)
Voss, R.F.
1981-01-01
Detailed computer simulations have been made of the effect of intrinsic noise current on the I--V characteristic and voltage noise spectral density S/sub v/(f) of an ideal Josephson element shunted by a capacitor and resistor. The minimum value of the parameter β/sub c/ at which hysteresis appears in the quasistatic I--V characteristic is greater than the noise-free value of approx. =1. Moreover, as β/sub c/ is increased, a region of large differential resistance R/sub d/ appears in the I--V characteristic that is associated with a large increase in S/sub v/(0). In this regime the noise current is seen to cause random switching between the super-conducting and nonzero voltage states. For all bias conditions, S/sub v/(f)>R/sub d/ 2 S/sub I/(f) where S/sub I/(f) is the spectral density of the intrinsic current noise. A comparison is made between these results and previous calculations. The implications for low-noise superconducting devices are discussed
Cheng, Qiang; Zhang, Kunhua; Ma, Hongyang
2018-03-01
We propose a new type of Josephson junction consisting of topologically nontrivial superconductors with inherent orthogonality and a ferromagnetic interface. It is found this type of junction can host rich ground states: 0 phase, π phase, 0 + π phase, φ0 phase and φ0 ± φ phase. Phase transitions can be controlled by changing the direction of the interfacial magnetization. Phase diagrams are presented in the orientation space. Novel selection rules for the lowest order current, sin ϕ or cos ϕ, of this kind of junction are derived. General conditions for the formation of various ground states are established, which possess guiding significance to the experimental design of required ground states for practical applications. We construct the succinct form of a Ginzburg-Landau type of free energy from the viewpoint of the interplay between topological superconductivity and ferromagnetism, which can immediately lead to the selection rules. The constructed terms are universally available to the topological Josephson junctions with or without inherent orthogonality reported recently. The spin supercurrent, its selection rules and their relations to the constructed energy are also investigated.
International Nuclear Information System (INIS)
Beasley, M.R.
1981-01-01
The main body of this chapter is organized as follows. In Section II we review the device principles that underlie the operation of superconducting electronic devices. The emphasis is on defining the most critical and characteristic materials issues and problems. In Section III we discuss the state of the art in the LSI circuit technology being developed for the Josephson computer. The problems associated with thermally-induced stresses in Josephson junctions are discussed in Section IV, and the importance and current understanding of the science of tunneling between superconductors is discussed in Section V. Finally, in Section VI we attempt to look ahead and discuss current work on advanced superconducting materials and devices
Low-frequency noise in Josephson junctions for superconducting qubits
Eroms, J.; Van Schaarenburg, L.C.; Driessen, E.F.C.; Plantenberg, J.H.; Huizinga, C.M.; Schouten, R.N.; Verbruggen, A.H.; Harmans, C.J.P.M.; Mooij, J.E.
2006-01-01
The authors have studied low-frequency resistance fluctuations in shadow-evaporated Al/AlOx/Al tunnel junctions. Between 300 and 5?K the spectral density follows a 1/f law. Below 5?K, individual defects distort the 1/f shape of the spectrum. The spectral density decreases linearly with temperature
Vortex dynamics in Josephson ladders with II-junctions
DEFF Research Database (Denmark)
Kornev, Victor K.; Klenov, N. V.; Oboznov, V.A.
2004-01-01
current versus applied magnetic field. At temperatures close to the 0-pi transition this dependence shows a doubling of its periodicity frequency that can be explained by 0-pi bistability of the SFS junctions. The change in the array behaviour with number of unit cells has been studied by means...
Gaussian tunneling model of c-axis twist Josephson junctions
International Nuclear Information System (INIS)
Bille, A.; Klemm, R.A.; Scharnberg, K.
2001-01-01
We calculate the critical current density J c J ((var p hi) 0 ) for Josephson tunneling between identical high-temperature superconductors twisted an angle (var p hi) 0 about the c axis. Regardless of the shape of the two-dimensional Fermi surface and for very general tunneling matrix elements, an order parameter (OP) with general d-wave symmetry leads to J c J (π/4)=0. This general result is inconsistent with the data of Li et al. [Phys. Rev. Lett. 83, 4160 (1999)] on Bi 2 Sr 2 CaCu 2 O 8+δ (Bi2212), which showed J c J to be independent of (var p hi) 0 . If the momentum parallel to the barrier is conserved in the tunneling process, J c J should vary substantially with the twist angle (var p hi) 0 when the tight-binding Fermi surface appropriate for Bi2212 is taken into account, even if the OP is completely isotropic. We quantify the degree of momentum nonconservation necessary to render J c J ((var p hi) 0 ) constant within experimental error for a variety of pair states by interpolating between the coherent and incoherent limits using five specific models to describe the momentum dependence of the tunneling matrix element squared. From the data of Li et al., we conclude that the c-axis tunneling in Bi2212 must be very nearly incoherent, and that the OP must have a nonvanishing Fermi-surface average for T c . We further show that the apparent conventional sum-rule violation observed by Basov et al. [Science 283, 49 (1999)] can be consistent with such strongly incoherent c-axis tunneling.
Inverse Spin Hall Effect in SNS Josephson Junctions
Mal'shukov, A. G.; Sadjina, Severin; Brataas, Arne
2009-01-01
We consider DC supercurrents in SNS junctions. Spin-orbit coupling in combination with Zeeman fields can induce an effective vector potential in the normal conductor. As a consequence, an out-of-plane spin-density varying along the transverse direction causes a longitudinal phase difference between the superconducting terminals. The resulting equilibrium phase coherent supercurrent is analogue to the non-equilibrium inverse spin Hall effect in normal conductors. We explicitly compute the effe...
Nguyen, D. V.; Basko, D. M.
2017-05-01
We report a theoretical study of the low-frequency impedance of a Josephson junction chain whose parameters vary in space. Our goal is to find the optimal spatial profile which maximizes the total inductance of the chain without shrinking the low-frequency window where the chain behaves as an inductor. If the spatial modulation is introduced by varying the junction areas, we find that the best result is obtained for a spatially homogeneous chain, reported earlier in the literature. An improvement over the homogeneous result can be obtained by representing the junctions by SQUIDs with different loop areas, so the inductances can be varied by applying a magnetic field. Still, we find that this improvement becomes less important for longer chains.
Experimental study of noise and Josephson oscillation linewidths in bicrystal YBCO junctions
DEFF Research Database (Denmark)
Constatinian, K.Y.; Ovsyannikov, G.A.; Borisenko, I.V.
2001-01-01
The intensities of the noise in a bicrystal high-T-c (HTS) Josephson junction have been precision-measured at 1-2 GHz frequency band at bias voltages up to 50 mV at T = 4.2 K. At large bias voltages, V > 30 mV, the dependence of current noise density was found exactly coinciding with the Schottky...... shot noise asymptote 2eI. At relatively low voltages, V frequencies in the nim and submm wave...... which may take place in the d-wave superconducting junctions. Experimental results on noise performance are also compared with the qualitatively similar dependences of the current noise, known for the s-superconducting ballistic point-like or diffusive-type SNS junctions, where the excess low...
Characterization of different types of Nb-AlOx based Josephson tunnel junctions
International Nuclear Information System (INIS)
Adelerhof, D.J.; Houwman, E.P.; Fransen, P.B.M.; Veldhuis, D.; Flokstra, J.; Rogalla, H.
1991-01-01
This paper reports on three types of Josephson tunnel junctions, standard Nb/Al,AlO x /Nb, symmetric Nb/Al,AlO x /Al/Nb, and Nb/Al,AlO x /AlO x /Nb containing a double oxide layer investigated by means of temperature dependent I-V measurements, conductance-voltage measurements, noise analysis, and Auger Electron Spectroscopy scanning across the edge of a sputtered crater profile. In standard junctions frequently small leakage currents have been observed as well as resistance fluctuations, leading to telegraph noise. Both effects can be related to the direct contact between the AlO x and the Nb counter electrode. In none of the symmetric junctions leakage currents larger than 0.01% of the theoretical maximum critical current have been observed
dc properties of series-parallel arrays of Josephson junctions in an external magnetic field
International Nuclear Information System (INIS)
Lewandowski, S.J.
1991-01-01
A detailed dc theory of superconducting multijunction interferometers has previously been developed by several authors for the case of parallel junction arrays. The theory is now extended to cover the case of a loop containing several junctions connected in series. The problem is closely associated with high-T c superconductors and their clusters of intrinsic Josephson junctions. These materials exhibit spontaneous interferometric effects, and there is no reason to assume that the intrinsic junctions form only parallel arrays. A simple formalism of phase states is developed in order to express the superconducting phase differences across the junctions forming a series array as functions of the phase difference across the weakest junction of the system, and to relate the differences in critical currents of the junctions to gaps in the allowed ranges of their phase functions. This formalism is used to investigate the energy states of the array, which in the case of different junctions are split and separated by energy barriers of height depending on the phase gaps. Modifications of the washboard model of a single junction are shown. Next a superconducting inductive loop containing a series array of two junctions is considered, and this model is used to demonstrate the transitions between phase states and the associated instabilities. Finally, the critical current of a parallel connection of two series arrays is analyzed and shown to be a multivalued function of the externally applied magnetic flux. The instabilities caused by the presence of intrinsic serial junctions in granular high-T c materials are pointed out as a potential source of additional noise
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
Josephson edge junctions on YBa2Cu3O7 thin films prepared with Br-ethanol etching
International Nuclear Information System (INIS)
Faley, M.I.; Poppe, U.; Daehne, U.; Goncharov, Yu.G.; Klein, N.; Urban, K.; Soltner, H.
1993-01-01
To produce damage-free edges is one of the main problems in the preparation of the Josephson edge-type junctions and interconnects in multilayer structures including high temperature superconductors. The commonly used ion beam etching has the disadvantages of the risk of contamination by redeposited material and structural damage to the surface of the edge. Vasquez et al and Gurvitch et al introduced a nonaqueous Br-ethanol etching for the preparation of clean surfaces of YBa 2 Cu 3 O 7 single crystals and thin films. We have developed a procedure of deep-UV-photolithography combined with nonaqueous Br-ethanol etching for the preparation of the Josephson edge-type junctions. Here we present the improvement of this method and report further results on the study of the electron transport properties of Josephson junctions with the edges of YBa 2 Cu 3 O 7 thin films produced by this technique. (orig.)
International Nuclear Information System (INIS)
McAdory, R.T. Jr.
1988-01-01
A theory is presented for the nonequilibrium voltage states of an irradiated Josephson junction shunted by an external resistor but with no external current or voltage biasing. This device, referred to as a free-running Josephson junction, is modeled in a small--radiation-amplitude, deterministic regime extending the previous work of Shenoy and Agarwal. The time-averaged induced voltage is treated as a dynamical variable, the external radiation is modeled as a current source, and the induced junction-radiation vector potential, with and without a mode structure, is treated to first order in the driving currents. A dynamical equation for the time-averaged induced voltage yields a (nonequilibrium) steady-state relation between the time-averaged induced voltage and the incident radiation amplitude valid for a wide range of voltages, including zero. Regions of bistability occur in the voltage--versus--incident-amplitude curves, some of which are dependent on the external resistor. The zero-voltage state breaks down, as the external radiation amplitude is increased, at a critical value of the incident-radiation amplitude inversely proportional to the external resistance
Energy Technology Data Exchange (ETDEWEB)
Huang, Hong [School of Physics, Sun Yat-sen University, Guangzhou 510275 (China); Liang, Qi-Feng [Department of Physics, Shaoxing University, Shaoxing 312000 (China); Yao, Dao-Xin, E-mail: yaodaox@mail.sysu.edu.cn [School of Physics, Sun Yat-sen University, Guangzhou 510275 (China); Wang, Zhi, E-mail: physicswangzhi@gmail.com [School of Physics, Sun Yat-sen University, Guangzhou 510275 (China)
2017-06-28
Majorana bound states in topological Josephson junctions induce a 4π period current-phase relation. Direct detection of the 4π periodicity is complicated by the quasiparticle poisoning. We reveal that Majorana bound states are also signaled by the anomalous enhancement on the critical current of the junction. We show the landscape of the critical current for a nanowire Josephson junction under a varying Zeeman field, and reveal a sharp step feature at the topological quantum phase transition point, which comes from the anomalous enhancement of the critical current at the topological regime. In multi-band wires, the anomalous enhancement disappears for an even number of bands, where the Majorana bound states fuse into Andreev bound states. This anomalous critical current enhancement directly signals the existence of the Majorana bound states, and also provides a valid signature for the topological quantum phase transition. - Highlights: • We introduce the critical current step as a signal for the topological quantum phase transition. • We study the quantum phase transition in the topological nanowire under a rotating Zeeman field. • We show that the critical current anomaly gradually disappears for systems with more sub-bands.
Period doubling and chaos in large area Josephson junctions induced by rf signals
DEFF Research Database (Denmark)
Olsen, O. H.; Samuelsen, Mogens Rugholm
1985-01-01
. In the intermediate regime lower and upper threshold values (for the amplitude) for transition to chaos are found. Feigenbaum period doubling (period-doubling bifurcation cascade) appears when chaos is approached for increasing amplitude. The findings are supported experimentally. Applied Physics Letters......The influence of an applied rf signal on the emitted radiation from a large area Josephson junction is examined. A model of the system is presented in the framework of the one-dimensional sine-Gordon equation. The model linearizes for small and large values of the amplitude of the applied signal...
Parametric amplification on rf-induced steps in a Josephson tunnel junction
DEFF Research Database (Denmark)
Sørensen, O.H.; Pedersen, Niels Falsig; Mygind, Jesper
1979-01-01
Parametric effects including amplification in a singly degenerate mode have been observed in Josephson tunnel junctions at dc bias points on rf-induced steps. Net gain at 9 GHz was achieved with a bias on the fundamental 18-GHz step and subharmonic self-oscillations were seen on 18 and 70-GHz rf-......-induced steps even at voltages approaching the energy gap. A qualitative explanation of the results is presented. Journal of Applied Physics is copyrighted by The American Institute of Physics....
Dynamics of an annular Josephson junction in a rotating magnetic field
DEFF Research Database (Denmark)
Grønbech-Jensen, Niels; Malomed, Boris A.; Samuelsen, Mogens Rugholm
1992-01-01
the edges of the step. For the case where the fluxon is slowly dragged by a fast traveling wave, the drift velocity is found. The analytical results are in very good agreement with numerical experiments performed on the perturbed sine-Gordon system. Finally the system is analyzed analytically for moderate......We study analytically and numerically the dynamics of a solitary fluxon in a long annular damped Josephson junction placed into a rotating magnetic field, which is produced by superposition of two mutually perpendicular ac fields with a phase difference of π/2. We demonstrate that the rotating...
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.
Fiske modes and Eck steps in long Josephson junctions: Theory and experiments
Cirillo, M.; Grønbech-Jensen, N.; Samuelsen, M. R.; Salerno, M.; Rinati, G. Verona
1998-11-01
We report on a systematic investigation of the properties of long Josephson junctions under the application of magnetic fields generating Fiske and Eck steps in the current-voltage characteristics. Numerical data and experimental results are compared with a cavity mode-based model predicting the voltage position and the amplitude of the current singularities. The comparison shows that this model can account for the shape and for the maximum current modulation of the singularities when the field penetration overcomes Meissner shielding above the value H0=2λjjc.
Tunnel Josephson junction as high-sensitive comparators in stroboscopic converters
International Nuclear Information System (INIS)
Askerzade, I.N.
2000-01-01
Paper presents the results of numerical simulation of dynamics of switching to the resistive state of several different type comparators based on the tunnel Josephson junctions within wide variation of their parameters. Particular attention was given to the design of comparator with the Faris generator. One determined dependences of comparator efficient operation on the circuit parameters. One demonstrated the application advisability of the balance comparator design under single-quanta pulses. The balance principle to design a comparator ensures better time resolution and high sensitivity as hysteresis of volt-ampere characteristic decreases [ru
Low-noise parametric amplification at 35 GHz in a single Josephson tunnel junction
DEFF Research Database (Denmark)
Mygind, Jesper; Pedersen, Niels Falsig; Sørensen, O. H.
1979-01-01
Parametric amplification at 35 GHz has been obtained using a single Josephson tunnel junction as the active element. The amplifier was operated in the singly quasidegenerate mode with a pump frequency at 70 GHz. The noise temperature was measured and found correlated with the gain. At the highest...... gain achieved, 11.6 dB, the noise temperature was 400 K. The noise temperature was reduced considerably by decreasing the gain. At 8 and 4 dB we found 165±25 K and 50±30 K, respectively. Applied Physics Letters is copyrighted by The American Institute of Physics....
DEFF Research Database (Denmark)
Monaco, Roberto; Aarøe, Morten; Mygind, Jesper
2008-01-01
We report on the spontaneous production of fluxons in annular Josephson tunnel junctions during a thermal quench in the presence of a symmetry-breaking magnetic field. The dependence on field intensity B of the probability (f) over bar (1) to trap a single defect during the N-S phase transition...... depends drastically on the sample circumferences. We show that this can be understood in the framework of the same picture of spontaneous defect formation that leads to the experimentally well attested scaling behavior of (f) over bar (1) with quench rate in the absence of an external field....
Svetogorov, Aleksandr E.; Taguchi, Masahiko; Tokura, Yasuhiro; Basko, Denis M.; Hekking, Frank W. J.
2018-03-01
We study coherent quantum phase slips which lift the ground state degeneracy in a Josephson junction ring, pierced by a magnetic flux of the magnitude equal to half of a flux quantum. The quantum phase-slip amplitude is sensitive to the normal mode structure of superconducting phase oscillations in the ring (Mooij-Schön modes). These, in turn, are affected by spatial inhomogeneities in the ring. We analyze the case of weak periodic modulations of the system parameters and calculate the corresponding modification of the quantum phase-slip amplitude.
Spectrum of Andreev bound states in Josephson junctions with a ferromagnetic insulator
International Nuclear Information System (INIS)
Kawabata, Shiro; Tanaka, Yukio; Golubov, Alexander A.; Vasenko, Andrey S.; Asano, Yasuhiro
2012-01-01
Ferromagnetic-insulator (FI) based Josephson junctions are promising candidates for a coherent superconducting quantum bit as well as a classical superconducting logic circuit. Recently the appearance of an intriguing atomic-scale 0–π transition has been theoretically predicted. In order to uncover the mechanism of this phenomena, we numerically calculate the spectrum of Andreev bound states in a FI barrier by diagonalizing the Bogoliubov–de Gennes equation. We show that Andreev spectrum drastically depends on the parity of the FI-layer number L and accordingly the π(0) state is always more stable than the 0 (π) state if L is odd (even).
Energy Technology Data Exchange (ETDEWEB)
Bai, Chunxu [Anyang Normal University, School of Physics, Anyang (China); Chinese Academy of Sciences, SKLSM, Institute of Semiconductors, Beijing (China); Wei, Ke-Wei; Shen, Yuanyuan; Yang, Yanling [Anyang Normal University, School of Physics, Anyang (China)
2015-11-15
To guide the potential applications of topological insulator, we provide a theoretical investigation for a finite temperature and an arbitrary length scale Josephson junction in the Furusaki-Tsukada formula. We have shown theoretically that a large degree of control over the generated critical supercurrent can be obtained by changing directions of the magnetizations in ferromagnet. The special importance for experimental measurements is the asymmetric character, oscillatory feature arising in the Fermi energy window, and energy shift phenomenon unveiled by a top gate voltage, which are independent of magnetization amplitude. (orig.)
Mesoscopic fluctuations in the critical current in InAs-coupled Josephson junctions
International Nuclear Information System (INIS)
Takayanagi, Hideaki; Hansen, J.B.; Nitta, Junsaku
1994-01-01
Mesoscopic fluctuations were confirmed for the critical current in a p-type InAs-coupled Josephson junction. The critical current was measured as a function of the gate voltage corresponding to the change in the Fermi energy. The critical current showed a mesoscopic fluctuation and its behavior was the same as that of the conductance measured at the same time in both the weak and strong localization regimes. The magnitude and the typical period of the fluctuation are discussed and compared to theoretical predictions. ((orig.))
Low-noise parametric amplification at 35 GHz in a single Josephson tunnel junction
International Nuclear Information System (INIS)
Mygind, J.; Pedersen, N.F.; Soerensen, O.H.; Dueholm, B.; Levinsen, M.T.
1979-01-01
Parametric amplification at 35 GHz has been obtained using a single Josephson tunnel junction as the active element. The amplifier was operated in the singly quasidegenerate mode with a pump frequency at 70 GHz. The noise temperature was measured and found correlated with the gain. At the highest gain achieved, 11.6 dB, the noise temperature was 400 K. The noise temperature was reduced considerably by decreasing the gain. At 8 and 4 dB we found 165 +- 25 K and 50 +- 30 K, respectively
Linear and nonlinear excitations in two stacks of parallel arrays of long Josephson junctions
DEFF Research Database (Denmark)
Carapella, G.; Constabile, Giovanni; Latempa, R.
2000-01-01
We investigate a structure consisting of two parallel arrays of long Josephson junctions sharing a common electrode that allows inductive coupling between the arrays. A model for this structure is derived starting from the description of its continuous limit. The excitation of linear cavity modes...... known from continuous and discrete systems as well as the excitation of a new state exhibiting synchronization in two dimensions are inferred from the mathematical model of the system. The stable nonlinear solution of the coupled sine-Gordon equations describing the system is found to consist...
Polaron effects on the dc- and ac-tunneling characteristics of molecular Josephson junctions
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.
Charge solitons in one-dimensional arrays of serially coupled Josephson junctions
International Nuclear Information System (INIS)
Hermon, Z.; Ben-Jacob, E.; Schoen, G.
1996-01-01
We study a 1D array of Josephson coupled superconducting grains with kinetic inductance which dominates over the Josephson inductance. In this limit the dynamics of excess Cooper pairs in the array is described in terms of charge solitons, created by polarization of the grains. We analyze the dynamics of these topological excitations, which are dual to the fluxons in a long Josephson junction, using the continuum sine-Gordon model. We find that their classical relativistic motion leads to saturation branches in the I-V characteristic of a ring-shaped array. We then discuss the semiclassical quantization of the charge soliton, and show that it is consistent with the large kinetic inductance of the array. We study the dynamics of a quantum charge soliton in a ring-shaped array biased by an external flux through its center. If the dephasing length of the quantum charge soliton is larger than the circumference of the array, quantum phenomena like persistent current and coherent current oscillations are expected. As the characteristic width of the charge soliton is of the order of 100μm, it is a macroscopic quantum object. We discuss the dephasing mechanisms which can suppress the quantum behavior of the charge soliton. copyright 1996 The American Physical Society
DEFF Research Database (Denmark)
Andersen, Christian Kraglund; Mølmer, Klaus
2013-01-01
We propose to use a time-dependent imaginary potential to describe quantum mechanical tunneling through time-varying potential barriers. We use Gamow solutions for stationary tunneling problems to justify our choice of potential, and we apply our method to describe tunneling of a mesoscopic quantum...... associated with voltage switching in Josephson junctions. Apart from applications as artificial atoms in quantum information studies, the Josephson junction may serve as an electric field sensitive detector, and our studies provide a detailed understanding of how the voltage switching dynamics couples...
Preparation of CN x /Carbon Nanotube Intramolecular Junctions by ...
African Journals Online (AJOL)
Preparation of CN x /Carbon Nanotube Intramolecular Junctions by Switching Gas Sources in Continuous Chemical Vapour Deposition. ... nanotubes were observed, and such different structures at both sides of the junctions indicated some interesting properties and offered potential applications for future nanodevices.
Electronic Properties of Carbon Nanotubes and Junctions
Anantram, M. P.; Han, Jie; Yang, Liu; Govindan, T. R.; Jaffe, R.; Saini, Subhash (Technical Monitor)
1998-01-01
Metallic and semiconducting Single Wall Carbon Nanotubes (CNT) have recently been characterized using scanning tunneling microscopy (STM) and the manipulation of individual CNT has been demonstrated. These developments make the prospect of using CNT as molecular wires and possibly as electronic devices an even more interesting one. We have been modeling various electronic properties such as the density of states and the transmission coefficient of CNT wires and junctions. These studies involve first calculating the stability of junctions using molecular dynamics simulations and then calculating the electronic properties using a pi-electron tight binding Hamiltonian. We have developed the expertise to calculate the electronic properties of both finite-sized CNT and CNT systems with semi-infinite boundary conditions. In this poster, we will present an overview of some of our results. The electronic application of CNT that is most promising at this time is their use as molecular wires. The conductance can however be greatly reduced because of reflection due to defects and contacts. We have modeled the transmission through CNT in the presence of two types of defects: weak uniform disorder and strong isolated scatterers. We find that the conductance is affected in significantly different manners due to these defects Junctions of CNT have also been imaged using STM. This makes it essential to derive rules for the formation of junctions between tubes of different chirality, study their relative energies and electronic properties. We have generalized the rules for connecting two different CNT and have calculated the transmission and density of states through CNT junctions. Metallic and semiconducting CNT can be joined to form a stable junction and their current versus voltage characteristics are asymmetric. CNT are deformed by the application of external forces including interactions with a substrate or other CNT. In many experiments, these deformation are expected to
Spatio-temporal chaos and thermal noise 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 map. Depending on the bias current the array can show Shapiro steps but also spatio-temporal chaos or ''turbulence'' 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 break down of the law of large numbers as seen in globally coupled maps. We study this phenomenon as a function of thermal noise. We find that when increasing the temperature the broad band noise decreases. (author). 8 refs, 1 fig
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
Possible method to observe the breathing mode of a magnetic domain wall in the Josephson junction
International Nuclear Information System (INIS)
Mori, Michiyasu; Maekawa, Sadamichi; Koshibae, Wataru; Hikino, Shin-ichi
2014-01-01
A magnetic domain wall (DW) behaves as a massive particle with elasticity. Sliding and oscillation of the DW have been observed experimentally, whereas vibration of a width in the DW, ‘breathing mode’, has not been measured so far. We theoretically propose how to observe the breathing mode by the Josephson junction having a ferromagnetic layer between superconducting electrodes. The current-voltage (I-V) curve is calculated by an equivalent circuit of the resistively shunted junction model. The breathing mode is identified by stepwise structures in the I-V curve, which appear at the voltages V = n (ℏ/2e)ω with the fundamental constant ℏ/e, integer number n and the frequency of the breathing mode ω. (paper)
Cross-sectional transmission electron microscopy observation of Nb/AlOx-Al/Nb Josephson junctions
International Nuclear Information System (INIS)
Imamura, T.; Hasuo, S.
1991-01-01
A study of microstructure of Nb/AlO x -Al/Nb Josephson junctions by cross-sectional transmission electron microscopy yielded much information regarding the junction barrier region. Both thick Nb and several-nanometer Al form polycrystalline films with columnar structures. Nb is oriented to the (110) plane, and Al is (111). The 200 nm lower Nb has a wavy surface with ∼5 nm smoothness, but its surface is planarized by several nanometers Al deposited on it. Thus AlO x with a smoothness under 1 nm can be formed on Al. The upper Nb has a good crystalline structure even just above the AlO x barrier
Planar intrinsic Josephson junctions with in-plane aligned YBCO films
Zhang, L; Kobayashi, T; Goto, T; Mukaida, M
2002-01-01
Planar type devices were fabricated by patterning in-plane aligned YBa sub 2 Cu sub 3 O sub 7 sub - subdelta (YBCO) films. The current-voltage characteristics along the c-axis at various temperatures and oxygen contents were measured. The current voltage curves showing supercurrent and hysteresis were obtained for the samples annealed at an oxygen pressure of 1.3 x 10 sup 4 Pa, while the supercurrent and hysteresis became smaller and even disappeared as the oxygen pressure decreased. The relationships between the critical currents and temperatures are similar to those of d-wave superconducting tunnel junctions. These results indicate the formation of stacks of intrinsic Josephson junctions, which are useful for developing high-frequency electron devices.
Energy Technology Data Exchange (ETDEWEB)
Dambach, Simon; Kubala, Bjoern; Gramich, Vera; Ankerhold, Joachim [Institute for Complex Quantum Systems, Ulm University, Ulm (Germany)
2015-07-01
The interplay of the tunneling transfer of charges and the emission and absorption of light can be investigated in a set-up, where a voltage-biased Josephson junction is placed in series to a microwave cavity. In such devices measurements of the emitted microwave radiation can yield information about the Cooper pair current and its fluctuations and vice versa. Due to the inherent nonlinearity of the Josephson junction tunneling Cooper-pairs can create a variety of non-classical states of light already at weak driving. Depending on experimental parameters and tuning, the device can be described by effective Hamiltonians, indicating specific photon creation mechanisms which lead to strongly bunched or anti-bunched light emission. We will use the waiting-time distribution of emitted photons to highlight how charge quantization of the Cooper pair current drives a crossover from a coherent light source to a single-photon source. Analytical results for the weak driving regime, based on a quantum regression approach, are complemented by numerical results for the full nonlinear quantum case.
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.
Frequency Combs in a Lumped-Element Josephson-Junction Circuit
Khan, Saeed; Türeci, Hakan E.
2018-04-01
We investigate the dynamics of a microwave-driven Josephson junction capacitively coupled to a lumped-element L C oscillator. In the regime of driving where the Josephson junction can be approximated as a Kerr oscillator, this minimal nonlinear system has been previously shown to exhibit a bistability in phase and amplitude. In the present study, we characterize the full phase diagram and show that besides a parameter regime exhibiting bistability, there is also a regime of self-oscillations characterized by a frequency comb in its spectrum. We discuss the mechanism of comb generation which appears to be different from those studied in microcavity frequency combs and mode-locked lasers. We then address the fate of the comblike spectrum in the regime of strong quantum fluctuations, reached when nonlinearity becomes the dominant scale with respect to dissipation. We find that the nonlinearity responsible for the emergence of the frequency combs also leads to its dephasing, leading to broadening and ultimate disappearance of sharp spectral peaks. Our study explores the fundamental question of the impact of quantum fluctuations for quantum systems which do not possess a stable fixed point in the classical limit.
Linear arrays of Josephson junctions: A stability analysis of characteristic modes
International Nuclear Information System (INIS)
Trees, B.R.; Harris, E.B.
1998-01-01
We have performed a linear stability analysis of two arrays of resistively shunted Josephson junctions: a ladder array and a so-called modified linear array. We find the periodic solutions to be linearly stable for a wide range of bias currents in the absence of a load. This is contrasted with the well-studied globally coupled linear array, where stability of the periodic solutions is a sensitive function of bias current and load parameters. For the ladder array, we have studied the nature of the mesh currents for the different decay modes. Numerical evidence leads us to conclude that the branches of the ladder parallel to the bias current play an important role in helping to damp out perturbed currents. We also compare the long-time dynamics of these Josephson-junction arrays with that of an RL network, which is a ladder of resistors and inductors, and for which the decay rates and mesh currents are calculated exactly. We find that at long times the dynamics of all three arrays are basically identical. copyright 1998 The American Physical Society
Energy Technology Data Exchange (ETDEWEB)
Cristofano, Gerardo; Marotta, Vincenzo [Dipartimento di Scienze Fisiche, Universita di Napoli ' Federico II' , and INFN, Sezione di Napoli, Via Cintia, Complesso Universitario M. Sant' Angelo, 80126 Napoli (Italy); Naddeo, Adele [Dipartimento di Fisica ' E.R. Caianiello' , Universita degli Studi di Salerno and CNISM, Unita di Ricerca di Salerno, Via Salvador Allende, 84081 Baronissi (Italy)], E-mail: naddeo@sa.infn.it; Niccoli, Giuliano [Theoretical Physics Group, DESY, NotkeStrasse 85, 22603 Hamburg (Germany)
2008-11-17
Recently a one-dimensional closed ladder of Josephson junctions has been studied [G. Cristofano, V. Marotta, A. Naddeo, G. Niccoli, Phys. Lett. A 372 (2008) 2464] within a twisted conformal field theory (CFT) approach [G. Cristofano, G. Maiella, V. Marotta, Mod. Phys. Lett. A 15 (2000) 1679; G. Cristofano, G. Maiella, V. Marotta, G. Niccoli, Nucl. Phys. B 641 (2002) 547] and shown to develop the phenomenon of flux fractionalization [G. Cristofano, V. Marotta, A. Naddeo, G. Niccoli, Eur. Phys. J. B 49 (2006) 83]. That led us to predict the emergence of a topological order in such a system [G. Cristofano, V. Marotta, A. Naddeo, J. Stat. Mech.: Theory Exp. (2005) P03006]. In this Letter we analyze the ground states and the topological properties of fully frustrated Josephson junction arrays (JJA) arranged in a Corbino disk geometry for a variety of boundary conditions. In particular minimal configurations of fully frustrated JJA are considered and shown to exhibit the properties needed in order to build up a solid state qubit, protected from decoherence. The stability and transformation properties of the ground states of the JJA under adiabatic magnetic flux changes are analyzed in detail in order to provide a tool for the manipulation of the proposed qubit.
International Nuclear Information System (INIS)
Kawabata, S.; Kashiwaya, S.; Tanaka, Y.; Golubov, A. A.; Asano, Y.
2011-01-01
Full text: A superconducting ring with a π-junction made from superconductor (S) / ferromagnetic- metal (FM) / superconductor (S) exhibits a spontaneous current without an external magnetic field and the corresponding magnetic flux is half a flux quantum in the ground state. Such a π-ring provides so-called 'quiet qubit' that can be efficiently decoupled from the fluctuation of the external field. However, the usage of FM gives rise to strong Ohmic dissipation. Therefore, the realization of π-junctions without FM is highly desired for qubit applications. We theoretically consider the possibility of the π-junction formation in the mesoscopic Josephson junctions with ferromagnetic insulators (FI) by taking into account the band structure of such materials explicitly. In the case of the fully polarized FIs, e.g., La 2 BaCuO 5 (LBCO) and K 2 CuF 4 , we found the formation of a π-junction and a novel atomic-scale 0-π transition induced by increasing the FI thickness LF. In this talk, I will discuss a thermal stability and material-parameter dependences of the atomic-scale 0-π transition as well as possibility of the odd-frequency pairing in such systems. (author)
International Nuclear Information System (INIS)
Lazarides, N
2004-01-01
An analytical expression for the magnetic-field-dependent critical current I c (H) of Josephson junctions with periodically alternating critical current density J c (x) is derived within the uniform field approximation. Comparison with numerically calculated I c (H) patterns for junctions with identical, thick, periodically arranged defects with the corresponding analytical expression reveals fair agreement for a wide range of parameters, due to increased characteristic length. Based on qualitative arguments, we give the dependence of the new characteristic length on the geometrical parameters of the junction, which is in agreement with self-consistent calculations with the static sine-Gordon equation. The analytical expression captures the observed qualitative features of the I c (H) patterns, while it is practically exact for short junctions or high fields. It also produces the shift of the major peak from the zero-field position of the standard Fraunhofer pattern to another position related to the periodicity of the critical current density in φ-junctions
Direct fabrication of a W-C SNS Josephson junction using focused-ion-beam chemical vapour deposition
International Nuclear Information System (INIS)
Dai, Jun; Kometani, Reo; Ishihara, Sunao; Warisawa, Shin’ichi; Onomitsu, Koji; Krockenberger, Yoshiharu; Yamaguchi, Hiroshi
2014-01-01
A tungsten-carbide (W-C) superconductor/normal metal/superconductor (SNS) Josephson junction has been fabricated using focused-ion-beam chemical vapour deposition (FIB-CVD). Under certain process conditions, the component ratio has been tuned from W: C: Ga = 26%: 66%: 8% in the superconducting wires to W: C: Ga = 14%: 79%: 7% in the metallic junction. The critical current density at 2.5 K in the SNS Josephson junction is 1/3 of that in W-C superconducting nanowire. Also, a Fraunhofer-like oscillation of critical current in the junction with four periods is observed. FIB-CVD opens avenues for novel functional superconducting nanodevices. (paper)
Josephson spectroscopy of terahertz losses in [100]-tilt YBa2Cu3O7-x bicrystal junctions
International Nuclear Information System (INIS)
Divin, Y; Lyatti, M
2008-01-01
Terahertz losses in the [100]-tilt YBa 2 Cu 3 O 7-x grain-boundary junctions were studied using admittance Josephson spectroscopy. The I-Vcurves of the [100]-tilt YBa 2 Cu 3 O 7-x junctions, when annealed in atomic oxygen, were described by the resistively shunted junction model (RSJ) with an accuracy of better than 0.5% at the temperature range, where the characteristic voltage I c R n n -1 . At low temperatures, where I c R n >> kT/2e, the absorption of Josephson radiation by optical phonon modes in YBa 2 Cu 3 O 7-x was found to be reflected in the I-V curve of the [100]-tilt junctions. The most prominent structure is situated at the voltages V ∼ 9.5 mV, which gives the corresponding Josephson frequency of 4.6 THz in good agreement with the frequency of the strongest IR active optical phonon mode in YBa 2 Cu 3 O 7-x . Assignment of additional lines in the derived losses is discussed according to available data on lattice dynamic calculations and experimental data for a dynamic conduction Reσ 1 (f) of YBa 2 Cu 3 O 7-x . Josephson spectroscopy might be useful for study of low-energy excitations in high-T c materials
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.
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
Coherent quantum transport in hybrid Nb-InGaAs-Nb Josephson junctions
Delfanazari, Kaveh; Puddy, R.; Ma, P.; Cao, M.; Yi, T.; Gul, Y.; Farrer, I.; Ritchie, D.; Joyce, H.; Kelly, M.; Smith, C.
Because of the recently reported detection of Majorana fermions states at the superconductor-semiconductor (S-Sm) interface in InAs nanowire devices, the study of hybrid structures has received renewed interest. In this paper we present experimental results on proximity induced superconductivity in a high-mobility two-dimensional electron gas in InGaAs heterostructures. Eight symmetric S-Sm-S Josephson junctions were fabricated on a single InGaAs chip and each junction was measured individually using a lock-in measurement technique. The superconducting electrodes were made of Niobium (Nb). The measurements were carried out in a dilution fridge with a base temperature of 40 mK, and the quantum transport of junctions were measured below 800 mK. Owing to Andreev reflections at the S-Sm interfaces, the differential resistance (dV/dI) versus V curve shows the well-known subharmonic energy gap structure (SGS) at V = 2ΔNb/ne. The SGS features suppressed significantly with increasing temperature and magnetic field, leading to a shift of the SGSs toward zero bias. Our result paves the way for development of highly transparent hybrid S-Sm-S junctions and coherent circuits for quantum devices capable of performing quantum logic and processing functions.
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....
Multi-scale simulation for terahertz wave emission from the intrinsic Josephson junctions
Energy Technology Data Exchange (ETDEWEB)
Koyama, T; Matsumoto, H [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Machida, M; Ota, Y [CREST (JST), 4-1-8 Honcho, Kawaguchi, Saitama 332-0012 (Japan)
2011-08-15
A numerical method applicable to the analysis of the multi-scale electromagnetic (EM) excitations in intrinsic Josephson junctions (IJJs) is presented. Using this method, we investigate the EM wave emission from the IJJs observed in Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} mesas. The IJJs have three length scales that are greatly different in magnitude, i.e. the distance between superconducting layers (d {approx} 10{sup -3} {mu}m), the Josephson length ({lambda}{sub J} {approx} 1 {mu}m) and the c-axis penetration depth ({lambda}{sub c} {approx} 10{sup 2} {mu}m). The EM field excited in the IJJs generally shows spatial variation of these three length scales at the same time. In our numerical method the coupled dynamical equations for the phase differences and the EM field can be solved simultaneously in all the scales in the whole space composed of the IJJs and the surrounding vacuum. We clarify that the spatial symmetry of the EM field excited at the resonance with the {pi}-cavity-mode is different from that with the 2{pi}-cavity-mode. The strong EM wave emission originating from the {pi}-cavity-mode resonance takes place in the region where the uniform branch becomes unstable in the I-V characteristics.
Sub-terahertz sound excitation and detection by a long Josephson junction
Koshelets, V. P.
2014-06-01
The paper reports on experimental observations of sub-terahertz sound wave generation and detection by a long Josephson junction. This effect was discovered in spectral measurements of sub-terahertz electromagnetic emission from a flux-flow oscillator (FFO) deposited on an optically polished Si substrate. The ‘back action’ of the acoustic waves generated by the FFO and reflected by the bottom surface of the Si substrate results in the appearance of resonant steps in the FFO IVCs with spacings as small as 29 nV for a 0.3 mm substrate thickness; these steps manifest themselves in a pronounced resonant structure in the emission spectra, with spacings of about 14 MHz, precisely according to the Josephson relation. The mechanism of acoustic wave generation and detection by the FFO is discussed; a possibility for employing the discovered effect for FFO frequency stabilization has been demonstrated. A simple and reliable way to suppress the superfine resonant structure has been developed and proved; this invention allows continuous frequency tuning and FFO phase locking at any desired frequency, all of which are vitally important for most applications.
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
International Nuclear Information System (INIS)
Kim, JunHo; Kim, Sang Hyeob; Sung, Gun Yong
2002-01-01
We designed and fabricated a rapid-single-flux-quantum T flip-flop (TFF) with high-T c interface-engineered Josephson junctions. Y 1 Ba 2 Cu 3 O 7-d and Sr 2 AlTaO 6 were deposited for the superconducting layer and the insulating layer, respectively. The Josephson junction was formed through an interface treatment process using Ar ion milling and vacuum annealing. We simulated a TFF circuit and designed a physical layout using WRspice and Xic. The fabricated TFF has a minimum junction width of 3 μ m. Through the measurement of the voltage divider operation, the maximum operation frequency was estimated to be 53 GHz at 22 K and 106 GHz at 12 K. (author)
Lin, Shi-Zeng; Hu, Xiao
2011-04-01
The nano-scale intrinsic Josephson junctions in highly anisotropic cuprate superconductors have potential for generation of terahertz electromagnetic waves. When the thickness of a superconductor sample is much smaller than the wavelength of electromagnetic waves in vacuum, the superconductor renders itself as a cavity. Unlike conventional lasers, the presence of the cavity does not guarantee a coherent emission because of the internal degree of freedom of the superconductivity phase in long junctions. We study the excitation of terahertz wave by solitons in a stack of intrinsic Josephson junctions, especially for relatively short junctions. Coherent emission requires a rectangular configuration of solitons. However such a configuration is unstable against weak fluctuations, contrarily solitons favor a triangular lattice corresponding to an out-phase oscillation of electromagnetic waves. To utilize the cavity, we propose to use an array of stacks of short intrinsic Josephson junctions to generate powerful terahertz electromagnetic waves. The cavity synchronizes the plasma oscillation in different stacks and the emission intensity is predicted to be proportional to the number of stacks squared.
Characterization of double-loop four-Josephson-junction flux qubit
International Nuclear Information System (INIS)
Shimazu, Y.; Saito, Y.; Wada, Z.
2009-01-01
An advantage of a double-loop four-Josephson-junction (4-JJ) flux qubit is the tunability of the energy gap at a symmetry point, i.e., the point at which the double-well potential of the qubit is symmetric. The energy gap is controlled via the magnetic flux in a DC superconducting quantum interference device (DC-SQUID) loop incorporated in a 4-JJ qubit. We investigate the locus of the symmetry point in the plane of two control fluxes of the qubit, taking into account the asymmetry in the DC-SQUID, which is inevitable in practical cases. The observed positions of the qubit steps are in reasonable agreement with the calculated locus of the symmetry point. We estimate the asymmetry parameter of the DC-SQUID from this analysis.
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
Magnetic field dependence of microwave radiation in intermediate-length Josephson junctions
DEFF Research Database (Denmark)
Sørensen, Mads Peter; Parmentier, R. D.; Christiansen, Peter Leth
1984-01-01
Experimental measurements of current-voltage structure and emitted X-band radiation in applied magnetic field from overlap-geometry Josephson tunnel junctions of normalized length about 2 are compared with numerical simulations obtained with the use of a perturbed sine-Gordon model. The simulations...... Fiske step in magnetic field and the field dependence of the radiation frequency within the various lobes, including details such as hysteresis between lobes. The simulations predict an alternation of the dominant frequency component with increasing field that accounts well for the experimental...... furnish the current and field dependence of the oscillation configuration, from which can be calculated average voltages, frequencies, and power spectra. Simulation and experimental results are in good agreement with regard to the lobe structure of the height of the first zero-field step and/or second...
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.
Synchronization of chaos in RCL-shunted Josephson junction using a simple adaptive controller
International Nuclear Information System (INIS)
Guo, R; Vincent, U E; Idowu, B A
2009-01-01
In this paper, a simple adaptive control is proposed for the synchronization of chaotic dynamics of resistive-capacitive-inductive-shunted Josephson junctions (RCLSJ). The synchronization problem is investigated based on a drive-response system configuration consisting of two identical RCLSJ with and without identical system parameters. In addition, the synchronization when the system parameters are unknown is considered based on adaptive parameter control estimation. Sufficient conditions for global asymptotic synchronization are given and numerical simulations are employed to demonstrate the efficiency of the adaptive control scheme. In the presence of noise, we also show that the synchronization is robust and discuss the implication of our adaptive control technique in rapid single flux quantum (RSFQ) devices.
Energy Technology Data Exchange (ETDEWEB)
Meister, Selina; Kubala, Bjoern; Gramich, Vera; Mecklenburg, Michael; Stockburger, Juergen T.; Ankerhold, Joachim [Institute for Complex Quantum Systems, Ulm University, Albert-Einstein-Allee 11, 89069 Ulm (Germany)
2015-07-01
Motivated by recent experiments a superconducting hybrid circuit consisting of a voltage biased Josephson junction in series with a resonator is studied. For strong driving the dynamics of the system can be very complex, even in the classical regime. Studying the dissipative dynamics within a Langevin-type description, we obtain well-defined dynamical steady states. In contrast to the well-known case of anharmonic potentials, like the Duffing or parametric oscillator, in our case the non-linearity stems from the peculiar way the external drive couples to the system [2]. We investigate the resonance behaviour of this non-linear hybrid system, in particular when driving at higher- or subharmonics. The resulting down- and up-conversions can be observed both, as resonances in the I-V curve, and in the emitted microwave radiation, which yields additional spectral information.
Spectral density of Cooper pairs in two level quantum dot–superconductors Josephson junction
Energy Technology Data Exchange (ETDEWEB)
Dhyani, A., E-mail: archana.d2003@gmail.com [Department of Physics, University of Petroleum and Energy Studies, Dehradun 248007, Uttarakhand (India); Rawat, P.S. [Department of Nuclear Science and Technology, University of Petroleum and Energy Studies, Dehradun 248007, Uttarakhand (India); Tewari, B.S., E-mail: bstewari@ddn.upes.ac.in [Department of Physics, University of Petroleum and Energy Studies, Dehradun 248007, Uttarakhand (India)
2016-09-15
Highlights: • The present work deals with the study of the electronic spectral density of electron pairs and its effect in charge transport in superconductor-quantum dot-superconductor junctions. • The charge transfer across such junctions can be controlled by changing the positions of the dot level. • The Josephson supercurrent can also be tuned by controlling the position of quantum dot energy levels. - Abstract: In the present paper, we report the role of quantum dot energy levels on the electronic spectral density for a two level quantum dot coupled to s-wave superconducting leads. The theoretical arguments in this work are based on the Anderson model so that it necessarily includes dot energies, single particle tunneling and superconducting order parameter for BCS superconductors. The expression for single particle spectral function is obtained by using the Green's function equation of motion technique. On the basis of numerical computation of spectral function of superconducting leads, it has been found that the charge transfer across such junctions can be controlled by the positions and availability of the dot levels.
Development of NbN Josephson junctions with TaxN semi-metal barrier; application to RSFQ circuits
International Nuclear Information System (INIS)
Setzu, R.
2007-11-01
This thesis research, brought to the development and optimization of SNS (Superconductor / Normal Metal / Superconductor) Josephson junctions with NbN electrodes and a high resistivity Ta x N barrier. We were able to point out Josephson oscillations for frequencies above 1 THz and operation temperatures up to 10 K, which constituted the original goal of the project. This property makes these junctions unique and well adapted for realizing ultra-fast RSFQ (Rapid Single Flux Quantum) logic circuits suitable for spatial telecommunications. We showed a good reproducibility of Ta x N film properties as a function of the sputtering parameters. The NbN/Ta x N/NbN tri-layers exhibit high critical temperature (16 K). The junctions showed a clear dependence of the R n I c product as a function of the partial nitrogen pressure inside the reactive plasma; the R n I c is the product between the junction critical current and its normal resistance, and indicates the upper limit Josephson frequency. We have also obtained some really high R n I c products, up to 3.74 mV at 4.2 K for critical current densities of about 15 kA/cm 2 . Junctions show the expected Josephson behaviors, respectively Fraunhofer diffraction and Shapiro steps. up to 14 K. This allows expecting good circuit operations in a relaxed cryogenics environment (with respect to the niobium circuits limited at 4.2 K). The junctions appear to be self-shunted. The SNOP junctions J c -temperature dependence has been fitted by using the long SNS junction model in the dirty limit, which gives a normal metal coherence length of about 3.8 nm at 4.2 K. We have finally studied a multilayer fabrication process, including a common ground plane and bias resistors, suitable for RSFQ logic basic circuits. To conclude we have been able to show the performance superiority of NbN/Ta x N/NbN junctions over the actual niobium junctions, as well as their interest for realizing compact RSFQ logic circuits. In fact these junctions do not
Overdamped Josephson junctions with Nb/AlOx/Al/AlOx/Nb structure for integrated circuit application
International Nuclear Information System (INIS)
Maezawa, M.; Shoji, A.
1997-01-01
We present characteristics of overdamped Josephson junctions consisting of Nb/AlO x /Al/ AlO x /Nb structures. The junctions were fabricated using a well-developed Nb/AlO x /Nb-junction technology and showed well-defined Josephson characteristics at 4.2 K. The characteristic voltage V c [the product of the critical current I c and the effective normal resistance R n(eff) ] of junctions, which determines high-frequency performance of the junction, was in the range of 0.1 endash 0.5 mV, and the critical current density J c in the range of 10 2 endash 10 4 A/cm 2 . Maximum-to-minimum variations in I c over a wafer were ±4% for junctions with V c =0.15mV and ±13% for junctions with V c =0.5mV. copyright 1997 American Institute of Physics
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
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
International Nuclear Information System (INIS)
Duwel, A.E.; Watanabe, S.; Trias, E.; Orlando, T.P.; van der Zant, H.S.; Strogatz, S.H.
1997-01-01
New resonance steps are found in the experimental current-voltage characteristics of long, discrete, one-dimensional Josephson junction arrays with open boundaries and in an external magnetic field. The junctions are underdamped, connected in parallel, and dc biased. Numerical simulations based on the discrete sine-Gordon model are carried out, and show that the solutions on the steps are periodic trains of fluxons, phase locked by a finite amplitude radiation. Power spectra of the voltages consist of a small number of harmonic peaks, which may be exploited for possible oscillator applications. The steps form a family that can be numbered by the harmonic content of the radiation, the first member corresponding to the Eck step. Discreteness of the arrays is shown to be essential for appearance of the higher order steps. We use a multimode extension of the harmonic balance analysis, and estimate the resonance frequencies, the ac voltage amplitudes, and the theoretical limit on the output power on the first two steps. copyright 1997 American Institute of Physics
The road to magnesium diboride thin films, Josephson junctions and SQUIDs
International Nuclear Information System (INIS)
Brinkman, Alexander; Mijatovic, Dragana; Hilgenkamp, Hans; Rijnders, Guus; Oomen, Ingrid; Veldhuis, Dick; Roesthuis, Frank; Rogalla, Horst; Blank, Dave H A
2003-01-01
The remarkably high critical temperature at which magnesium diboride (MgB 2 ) undergoes transition to the superconducting state, T c ∼ 40 K, has aroused great interest and has encouraged many groups to explore the properties and application potential of this novel superconductor. For many electronic applications and further basic studies, the availability of superconducting thin films is of great importance. Several groups have succeeded in fabricating superconducting MgB 2 films. An overview of the deposition techniques for MgB 2 thin film growth will be given, with a special focus on the in situ two-step process. Although, meanwhile, many problems to obtain suitable films have been solved, such as oxygen impurities and magnesium volatility, the question of how single-phase epitaxial films can be grown still remains. The possibility of growing single-crystalline epitaxial films will be discussed from the deposition conditions' point of view as well as substrate choice. Necessary conditions are discussed and possible routes are reviewed. The applicability of MgB 2 in superconducting electronic devices depends on the possibility of making well-controlled, i.e., reproducible and stable, Josephson junctions. The first attempts to make MgB 2 -MgO-MgB 2 ramp-type junctions and SQUIDs from MgB 2 nanobridges are discussed
Electronic decoherence of two-level systems in a Josephson junction
Bilmes, Alexander; Zanker, Sebastian; Heimes, Andreas; Marthaler, Michael; Schön, Gerd; Weiss, Georg; Ustinov, Alexey V.; Lisenfeld, Jürgen
2017-08-01
The sensitivity of superconducting qubits allows for spectroscopy and coherence measurements on individual two-level systems present in the disordered tunnel barrier of an Al /AlOx /Al Josephson junction. We report experimental evidence for the decoherence of two-level systems by Bogoliubov quasiparticles leaking into the insulating AlOx barrier. We control the density of quasiparticles in the junction electrodes either by the sample temperature or by injecting them using an on-chip dc superconducting quantum interference device driven to its resistive state. The decoherence rates were measured by observing the two-level system's quantum state evolving under application of resonant microwave pulses and were found to increase linearly with quasiparticle density, in agreement with theory. This interaction with electronic states provides a noise and decoherence mechanism that is relevant for various microfabricated devices such as qubits, single-electron transistors, and field-effect transistors. The presented experiments also offer a possibility to determine the location of the probed two-level systems across the tunnel barrier, providing clues about the fabrication step in which they emerge.
Chaos and thermal noise in the rf-biased Josephson junction
International Nuclear Information System (INIS)
Kautz, R.L.
1985-01-01
The effect of thermal noise on chaotic behavior in the rf-biased Josephson junction is studied through digital simulations. In instances for which chaotic behavior occurs in the noise-free system, it is found that the dynamics of the system are almost unchanged by the addition of thermal noise unless the level of thermal noise exceeds that of the chaotic state. In instances for which the only stable states of the noise-free system are periodic solutions, small amounts of thermal noise can induce the junction to hop between two different dynamical states, producing a low-frequency noise level much higher than that of the thermal noise. Such noise-induced hopping can occur either between two periodic solutions or between a periodic solution and a metastable chaotic solution. When a metastable chaotic state is involved, temperatures somewhat higher than those which produce hopping can destablize the periodic solution to the point where the system spends virtually all of its time in the metastable chaotic state, creating noise-induced chaos. The similarities between chaotic behavior at zero temperature and noise-induced chaos are sufficiently strong that it may be difficult to distinguish the two cases experimentally
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.
Au/Ti resistors used for Nb/Pb-alloy Josephson junctions. I. Electrical stability
International Nuclear Information System (INIS)
Murakami, M.; Alessandrini, E.I.; Kim, K.K.
1984-01-01
Bilayered Au/Ti films are very attractive for use as resistor materials of experimental Nb/Pb-alloy Josephson junction devices. In order to predict the electrical stability of the Au/Ti resistors during storage at room temperature, changes in microstructure and electrical resistivity of Ti and Au/Ti films during isothermal annealing at temperatures ranging from 298--473 K were studied using transmission electron microscopy, x-ray diffraction, and electrical measurements. Growth of Ti grains during annealing was observed in these films. The activation energy for the grain growth was determined to be 1.51 eV. Decreases in the sheet resistance measured at 4.2 K were observed at the early stages of isothermal annealing. By analyzing the annealing temperature dependence of rates of resistance changes, the activation energy of 1.49 eV was obtained. This energy value is very close to that obtained for the grain growth and, therefore, one of the main causes in the resistance decrease is believed to be due to the growth of Ti grains. Based on the present results, a model to predict the electrical resistance change for the Au/Ti films during storage at room temperature was established. The model predicted that change in the resistance can be significantly reduced by preannealing the resistors at an elevated temperature. The prediction was supported by the experiment and an excellent quantitative agreement between measured resistance values and those predicted by the model was obtained. Based on this model, the change was predicted to be -1.5% after about 3 years at room temperature, if the resistors were preannealed at 353 K for 10 h. This resistor stability is satisfactory for designing logic and memory circuits of Josephson devices, and it can be increased simply by preannealing for longer times at 353 K
International Nuclear Information System (INIS)
Buckenmaier, Kai
2010-01-01
This thesis is divided into two parts, the measurement of the activation energy of a fractional vortex and the spectroscopy of a vortex-molecule. Fractional vortices can be studied in long 0-κ Josephson junctions, where a jump of the Josephson phase is created artificially with a pair of tiny current injectors. To compensate for this phase discontinuity, a ρ vortex is formed. Here, ρ describes the vortex's so called topological charge. The ρ vortices are pinned at the discontinuity and they carry the fraction (ρ/2).Φ 0 of magnetic flux, with the magnetic flux quantum Φ 0 2.07.10 -15 . Two stable vortex configurations are possible, a direct Vortex and a complementary one. ρ depends on the injector current. When the bias current of the junction exceeds a characteristic threshold, which dependents on ρ, the Lorentz force is bigger than the pinning force of the vortex and a fluxon is pulled away. In this case a complementary (ρ-2π) vortex is left behind. This switching of the ρ vortex and the resulting emission of a fluxon can be described as a Kramers like escape of a particle out of a tilted washboard potential. The washboard potential is tilted to the point where the barrier is small enough, so that the particle can escape via thermal or quantum fluctuations. In the case of thermal fluctuations the barrier height is called activation energy. The activation energy can be determined by measuring the junction's switching current statistics. In this thesis, the activation energy, necessary for the vortex escape, was measured as a function of ρ and a homogenous external magnetic field perpendicular to the junction. The main focus was the investigation of 0-π junctions. The temperature dependence of the activation energy was investigated, too. It turns out, that the transition-state-theory is convenient to describe the switching probability of the standard Nb-AlO x -Nb junctions at 4.2 K. For the measurements at 0.5 K a model of low to intermediate damping
Kaul, Anupama Bhat
Superconductor electronics promises some of the highest circuit speeds of any known digital technology. Two classes of superconducting logic families exist: voltage-state logic, and Rapid-Single-Flux-Quantum (RSFQ) logic. The ideal devices for the two logic families are fundamentally different. In this dissertation, we describe alterations in the barrier materials of the respective devices, coupled with process innovations, which lead to junctions that enable higher speed operation. For voltage-state logic, where speeds are limited by junction capacitance, a high-Jc process was developed, where thin AlOx barrier layers were formed in Nb/Al-AlOx/Nb trilayers. Small-area devices of inherently lower capacitance were fabricated, which was made possible by an anodization step, and this obviated complicated planarization techniques. This high-Jc process was used to demonstrate a clocked Josephson amplifier, whose design, simulation and high-speed test results were presented. The circuit was fabricated in a 9.4 kA/cm2 process, and was operational to speeds of at least 10 GHz. It exhibited error rates as low as 5 x 10-12 at 5 GHz, and eye diagram measurements revealed a clear-eye area, even up to 10 GHz. This Josephson amplifier represents the first circuit to be fabricated and successfully tested in a ˜10 kA/cm 2 process, and is of importance for interfacing superconductive circuitry with semiconductor electronics. While the basic device for voltage-state logic is the superconductor/insulator/superconductor (SIS) junction, the ideal device for RSFQ technology is a superconductor/normal-conductor/superconductor (SNS) junction. Since the figure of merit of this device, the IcR n, is directly influenced by the resistivity of the barrier material, high resistivity materials are desired to raise Rn, without significantly reducing Ic. We have proposed and demonstrated a new barrier material TaNx with NbN electrodes for the realization of an all-nitride SNS junction technology
Hamdipour, Mohammad
2018-04-01
We study an array of coupled Josephson junction of superconductor/insulator/superconductor type (SIS junction) as a model for high temperature superconductors with layered structure. In the current-voltage characteristics of this system there is a breakpoint region in which a net electric charge appear on superconducting layers, S-layers, of junctions which motivate us to study the charge dynamics in this region. In this paper first of all we show a current voltage characteristics (CVC) of Intrinsic Josephson Junctions (IJJs) with N=3 Junctions, then we show the breakpoint region in that CVC, then we try to investigate the chaos in this region. We will see that at the end of the breakpoint region, behavior of the system is chaotic and Lyapunov exponent become positive. We also study the route by which the system become chaotic and will see this route is bifurcation. Next goal of this paper is to show the self similarity in the bifurcation diagram of the system and detailed analysis of bifurcation diagram.
International Nuclear Information System (INIS)
Kromann, R.; Vase, P.; Shen, Y.Q.; Freltoft, T.
1993-01-01
The fabrication of Josephson junctions and SQUIDs using ceramic high T c superconductors continues to be a subject of great interest and activity. In the case of the YBCO family of superconductors, most of the research effort has been concentrated on the grain boundary junctions. This type of junction can be fabricated in a controlled way by a variety of approaches, such as the bi-crystal technique, the bi-epitaxial technique or the step-edge technique. From a fabrication point of view, the bi-crystal technique is by far the simplest of the three. The availability of (100) SrTiO 3 bi-crystals on a commercial basis has lead to the possibility of making Josephson junctions by a simple process involving only one deposition and one patterning step. Reproducibility of the junction parameters between junctions on the same chip is a key point for electronic applications of Josephson junctions requiring a large amount of Josephson junctions working at the same time, as for example in the voltage standard. Another key point is the uniformity of the barrier, i.e. the extent to which the junction behaves as an ideal SIS junction. In this work junction uniformity has been studied by Frauenhofer diffraction patterns. The Josephson junctions have also been used in the fabrication of dc SQUIDs. In this work we have tried to optimize the magnitude of the voltage modulation from the SQUID by varying the design parameters. The SQUIDs have been characterized in terms of I c , R n , voltage modulation and noise properties. (orig.)
Lu, Wen-Ting; Zhao, Hong-Kang; Wang, Jian
2018-03-01
Photon heat current tunneling through a series coupled two mesoscopic Josephson junction (MJJ) system biased by dc voltages has been investigated by employing the nonequilibrium Green’s function approach. The time-oscillating photon heat current is contributed by the superposition of different current branches associated with the frequencies of MJJs ω j (j = 1, 2). Nonlinear behaviors are exhibited to be induced by the self-inductance, Coulomb interaction, and interference effect relating to the coherent transport of Cooper pairs in the MJJs. Time-oscillating pumping photon heat current is generated in the absence of temperature difference, while it becomes zero after time-average. The combination of ω j and Coulomb interactions in the MJJs determines the concrete heat current configuration. As the external and intrinsic frequencies ω j and ω 0 of MJJs match some specific combinations, resonant photon heat current exhibits sinusoidal behaviors with large amplitudes. Symmetric and asymmetric evolutions versus time t with respect to ω 1 t and ω 2 t are controlled by the applied dc voltages of V 1 and V 2. The dc photon heat current formula is a special case of the general time-dependent heat current formula when the bias voltages are settled to zero. The Aharonov-Bohm effect has been investigated, and versatile oscillation structures of photon heat current can be achieved by tuning the magnetic fluxes threading through separating MJJs.
Anomalous transport effects on switching currents of graphene-based Josephson junctions
Guarcello, Claudio; Valenti, Davide; Spagnolo, Bernardo; Pierro, Vincenzo; Filatrella, Giovanni
2017-03-01
We explore the effect of noise on the ballistic graphene-based small Josephson junctions in the framework of the resistively and capacitively shunted model. We use the non-sinusoidal current-phase relation specific for graphene layers partially covered by superconducting electrodes. The noise induced escapes from the metastable states, when the external bias current is ramped, given the switching current distribution, i.e. the probability distribution of the passages to finite voltage from the superconducting state as a function of the bias current, that is the information more promptly available in the experiments. We consider a noise source that is a mixture of two different types of processes: a Gaussian contribution to simulate an uncorrelated ordinary thermal bath, and non-Gaussian, α-stable (or Lévy) term, generally associated to non-equilibrium transport phenomena. We find that the analysis of the switching current distribution makes it possible to efficiently detect a non-Gaussian noise component in a Gaussian background.
Energy Technology Data Exchange (ETDEWEB)
Cristofano, Gerardo; Marotta, Vincenzo [Dipartimento di Scienze Fisiche, Universita di Napoli ' Federico II' and INFN, Sezione di Napoli, Via Cintia, Complesso Universitario M. Sant' Angelo, 80126 Napoli (Italy); Naddeo, Adele [Dipartimento di Fisica ' E.R. Caianiello' , Universita degli Studi di Salerno and CNISM, Unita di Ricerca di Salerno, Via Salvador Allende, 84081 Baronissi (Saudi Arabia) (Italy)], E-mail: naddeo@sa.infn.it; Niccoli, Giuliano [LPTM, Universite de Cergy-Pontoise, 2 avenue Adolphe Chauvin, 95302 Cergy-Pontoise (France)
2008-03-31
We show how to realize a 'protected' qubit by using a fully frustrated Josephson junction ladder (JJL) with Mobius boundary conditions. Such a system has been recently studied within a twisted conformal field theory (CFT) approach [G. Cristofano, G. Maiella, V. Marotta, Mod. Phys. Lett. A 15 (2000) 1679; G. Cristofano, G. Maiella, V. Marotta, G. Niccoli, Nucl. Phys. B 641 (2002) 547] and shown to develop the phenomenon of flux fractionalization [G. Cristofano, V. Marotta, A. Naddeo, G. Niccoli, Eur. Phys. J. B 49 (2006) 83]. The relevance of a 'closed' geometry has been fully exploited in relating the topological properties of the ground state of the system to the presence of half flux quanta and the emergence of a topological order has been predicted [G. Cristofano, V. Marotta, A. Naddeo, J. Stat. Mech.: Theory Exp. (2005) P03006]. In this Letter the stability and transformation properties of the ground states under adiabatic magnetic flux change are analyzed and the deep consequences on the realization of a solid state qubit, protected from decoherence, are presented.
Structured chaos in a devil's staircase of the Josephson junction
Energy Technology Data Exchange (ETDEWEB)
Shukrinov, Yu. M. [BLTP, JINR, Dubna, Moscow Region 141980 (Russian Federation); Botha, A. E., E-mail: bothaae@unisa.ac.za [Department of Physics, University of South Africa, Science Campus, Private Bag X6, Florida Park 1710 (South Africa); Medvedeva, S. Yu. [BLTP, JINR, Dubna, Moscow Region 141980 (Russian Federation); Moscow Institute of Physics and Technology (State University), Dolgoprudny, Moscow Region 141700 (Russian Federation); Kolahchi, M. R. [Institute for Advanced Studies in Basic Sciences, P.O. Box 45195-1159, Zanjan (Iran, Islamic Republic of); Irie, A. [Department of Electrical and Electronic Systems Engineering, Utsunomiya University, 7-1-2 Yoto, Utsunomiya 321-8585 (Japan)
2014-09-01
The phase dynamics of Josephson junctions (JJs) under external electromagnetic radiation is studied through numerical simulations. Current-voltage characteristics, Lyapunov exponents, and Poincaré sections are analyzed in detail. It is found that the subharmonic Shapiro steps at certain parameters are separated by structured chaotic windows. By performing a linear regression on the linear part of the data, a fractal dimension of D = 0.868 is obtained, with an uncertainty of ±0.012. The chaotic regions exhibit scaling similarity, and it is shown that the devil's staircase of the system can form a backbone that unifies and explains the highly correlated and structured chaotic behavior. These features suggest a system possessing multiple complete devil's staircases. The onset of chaos for subharmonic steps occurs through the Feigenbaum period doubling scenario. Universality in the sequence of periodic windows is also demonstrated. Finally, the influence of the radiation and JJ parameters on the structured chaos is investigated, and it is concluded that the structured chaos is a stable formation over a wide range of parameter values.
Wideband Isolation by Frequency Conversion in a Josephson-Junction Transmission Line
Ranzani, Leonardo; Kotler, Shlomi; Sirois, Adam J.; DeFeo, Michael P.; Castellanos-Beltran, Manuel; Cicak, Katarina; Vale, Leila R.; Aumentado, José
2017-11-01
Nonreciprocal transmission and isolation at microwave frequencies are important in many practical applications. In particular, compact isolators are useful in protecting sensitive quantum circuits operating at cryogenic temperatures from amplifier backaction and other environmental noise such as black-body radiation from higher temperature stages. However, the size of commercial cryogenic isolators limits the ability to measure multiple quantum circuits because of space constraints in typical dilution refrigerator systems. Furthermore, isolators usually require the use of ferrite components that cannot be integrated at the chip level and, since they also need large biasing magnetic fields, are incompatible with superconducting quantum circuits. In this work we show one way to accomplish isolation in a superconducting chip-scale device, a traveling-wave unidirectional frequency converter based on a parametrically pumped superconducting Josephson-junction transmission line, demonstrating better than 4.8 dB of inferred signal isolation from 6.6 to 11.4 GHz, with a maximum of 12 dB at 9.5 GHz. By using frequency diplexing techniques a conventional isolator could be implemented over this bandwidth.
Josephson magnetic rotary valve
Soloviev, I.I.; Klenov, N.V.; Bakurskiy, S.V.; Bol’ginov, V.V.; Ryazanov, V.V.; Kupriyanov, M..Y.; Golubov, Alexandre Avraamovitch
2014-01-01
We propose a control element for a Josephson spin valve. It is a complex Josephson device containing ferromagnetic (F) layer in the weak-link area consisting of two regions, representing 0 and π Josephson junctions, respectively. The valve's state is defined by mutual orientations of the F-layer
Energy Technology Data Exchange (ETDEWEB)
Guerlich, Christian
2010-05-11
With Low-Temperature-Electron-Microscopy (LTSEM) it is possible to analyse the transport properties of solids at low temperatures. In particular it is possible to image the supercurrent density j{sub s} in Josephson junctions. This was demonstrated by comparing TTREM-images with calculated values for j{sub s}. In this thesis ramp-type Nd{sub 2-x}Ce{sub x}CuO{sub 4-y}/Nb-Josephson-junctions (NCCO/Nb) and Josephson junctions with a ferromagnetic interlayer Nb/Al-Al{sub 2}O{sub 3}/NiCu/Nb, so-called SIFS (superconductor-insulator-ferromagnet-superconductor) Josephson junctions were studied.It was demonstrated that LTSEM provides direct imaging of the sign change of the order parameter in superconductors with d{sub x{sup 2}-y{sup 2}}-symmetry. This was a controversial issue over the last decade. A step like variation in the thickness of the F-layer allows the fabrication of linear and annular Josephson junctions with different numbers of 0 and {pi} facets. With the LTSEM 0-, {pi}-, 0-{pi}-, 0-{pi}-0-, 0/2-{pi}-0/2-, 20 x (0-{pi})- as well as square-shaped-, circular- and annular-Josephson-junctions were studied. It was demonstrated, that these junctions are of good quality and have critical current densities up to 42 A/cm{sup 2} at T=4.2 K, which is a record value for SIFS junctions with a NiCu F-layer so far. By comparing the measurements with simulations a first indication of a semifluxon at the 0-{pi}-boundary was found. (orig.)
Berdiyorov, Golibjon R.; Savel'ev, Sergey; Kusmartsev, Feodor V.; Peeters, François M.
2015-11-01
We use the anisotropic time-dependent Ginzburg-Landau theory to investigate the effect of a square array of out-of-plane magnetic dots on the dynamics of Josephson vortices (fluxons) in artificial stacks of superconducting-normal-superconducting (SNS) Josephson junctions in the presence of external DC and AC currents. Periodic pinning due to the magnetic dots distorts the triangular lattice of fluxons and results in the appearance of commensurability features in the current-voltage characteristics of the system. For the larger values of the magnetization, additional peaks appear in the voltage-time characteristics of the system due to the creation and annihilation of vortex-antivortex pairs. Peculiar changes in the response of the system to the applied current is found resulting in a "superradiant" vortex-flow state at large current values, where a rectangular lattice of moving vortices is formed. Synchronizing the motion of fluxons by adding a small ac component to the biasing dc current is realized. However, we found that synchronization becomes difficult for large magnetization of the dots due to the formation of vortex-antivortex pairs.
Delfanazari, K; Asai, H; Tsujimoto, M; Kashiwagi, T; Kitamura, T; Yamamoto, T; Sawamura, M; Ishida, K; Watanabe, C; Sekimoto, S; Minami, H; Tachiki, M; Klemm, R A; Hattori, T; Kadowaki, K
2013-01-28
In order to determine if the mesa geometry might affect the properties of the coherent terahertz (THz) radiation emitted from the intrinsic Josephson junctions in mesas constructed from single crystals of the high-temperature superconductor, Bi₂Sr₂CaCu₂O₈+δ, we studied triangular mesas. For equilateral triangular mesas, the observed emission was found to be limited to the single mesa TM(1,0) mode. However, tunable radiation over the range from 0.495 to 0.934 THz was found to arise from an acute isosceles triangular mesa. This 47% tunability is the widest yet observed from the outer current-voltage characteristic branch of such mesas of any geometry. Although the radiation at a few of the frequencies in the tunable range appear to have been enhanced by cavity resonances, most frequencies are far from such resonance frequencies, and can only be attributed to the ac-Josephson effect.
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.
Energy Technology Data Exchange (ETDEWEB)
Freitas, Gustavo Quereza; Moreto, Jeferson Aparecido [Instituto Federal de Educacao, Ciencia e Tecnologia Goiano (IFGO), Rio Verde, GO (Brazil); Zadorosny, Rafael; Silveira, Joao Borsil; Carvalho, Claudio Luiz [Universidade Estadual Paulista Julio de Mesquita Filho (UNESP), Ilha Solteira, SP (Brazil); Cena, Cicero Rafael, E-mail: gustavoquereza@yahoo.com.br [Instituto Federal de Educacao, Ciencia e Tecnologia de Sao Paulo (IFSP), Birigui, SP (Brazil)
2016-03-15
A homemade Josephson junction was successfully obtained using a superconductor thin film of the BSCCO system. The film was deposited on a lanthanum aluminate, produced from a commercial powder with a nominal composition Bi{sub 1.8}Pb{sub 0.4}Sr{sub 2}CaCu{sub 2}O{sub x}, was thermally treated by a domestic microwave oven. The XRD analysis of the film indicated the coexistence of Bi-2212 and Bi-2223 phases and SEM images revealed that a typical superconductor plate-like morphology was formed. From the electrical characterization, performed using DC four probes technique, it was observed an onset superconducting transition temperature measured around 81K. At the current-voltage characteristics curve, a step of electric current at zero-voltage could be observed, an indicative that the tunneling Josephson occurred. (author)
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...
Improved synthesis of carbon nanotubes with junctions and of single ...
Indian Academy of Sciences (India)
Unknown
Abstract. Pyrolysis of thiophene over nickel nanoparticles dispersed on silica is shown to yield Y- junction carbon nanotubes with smaller diameters than those obtained by the pyrolysis of organometallic- thiophene mixtures. In the presence of water vapour, the pyrolysis of organometallic-hydrocarbon mixtures.
Energy Technology Data Exchange (ETDEWEB)
Yu Lei [Department of Electrical Engineering, Arizona State University, Tempe, AZ 85287-6006 (United States); Gandikota, Raghuram [Chemical and Materials Engineering, Arizona State University, Tempe, AZ 85287-6006 (United States); Singh, Rakesh K [Chemical and Materials Engineering, Arizona State University, Tempe, AZ 85287-6006 (United States); Gu Lin [Center for Solid State Science, Arizona State University, Tempe, AZ 85287 (United States); Smith, David J [Center for Solid State Science, Arizona State University, Tempe, AZ 85287 (United States); Meng Xiaofan [Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, CA 94720 (United States); Zeng Xianghui [Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, CA 94720 (United States); Duzer, Theodore van [Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, CA 94720 (United States); Rowell, John M [Chemical and Materials Engineering, Arizona State University, Tempe, AZ 85287-6006 (United States); Newman, N [Department of Electrical Engineering, Arizona State University, Tempe, AZ 85287-6006 (United States)
2006-08-15
The fabrication of self-shunted SNS (superconductor/normal conductor/superconductor) Josephson junctions for rapid single flux quantum (RSFQ) logic could potentially facilitate increased circuit density, as well as reduced parasitic capacitance and inductance over the currently used externally shunted SIS (superconductor/insulator/superconductor) trilayer junction process. We report the deposition, fabrication, and device characterization of Josephson junctions prepared with Nb{sub 1-y}Ti{sub y}N electrodes and Ta{sub x}N barriers tuned near the metal-insulator transition, deposited on practical large-area oxide-buffered silicon wafers. When scaled to practical device dimensions, this type of junction is found to have an I{sub c}R{sub n} product of over 0.5 mV and a critical current (I{sub c}) and normal resistance (R{sub n}) of magnitudes suitable for single flux quantum digital circuits. A longer than expected normal-metal coherence length ({xi}{sub n}) of 5.8 nm is inferred from the thickness dependence of J{sub c} at 4.2 K for junctions fabricated using a barrier resistivity of 13 m{omega} cm. Although not well understood and not quantitatively predicted by conventional theories, this results in a sufficiently high I{sub c} and I{sub c}R{sub n} to make the junctions suitable for practical applications. Similar observations of unexpectedly large Josephson coupling currents in SNS junctions have been documented in other systems, particularly in cases when the barrier is near the M-I transition, and have become known as the giant proximity effect. The temperature dependence of {xi}{sub n}, I{sub c}R{sub n}, and J{sub c} are also reported. For this technology to be used in practical applications, significant improvements in our fabrication process are needed as we observe large variations in I{sub c} and R{sub n} values across a 100 mm wafer, presumably as a result of variations in the Ta:N stoichiometry and the resulting changes in the Ta{sub x}N barrier
Tahvildar-Zadeh, A. N.; Freericks, J. K.; Nikolić, B. K.
2006-05-01
The Thouless energy was introduced in the 1970s as a semiclassical energy for electrons diffusing through a finite-sized conductor. It turns out to be an important quantum-mechanical energy scale for many systems ranging from disordered metals to quantum chaos to quantum chromodynamics. In particular, it has been quite successful in describing the properties of Josephson junctions when the barrier is a diffusive normal-state metal. The Thouless energy concept can be generalized to insulating barriers by extracting an energy scale from the two-probe Kubo conductance of a strongly correlated electron system (metallic or insulating) via a generalized definition of the quantum-mechanical level spacing to many-body systems. This energy scale is known to determine the crossover from tunneling to Ohmic (thermally activated) transport in normal tunnel junctions. Here we use it to illustrate how the quasiclassical picture of transport in Josephson junctions is modified as the strongly correlated barrier passes through the Mott transition. Surprisingly, we find the quasiclassical form holds well beyond its putative realm of validity.
International Nuclear Information System (INIS)
Sirena, M.; Fabreges, X.; Bergeal, N.; Lesueur, J.; Faini, G.; Bernard, R.; Briatico, J.
2007-01-01
A simple model has been proposed to explain the spread in the characteristics of high T c Josephson junctions made by ion irradiation, assuming that the source of dispersion is the slit's size variation. Accordingly, increasing ion energy should lead to a significant reduction of inhomogeneities. Test samples have been fabricated using two different beam energies. As predicted, the spread in critical current decreases upon increasing energy. Moreover, since the actual width of the barrier is reduced in this case, the I c R n product increases significantly. These results seem promising for future technological applications
DEFF Research Database (Denmark)
Aarøe, Morten; Monaco, Roberto; Dmitriev, P
2007-01-01
We report on new investigations of spontaneous symmetry breaking in non-adiabatic phase transitions. This Zurek-Kibble (ZK) process is mimicked in solid state systems by trapping of magnetic flux quanta, fluxons, in a long annular Josephson tunnel junction quenched through the normal.......5 for the ZK critical scaling exponent sigma, which does not agree with an earlier theoretical prediction of sigma = 0.25. A novel theory based on the proximity effect leading to sigma = 0.50 has been proposed. The dependence of the gap voltage on temperature is measured and used for precise monitoring...
International Nuclear Information System (INIS)
Hansen, J.B.; Divin, Y.Y.; Mygind, J.
1986-01-01
We report on the observation of full splitting of the first zero-field steps in the I-V curves of Josephson transmission lines of intermediate length Lroughly-equal(3--5)lambda/sub J/, where lambda/sub J/ is the Josephson penetration length. We study in detail how this splitting of the step into two branches depends on the temperature of the junction and on a weak applied magnetic field. We relate the splitting to excitations in the junctions whose behavior is described by the perturbed Sine-Gordon equation
International Nuclear Information System (INIS)
The effects of particle size and temperature on the microwave noise and low-field microwave absorption in YBa 2 Cu 3 O/sub 7-//sub y/ powders have been studied by the magnetically modulated microwave absorption technique. The results can be interpreted in terms of a network of random Josephson junctions in the individual superconducting grains but are not consistent with the thermally activated flux creep model. An estimate of the size of the Josephson junctions is also obtained from the variation of the microwave noise with particle size
Katase, Takayoshi; Ishimaru, Yoshihiro; Tsukamoto, Akira; Hiramatsu, Hidenori; Kamiya, Toshio; Tanabe, Keiichi; Hosono, Hideo
2010-04-01
Josephson junctions were fabricated in epitaxial films of cobalt-doped BaFe2As2 on [001]-tilt (La,Sr)(Al,Ta)O3 bicrystal substrates. 10-μm-wide microbridges spanning a 30°-tilted bicrystal grain boundary (BGB bridge) exhibited resistively-shunted-junction (RSJ)-like current-voltage characteristics up to 17 K, and the critical current was suppressed remarkably by a magnetic field. Microbridges without a BGB did not show the RSJ-like behavior, and their critical current densities were 20 times larger than those of BGB bridges, confirming BGB bridges display a Josephson effect originating from weakly-linked BGB.
DEFF Research Database (Denmark)
Hansen, Jørn Bindslev; Divin, Yu. Ya.; Mygind, Jesper
1986-01-01
We report on the observation of full splitting of the first zero-field steps in the I-V curves of Josephson transmission lines of intermediate length L≊(3–5)λJ, where λJ is the Josephson penetration length. We study in detail how this splitting of the step into two branches depends...... on the temperature of the junction and on a weak applied magnetic field. We relate the splitting to excitations in the junctions whose behavior is described by the perturbed sine-Gordon equation....
InAs/Si Hetero-Junction Nanotube Tunnel Transistors
Hanna, Amir N.; Fahad, Hossain M.; Hussain, Muhammad M.
2015-01-01
Hetero-structure tunnel junctions in non-planar gate-all-around nanowire (GAA NW) tunnel FETs (TFETs) have shown significant enhancement in ?ON? state tunnel current over their all-silicon counterpart. Here we show the unique concept of nanotube TFET in a hetero-structure configuration that is capable of much higher drive current as opposed to that of GAA NW TFETs.Through the use of inner/outer core-shell gates, a single III-V hetero-structured nanotube TFET leverages physically larger tunnel...
International Nuclear Information System (INIS)
Azbel, M.Y.; Bak, P.
1984-01-01
The differential equation epsilonphi-dieresis+phi-dot-(1/2)α sin(2phi) = I+summation/sub n/ = -infinity/sup infinity/A/sub n/delta(t-t/sub n/) describing the periodically driven damped pendulum is analyzed in the strong damping limit epsilon<<1, using first-order perturbation theory. The equation may represent the motion of a sliding charge-density wave (CDW) in ac plus dc electric fields, and the resistively shunted Josephson junction driven by dc and microwave currents. When the torque I exceeds a critical value the pendulum rotates with a frequency ω. For infinite damping, or zero mass (epsilon = 0), the equation can be transformed to the Schroedinger equation of the Kronig-Penney model. When A/sub n/ is random the pendulum exhibits chaotic motion. In the regular case A/sub n/ = A the frequency ω is a smooth function of the parameters, so there are no phase-locked subharmonic plateaus in the ω(I) curve, or the I-V characteristics for the CDW or Josephson-junction systems. For small nonzero epsilon the return map expressing the phase phi(t/sub n/+1) as a function of the phase phi(t/sub n/) is a one-dimensional circle map. Applying known analytical results for the circle map one finds narrow subharmonic plateaus at all rational frequencies, in agreement with experiments on CDW systems
Solve, S.; Chayramy, R.; Maruyama, M.; Urano, C.; Kaneko, N.-H.; Rüfenacht, A.
2018-04-01
BIPM’s new transportable programmable Josephson voltage standard (PJVS) has been used for an on-site comparison at the National Metrology Institute of Japan (NMIJ) and the National Institute of Advanced Industrial Science and Technology (AIST) (NMIJ/AIST, hereafter called just NMIJ unless otherwise noted). This is the first time that an array of niobium-based Josephson junctions with amorphous niobium silicon Nb x Si1-x barriers, developed by the National Institute of Standards and Technology4 (NIST), has been directly compared to an array of niobium nitride (NbN)-based junctions (developed by the NMIJ in collaboration with the Nanoelectronics Research Institute (NeRI), AIST). Nominally identical voltages produced by both systems agreed within 5 parts in 1012 (0.05 nV at 10 V) with a combined relative uncertainty of 7.9 × 10-11 (0.79 nV). The low side of the NMIJ apparatus is, by design, referred to the ground potential. An analysis of the systematic errors due to the leakage current to ground was conducted for this ground configuration. The influence of a multi-stage low-pass filter installed at the output measurement leads of the NMIJ primary standard was also investigated. The number of capacitances in parallel in the filter and their insulation resistance have a direct impact on the amplitude of the systematic voltage error introduced by the leakage current, even if the current does not necessarily return to ground. The filtering of the output of the PJVS voltage leads has the positive consequence of protecting the array from external sources of noise. Current noise, when coupled to the array, reduces the width or current range of the quantized voltage steps. The voltage error induced by the leakage current in the filter is an order of magnitude larger than the voltage error in the absence of all filtering, even though the current range of steps is significantly decreased without filtering.
InAs/Si Hetero-Junction Nanotube Tunnel Transistors
Hanna, Amir
2015-04-29
Hetero-structure tunnel junctions in non-planar gate-all-around nanowire (GAA NW) tunnel FETs (TFETs) have shown significant enhancement in ‘ON’ state tunnel current over their all-silicon counterpart. Here we show the unique concept of nanotube TFET in a hetero-structure configuration that is capable of much higher drive current as opposed to that of GAA NW TFETs.Through the use of inner/outer core-shell gates, a single III-V hetero-structured nanotube TFET leverages physically larger tunneling area while achieving higher driver current (ION) and saving real estates by eliminating arraying requirement. Numerical simulations has shown that a 10 nm thin nanotube TFET with a 100 nm core gate has a 5×normalized output current compared to a 10 nm diameter GAA NW TFET.
Nanotube junctions and the genus of multi-tori.
Diudea, Mircea V; Szefler, Beata
2012-06-14
Carbon nanotube junctions can be modeled by fullerene spanning or by using some operations on map. They can self-assemble into more complex structures, such as finite or infinite high genera multi-tori. Four junctions of tetrahedral and octahedral symmetry, covered by patches consisting only of hexagons, were designed. Their stability is discussed in terms of total energy, evaluated at Hartree-Fock (HF) level of theory, HOMO-LUMO gap, strain energy, HOMA index of aromaticity and the Kekulé structure count. Vibrational spectra of these junctions are given as well. A new multi-toroidal structure, of octahedral symmetry, is presented for the first time. The study on topology of the multi-tori herein designed revealed the relation of these structures with the genus of their embedding surface.
Tunable oscillator using pulsons on large-area lossy Josephson junctions
DEFF Research Database (Denmark)
Christiansen, Peter Leth; Lomdahl, Peter S.; Zabusky, Norman J.
1981-01-01
'' resistance). We propose to control the constant bias current with an autonomous pulson velocity-sensitive switch. One possibility for fine tuning the oscillations is to vary the strength of the Josephson impurity current. Applied Physics Letters is copyrighted by The American Institute of Physics....
2016-09-01
Liquid Helium Temperatures Osama Nayfeh SSC Pacific Lance Lerum Hector Romero NREIP Mohammed Fahem SDSURF Approved for public ...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
Dias, R G; Coutinho, B C; Martins, L P
2014-01-01
We present a study of Josephson junctions arrays with two-band superconducting elements in the highcapacitance limit. We consider two particular geometries for these arrays: a single rhombus and a rhombi chain with two-band superconducting elements at the spinal positions. We show that the rhombus shaped JJ circuit and the rhombi chain can be mapped onto a triangular JJ circuit and a JJ two-leg ladder, respectively, with zero effective magnetic flux, but with Josephson couplings that are magnetic flux dependent. If the two-band superconductors are in a sign-reversed pairing state, one observes transitions to or from chiral phase configurations in the mapped superconducting arrays when magnetic flux or temperature are varied. The phase diagram for these chiral configurations is discussed. When half-flux quantum threads each rhombus plaquette, new phase configurations of the rhombi chain appear that are characterized by the doubling of the periodicity of the energy density along the chain, with every other two-...
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
Energy Technology Data Exchange (ETDEWEB)
Cybart, Shane A; Anton, Steven; Wu, Stephen; Clarke, John; Dynes, Robert
2009-09-01
Very large scale integration of Josephson junctions in a two-dimensional series-parallel array has been achieved by ion irradiating a YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} film through slits in a nano-fabricated mask created with electron beam lithography and reactive ion etching. The mask consisted of 15,820 high-aspect ratio (20:1), 35-nm wide slits that restricted the irradiation in the film below to form Josephson junctions. Characterizing each parallel segment k, containing 28 junctions, with a single critical current I{sub ck} we found a standard deviation in I{sub ck} of about 16%.
Gao, Xiang; Zhang, Ting; Du, Jia; Weily, Andrew R.; Guo, Yingjie Jay; Foley, Cathy P.
2017-09-01
This paper presents a wideband terahertz (THz) mixer based on a thin-film antenna-coupled high-temperature superconducting (HTS) YBa2Cu3O7-x (YBCO) step-edge Josephson junction. The HTS mixer enables the flexible harmonic mixing operation at multiple THz bands with the same microwave local oscillator (LO) source, and features very wide intermediate-frequency or instantaneous bandwidth. In order to optimize the frequency down-conversion performance of the mixer, systematic electromagnetic design and analysis have been carried out to improve the power coupling of THz radiation as well as wideband transmission of microwave signals. Experimental characterization of a fabricated device prototype has demonstrated that the mixer exhibits good performance at both the 200 GHz and 600 GHz bands. Detailed measurement results including the DC characteristics, LO pumping requirement, frequency response, mixing linearity and conversion gain are presented in this paper.
Kevrekidis, Panayotis; Williams, Floyd
2014-01-01
The sine-Gordon model is a ubiquitous model of Mathematical Physics with a wide range of applications extending from coupled torsion pendula and Josephson junction arrays to gravitational and high-energy physics models. The purpose of this book is to present a summary of recent developments in this field, incorporating both introductory background material, but also with a strong view towards modern applications, recent experiments, developments regarding the existence, stability, dynamics and asymptotics of nonlinear waves that arise in the model. This book is of particular interest to a wide range of researchers in this field, but serves as an introductory text for young researchers and students interested in the topic. The book consists of well-selected thematic chapters on diverse mathematical and physical aspects of the equation carefully chosen and assigned.
Noise and conversion performance of a high-Tc superconducting Josephson junction mixer at 0.6 THz
Gao, Xiang; Du, Jia; Zhang, Ting; Guo, Yingjie Jay
2017-11-01
This letter presents both theoretical and experimental investigations on the noise and conversion performance of a high-Tc superconducting (HTS) step-edge Josephson-junction mixer at the frequency of 0.6 THz and operating temperatures of 20-40 K. Based on the Y-factor and U-factor methods, a double-sideband noise temperature of around 1000 K and a conversion gain of -3.5 dB were experimentally obtained at 20 K. At the temperature of 40 K, the measured mixer noise and conversion efficiency are around 2100 K and -10 dB, respectively. The experimental data are in good agreement with the numerical analysis results using the three-port model. A detailed performance comparison with other reported HTS terahertz mixers has confirmed the superior performance of our presented mixer device.
Doped Josephson tunneling junction for use in a sensitive IR detector
International Nuclear Information System (INIS)
Fletcher, J.C.; Saffren, M.M.
1975-01-01
A superconductive tunneling device having a modified tunnel barrier capable of supporting Josephson tunneling current is provided. The tunnel barrier located between a pair of electrodes includes a molecular species which is capable of coupling incident radiation of a spectrum characteristic of the molecular species into the tunnel barrier. The coupled radiation modulates the known Josephson characteristics of the superconducting device. As a result of the present invention, a superconductive tunneling device can be tuned or made sensitive to a particular radiation associated with the dopant molecular species. The present invention is particularly useful in providing an improved infrared detector. The tunnel barrier region can be, for example, an oxide of an electrode or frozen gas. The molecular species can be intermixed with the barrier region such as the frozen gas or deposited as one or more layers of molecules on the barrier region. The deposited molecules of the molecular species are unbonded and capable of responding to a radiation characteristic of the molecules. Semi-conductor material can be utilized as the molecular species to provide an increased selective bandwidth response. Finally, appropriate detector equipment can be utilized to measure the modulation of any of the Josephson characteristics such as critical current, voltage steps, Lambe-Jaklevic peaks and plasma frequency. (auth)
NbN Josephson and Tunnel Junctions for Space THz Observation and Signal Processing
National Research Council Canada - National Science Library
Setzu, Romano; Hadacek, Nicolas; Larrey, Vincent; Beaudin, Gerard; Villegier, Jean-Claude
2005-01-01
... (superconductor-normal metal-superconductor) self-shunted junctions are preferred. We present the advantages of the nitride junction technology currently developed at CEA-Grenoble, based on high-performance MTS...
Structural Deformation and Intertube Conductance of Crossed Carbon Nanotube Junctions
International Nuclear Information System (INIS)
Yoon, Young-Gui; Mazzoni, Mario S. C.; Choi, Hyoung Joon; Ihm, Jisoon; Louie, Steven G.
2001-01-01
We present a first-principles study of the structure and quantum electronic conductance of junctions consisting of two crossed (5,5) single-walled carbon nanotubes. The structures are determined by constrained minimization of total energy at a given force between the two tubes, simulating the effects of substrate-tube attraction or an applied force. We find that the intertube contact distance is very sensitive to the applied force in the range of 0--10nN. The intertube conductance is sizable for realistic deformation expected from substrate interaction. The results explain the recent transport data on crossed nanotubes and show that these systems may be potentially useful as electromechanical devices
Carrier transport in multi-terminal superconductor/two-dimensional electron gas Josephson junctions
Guzenko, V.A.; Schäpers, Th.; Müller, R.P.; Golubov, Alexandre Avraamovitch; Brinkman, Alexander; Crecelius, G.; Kaluza, A.; Lüth, H.
2001-01-01
The critical current in a superconductor/two-dimensional electron gas junction/superconductor junction is controlled by an injection current. In case of a carrier injection from one contact to the semiconductor through the two-dimensional electron gas region of the junction to an ohmic contact at
Momentum-Space Josephson Effects
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.
Energy Technology Data Exchange (ETDEWEB)
Bhat, Anupama; Meng, Xiaofan; Wong, Andre; Van Duzer, Theodore [Department of Electrical Engineering and Computer Sciences and the Electronics Research Laboratory, University of California, Berkeley, CA 720 1770 (United States)
1999-11-01
We have grown superconducting NbN films using a pulsed KrF laser for potential use as superconducting electrodes in SNS Josephson junctions being developed for nonlatching logic applications. The NbN films show a superconducting transition of 16 K using an Nb target in background N{sub 2} gas. The T{sub c} dependence on N{sub 2} pressure in the range of 50-80 mTorr was investigated at a growth temperature of 600 deg. C. The NbN films were grown on MgO(100) and amorphous SiN{sub x}/Si substrates. In the latter case, the films had a lower T{sub c}, and appeared amorphous from x-ray diffraction measurements, while those on the MgO(100) substrates were strongly textured. AFM measurements reveal RMS surface roughness as low as 1 nm, over a 5 {mu}m x 5 {mu}m area, indicating that these films appear suitable for SNS junctions. (author)
The computational design of junctions between carbon nanotubes and graphene nanoribbons
International Nuclear Information System (INIS)
Li Yefei; Li Bingrui; Zhang Haoli
2009-01-01
Using first-principles density functional theory calculations, various junction models constructed from different carbon nanotube and graphene nanoribbon units via covalent linkage have been envisioned. These models consist of linear, T- and H-shaped junctions within the connection modes between carbon nanotube and graphene nanoribbon units. The electronic transport properties of different junctions have been systematically investigated by using the non-equilibrium Green's function. The simulation results suggested that the proposed models are promising for future applications in novel nanoelectronics.
The Shapiro steps revealed by Josephson junctions embedded in silicon microcavities
Energy Technology Data Exchange (ETDEWEB)
Bagraev, Nikolay; Danilovsky, Eduard; Gets, Dmitry; Klyachkin, Leonid; Kudryavtsev, Andrey; Kuzmin, Roman; Malyarenko, Anna [Ioffe Physical-Technical Institute, Polytekhnicheskaya 26, 194021 St. Petersburg (Russian Federation)
2012-05-15
One of the best candidate on the role of the THz optoelectronic pairs appears to be the high mobility p -type silicon quantum well (Si-QW), 2 nm, confined by the {delta}-barriers heavily doped with boron on the n -type Si (100) surface. The {delta}-barriers heavily doped with boron are already shown to exhibit the high temperature superconductor properties, T{sub c} = 145 K, 2{delta} = 44 meV and H{sub c} {sub 2} = 0.22 T. This Si-QW confined by the superconductor {delta}-barriers is a basis of the sandwich nanostructure device that is used to register the Shapiro steps and the Fiske steps by measuring the Josephson CV characteristics. The Josephson GHz and THz emission is controlled, for the first time, by stabilizing the drain-source current and by varying the top gate voltage. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Strong mechanically induced effects in DC current-biased suspended Josephson junctions
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.
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 ...
Sputter fabricated Nb-oxide-Nb josephson junctions incorporating post-oxidation noble metal layers
International Nuclear Information System (INIS)
Bain, R.J.P.; Donaldson, G.B.
1985-01-01
We present an extension, involving other metals, of the work of Hawkins and Clarke, who found that a thin layer of copper prevented the formation of the superconductive shorts which are an inevitable consequence of sputtering niobium counter-electrodes directly on top of niobium oxide. We find gold to be the most satisfactory, and that 0.3 nm is sufficient to guarantee short-free junctions of excellent electrical and mechanical stability, though high excess conductance means they are best suited to shunted-junction applications, as in SQUIDs. We present results for critical current dependence on oxide thickness and on gold thickness. Our data shows that thermal oxide growth is described by the Cabrera-Mott mechanism. We show that the protective effect of the gold layer can be understood in terms of the electro-chemistry of the Nb-oxide-Au structure, and that the reduced quasi-particle resistance of the junctions relative to goldfree junctions with evaporated counterelectrodes can be explained in terms of barrier shape modification, and not by proximity effect mechanisms. The performance of a DC SQUID based on these junctions is described
Gao, J; Wang, Z H
2002-01-01
High-T sub c ramp-type Josephson junctions were fabricated using a Nd sub 2 CuO sub 4 barrier. Such a Nd sub 2 CuO sub 4 material has excellent structural, thermal and chemical compatibility with YBa sub 2 Cu sub 3 O sub 7 sub - subdelta. Its very stable 214-T' structure, superior electric properties and closed lattice matching make it desirable to construct multilayer junctions. The growth and nature of the heteroepitaxial Nd sub 2 CuO sub 4 /YBa sub 2 Cu sub 3 O sub 7 sub - subdelta structures were investigated by using x-ray diffraction, small angle x-ray reflection, rocking curve, electron microscopy and surface scan measurements. Junctions with a Nd sub 2 CuO sub 4 barrier display typical resistively shunted junction-like I-V characteristics with reasonable I sub c R sub n products. The large normal resistance, absence of the potential barrier at the SN boundary and a high transparency for the quasi-particles show the advantages of the Nd sub 2 CuO sub 4 barrier. The temperature dependence of Josephson p...
Simulations of fine structures on the zero field steps of Josephson tunnel junctions
DEFF Research Database (Denmark)
Scheuermann, M.; Chi, C. C.; Pedersen, Niels Falsig
1986-01-01
are generated by the interaction of the bias current with the fluxon at the junction edges. On the first zero field step, the voltages of successive fine structures are given by Vn=[h-bar]/2e(2omegap/n), where n is an even integer. Applied Physics Letters is copyrighted by The American Institute of Physics....
Experiments on the interaction between long Josephson junctions and a coplanar strip resonator
DEFF Research Database (Denmark)
Davidson, A.; Pedersen, Niels Falsig
1992-01-01
incorporated directly as part of a coplanar strip half-wave resonator, with fundamental mode of about 34 GHz. Both the current density and oscillation frequency are higher than in previous experiments. Evidence for phase locking of multiple junctions is presented. Applied Physics Letters is copyrighted...... by The American Institute of Physics....
Ohmic contact junction of carbon nanotubes fabricated by in situ electron beam deposition
International Nuclear Information System (INIS)
Wang, Y G; Wang, T H; Lin, X W; Dravid, V P
2006-01-01
We present experimental evidence of in situ fabrication of multi-walled carbon nanotube junctions via electron beam induced deposition. The tip-to-tip interconnection of the nanotubes involves the alignment of two nanotubes via a piezodriven nanomanipulator and nano-welding by electron beam deposition. Hydrocarbon contamination from the pump oil vapour of the vacuum system of the TEM chamber was used as the solder; this is superior to the already available metallic solders because its composition is identical to the carbon nanotube. The hydrocarbon deposition, with perfect wettability, on the nanotubes establishes strong mechanical binding between the two nanotubes to form an integrated structure. Consequently, the nanotubes cross-linked by the hydrocarbon solder produce good electrical and mechanical connections. The joint dimension was determined by the size of the electron beam, which results in a sound junction with well-defined geometry and the smallest junction size obtained so far. In situ electric measurement showed a linear current-voltage property for the multi-walled nanotube junction
Josephson stroboscopic converters. Review
International Nuclear Information System (INIS)
Askerzade, I.N.
2006-01-01
One reviews studies dealing with the Josephson stroboscopic converters. One analyzed dynamic properties of the Josephson junctions serving as sensitive comparators in converters. One elaborates a theory to evaluate time resolution and sensitivity of the Josephson comparators. One derived analytical formulae for the limiting characteristics of superconductors of strobe-converters. One discusses peculiar features of strobe-converters on the basis of high-temperature superconductors. Evaluations show feasibility of designing of strobe-converters with subpicosecond time resolution and nanoampere sensitivity [ru
International Nuclear Information System (INIS)
Pedersen, N.F.; Soerensen, O.H.; Mygind, J.
1978-01-01
The microwave response at 9 GHz of Sn-O-Sn tunnel-junction current biased at zero dc voltage has been measured just below the critical temperature T/sub c/ of the Sn films. The temperature dependence of the cosphi conductance is determined from the resonant response at the junction plasma frequency f/sub p/ as the temperature is decreased from T/sub c/. We used three different schemes for observation of the plasma oscillations: (a) second-harmonic generation (excitation at approx. 4.5 GHz, f/sub p/ approx. 4.5 GHz); (b) mixing (excitations at approx. 9 and approx. 18 GHz, f/sub p/ approx. 9 GHz); (c) parametric half-harmonic oscillation (excitation at approx. 18 GHz, f/sub p/ approx. 9 GHz). Measurements were possible in two temperature intervals; 0.994 or = T/T/sub c/ > or = 0.930, with the result that as the temperature was decreased the cosphi amplitude first increased from about zero to positive values and then at lower temperatures decreased approaching -1 at the lowest temperatures of the experiment
Minami, H.; Kakeya, I.; Yamaguchi, H.; Yamamoto, T.; Kadowaki, K.
2009-01-01
Characteristic features of terahertz radiation emitted from a rectangular mesa comprised stacked intrinsic Josephson junctions in the layered high-Tc superconductor Bi2Sr2CaCu2O8+delta are reported. The emission with the total power of ~5 µW at 0.63 THz shows a characteristic spatial distribution reflecting the rectangular shape. The stability of the emission was measured for at least 20 min. and the power fluctuation was found to be less than 4%. Furthermore, the radiation is highly polariz...
Energy Technology Data Exchange (ETDEWEB)
Kashiwagi, T., E-mail: kashiwagi@ims.tsukuba.ac.jp; Minami, H.; Kadowaki, K. [Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba (Japan); Division of Materials Science, Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1, Tennodai, Tsukuba, Ibaraki 305-8573 (Japan); Nakade, K.; Saiwai, Y.; Kitamura, T.; Watanabe, C.; Ishida, K.; Sekimoto, S.; Asanuma, K.; Yasui, T.; Shibano, Y. [Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba (Japan); Tsujimoto, M. [Department of Electronic Science and Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510 (Japan); Yamamoto, T. [Wide Bandgap Materials Group, Optical and Electronic Materials Unit, Environment and Energy Materials Division, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Marković, B. [Faculty of Sciences, University of Montenegro, George Washington Str., 81000 Podgorica (Montenegro); Mirković, J. [Faculty of Science, University of Montenegro, and CETI, Put Radomira Ivanovica, 81000 Podgorica (Montenegro); Klemm, R. A. [Department of Physics, University of Central Florida, 4000 Central Florida Blvd., Orlando, Florida 32816-2385 (United States)
2014-02-24
A computed tomography (CT) imaging system using monochromatic sub-terahertz coherent electromagnetic waves generated from a device constructed from the intrinsic Josephson junctions in a single crystalline mesa structure of the high-T{sub c} superconductor Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+δ} was developed and tested on three samples: Standing metallic rods supported by styrofoam, a dried plant (heart pea) containing seeds, and a plastic doll inside an egg shell. The images obtained strongly suggest that this CT imaging system may be useful for a variety of practical applications.
DEFF Research Database (Denmark)
Monaco, R.; Mygind, Jesper; Aarøe, Morten
2006-01-01
New scaling behavior has been both predicted and observed in the spontaneous production of fluxons in quenched Nb-Al/Al-ox/Nb annular Josephson tunnel junctions (JTJs) as a function of the quench time, tau(Q). The probability f(1) to trap a single defect during the normal-metal-superconductor phase...... transition clearly follows an allometric dependence on tau(Q) with a scaling exponent sigma=0.5, as predicted from the Zurek-Kibble mechanism for realistic JTJs formed by strongly coupled superconductors. This definitive experiment replaces one reported by us earlier, in which an idealized model was used...
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
Phonon scattering at SWCNT–SWCNT junctions in branched carbon nanotube networks
Energy Technology Data Exchange (ETDEWEB)
Park, Jungkyu [Case Western Reserve University, Department of Mechanical and Aerospace Engineering (United States); Lee, Jonghoon [Wright Patterson Air Force Base, Air Force Research Laboratory (United States); Prakash, Vikas, E-mail: vikas.prakash@case.edu [Case Western Reserve University, Department of Mechanical and Aerospace Engineering (United States)
2015-01-15
In this research article, we analyze phonon scattering in branched single-walled carbon nanotube (SWCNT) networks with SWCNT–SWCNT T- and X- junctions using the wave packet method. Five phonon branches including the longitudinal acoustic, twisting, transverse acoustic, radial breathing, and flexural optical modes are selected to study energy reflection, ramification, and transmission through T- and X-junctions with (6,6) and (4,4) SWCNTs. The results of the simulations indicate that the diameter of SWCNTs affects phonon scattering at carbon nanotube junctions; T-junctions of (6,6) SWCNTs transmit energy more efficiently when compared to T-junctions with (4,4) SWCNTs. In addition, T-junctions of both (6,6) and (4,4) SWCNTs transmit vibrational energy more efficiently when compared to X-junctions in the same phonon frequency range—for example, in the case of the longitudinal acoustic branch, the average energy transmission at T-junctions for low-frequency phonons (lower than 6 THz) was found to be 1.8–2.4 times higher [for the case of (6.6) and (4,4) SWCNTs, respectively] when compared to the X-junctions. It is also observed that energy transmission at the T-junctions shows a dependency on the phonon group velocity with the higher group velocity phonons showing higher energy transmission; however, for the case of the X-junctions, there is little or no correlation observed between the group velocity and energy transmission indicating a complete energy redistribution of the incoming phonons at the junction. Moreover, for the SWCNT–SWCNT branched networks, the energy ramification at the T-junctions was found to be very similar to that at the X-junctions for both (6,6) and (4,4) SWCNTs indicating transverse thermal transport at the X-junctions to be as efficient as the T-junctions.
Phonon scattering at SWCNT–SWCNT junctions in branched carbon nanotube networks
International Nuclear Information System (INIS)
Park, Jungkyu; Lee, Jonghoon; Prakash, Vikas
2015-01-01
In this research article, we analyze phonon scattering in branched single-walled carbon nanotube (SWCNT) networks with SWCNT–SWCNT T- and X- junctions using the wave packet method. Five phonon branches including the longitudinal acoustic, twisting, transverse acoustic, radial breathing, and flexural optical modes are selected to study energy reflection, ramification, and transmission through T- and X-junctions with (6,6) and (4,4) SWCNTs. The results of the simulations indicate that the diameter of SWCNTs affects phonon scattering at carbon nanotube junctions; T-junctions of (6,6) SWCNTs transmit energy more efficiently when compared to T-junctions with (4,4) SWCNTs. In addition, T-junctions of both (6,6) and (4,4) SWCNTs transmit vibrational energy more efficiently when compared to X-junctions in the same phonon frequency range—for example, in the case of the longitudinal acoustic branch, the average energy transmission at T-junctions for low-frequency phonons (lower than 6 THz) was found to be 1.8–2.4 times higher [for the case of (6.6) and (4,4) SWCNTs, respectively] when compared to the X-junctions. It is also observed that energy transmission at the T-junctions shows a dependency on the phonon group velocity with the higher group velocity phonons showing higher energy transmission; however, for the case of the X-junctions, there is little or no correlation observed between the group velocity and energy transmission indicating a complete energy redistribution of the incoming phonons at the junction. Moreover, for the SWCNT–SWCNT branched networks, the energy ramification at the T-junctions was found to be very similar to that at the X-junctions for both (6,6) and (4,4) SWCNTs indicating transverse thermal transport at the X-junctions to be as efficient as the T-junctions
Energy Technology Data Exchange (ETDEWEB)
Rudau, Fabian; Gross, Boris; Wieland, Raphael; Judd, Thomas; Koelle, Dieter; Kleiner, Reinhold [Physikalisches Institut and Center for Collective Quantum Phenomena in LISA" +, Universitaet Tuebingen, Tuebingen (Germany); Kinev, Nickolay; Koshelets, Valery [Kotel' nikov Institute of Radio Engineering and Electronics, Moscow (Russian Federation); Tsujimoto, Manabu [Kyoto University, Kyoto (Japan); Ji, Min; Huang, Ya; Zhou, Xianjing; An, Deyue; Wang, Huabing [National Institute for Materials Science, Tsukuba (Japan); Research Institute of Superconductor Electronics, Nanjing University, Nanjing (China); Wu, Peiheng [Research Institute of Superconductor Electronics, Nanjing University, Nanjing (China); Hatano, Takeshi [National Institute for Materials Science, Tsukuba (Japan)
2015-07-01
Stacks of intrinsic Josephson junctions, made of the high temperature superconductor Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8}, are promising candidates to be used as generators of electromagnetic waves in the terahertz regime, in principle allowing frequencies up to ∝10 THz. Ranging from 0.4 to 1 THz, coherent emission was detected from large, rectangular stacks, producing several tens of microwatt in power. Despite of several years of research, the mechanism of synchronizing all the junctions in the stack is still not fully understood. We investigated the heat distribution and electromagnetic standing waves in such stacks, as well as the generation of terahertz radiation, using a combination of electric transport measurements, direct radiation detection and low temperature scanning laser microscopy. Recent experimental results from our collaboration will be presented and compared to numerical simulations.
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
Nogawa, Tomoaki
2012-05-22
We investigate the ground state of the irrationally frustrated Josephson junction array with a controlling anisotropy parameter λ that is the ratio of the longitudinal Josephson coupling to the transverse one. We find that the ground state has one-dimensional periodicity whose reciprocal lattice vector depends on λ and is incommensurate with the substrate lattice. Approaching the isotropic point λ=1, the so-called hull function of the ground state exhibits analyticity breaking similar to the Aubry transition in the Frenkel-Kontorova model. We find a scaling law for the harmonic spectrum of the hull functions, which suggests the existence of a characteristic length scale diverging at the isotropic point. This critical behavior is directly connected to the jamming transition previously observed in the current-voltage characteristics by a numerical simulation. On top of the ground state there is a gapless continuous band of metastable states, which exhibit the same critical behavior as the ground state. © 2012 American Physical Society.
Klemm, Richard A.; Davis, Andrew E.; Wang, Qing X.; Yamamoto, Takashi; Cerkoney, Daniel P.; Reid, Candy; Koopman, Maximiliaan L.; Minami, Hidetoshi; Kashiwagi, Takanari; Rain, Joseph R.; Doty, Constance M.; Sedlack, Michael A.; Morales, Manuel A.; Watanabe, Chiharu; Tsujimoto, Manabu; Delfanazari, Kaveh; Kadowaki, Kazuo
2017-12-01
We show for high-symmetry disk, square, or equilateral triangular thin microstrip antennas of any composition respectively obeying C ∞v , C 4v , and C 3v point group symmetries, that the transverse magnetic electromagnetic cavity mode wave functions are restricted in form to those that are one-dimensional representations of those point groups. Plots of the common nodal points of the ten lowest-energy non-radiating two-dimensional representations of each of these three symmetries are presented. For comparison with symmetry-broken disk intrinsic Josephson junction microstrip antennas constructed from the highly anisotropic layered superconductor Bi2Sr2CaCu2O8+δ (BSCCO), we present plots of the ten lowest frequency orthonormal wave functions and of their emission power angular distributions. These results are compared with previous results for square and equilateral triangular thin microstrip antennas.
On the universality of the ''smile''-gap in the density of states of a chaotic Josephson junction
Energy Technology Data Exchange (ETDEWEB)
Reutlinger, Johannes; Belzig, Wolfgang [University of Konstanz, Department of Physics (Germany); Nazarov, Yuli [Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft (Netherlands); Glazman, Leonid [Department of Physics, Yale University, New Haven, CT (United States)
2015-07-01
The superconducting proximity effect strongly modifies the local density of states in chaotic Josephson junctions. Recently we found that besides the well-known minigap a secondary gap appears just below the superconducting gap edge Δ in the limit of a large Thouless energy E{sub Th} >or similar Δ. To check the universality of this novel gap phenomenon we study the effect of nonideal contacts and show that the ''smile''-gap crucially depends on the transmission eigenvalue distribution. In a next step we use the random matrix method to investigate the ''smile''-gap. This allows us to approach the statistics of Andreev levels, going beyond the quasiclassical Greens function method. It turns out that the hard gap edge softens similar to what is already known from the minigap.
Energy Technology Data Exchange (ETDEWEB)
Hatsukade, Y., E-mail: hatukade@ens.tut.ac.jp [Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku-cho, Toyohashi, Aichi 441-8580 (Japan); Hayashi, K.; Shinyama, Y.; Kobayashi, Y. [Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku-cho, Toyohashi, Aichi 441-8580 (Japan); Adachi, S.; Tanabe, K. [International Superconductivity Technology Center/Superconductivity Research Laboratory, 10-13, Shinonome 1-chome, Koto-ku, Tokyo 135-0062 (Japan); Tanaka, S. [Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku-cho, Toyohashi, Aichi 441-8580 (Japan)
2011-11-15
We investigated behavior of HTS-dc-SQUID gradiometers with ramp-edge Josephson junctions (JJs) in ac and dc magnetic fields. In the both fields, the gradiometers show higher durability against entry of flux vortices than SQUIDs with bicrystal JJs. A robot-based SQUID NDE system utilizing the gradiometer was developed in an unshielded environment. Detectability of the system to detect non-through cracks in double-layer structures was demonstrated. A new excitation coil was applied to detect cracks that oriented vertical and parallel to the baseline of the gradiometer. In this paper, we investigated detailed behavior of novel HTS-dc-SQUID gradiometers with ramp-edge Josephson junctions (JJs) in both an ac magnetic field and a dc magnetic field. In the both fields, the novel gradiometers shows the superior performance to the conventional YBa{sub 2}Cu{sub 3}O{sub 7-x} (YBCO) HTS-dc-SQUID gradiometer and a bare HTS-dc-SQUID ring with bicrystal JJs concerning durability against entry and hopping of flux vortices, probably due to their differential pickup coils without a grain boundary and multilayer structure of the ramp-edge JJs. A robot-based compact HTS-SQUID NDE system utilizing the novel gradiometer was reviewed, and detectability of the system to detect non-through cracks in a carbon fiber reinforced plastic (CFRP)/Al double-layer structure was demonstrated. A new excitation coil in which the supplied currents flowed in the orthogonal directions was applied to detect cracks that oriented vertical and parallel to the baseline of the gradiometer.
Energy Technology Data Exchange (ETDEWEB)
Devoret, M.H. [College de France, 75231 Paris cedex 05 (France); Girvin, Steven; Schoelkopf, Robert [Applied Physics Department, Yale University, New Haven, CT 06520-8284 (United States)
2007-10-15
After reviewing the limitation by the fine structure constant {alpha} of the dimensionless coupling constant of an hydrogenic atom with a mode of the electromagnetic field in a cavity, we show that the situation presents itself differently for an artificial Josephson atom coupled to a transmission line resonator. Whereas the coupling constant for the case where such an atom is placed inside the dielectric of the resonator is proportional to {alpha}{sup 1/2}, the coupling of the Josephson atom when it is placed in series with the conducting elements of the resonator is proportional to {alpha}{sup -1/2} and can reach values greater than 1. (Abstract Copyright [2007], Wiley Periodicals, Inc.)
Energy Technology Data Exchange (ETDEWEB)
Setzu, R
2007-11-15
This thesis research, brought to the development and optimization of SNS (Superconductor / Normal Metal / Superconductor) Josephson junctions with NbN electrodes and a high resistivity Ta{sub x}N barrier. We were able to point out Josephson oscillations for frequencies above 1 THz and operation temperatures up to 10 K, which constituted the original goal of the project. This property makes these junctions unique and well adapted for realizing ultra-fast RSFQ (Rapid Single Flux Quantum) logic circuits suitable for spatial telecommunications. We showed a good reproducibility of Ta{sub x}N film properties as a function of the sputtering parameters. The NbN/Ta{sub x}N/NbN tri-layers exhibit high critical temperature (16 K). The junctions showed a clear dependence of the R{sub n}I{sub c} product as a function of the partial nitrogen pressure inside the reactive plasma; the R{sub n}I{sub c} is the product between the junction critical current and its normal resistance, and indicates the upper limit Josephson frequency. We have also obtained some really high R{sub n}I{sub c} products, up to 3.74 mV at 4.2 K for critical current densities of about 15 kA/cm{sup 2}. Junctions show the expected Josephson behaviors, respectively Fraunhofer diffraction and Shapiro steps. up to 14 K. This allows expecting good circuit operations in a relaxed cryogenics environment (with respect to the niobium circuits limited at 4.2 K). The junctions appear to be self-shunted. The SNOP junctions J{sub c}-temperature dependence has been fitted by using the long SNS junction model in the dirty limit, which gives a normal metal coherence length of about 3.8 nm at 4.2 K. We have finally studied a multilayer fabrication process, including a common ground plane and bias resistors, suitable for RSFQ logic basic circuits. To conclude we have been able to show the performance superiority of NbN/Ta{sub x}N/NbN junctions over the actual niobium junctions, as well as their interest for realizing compact
Energy Technology Data Exchange (ETDEWEB)
Gross, Boris Andre
2013-02-05
In recent years, terahertz technology has become a rapidly growing sector, driven by the demands of a vast range of (potential) applications. The terahertz spectral range roughly spans from 300 GHz to 30 THz. In the low terahertz range, there is a lack of good and compact devices, that emit electromagnetic waves. Particularly, coherent, narrow-band and continuous-wave sources are lacking, and researchers are following many different approaches to fill this gap. The thesis at hand contributes to the exploration of one of those sources: Operating intrinsic Josephson junctions as emitters in the terahertz spectral range. Josephson junctions (JJs) work as direct current (dc) voltage to frequency converters, if operated in the resistive state. 1 mV voltage drop generates a frequency of about 484 GHz. Intrinsic Josephson junctions (IJJs) in the high temperature superconductor Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+δ} (BSCCO) are adequate candidates for emitting devices; the layered structure of the material intrinsically provides stacks consisting of 1.5 nm thick, nearly perfectly equal JJs. The fabrication of a series of hundreds of JJs in a stack of micrometer thickness is easily feasible, which is essential for high power frequency generation. Further, the energy gap of BSCCO is in principle large enough to allow for frequencies up to more than 10 THz. The key challenge is the synchronization of all IJJs in order to produce coherent radiation. In 2007, a research team from Argonne National Laboratories succeeded in detecting coherent terahertz radiation from more than 500 synchronized IJJs in a mesa structure. The frequencies ranged from 350 to 850 GHz with output powers up to 0.5 μW. They proposed the formation of electromagnetic standing waves in the cavity of the mesa as synchronization mechanism. Coming from the fully resistive state (nonzero voltage across all junctions), the radiation occurred in the bias regime, where groups of junctions switch back to the zero
Nomura, Y.; Okamoto, R.; Kakeya, I.
2017-10-01
We have investigated the switching dynamics of the first and second switches in intrinsic Josephson junctions (IJJs) of Bi2Sr2CaCu2O{}8+δ with different maximum Josephson current density J c to reveal the doping evolution of interaction between IJJs. For the second switch, the crossover temperature between temperature-independent switching similar to quantum tunneling and thermally activated switching {T}2{nd}* is remarkably higher than that for the first switch. Moreover, {T}2{nd}* slightly decreases with increasing J c, which violates the conventional relation between the crossover temperature and the critical current density. These features can be explained not by a change in the Josephson coupling energy but by a change in the charging energy of the Josephson junction. We argue that the capacitive coupling model explains the increase in the fluctuation in the quantum regime of the second switch and the anti-correlation between {T}2{nd}* and J c. Furthermore, inductive coupling does not contribute to these peculiar phenomena in the switching dynamics of stacked IJJs.
Energy Technology Data Exchange (ETDEWEB)
Rudau, Fabian; Wieland, Raphael; Koelle, Dieter; Kleiner, Reinhold [Physikalisches Institut and Center for Quantum Science (CQ) in LISA+, Universitaet Tuebingen (Germany); Zhou, Xianjing; Ji, Min; Hao, Luyao; Huang, Ya; Wang, Huabing [Research Institute of Superconductor Electronics, Nanjing University (China); National Institute for Materials Science, Tsukuba (Japan); Kinev, Nickolay; Koshelets, Valery [Kotel' nikov Institute of Radio Engineering and Electronics, Moscow (Russian Federation); Li, Jun; Wu, Peiheng [Research Institute of Superconductor Electronics, Nanjing University (China); Hatano, Takeshi [National Institute for Materials Science, Tsukuba (Japan)
2016-07-01
Stacks of intrinsic Josephson junctions, made of the high-T{sub c} superconductor Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8}, can be used as emitters of electromagnetic waves at terahertz frequencies. Coherent emission from 0.3 to 2.4 THz was detected from large, rectangular or disc-shaped mesa structures. Having a linewidth of only a few MHz, emission powers of several tens of microwatt can be produced for single stacks and up to 0.61 mW for an array of mesas. Since the mechanisms of synchronizing all the junctions in the stack is still not fully understood, we investigated the temperature distribution and electromagnetic standing waves in such stacks, as well as the generation of terahertz radiation, using a combination of electric transport measurements, direct radiation detection and low temperature scanning laser microscopy. Recent experimental results from our collaboration will be presented and compared to numerical simulations.
Preparation of CN /Carbon Nanotube Intramolecular Junctions by ...
African Journals Online (AJOL)
NICO
middle during the growth process of the tubes. The phenomenon has been observed previously in preparing CNx/C intra- molecular junctions via the CVD method by pyrolysis of ferrocene and melamine.23 It should be pointed out that no catalyst is necessary for connecting CNx and MWCNT segments. As shown in Figs.
Energy Technology Data Exchange (ETDEWEB)
Buckenmaier, Kai
2010-06-09
This thesis is divided into two parts, the measurement of the activation energy of a fractional vortex and the spectroscopy of a vortex-molecule. Fractional vortices can be studied in long 0-{kappa} Josephson junctions, where a jump of the Josephson phase is created artificially with a pair of tiny current injectors. To compensate for this phase discontinuity, a {rho} vortex is formed. Here, {rho} describes the vortex's so called topological charge. The {rho} vortices are pinned at the discontinuity and they carry the fraction ({rho}/2).{phi}{sub 0} of magnetic flux, with the magnetic flux quantum {phi}{sub 0} 2.07.10{sup -15}. Two stable vortex configurations are possible, a direct Vortex and a complementary one. {rho} depends on the injector current. When the bias current of the junction exceeds a characteristic threshold, which dependents on {rho}, the Lorentz force is bigger than the pinning force of the vortex and a fluxon is pulled away. In this case a complementary ({rho}-2{pi}) vortex is left behind. This switching of the {rho} vortex and the resulting emission of a fluxon can be described as a Kramers like escape of a particle out of a tilted washboard potential. The washboard potential is tilted to the point where the barrier is small enough, so that the particle can escape via thermal or quantum fluctuations. In the case of thermal fluctuations the barrier height is called activation energy. The activation energy can be determined by measuring the junction's switching current statistics. In this thesis, the activation energy, necessary for the vortex escape, was measured as a function of {rho} and a homogenous external magnetic field perpendicular to the junction. The main focus was the investigation of 0-{pi} junctions. The temperature dependence of the activation energy was investigated, too. It turns out, that the transition-state-theory is convenient to describe the switching probability of the standard Nb-AlO{sub x}-Nb junctions at 4.2 K
Effect of eccentricity on junction and junctionless based silicon nanowire and silicon nanotube FETs
Scarlet, S. Priscilla; Ambika, R.; Srinivasan, R.
2017-07-01
In this paper, the effect of eccentricity on Junction-based Silicon Nanowire FET, Junction-based Silicon Nanotube FET, Junctionless-based Silicon Nanowire FET, and Junctionless-based Silicon Nanotube FET is investigated. Three kinds of eccentric structures are considered here. The impact of eccentricity on effective gate oxide thickness thereby gate oxide capacitance, and effective channel width are studied using 3D numerical simulations. Average radius of an ellipse is used to generate a model which captures the impact of eccentricity on gate oxide capacitance, and verified using TCAD simulations in MOS nanowire structure. The impact of eccentricity on ON current (ION), OFF current (IOFF), ION/IOFF ratio, and Unity gain cutoff frequency are investigated. Eccentricity increases the effective gate oxide thickness, the effective channel width, ION, and IOFF but reduces ION/IOFF ratio.
2018-01-18
AFRL-RV-PS- AFRL-RV-PS- TR-2017-0125 TR-2017-0125 ENHANCED CONTACTS FOR INVERTED METAMORPHIC MULTI-JUNCTION SOLAR CELLS USING CARBON NANOTUBE METAL...Rochester, NY 14604-5603 18 Jan 2018 Final Report APPROVED FOR PUBLIC RELEASE; DISTRIBUTION IS UNLIMITED. AIR FORCE RESEARCH LABORATORY Space...ACCORDANCE WITH ASSIGNED DISTRIBUTION STATEMENT. DAVID WILT PAUL HAUSGEN, Ph.D. Program Manager Technical Advisor, Spacecraft Component Technology
Molecular dynamics investigation of carbon nanotube junctions in non-aqueous solutions
Gkionis, Konstantinos
2014-07-23
The properties of liquids in a confined environment are known to differ from those in the bulk. Extending this knowledge to geometries defined by two metallic layers in contact with the ends of a carbon nanotube is important for describing a large class of nanodevices that operate in non-aqueous environments. Here we report a series of classical molecular dynamics simulations for gold-electrode junctions in acetone, cyclohexane and N,N-dimethylformamide solutions and analyze the structure and the dynamics of the solvents in different regions of the nanojunction. The presence of the nanotube has little effect on the ordering of the solvents along its axis, while in the transversal direction deviations are observed. Importantly, the orientational dynamics of the solvents at the electrode-nanotube interface differ dramatically from that found when only the electrodes are present.
Controlling Josephson dynamics by strong microwave fields
Chesca, B.; Savel'ev, E.; Rakhmanov, A.L.; Smilde, H.J.H.; Hilgenkamp, Johannes W.M.
2008-01-01
We observe several sharp changes in the slope of the current-voltage characteristics (CVCs) of thin-film ramp-edge Josephson junctions between YBa2Cu3O7−delta and Nb when applying strong microwave fields. Such behavior indicates an intriguing Josephson dynamics associated with the switching from a
Properties of all YBa2Cu3O7 Josephson edge junctions prepared by in situ laser ablation deposition
International Nuclear Information System (INIS)
Koren, G.; Aharoni, E.; Polturak, E.; Cohen, D.
1991-01-01
Thin-film YBa 2 Cu 3 O 7 -YBa 2 Cu 3 O 7 edge junctions of 0.4x10 μm 2 cross section were prepared in situ by a multistep laser ablation deposition process. The fabrication time was about 3 h and the yield of good devices was 50%. Typical junctions reached zero resistance at 72 K and had a critical current density J c of 300 A/cm 2 at 70 K. Their J c as a function of temperature increased slowly with decreasing temperature down to 65 K and much faster below it. In the region of low J c we observed suppression of the critical current by a magnetic field. Under microwave radiation clear Shapiro steps were observed whose magnitude versus the microwave field agreed qualitatively with the resistively shunted junction model of a current biased junction
Hu, Ping'an; Xiao, Kai; Liu, Yunqi; Yu, Gui; Wang, Xianbao; Fu, Lei; Cui, Guanglei; Zhu, Daoben
2004-06-01
We prepared a large quantity of multiwall nanotubes with intramolecular junctions (CNx/C) by pyrolysis of iron phthalocyanine with or without an inlet of ammonia gas. The nanotubes consist of two sections, one section made of carbon nitride featuring bamboo-like structure and the other one made of carbon featuring empty hollow cylinder structure, and thus the intramolecular junctions were formed in the middle as a result of being doped or undoped with nitrogen. Nanodiode based on a single CNx/C junction shows reproducible rectifying behavior with a rectification ratio of 1.3×103 at ±2 V. In addition, the nanodiode demonstrated as a half-wave rectifier worked at an input sine wave of 1 kHz. Two CNx/C junctions were configured together to exhibit functions of OR and AND logic gates. Moreover, after substituting the wave-detection silicon diode in common transistor radio set with our nanodiode, the radio set still worked normally, representing an important step toward the potential application for nano-scale devices.
Hetero-junctions of Boron Nitride and Carbon Nanotubes: Synthesis and Characterization
Energy Technology Data Exchange (ETDEWEB)
Yap, Yoke Khin
2013-03-14
Hetero-junctions of boron nitride nanotubes (BNNTs) and carbon nanotubes (CNTs) are expected to have appealing new properties that are not available from pure BNNTs and CNTs. Theoretical studies indicate that BNNT/CNT junctions could be multifunctional and applicable as memory, spintronic, electronic, and photonics devices with tunable band structures. This will lead to energy and material efficient multifunctional devices that will be beneficial to the society. However, experimental realization of BNNT/CNT junctions was hindered by the absent of a common growth technique for BNNTs and CNTs. In fact, the synthesis of BNNTs was very challenging and may involve high temperatures (up to 3000 degree Celsius by laser ablation) and explosive chemicals. During the award period, we have successfully developed a simple chemical vapor deposition (CVD) technique to grow BNNTs at 1100-1200 degree Celsius without using dangerous chemicals. A series of common catalyst have then been identified for the synthesis of BNNTs and CNTs. Both of these breakthroughs have led to our preliminary success in growing two types of BNNT/CNT junctions and two additional new nanostructures: 1) branching BNNT/CNT junctions and 2) co-axial BNNT/CNT junctions, 3) quantum dots functionalized BNNTs (QDs-BNNTs), 4) BNNT/graphene junctions. We have started to understand their structural, compositional, and electronic properties. Latest results indicate that the branching BNNT/CNT junctions and QDs-BNNTs are functional as room-temperature tunneling devices. We have submitted the application of a renewal grant to continue the study of these new energy efficient materials. Finally, this project has also strengthened our collaborations with multiple Department of Energy's Nanoscale Science Research Centers (NSRCs), including the Center for Nanophase Materials Sciences (CNMS) at Oak Ridge National Laboratory, and the Center for Integrated Nanotechnologies (CINTs) at Sandia National Laboratories and Los
Energy Technology Data Exchange (ETDEWEB)
Rozeveld, S.; Merkle, K.L. [Argonne National Lab., IL (United States); Char, K. [Conductus, Inc., Sunnyvale, CA (United States)
1994-10-01
Superconductor - normal - superconductor (SNS) edge junctions consisting of YBa{sub 2}Cu{sub 3}O{sub 7-x}/CaRuO{sub 3}/YBa{sub 2}Cu{sub 3}O{sub 7-x} were fabricated on (001) LaA1O{sub 3} substrates. These devices display an excess interface resistance which is not well understood but is related to the SN interface and interlayer structure. High-resolution and conventional transmission electron microscopy were employed to investigate the SN interface to determine the structure and possible interface defects. Energy-loss spectroscopy and energy dispersive x-ray analysis were performed on the CaRuO{sub 3} film and near interface regions to quantify the extent of interdiffusion between the CiRuO{sub 3} and YBCO films. Changes in either the interface structure or the normal layer chemistry are expected to greatly influence the junction properties.
Microstructure and composition of a SNS Josephson junction using CaRuO3 as the metallic barrier
International Nuclear Information System (INIS)
Rozeveld, S.; Merkle, K.L.; Char, K.
1994-10-01
Superconductor - normal - superconductor (SNS) edge junctions consisting of YBa 2 Cu 3 O 7-x /CaRuO 3 /YBa 2 Cu 3 O 7-x were fabricated on (001) LaA1O 3 substrates. These devices display an excess interface resistance which is not well understood but is related to the SN interface and interlayer structure. High-resolution and conventional transmission electron microscopy were employed to investigate the SN interface to determine the structure and possible interface defects. Energy-loss spectroscopy and energy dispersive x-ray analysis were performed on the CaRuO 3 film and near interface regions to quantify the extent of interdiffusion between the CiRuO 3 and YBCO films. Changes in either the interface structure or the normal layer chemistry are expected to greatly influence the junction properties
Josephson noise thermometry with high temperature superconducting devices
Peden, D A
2000-01-01
High Temperature Superconducting devices for absolute Noise Thermometry are under development for the measurement of temperature in the 10-50 K range. This Thesis is concerned with two complementary methods which have been developed in parallel. The first technique, Josephson Linewidth Thermometry, uses a HTS Josephson junction shunted by a low resistance noble metal resistor. The conversion of thermal voltage fluctuations via the ac Josephson effect results in thermal broadening of the Josephson oscillation linewidth. Single and double junction HTS R-SQUIDs have been fabricated where a shunt resistance approx 25 mu OMEGA has been achieved. In the double junction R-SQUIDs, where the voltage across the terminals is modulated at the Josephson heterodyne frequency, the first reported observations of Josephson heterodyne oscillations in HTS R-SQUIDs have been made and the linearity of the voltage-frequency relationship established. The second approach, known as the Quantum Roulette Noise Thermometer, uses the the...
Low-frequency noise in high-T_{c} superconductor Josephson junctions, SQUIDs, and magnetometers
Energy Technology Data Exchange (ETDEWEB)
Miklich, Andrew Hostetler [Univ. of California, Berkeley, CA (United States)
1994-05-01
Design and performance of high-T_{c} dc superconducting quantum interference devices (SQUEDs), junctions that comprise them, and magnetometers made from them are described, with attention to sources of 1/f noise. Biepitaxial junctions are found to have large levels of critical current fluctuations which make them unsuitable for low-noise SQUIDS; this suggests a poorly connected interface at the grain boundary junction. SQUIDs from bicrystal junctions have levels of critical current noise controllable using bias current reversal techniques which leave the noise white down to frequencies of a few Hz. A SQUID with an energy resolution of 1.5 x 10^{-30} J Hz^{-1} at 1 Hz is reported. Magnetometers in which a (9 mm)^{2} pickup loop is directly coupled to a SQUID body have achieved field resolutions of 93 fT Hz^{-1/2} down to frequencies below I Hz, improving to 39 fT Hz^{-1/2} at 1 Hz with the addition of a 50mm-diameter single-turn flux transformer. Poor coupling to pickup loop makes it difficult to satisfy competing goals of high field resolution and small detector size necessary for multichannel biomagnetic imaging. Improved coupling is demonstrated by the use of multiturn-input-coil flux transformers, and a resolution of 35 fT Hz^{-1/2} in the white noise region is reported with a (10 mm)^{2} pickup loop. However, additional 1/f noise from processed multilayer structures in the transformer limits the resolution at 1 Hz to 114 fT Hz^{-1/2}. High-T_{c} SQUIDs exhibit additional 1/f noise when cooled in a nonzero static magnetic field because of additional flux vortices trapped in the film, with the noise power at 1 Hz typically increasing by a factor of 10--20 in a field of 0.05mT (0.5 G). Finally, a SQUID-based voltmeter with a resolution of 9.2 pV.Hz^{-1/2} at 10 Hz (24 pV Hz^{-1/2} at 1 Hz) is described.
International Nuclear Information System (INIS)
Narla, A.; Sliwa, K. M.; Hatridge, M.; Shankar, S.; Frunzio, L.; Schoelkopf, R. J.; Devoret, M. H.
2014-01-01
Josephson junction parametric amplifiers are playing a crucial role in the readout chain in superconducting quantum information experiments. However, their integration with current 3D cavity implementations poses the problem of transitioning between waveguide, coax cables, and planar circuits. Moreover, Josephson amplifiers require auxiliary microwave components, like directional couplers and/or hybrids, that are sources of spurious losses and impedance mismatches that limit measurement efficiency and amplifier tunability. We have developed a wireless architecture for these parametric amplifiers that eliminates superfluous microwave components and interconnects. This greatly simplifies their assembly and integration into experiments. We present an experimental realization of such a device operating in the 9–11 GHz band with about 100 MHz of amplitude gain-bandwidth product, on par with devices mounted in conventional sample holders. The simpler impedance environment presented to the amplifier also results in increased amplifier tunability.
Reutlinger, J.; Glazman, L.; Nazarov, Yu. V.; Belzig, W.
2014-07-01
The superconducting proximity effect leads to strong modifications of the local density of states in diffusive or chaotic cavity Josephson junctions, which displays a phase-dependent energy gap around the Fermi energy. The so-called minigap of the order of the Thouless energy ETh is related to the inverse dwell time in the diffusive region in the limit ETh≪Δ, where Δ is the superconducting energy gap. In the opposite limit of a large Thouless energy ETh≫Δ, a small new feature has recently attracted attention, namely, the appearance of a further secondary gap, which is around two orders of magnitude smaller compared to the usual superconducting gap. It appears in a chaotic cavity just below the superconducting gap edge Δ and vanishes for some value of the phase difference between the superconductors. We extend previous theory restricted to a normal cavity connected to two superconductors through ballistic contacts to a wider range of contact types. We show that the existence of the secondary gap is not limited to ballistic contacts, but is a more general property of such systems. Furthermore, we derive a criterion which directly relates the existence of a secondary gap to the presence of small transmission eigenvalues of the contacts. For generic continuous distributions of transmission eigenvalues of the contacts, no secondary gap exists, although we observe a singular behavior of the density of states at Δ. Finally, we provide a simple one-dimensional scattering model which is able to explain the characteristic "smile" shape of the secondary gap.
Dynamics of pi-junction interferometer circuits
DEFF Research Database (Denmark)
Kornkev, V.K.; Mozhaev, P.B.; Borisenko, I.V.
2002-01-01
The pi-junction superconducting circuit dynamics was studied by means of numerical simulation technique. Parallel arrays consisting of Josephson junctions of both 0- and pi-type were studied as a model of high-T-c grain-boundary Josephson junction. The array dynamics and the critical current...... dependence on magnetic field are discussed. Experimental results for dc interferometers with 0 and pi high-T-c bi-crystal Josephson junctions are reported and discussed in comparison with numerical simulation....
Sirena, Martin; Aviles Felix, Luis Steven; Carvacho Vera, G. A.; Navarro Fernández, Henry Luciano; Steren, Laura Beatriz; Bernard, R.; Briático, J.; Bergeal, N.; Lesueur, J.; Faini, G.
2017-01-01
A phenomenological approach was used to obtain critical information about the structure and electrical properties of ultra thin Ba0.05Sr0.95TiO3 (BSTO) layers over Nb electrodes. The method allows, in a simple way, to study and to optimize the growth of the barrier in order to improve the performance and application of Josephson junctions. A very good control of the layer thickness with a low roughness was achieved during the deposition process. The BSTO layers present an energy barrier of 0....
International Nuclear Information System (INIS)
Chesca, Boris; John, Daniel; Mellor, Christopher J
2014-01-01
When a soliton propagates in a discrete lattice it excites small-amplitude linear waves in its wake. In a dc current-biased Josephson-junction (JJ) array these manifest as electromagnetic (EM) waves excited by a (magnetic field induced) chain of propagating magnetic vortices. When the vortex velocity and the phase velocity of one of the excited EM waves match, phase-locking occurs. This produces resonant steps in the current–voltage characteristics where amplification of EM radiation occurs. We report the first observation of phase-locking-induced amplification of EM radiation at 77 K and above in JJ arrays made of high temperature superconductors. (paper)
Resonant modes in Josephson structures
International Nuclear Information System (INIS)
Paterno, G.
1985-01-01
It is well-know that a Josephson junction held at finite voltage V generates an alternating current at a frequency *o=(2e/h)V. When the junction is coupled to an external resonator self-induced dc current modes occur in the structure. The nonlinear interaction with the ac Josephson radiation gives rise to current singularities at voltages corresponding to the resonance frequencies of the resonator. These resonances appear in the dc current voltage characteristics as current singularities. They are due to a conversion of dc power to ac power that in turn is internally dissipated. In a tunneling junction the resonator is formed of the two superconducting electrodes separated by the oxide layer. In a two junctions interferometer the resonant structure is formed of the loop inductance and the junction capacitances. A good knowledge of the behaviour of these singularities is very important when switching properties are considered or ac power has to be extracted from the structure. In this paper we review the behaviour of resonant modes in Josephson junctions coupled to a resonant structure. A comparison between experimental data and the theoretical description at present available is reported
Anomalous Josephson effect controlled by an Abrikosov vortex
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.
Broadband photodetector based on carbon nanotube thin film/single layer graphene Schottky junction
Zhang, Teng-Fei; Li, Zhi-Peng; Wang, Jiu-Zhen; Kong, Wei-Yu; Wu, Guo-An; Zheng, Yu-Zhen; Zhao, Yuan-Wei; Yao, En-Xu; Zhuang, Nai-Xi; Luo, Lin-Bao
2016-12-01
In this study, we present a broadband nano-photodetector based on single-layer graphene (SLG)-carbon nanotube thin film (CNTF) Schottky junction. It was found that the as-fabricated device exhibited obvious sensitivity to a wide range of illumination, with peak sensitivity at 600 and 920 nm. In addition, the SLG-CNTF device had a fast response speed (τr = 68 μs, τf = 78 μs) and good reproducibility in a wide range of switching frequencies (50-5400 Hz). The on-off ratio, responsivity, and detectivity of the device were estimated to be 1 × 102, 209 mAW-1 and 4.87 × 1010 cm Hz1/2 W-1, respectively. What is more, other device parameters including linear performance θ and linear dynamic range (LDR) were calculated to be 0.99 and 58.8 dB, respectively, which were relatively better than other carbon nanotube based devices. The totality of the above study signifies that the present SLG-CNTF Schottky junction broadband nano-photodetector may have promising application in future nano-optoelectronic devices and systems.
Dominiczak, Maguy; Otubo, Larissa; Alamarguy, David; Houzé, Frédéric; Volz, Sebastian; Noël, Sophie; Bai, Jinbo
2011-04-14
Using an atomic force microscope (AFM) at a controlled contact force, we report the electrical signal response of multi-walled carbon nanotubes (MWCNTs) disposed on a golden thin film. In this investigation, we highlight first the theoretical calculation of the contact resistance between two types of conductive tips (metal-coated and doped diamond-coated), individual MWCNTs and golden substrate. We also propose a circuit analysis model to schematize the «tip-CNT-substrate» junction by means of a series-parallel resistance network. We estimate the contact resistance R of each contribution of the junction such as Rtip-CNT, RCNT-substrate and Rtip-substrate by using the Sharvin resistance model. Our final objective is thus to deduce the CNT intrinsic radial resistance taking into account the calculated electrical resistance values with the global resistance measured experimentally. An unwished electrochemical phenomenon at the tip apex has also been evidenced by performing measurements at different bias voltages with diamond tips. For negative tip-substrate bias, a systematic degradation in color and contrast of the electrical cartography occurs, consisting of an important and non-reversible increase of the measured resistance. This effect is attributed to the oxidation of some amorphous carbon areas scattered over the diamond layer covering the tip. For a direct polarization, the CNT and substrate surface can in turn be modified by an oxidation mechanism.
Directory of Open Access Journals (Sweden)
Alamarguy David
2011-01-01
Full Text Available Abstract Using an atomic force microscope (AFM at a controlled contact force, we report the electrical signal response of multi-walled carbon nanotubes (MWCNTs disposed on a golden thin film. In this investigation, we highlight first the theoretical calculation of the contact resistance between two types of conductive tips (metal-coated and doped diamond-coated, individual MWCNTs and golden substrate. We also propose a circuit analysis model to schematize the «tip-CNT-substrate» junction by means of a series-parallel resistance network. We estimate the contact resistance R of each contribution of the junction such as R tip-CNT, R CNT-substrate and R tip-substrate by using the Sharvin resistance model. Our final objective is thus to deduce the CNT intrinsic radial resistance taking into account the calculated electrical resistance values with the global resistance measured experimentally. An unwished electrochemical phenomenon at the tip apex has also been evidenced by performing measurements at different bias voltages with diamond tips. For negative tip-substrate bias, a systematic degradation in color and contrast of the electrical cartography occurs, consisting of an important and non-reversible increase of the measured resistance. This effect is attributed to the oxidation of some amorphous carbon areas scattered over the diamond layer covering the tip. For a direct polarization, the CNT and substrate surface can in turn be modified by an oxidation mechanism.
Schmelz, M.; Stolz, R.; Zakosarenko, V.; Schönau, T.; Anders, S.; Fritzsch, L.; Mück, M.; Meyer, M.; Meyer, H.-G.
2012-11-01
We review the development of low parasitic capacitance sub-micrometer cross-type Josephson tunnel junctions for their use in highly sensitive and field-stable SQUID magnetometers. The potential of such junctions is shown on I-V characteristics as well as on Fraunhofer diffraction patterns. The evaluation of Fiske steps lead to a specific junction capacitance of about 62 fF/μm2 for a critical current density of about 1.7 kA/cm2. The avoidance of any idle-region - the undesired overlap between superconducting electrodes around the junction - due to a self-aligned junction definition process lead to highly sensitive SQUIDs; multiloop SQUID magnetometers exhibiting exceptionally low magnetic field noise levels as low as 0.3 fT/Hz1/2, as well as large usable voltage swings of more than 150 μVpp. Furthermore, junction dimensions in the sub-micrometer range allowed for very high tolerable background fields during cool-down of up to 6.5 mT. In operation mode, the SQUID magnetometers recovered completely from magnetization pulses of up to 76 mT. With respect to their easy and reliable usage as well as their high sensitivity, the presented SQUID sensors are adequate for many applications, like in geophysics, biomagnetism or low-field magnetic resonance imaging.
Energy Technology Data Exchange (ETDEWEB)
Schmelz, M., E-mail: matthias.schmelz@ipht-jena.de [Institute of Photonic Technology, PO Box 100239, D-07702 Jena (Germany); Stolz, R.; Zakosarenko, V.; Schoenau, T.; Anders, S.; Fritzsch, L. [Institute of Photonic Technology, PO Box 100239, D-07702 Jena (Germany); Mueck, M. [Institute of Applied Physics, Justus-Liebig University Giessen, D-35392 Giessen (Germany); Meyer, M. [Supracon AG, Wildenbruchstrasse 15, D-07745 Jena (Germany); Meyer, H.-G. [Institute of Photonic Technology, PO Box 100239, D-07702 Jena (Germany)
2012-11-20
We review the development of low parasitic capacitance sub-micrometer cross-type Josephson tunnel junctions for their use in highly sensitive and field-stable SQUID magnetometers. The potential of such junctions is shown on I-V characteristics as well as on Fraunhofer diffraction patterns. The evaluation of Fiske steps lead to a specific junction capacitance of about 62 fF/{mu}m{sup 2} for a critical current density of about 1.7 kA/cm{sup 2}. The avoidance of any idle-region - the undesired overlap between superconducting electrodes around the junction - due to a self-aligned junction definition process lead to highly sensitive SQUIDs; multiloop SQUID magnetometers exhibiting exceptionally low magnetic field noise levels as low as 0.3 fT/Hz{sup 1/2}, as well as large usable voltage swings of more than 150 {mu}Vpp. Furthermore, junction dimensions in the sub-micrometer range allowed for very high tolerable background fields during cool-down of up to 6.5 mT. In operation mode, the SQUID magnetometers recovered completely from magnetization pulses of up to 76 mT. With respect to their easy and reliable usage as well as their high sensitivity, the presented SQUID sensors are adequate for many applications, like in geophysics, biomagnetism or low-field magnetic resonance imaging.
Modern aspects of Josephson dynamics and superconductivity electronics
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.
Single walled carbon nanotube-based junction biosensor for detection of Escherichia coli.
Directory of Open Access Journals (Sweden)
Kara Yamada
Full Text Available Foodborne pathogen detection using biomolecules and nanomaterials may lead to platforms for rapid and simple electronic biosensing. Integration of single walled carbon nanotubes (SWCNTs and immobilized antibodies into a disposable bio-nano combinatorial junction sensor was fabricated for detection of Escherichia coli K-12. Gold tungsten wires (50 µm diameter coated with polyethylenimine (PEI and SWCNTs were aligned to form a crossbar junction, which was functionalized with streptavidin and biotinylated antibodies to allow for enhanced specificity towards targeted microbes. In this study, changes in electrical current (ΔI after bioaffinity reactions between bacterial cells (E. coli K-12 and antibodies on the SWCNT surface were monitored to evaluate the sensor's performance. The averaged ΔI increased from 33.13 nA to 290.9 nA with the presence of SWCNTs in a 10(8 CFU/mL concentration of E. coli, thus showing an improvement in sensing magnitude. Electrical current measurements demonstrated a linear relationship (R2 = 0.973 between the changes in current and concentrations of bacterial suspension in range of 10(2-10(5 CFU/mL. Current decreased as cell concentrations increased, due to increased bacterial resistance on the bio-nano modified surface. The detection limit of the developed sensor was 10(2 CFU/mL with a detection time of less than 5 min with nanotubes. Therefore, the fabricated disposable junction biosensor with a functionalized SWCNT platform shows potential for high-performance biosensing and application as a detection device for foodborne pathogens.
Structural optimization and shear performances of the nanopins based on Y-junction carbon nanotubes
Energy Technology Data Exchange (ETDEWEB)
Zhang, Zhong-Qiang, E-mail: zhangzq@mail.ujs.edu.cn [Micro/Nano Science and Technology Center, Jiangsu University, Zhenjiang 212013 (China); Jiangsu Collaborative Innovation Center of Photovoltaic Science and Engineering, Changzhou University, Changzhou 213164, Jiangsu (China); State Key Laboratory of Structural Analysis for Industrial Equipment, Department of Engineering Mechanics, Faculty of Vehicle Engineering and Mechanics, Dalian University of Technology, Dalian 116024 (China); Zhong, Jun [Micro/Nano Science and Technology Center, Jiangsu University, Zhenjiang 212013 (China); Ye, Hong-Fei [State Key Laboratory of Structural Analysis for Industrial Equipment, Department of Engineering Mechanics, Faculty of Vehicle Engineering and Mechanics, Dalian University of Technology, Dalian 116024 (China); Cheng, Guang-Gui [Micro/Nano Science and Technology Center, Jiangsu University, Zhenjiang 212013 (China); Ding, Jian-Ning, E-mail: dingjn@ujs.edu.cn [Micro/Nano Science and Technology Center, Jiangsu University, Zhenjiang 212013 (China); Jiangsu Collaborative Innovation Center of Photovoltaic Science and Engineering, Changzhou University, Changzhou 213164, Jiangsu (China)
2017-01-01
Utilizing the classical molecular dynamic, we have briefly conducted geometry optimization on several typical nanopins based on Y-junction carbon nanotubes (CNTs), and further investigated their shear performance. The service performance of the nanopin is not sensitive to the length of the inserting end, while as the height of the branch tube increases, the maximum unloading force increases firstly and then keeps relatively stable. The overlong inserting end and high branch tube can lead to the severe oscillation in unloading force due to the continuous morphology change. Moreover, results show that a small angle included in Y-junction CNTs can contribute to both of the fixity of the nanopin and instability of the uninstallation process. Further investigation indicates that the orientation of the branch tubes of the nanopin determines the maximum shear performance, while the radial stability of the CNTs plays an important role in the shear performance of the nanopin. And the microstructure of the Y-junction CNT occurred during the using process can also influence its service performance.
Mechanics of lipid bilayer junctions affecting the size of a connecting lipid nanotube
Directory of Open Access Journals (Sweden)
Voinova Marina
2011-01-01
Full Text Available Abstract In this study we report a physical analysis of the membrane mechanics affecting the size of the highly curved region of a lipid nanotube (LNT that is either connected between a lipid bilayer vesicle and the tip of a glass microinjection pipette (tube-only or between a lipid bilayer vesicle and a vesicle that is attached to the tip of a glass microinjection pipette (two-vesicle. For the tube-only configuration (TOC, a micropipette is used to pull a LNT into the interior of a surface-immobilized vesicle, where the length of the tube L is determined by the distance of the micropipette to the vesicle wall. For the two-vesicle configuration (TVC, a small vesicle is inflated at the tip of the micropipette tip and the length of the tube L is in this case determined by the distance between the two interconnected vesicles. An electrochemical method monitoring diffusion of electroactive molecules through the nanotube has been used to determine the radius of the nanotube R as a function of nanotube length L for the two configurations. The data show that the LNT connected in the TVC constricts to a smaller radius in comparison to the tube-only mode and that tube radius shrinks at shorter tube lengths. To explain these electrochemical data, we developed a theoretical model taking into account the free energy of the membrane regions of the vesicles, the LNT and the high curvature junctions. In particular, this model allows us to estimate the surface tension coefficients from R(L measurements.
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.
Solitonic Josephson Thermal Transport
Guarcello, Claudio; Solinas, Paolo; Braggio, Alessandro; Giazotto, Francesco
2018-03-01
We explore the coherent thermal transport sustained by solitons through a long Josephson junction as a thermal gradient across the system is established. We observe that a soliton causes the heat current through the system to increase. Correspondingly, the junction warms up in conjunction with the soliton, with temperature peaks up to, e.g., approximately 56 mK for a realistic Nb-based proposed setup at a bath temperature Tbath=4.2 K . The thermal effects on the dynamics of the soliton are also discussed. Markedly, this system inherits the topological robustness of the solitons. In view of these results, the proposed device can effectively find an application as a superconducting thermal router in which the thermal transport can be locally mastered through solitonic excitations, whose positions can be externally controlled through a magnetic field and a bias current.
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
2014-09-01
Relationship,” Technical Physics Letters 33:723. 7. R. Gross and A. Marx . 2005. “Chapter 4: Superconducting Quantum Interference Devices , Applied...explore the effects of altering the third junction in an array of bi-superconducting quantum interference devices (bi-SQUIDs) on the overall performance...temperature and capacitance terms on the bisecting junctions only. This setup represents a device with traditional main junctions and different third junction
In-situ YBa2Cu3O7/SrTiO3/YBa2Cu3O7 a-b plane Josephson edge junctions
International Nuclear Information System (INIS)
Aharoni, E.; Koren, G.; Polturak, E.; Cohen, D.; Iskevitch, E.
1992-01-01
YBCO/SrTiO 3 /YBCO thin film edge junctions were prepared in-situ and characterized. The epitaxial growth of SrTiO 3 on YBCO led to a sharp and well defined junction edge with a very high yield. Typical junctions showed critical currents up to 83 K, with I c ∝ (1 - T/Tc) 2 temperature dependence. Sharp Shapiro steps were observed under microwave radiation at temperatures up to 82 K. A typical diffraction pattern was found in the voltage response of the junctions to transverse magnetic field. (orig.)
Nanotechnology with Carbon Nanotubes: Mechanics, Chemistry, and Electronics
Srivastava, Deepak
2003-01-01
This viewgraph presentation reviews the Nanotechnology of carbon nanotubes. The contents include: 1) Nanomechanics examples; 2) Experimental validation of nanotubes in composites; 3) Anisotropic plastic collapse; 4) Spatio-temporal scales, yielding single-wall nanotubes; 5) Side-wall functionalization of nanotubes; 6) multi-wall Y junction carbon nanotubes; 7) Molecular electronics with Nanotube junctions; 8) Single-wall carbon nanotube junctions; welding; 9) biomimetic dendritic neurons: Carbon nanotube, nanotube electronics (basics), and nanotube junctions for Devices,
Energy Technology Data Exchange (ETDEWEB)
Oehmichen, V.
2007-09-29
Goal of this thesis was to extend the knowledge of fluxon dynamics in intrinsic Josephson junctions out of BSCCO and to manipulate this dynamics in a purposeful way. New approaches to create ThZ-radiation were investigated. Step stacks out of BSCCO have been prepared with dimensions of 1-3 {mu}m (width) and 3-10 {mu}m (length). The necessary fabrication process was established based on Wang's double-sided technique. Transport measurements without and with magnetic field were realised on the so produced samples. The magnetic field of some Tesla was oriented parallel to the CuO{sub 2}-double layers. Collective plasma resonances were observed. Those were more stable than the resonances in mesa-structures. The resonances in the low current range can be assigned to an out-of-phase configuration, whereas in the high current range there are some possible configurations. Flux-flow-oscillations measured at these step stacks support the arrangement of the fluxons in an out-of-phase configuration. The in-phase configuration couldn't be observed clearly, so two approaches were followed to manipulate aimingly the fluxon dynamics to create THz-radiation: * control current * geometric manipulation: width-modulated stack For electronic manipulation an additional current line (control current line) was prepared along the stack's bottom. During transport measurements in zero field a current of 0-30 {mu}A was sent through this control current line. The so created inhomogeneity should have provoked fluxons without the help of a magnetic field. A visible effect couldn't be measured. Geometric manipulation of fluxon dynamics to reach in-phase configuration relys on modulation of the stack's width: it has periodic necks (comb structure). First measurements on comb structures prepared in double-side technique show promising hints, that manipulation on purpose of fluxon dynamics is possible using width-modulation. Simulations were performed for different depths of
DEFF Research Database (Denmark)
Pedersen, Niels Falsig; Sakai, Shigeki
2000-01-01
We demonstrate analytically that parametric excitation of certain plasma resonance modes in Bi2Sr2CaCu2Ox single crystals is possible. The model we use is that of a Josephson stack, and the fundamental mechanism is that of half harmonic generation in time and space when a threshold of the applied...... rf signal is exceeded. The phenomenon is important as a diagnostic tool for the investigation of plasma resonance in Bi2Sr2CaCu2Ox-like materials, as well as being a basis for making high-T-c high-frequency parametric amplifiers. It has same unique features of space and time nonlinear behavior....
Energy Technology Data Exchange (ETDEWEB)
Moradian, Rostam, E-mail: moradian.rostam@gmail.com [Physics Department, Faculty of Science, Razi University, Kermanshah (Iran, Islamic Republic of); Nano Science and Technology Research Center, Razi University, Kermanshah (Iran, Islamic Republic of); Computational Physical Science Research Laboratory, Department of Nano-Science, Institute for Studies in Theoretical Physics and Mathematics (IPM), P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of); Shahrokhi, Masoud, E-mail: sharokhimasoud37@gmail.com [Physics Department, Faculty of Science, Razi University, Kermanshah (Iran, Islamic Republic of); Nano Science and Technology Research Center, Razi University, Kermanshah (Iran, Islamic Republic of); Karami Pourian, Aazam [Physics Department, Faculty of Science, Razi University, Kermanshah (Iran, Islamic Republic of); Nano Science and Technology Research Center, Razi University, Kermanshah (Iran, Islamic Republic of)
2013-10-15
By using first-principles calculations within the density function theory, the structural, electronic and magnetic properties of BeO nanotube filled with Fe{sub n} nanoparticles are investigated. We found that all these Fe{sub n} nanoparticle@BeONTs systems are ferromagnetic (FM) and a spin splitting between spin up and down electrons is observed. In terms of nanoparticle diameter, the Fe{sub n} nanoparticle@BeONT system could be a semiconductor, half-metal or metal. Also the BeONT locally become non-magnetic semiconductor/magnetic semiconductor junctions or non-magnetic semiconductor/magnetic metal junctions in terms of nanoparticle diameter. The high magnetic moment and spin polarization of the Fe{sub n}@BeONTs systems imply that it can be used as heterojunctions in electronic devices, magnetic recording, spintronics and are vital for the fabrication of robust nanotube-metal composite materials. - Highlights: • Physical properties of BeONT filled with Fe{sub n} nanoparticles are investigated. • Fe{sub n}NP@BeONTs systems are ferromagnetic, exothermic and stable. • The Fe{sub n}NP@BeONT system could be a semiconductor, half-metal or metal. • The systems with small nanoparticles are more stable than large nanoparticles.
Energy Technology Data Exchange (ETDEWEB)
Delfanazari, Kaveh, E-mail: s-kaveh@ims.tsukuba.ac.jp [Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1, Tennodai, Tsukuba, Ibaraki 305-8573 (Japan); CREST, Japan Science and Technology Agency, Kawaguchi Center Building, 4-1-8, Honcho, Kawaguchi, Saitama 332-0012 (Japan); WPI-MANA, International Center for Materials Nanoarchitectonics, Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Asai, Hidehiro [Electronics and Photonics Research Institute, The National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568 (Japan); Tsujimoto, Manabu; Kashiwagi, Takanari; Kitamura, Takeo [Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1, Tennodai, Tsukuba, Ibaraki 305-8573 (Japan); CREST, Japan Science and Technology Agency, Kawaguchi Center Building, 4-1-8, Honcho, Kawaguchi, Saitama 332-0012 (Japan); WPI-MANA, International Center for Materials Nanoarchitectonics, Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Yamamoto, Takashi [Semiconductor Analysis and Radiation Effects Group, Japan Atomic Energy Agency, Gunma 370-1292 (Japan); Sawamura, Masashi; Ishida, Kazuya [Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1, Tennodai, Tsukuba, Ibaraki 305-8573 (Japan); CREST, Japan Science and Technology Agency, Kawaguchi Center Building, 4-1-8, Honcho, Kawaguchi, Saitama 332-0012 (Japan); WPI-MANA, International Center for Materials Nanoarchitectonics, Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Tachiki, Masashi [Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1, Tennodai, Tsukuba, Ibaraki 305-8573 (Japan); CREST, Japan Science and Technology Agency, Kawaguchi Center Building, 4-1-8, Honcho, Kawaguchi, Saitama 332-0012 (Japan); Klemm, Richard A. [Department of Physics, University of Central Florida, Orlando, FL 32816 (United States); and others
2013-08-15
Highlights: ► We observed intense and coherent THz waves in the equilateral triangular mesas. ► We numerically investigated EM modes of the mesas which emitted intense THz waves. ► Irreversible (IR)-type THz radiation is observed in the equilateral triangular mesas. -- Abstract: We report on intense and coherent terahertz (THz) electromagnetic (EM) waves emitted from equilateral triangular mesa structures of the intrinsic Josephson junctions (IJJs) in single crystalline high-T{sub c} superconducting Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+δ}. The focused ion beam milling technique is used for mesa fabrication. THz radiation is observed when the emission frequency is in the vicinity of the primary cavity resonance frequency determined by the mesa geometry. We also investigated numerically the THz radiation from such mesas using the finite difference time domain method. We found an apparent EM mode similar to the known TM(1, 0) = TM(0, 1) cavity mode during the THz emission.
Energy Technology Data Exchange (ETDEWEB)
Navacerrada, M.A., E-mail: mdelosangeles.navacerrada@upm.es [Grupo de Acustica Arquitectonica, Escuela Tecnica Superior de Arquitectura, Universidad Politecnica de Madrid, Avenida Juan de Herrera 4, 28040 Madrid (Spain); Lucia, M.L.; Sanchez-Quesada, F. [Departamento Fisica Aplicada III (Electricidad y Electronica), Facultad de Cc. Fisicas, Universidad Complutense, Avenida Complutense s/n, 28040 Madrid (Spain)
2012-12-14
We have analyzed a resonant behavior in the dielectric constant associated to the barrier of YBa{sub 2}Cu{sub 3}O{sub 7} (YBCO) grain boundary Josephson junctions (GBJJs) fabricated on a wide variety of bicrystalline substrates: 12 Degree-Sign [0 0 1] tilt asymmetric, 24 Degree-Sign [0 0 1] tilt asymmetric, 24 Degree-Sign [0 0 1] tilt symmetric, 24 Degree-Sign [1 0 0] tilt asymmetric, 45 Degree-Sign [1 0 0] tilt asymmetric and 24 Degree-Sign [0 0 1] tilt symmetric +45 Degree-Sign [1 0 0] tilt asymmetric bicrystals. The resonance analysis allows us to estimate a more appropriate value of the relative dielectric constant, and so a more adequate value for the length L of the normal N region assuming a SNINS model for the barrier. In this work, the L dependence on the critical current density Jc has been investigated. This analysis makes possible a single representation for all the substrate geometries independently on around which axes the rotation is produced to generate the grain boundary. On the other hand, no clear evidences exist on the origin of the resonance. The resonance frequency is in the order of 10{sup 11} Hz, pointing to a phonon dynamic influence on the resonance mechanism. Besides, its position is affected by the oxygen content of the barrier: a shift at low frequencies is observed when the misorientation angle increases.
Ultrasensitive proximity Josephson sensor with kinetic inductance readout
Giazotto, Francesco; Heikkilä, Tero T.; Pepe, Giovanni Piero; Helistö, Panu; Luukanen, Arttu; Pekola, Jukka P.
2008-01-01
We propose a mesoscopic kinetic-inductance radiation detector based on a long superconductor-normal metal-superconductor Josephson junction. The operation of this proximity Josephson sensor relies on large kinetic inductance variations under irradiation due to the exponential temperature dependence of the critical current. Coupled with a dc superconducting quantum interference device readout, the PJS is able to provide a signal to noise (S/N) ratio up to ∼103 in the terahertz regime if operat...
Directory of Open Access Journals (Sweden)
Ning Yang
2017-11-01
Full Text Available The new three-dimensional structure that the graphene connected with SWCNTs (G-CNTs, Graphene Single-Walled Carbon Nanotubes can solve graphene and CNTs′ problems. A comprehensive study of the mechanical and electrical performance of the junctions was performed by first-principles theory. There were eight types of junctions that were constituted by armchair and zigzag graphene and (3,3, (4,0, (4,4, and (6,0 CNTs. First, the junction strength was investigated. Generally, the binding energy of armchair G-CNTs was stronger than that of zigzag G-CNTs, and it was the biggest in the armchair G-CNTs (6,0. Likewise, the electrical performance of armchair G-CNTs was better than that of zigzag G-CNTs. Charge density distribution of G-CNTs (6,0 was the most homogeneous. Next, the impact factors of the electronic properties of armchair G-CNTs were investigated. We suggest that the band gap is increased with the length of CNTs, and its value should be dependent on the combined effect of both the graphene’s width and the CNTs’ length. Last, the relationship between voltage and current (U/I were studied. The U/I curve of armchair G-CNTs (6,0 possessed a good linearity and symmetry. These discoveries will contribute to the design and production of G-CNT-based devices.
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
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.
Nonlinearities in Josephson-photonics
Energy Technology Data Exchange (ETDEWEB)
Kubala, Bjoern; Ankerhold, Joachim [Institute for Complex Quantum Systems and IQST, Ulm University, Ulm (Germany)
2016-07-01
Embedding a voltage-biased Josephson junction within a high-Q superconducting microwave cavity provides a new way to explore the interplay of the tunneling transfer of charges and the emission and absorption of light. While for weak driving the system can be reduced to simple cases, such as a (damped) harmonic or parametric oscillator, the inherent nonlinearity of the Josephson junction allows to access regimes of strongly non-linear quantum dynamics. Classically, dynamical phenomena such as thresholds for higher-order resonances, other bifurcations, and up- and down-conversion have been found. Here, we will investigate how and to which extent these features appear in the deep quantum regime, where charge quantization effects are crucial. Theory allows to employ phase-space quantities, such as the Wigner-density of the cavity mode(s), but also observables amenable to more immediate experimental access, such as correlations in light emission and charge transport, to probe these novel non-equilibrium transitions.
Energy Technology Data Exchange (ETDEWEB)
Seidel, P.; Schmidl, F.; Schneidewind, H.; Linzen, S.; Doerrer, L.; Pfuch, A.; Schmauder, T.; Kaiser, G.; Matthes, A.; Machalett, F.; Barholz, K.U.; Brabetz, S.
1996-06-01
Based on improved thin film technologies for high-Tc superconductors (YBCO, Bi-2212) Josephson junctions and DC-SQUIDs were developed. A lot of different kinds of junctions (bicrystal, step-edge, SNS-like, biepitaxial etc.) were investigated for comparison. DC-SQUIDs and planar SQUID-gradiometers with these junctions show parameters to realize first applications in nondestructive evaluation or biomagnetism, respectively. (orig.) [Deutsch] Auf Grundlage von verbesserten Duennschichttechnologien fuer Hochtemperatursupraleiter (YBCO, Bi-2212) wurden Josephsonkontake und DC-SQUIDs entwickelt. Eine Vielzahl von Kontaktypen (Bikristall, Step-Edge, SNS-artige, biepitaktische etc.) wurden vergleichend untersucht. Die damit realisierten DC-SQUIDs und planarer SQUID-Gradiometer zeigen Parameter, die erste Anwendungen in der zerstoerungsfreien Werkstoffpruefung oder dem Biomagnetismus ermoeglichen. (orig.)
Possible analog gain in a current injection Josephson network
International Nuclear Information System (INIS)
Biswas, J.C.; Dutta Roy, S.K.
1986-01-01
A possible analog gain in Cooper-pair tunneling mode in a current injection Josephson network is theoretically investigated. The network consists of three Josephson junctions A, B, and C, and its gain can be widely controlled by varying the external shunt resistances of junctions B and C. Two different configurations of the planar structure of the network are suggested and their detailed principles of operation are explained. It is expected that the network will function at a higher speed than that possible in an amplifying device working in quasiparticle mode. A comparison between the present network and Faris QUITERON is also given
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...
Energy Technology Data Exchange (ETDEWEB)
Sengupta, Amretashis [Hanse-Wissenschaftskolleg (HWK), Delmenhorst (Germany); Universitaet Bremen, Bremen Center for Computational Materials Science (BCCMS), Bremen (Germany)
2017-04-15
Armchair nanotubes of MoS{sub 2} and WS{sub 2} offer a sizeable band gap, with the advantage of a one dimensional (1D) electronic material, but free from edge roughness and thermodynamic instability of nanoribbons. Use of such semiconducting MX{sub 2} (MoS{sub 2}, WS{sub 2}) armchair nanotubes (NTs) in conjunction with metallic carbon nanotubes (CNT) can be useful for nanoelectronics and photonics applications. In this work, atomistic simulations of MoS{sub 2} NT-CNT and WS{sub 2} NT-CNT junctions are carried out to study the physics of such junctions. With density functional theory (DFT) we study the carrier density distribution, effective potential, electron difference density, electron localization function, electrostatic difference potential and projected local density of states of such MX{sub 2} NT-CNT 1D junctions. Thereafter the conductance of such a junction under moderate bias is studied with non-equilibrium Green's function (NEGF) method. From the forward bias characteristics simulated from NEGF, we extract diode parameters of the junction. The electrostatic simulations from DFT show the formation of an inhomogeneous Schottky barrier with a tendency towards charge transfer from metal and chalcogen atoms towards the C atoms. For low bias conditions, the ideality factor was calculated to be 1.1322 for MoS{sub 2} NT-CNT junction and 1.2526 for the WS{sub 2} NT-CNT junction. The Schottky barrier heights displayed significant bias dependent modulation and are calculated to be in the range 0.697-0.664 eV for MoS{sub 2} NT-CNT and 0.669-0.610 eV for the WS{sub 2} NT-CNT, respectively. (orig.)
Directory of Open Access Journals (Sweden)
Jungkyu Park
2014-01-01
Full Text Available In the present study, reverse nonequilibrium molecular dynamics is employed to study thermal resistance across interfaces comprising dimensionally mismatched junctions of single layer graphene floors with (6,6 single-walled carbon nanotube (SWCNT pillars in 3D carbon nanomaterials. Results obtained from unit cell analysis indicate the presence of notable interfacial thermal resistance in the out-of-plane direction (along the longitudinal axis of the SWCNTs but negligible resistance in the in-plane direction along the graphene floor. The interfacial thermal resistance in the out-of-plane direction is understood to be due to the change in dimensionality as well as phonon spectra mismatch as the phonons propagate from SWCNTs to the graphene sheet and then back again to the SWCNTs. The thermal conductivity of the unit cells was observed to increase nearly linearly with an increase in cell size, that is, pillar height as well as interpillar distance, and approaches a plateau as the pillar height and the interpillar distance approach the critical lengths for ballistic thermal transport in SWCNT and single layer graphene. The results indicate that the thermal transport characteristics of these SWCNT-graphene hybrid structures can be tuned by controlling the SWCNT-graphene junction characteristics as well as the unit cell dimensions.
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.)
Zhang, W J; Zhang, Q F; Chai, Y; Shen, X; Wu, J L
2007-10-03
The electrical transport characteristics of multiwall CN(x)/carbon nanotube intramolecular junctions were studied. The junctions could be used as diodes. We found that the rectification resulted from p-n junctions, not from metal-semiconductor junctions. The gate effect was very weak when the diodes were reverse biased. At forward bias, however, some of the p-n diodes could be n-type transistors. Experimental results supported the opinion that the gate voltage dependent property is derived from the Schottky barrier between the CN(x) part and the electrode. Using p-n diodes, a bipolar transistor with nanoscale components was built, whose behavior was very similar to that of a conventional planar bipolar transistor.
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
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
Fractional Josephson vortices at YBa$_2$Cu$_3$O$_{7-x}$ grain boundaries
Mints, R. G.; Papiashvili, Ilya
2001-01-01
We report numerical simulations of magnetic flux patterns in asymmetric 45$^{\\circ}$ [001]-tilt grain boundaries in YBa$_2$Cu$_3$O$_{7-x}$ superconducting films. The grain boundaries are treated as Josephson junctions with the critical current density $j_c(x)$ alternating along the junctions. We demonstrate the existence of Josephson vortices with fractional flux quanta for both periodic and random $j_c(x)$. A method is proposed to extract fractional vortices from experimental flux patterns.
Josephson Vortex Qubit based on a Confocal Annular Josephson Junction
DEFF Research Database (Denmark)
Monaco, Roberto; Mygind, Jesper; Koshelets, Valery P.
2017-01-01
. Thisintrinsic vortex potential can be tuned by an externally applied magnetic fieldand tilted by a bias current. The two-state system is accurately modeled by aone-dimensional sine-Gordon like equation by means of which one can numericallycalculate both the magnetic field needed to set the vortex in a given...... state aswell as the vortex depinning currents. Experimental data taken at 4.2K onhigh-quality Nb/Al-AlOx/Nb CAJTJs with an individual trapped fluxon advocatethe presence of a robust and finely tunable double-well potential for whichreliable manipulation of the vortex state has been classically...... demonstrated.The vortex is prepared in a given potential by means of an externally appliedmagnetic field, while the state readout is accomplished by measuring thevortex-depinning current in a small magnetic field. Our proof of principleexperiment convincingly demonstrates that the proposed vortex qubit based...
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
Solitonic Josephson-based meminductive systems.
Guarcello, Claudio; Solinas, Paolo; Di Ventra, Massimiliano; Giazotto, Francesco
2017-04-24
Memristors, memcapacitors, and meminductors represent an innovative generation of circuit elements whose properties depend on the state and history of the system. The hysteretic behavior of one of their constituent variables, is their distinctive fingerprint. This feature endows them with the ability to store and process information on the same physical location, a property that is expected to benefit many applications ranging from unconventional computing to adaptive electronics to robotics. Therefore, it is important to find appropriate memory elements that combine a wide range of memory states, long memory retention times, and protection against unavoidable noise. Although several physical systems belong to the general class of memelements, few of them combine these important physical features in a single component. Here, we demonstrate theoretically a superconducting memory based on solitonic long Josephson junctions. Moreover, since solitons are at the core of its operation, this system provides an intrinsic topological protection against external perturbations. We show that the Josephson critical current behaves hysteretically as an external magnetic field is properly swept. Accordingly, long Josephson junctions can be used as multi-state memories, with a controllable number of available states, and in other emerging areas such as memcomputing, i.e., computing directly in/by the memory.
A Josephson sampler with 2.1 ps resolution
International Nuclear Information System (INIS)
Wolf, P.; Deutsch, U.; Van Zeghbroeck, J.
1985-01-01
A Josephson sampler with 2.1 ps resolution is reported. The sampler was made with Nb edge junctions, and consists of a sampling junction to which a Faris pulser is coupled directly. Two experiments are connected to the sampler: a two-junction interferometer and another Faris pulser. A new and simple electronic delay allows a flicker-free display on an oscilloscope of the waveform sampled. A current sensitivity of 0.8 μA was achieved. It was possible to measure the switching transitions of the two-junction interferometer over its whole vortex boundary, including vortex-to-vortex transitions which occur at low bias currents. To our knowledge, this is the fastest Josephson sampler made to date
Enhanced transparency ramp-type Josephson contacts through interlayer deposition
Smilde, H.J.H.; Hilgenkamp, Johannes W.M.; Rijnders, Augustinus J.H.M.; Rogalla, Horst; Blank, David H.A.
2002-01-01
A thin interlayer is incorporated in ramp-type Josephson junctions to obtain an increased transparency. The interlayer restores the surface damaged by ion milling and has the advantage of an all in situ barrier deposition between two superconductors, leading to clean and well-defined interfaces. The
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
Josephson Circuits as Vector Quantum Spins
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.
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
The results of an experimental study of the magnetic field dependence of the Josephson-plasma-resonance frequency and linewidth in Pb-Pb oxide-Pb tunnel junctions are reported. In the presence of an external magnetic field, the plasma mode is found to be sensitive to an antisymmetric component...... 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...
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...
Controlling the dynamic range of a Josephson parametric amplifier
International Nuclear Information System (INIS)
Eichler, Christopher; Wallraff, Andreas
2014-01-01
One of the central challenges in the development of parametric amplifiers is the control of the dynamic range relative to its gain and bandwidth, which typically limits quantum limited amplification to signals which contain only a few photons per inverse bandwidth. Here, we discuss the control of the dynamic range of Josephson parametric amplifiers by using Josephson junction arrays. We discuss gain, bandwidth, noise, and dynamic range properties of both a transmission line and a lumped element based parametric amplifier. Based on these investigations we derive useful design criteria, which may find broad application in the development of practical parametric amplifiers. (orig.)
Invited review article: The Josephson bifurcation amplifier.
Vijay, R; Devoret, M H; Siddiqi, I
2009-11-01
We review the theory, fabrication, and implementation of the Josephson bifurcation amplifier (JBA). At the core of the JBA is a nonlinear oscillator based on a reactively shunted Josephson junction. A weak input signal to the amplifier couples to the junction critical current I(0) and results in a dispersive shift in the resonator plasma frequency omega(p). This shift is enhanced by biasing the junction with a sufficiently strong microwave current I(rf) to access the nonlinear regime where omega(p) varies with I(rf). For a drive frequency omega(d) such that Omega=2Q(1-omega(d)/omega(p))>3, the oscillator enters the bistable regime where two nondissipative dynamical states O(L) and O(H), which differ in amplitude and phase, can exist. The sharp I(0) dependent transition from O(L) to O(H) forms the basis for a sensitive digital threshold amplifier. In the vicinity of the bistable regime (Omegaamplifier performance and discuss two specific applications--the readout of superconducting qubits (digital mode) and dispersive microwave magnetometry (analog mode).
High temperature superconducting Josephson transmission lines for pulse and step sharpening
International Nuclear Information System (INIS)
Martens, J.S.; Wendt, J.R.; Hietala, V.M.; Ginley, D.S.; Ashby, C.I.H.; Plut, T.A.; Vawter, G.A.; Tigges, C.P.; Siegal, M.P.; Hou, S.Y.; Phillips, J.M.; Hohenwarter, G.K.G.
1992-01-01
An increasing number of high speed digital and other circuit applications require very narrow impulses or rapid pulse edge transitions. Shock wave transmission lines using series or shunt Josephson junctions are one way to generate these signals. Using two different high temperature superconducting Josephson junction processes (step-edge and electron beam defined nanobridges), such transmission lines have been constructed and tested at 77 K. Shock wave lines with approximately 60 YBaCuO nanobridges, have generated steps with fall times of about 10 ps. With step-edge junctions (with higher figures of merit but lower uniformity), step transition times have been reduced to an estimated 1 ps
Voltage splay modes and enhanced phase locking in a modified linear Josephson array
Harris, E. B.; Garland, J. C.
1997-02-01
We analyze a modified linear Josephson-junction array in which additional unbiased junctions are used to greatly enhance phase locking. This geometry exhibits strong correlated behavior, with an external magnetic field tuning the voltage splay angle between adjacent Josephson oscillators. The array displays a coherent in-phase mode for f=, where f is the magnetic frustration, while for 0tolerant of critical current disorder approaching 100%. The stability of the array has also been studied by computing Floquet exponents. These exponents are found to be negative for all array lengths, with a 1/N2 dependence, N being the number of series-connected junctions.
Kink motion in a curved Josephson junction
DEFF Research Database (Denmark)
Sørensen, Mads Peter
is investigated. The kink may be captured when a driving force, provided by a magnetic field, is applied to the kink. The approximate analytical tools are based on a variational approach of a Lagrangian. The variation is done with respect to collective coordinates, or slowly varying coefficients, in the 1D...
Materials For Improved Josephson-Junction Devices
Vasquez, Richard P.; Barner, Jeffrey B.
1996-01-01
Number of superconductive, normally conductive, and insulating materials proposed for use in fabricating improved superconductor/insulator/superconductor (SIS) and superconductor/normal conductor/superconductor (SNS) electronic devices capable of operation at frequencies up into terahertz range. Such devices particularly useful as electrically nonlinear circuit elements of mixers and local oscillators in heterodyne receivers.
Applications of Josephson junction squids and arrays
Silver, A. H.
1983-03-01
This report covers the period from 1 October 1982 to 28 February 1983 following the period covered by the last annual progress report. This period included the preparation and submission of the draft of the annual report, presentation of the paper SQUID Voltage-Controlled-Oscillator to the 1982 Applied Superconductivity Conference, continued fabrication and measurement of the 9GHz SQUID VCO, and design of the DC SQUID and SQUID array configuration. In addition, a number of important additions and modifications were made in the basic laboratory facilities. Work has continued on fabrication and measurements of the single resistive SQUID VCO with the 50/1 transformer ratio operating near 9GHz. Four chips are fabricated on a wafer, with different damping resistors for each one of the four devices.
Josephson Junction as a Magnetic Switch
Cai, Liufei; Chudnovsky, Eugene
2011-03-01
We study electromagnetic interaction of a nanomagnet with a weak superconducting link. Equations that govern coupled dynamics of the two systems are derived and investigated numerically. We show that despite very weak magnetic field generated by the weak link, a time-dependent bias voltage applied to the link can initiate a non-linear dynamics of the nanomagnet that leads to the reversal of its magnetic moment. We also consider quantum problem in which a nanomagnet interacting with a weak link is treated as a two-state spin system due to quantum tunneling between spin-up and spin-down states. L. Cai and E. M. Chudnovsky, Phys. Rev B 82, 104429 (2010).
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
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
Pumping $ac$ Josephson current in the Single Molecular Magnets by spin nutation
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...
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)
Energy Technology Data Exchange (ETDEWEB)
Khan, Azam, E-mail: azam.khan@liu.se; Edberg, Jesper; Nur, Omer; Willander, Magnus [Department of Science and Technology (ITN), Campus Norrköping, Linköping University, SE-601 74 Norrköping (Sweden)
2014-07-21
In the present work, three junctions were fabricated on textile fabric as an alternative substrate for harvesting piezoelectric potential. First junction was formed on ordinary textile as (textile/multi-walled carbon nanotube film/zinc oxide nanowires (S1: T/CNTs/ZnO NWs)) and the other two were formed on conductive textile with the following layer sequence: conductive textile/zinc oxide nanowires (S2: CT/ZnO NWs) and conductive textile/multi-walled carbon nanotubes film/zinc oxide nanowires (S3: CT/CNTs/ZnO NWs). Piezoelectric potential was harvested by using atomic force microscopy in contact mode for the comparative analysis of the generated piezoelectric potential. ZnO NWs were synthesized by using the aqueous chemical growth method. Surface analysis of the grown nanostructures was performed by using scanning electron microscopy and transmission electron microscopy. The growth orientation and crystalline size were studied by using X-ray diffraction technique. This study reveals that textile as an alternative substrate have many features like cost effective, highly flexible, nontoxic, light weight, soft, recyclable, reproducible, portable, wearable, and washable for nanogenerators fabrication with acceptable performance and with a wide choice of modification for obtaining large amount of piezoelectric potential.
Josephson current through a quantum dot molecule with a Majorana zero mode and Andreev bound states
Tang, Han-Zhao; Zhang, Ying-Tao; Liu, Jian-Jun
2018-04-01
Based on the Green's function method, we investigate the interplay between Majorana zero mode (MZM) and Andreev bound states (ABSs) in a quantum dot molecule side coupled to a topological superconducting nanowire with a pair of MZMs forming a Josephson junction. Since the strong electron-hole asymmetry induced by the nanowire with a topologically non-trivial phase, the MZM suppress the ABSs. The suppression induced by the MZM is robust against the Coulomb repulsion. The interplay between the MZM and the ABSs in Josephson junction presents a feasible experimental means for distinguish between the presence of MZM and ABSs.
Josephson parametric converter saturation and higher order effects
Liu, G.; Chien, T.-C.; Cao, X.; Lanes, O.; Alpern, E.; Pekker, D.; Hatridge, M.
2017-11-01
Microwave parametric amplifiers based on Josephson junctions have become indispensable components of many quantum information experiments. One key limitation which has not been well predicted by theory is the gain saturation behavior which limits the amplifier's ability to process large amplitude signals. The typical explanation for this behavior in phase-preserving amplifiers based on three-wave mixing, such as the Josephson Parametric Converter, is pump depletion, in which the consumption of pump photons to produce amplification results in a reduction in gain. However, in this work, we present experimental data and theoretical calculations showing that the fourth-order Kerr nonlinearities inherent in Josephson junctions are the dominant factor. The Kerr-based theory has the unusual property of causing saturation to both lower and higher gains, depending on bias conditions. This work presents an efficient methodology for optimizing device performance in the presence of Kerr nonlinearities while retaining device tunability and points to the necessity of controlling higher-order Hamiltonian terms to make further improvements in parametric devices.
The submm wave Josephson flux flow oscillator; Linewidth measurements and simple theory
DEFF Research Database (Denmark)
Mygind, Jesper; Koshelets, V. P.; Samuelsen, Mogens Rugholm
2005-01-01
The Flux Flow Oscillator (FFO) is a long Josephson junction in which a DC bias current and a DC magnetic field maintain a unidirectional viscous flow of magnetic flux quanta. The theoretical linewidth of the electromagnetic radiation generated at the end boundary is due to internal current...
Two Superconducting Charge Qubits Coupled by a Josephson Inductance
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.
DEFF Research Database (Denmark)
Jørgensen, E.; Koshelets, V. P.; Monaco, Roberto
1982-01-01
The radiation emission from long and narrow Josephson tunnel junctions dc-current biased on zero-field steps has been ascribed to resonant motion of fluxons on the transmission line. Within this dynamic model a theoretical expression for the radiation linewidth is derived from a full statistical ...... treatment of thermal fluctuations in the fluxon velocity. The result appears to be very general and is corroborated by experimental determination of linewidth and frequency of radiation emitted from overlap Nb-I-Pb junctions....
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
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
Multiple Josephson contact interferometer
International Nuclear Information System (INIS)
Zappe, H.H.
1978-01-01
The interferometer (quantum interference between two parallel contacts) displays a mid connector and contacts of the same size, or contacts at which the middle one is twice the size as the other two, or a double connector and three contacts by which the middle contact carries twice the current as the other two. Also there can be provided interferometers with three and four contacts as well as with symmetrical double current connectors and the same largest Josephson current through all contacts. Because all contacts display the same phase state in the voltage free switching state, the amplification property can be increased and current dissipation can be decreased in a way that logic circuits with high integration degree and high switching velocities can be designed. (DG) [de
2015-05-22
cryogenic temperatures and strong magnetic fields, and fund that chemical doping can enhance the carrier density and junction transport. Aligned CNT...Next we move to DC transport under cryogenic temperatures (1 K) and extreme magnetic field (60 T). Although applications are more specialized in...SWCNT length, alignment, and chirality is an evolving discipline and understanding its specific influences directs the development of SWCNT textiles
Large Effects of Magnetic Field on Josephson Currents Through Antiferromagnetic Barriers
Gor'kov, L. P.; Kresin, V. Z.
2002-07-01
Ferromagnetism being known to have a detrimental effect on superconductivity, we consider the Josephson current amplitude for junctions built up of antiferromagnetic metallic weak links. It is assumed that the latter consist of ferromagnetic layers with magnetizations aligned alternatively along perpendicular-to-the-layers direction. Currents between two superconducting electrodes flow along the layers. Such antiferromagnetic structure realizes itself in mixed valence manganites (the so-called A-phase), in an array of parallel ferromagnetic domains, or even in artificial GMR heterostructures. It is shown that even minor canting of magnetic moments in the presence of magnetic fields causes remarkable oscillations in the value of the Josephson current amplitude.
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
Voltage splay modes and enhanced phase locking in a modified linear Josephson array
International Nuclear Information System (INIS)
Harris, E.B.; Garland, J.C.
1997-01-01
We analyze a modified linear Josephson-junction array in which additional unbiased junctions are used to greatly enhance phase locking. This geometry exhibits strong correlated behavior, with an external magnetic field tuning the voltage splay angle between adjacent Josephson oscillators. The array displays a coherent in-phase mode for f=(1)/(2), where f is the magnetic frustration, while for 0 p (f)=2aV dc /Φ 0 (1-2f). The locked splay modes are found to be tolerant of critical current disorder approaching 100%. The stability of the array has also been studied by computing Floquet exponents. These exponents are found to be negative for all array lengths, with a 1/N 2 dependence, N being the number of series-connected junctions. copyright 1996 The American Physical Society
Josephson emission with frequency span 1-11 THz from small Bi2Sr2CaCu2O8+δmesa structures.
Borodianskyi, E A; Krasnov, V M
2017-11-23
Mesa structures made of Bi 2 Sr 2 CaCu 2 O 8+δ high-temperature superconductor represent stacks of atomic scale intrinsic Josephson junctions. They can be used for generation of high-frequency electromagnetic waves. Here we analyze Josephson emission from small-but-high mesas (with a small area, but containing many stacked junctions). We have found strong evidence for tunable terahertz emission with a good efficacy in a record high-frequency span 1-11 THz, approaching the theoretical upper limit for this superconductor. Emission maxima correspond to in-phase cavity modes in the mesas, indicating coherent superradiant nature of the emission. We conclude that terahertz emission requires a threshold number of junctions N ~ 100. The threshold behavior is not present in the classical description of stacked Josephson junctions and suggests importance of laser-like cascade amplification of the photon number in the cavity.
Energy Technology Data Exchange (ETDEWEB)
NONE
1998-03-01
In order to establish basic technology for hybrid systems of superconducting and semiconducting devices, study was made on ultrahigh speed and low energy consumption properties of Josephson devices. As Josephson IC technology, a logical circuit, ring network, memory circuit, and oxide superconductor logical circuit were studied. As superconducting hybrid system technology, a Josephson device- semiconductor device interface, formation technology of signal transmission lines, and Josephson-MOS IC technology were developed. In fiscal 1997, as Josephson IC technology, switch motion of 4GHz in clock frequency was achieved by new high-density wiring process. Integration of some semiconducting processor elements, junction of surface- stabilized superconducting thin films, and motion of combination structure of some SQUIDs were also confirmed. On the hybrid system, voltage conversion operation of all interfaces was confirmed. Proper logical operation of the Josephson device hybrid circuit was also confirmed. 95 refs., 90 figs., 5 tabs.
A Josephson four-bit full adder using direct coupled functional gates
International Nuclear Information System (INIS)
Matheron, G.; Migny, P.; Sie, O.
1984-09-01
A Josephson 4-bit full adder circuit using functional direct coupled gates has been designed and studied through computer simulations. The circuit consists of only 27 gates taken from a complete logic family composed of OR, AND, EXOR and MAJORITY gates. The proposed adder scheme needs 180 Josephson junctions and 150 thin film resistors. The computed critical path delay was found 180 ps/4bits for carry propagation, with a power dissipation estimated to be less than 100 μW on the basis of a Nb/Pb-In technology with 4 μm minimum linewidth and with a Josephson current density of 1000 A/cm 2 . The worst case total add time for the 4 bits has been found less than 300 ps
A near-quantum-limited Josephson traveling-wave parametric amplifier.
Macklin, C; O'Brien, K; Hover, D; Schwartz, M E; Bolkhovsky, V; Zhang, X; Oliver, W D; Siddiqi, I
2015-10-16
Detecting single-photon level signals—carriers of both classical and quantum information—is particularly challenging for low-energy microwave frequency excitations. Here we introduce a superconducting amplifier based on a Josephson junction transmission line. Unlike current standing-wave parametric amplifiers, this traveling wave architecture robustly achieves high gain over a bandwidth of several gigahertz with sufficient dynamic range to read out 20 superconducting qubits. To achieve this performance, we introduce a subwavelength resonant phase-matching technique that enables the creation of nonlinear microwave devices with unique dispersion relations. We benchmark the amplifier with weak measurements, obtaining a high quantum efficiency of 75% (70% including noise added by amplifiers following the Josephson amplifier). With a flexible design based on compact lumped elements, this Josephson amplifier has broad applicability to microwave metrology and quantum optics. Copyright © 2015, American Association for the Advancement of Science.
Fractional Spin and Josephson Effect in Time-Reversal-Invariant Topological Superconductors
Camjayi, Alberto; Arrachea, Liliana; Aligia, Armando; von Oppen, Felix
2017-07-01
Time-reversal-invariant topological superconducting (TRITOPS) wires are known to host a fractional spin ℏ/4 at their ends. We investigate how this fractional spin affects the Josephson current in a TRITOPS-quantum dot-TRITOPS Josephson junction, describing the wire in a model that can be tuned between a topological and a nontopological phase. We compute the equilibrium Josephson current of the full model by continuous-time Monte Carlo simulations and interpret the results within an effective low-energy theory. We show that in the topological phase, the 0-to-π transition is quenched via formation of a spin singlet from the quantum-dot spin and the fractional spins associated with the two adjacent topological superconductors.
Indian Academy of Sciences (India)
Unknown
nanotubes are likely to be useful as nanochips since they exhibit diode properties at the junction. By making use of carbon nanotubes, nanowires of metals, metal oxides and GaN have been obtained. Both the oxide and GaN nanowires are single crystalline. Gold nanowires exhibit plasmon bands varying markedly with.
Identifying the chiral d-wave superconductivity by Josephson φ0-states.
Liu, Jun-Feng; Xu, Yong; Wang, Jun
2017-03-07
We propose the Josephson junctions linked by a normal metal between a d + id superconductor and another d + id superconductor, a d-wave superconductor, or a s-wave superconductor for identifying the chiral d + id superconductivity. The time-reversal breaking in the chiral d-wave superconducting state is shown to result in a Josephson φ 0 -junction state where the current-phase relation is shifted by a phase φ 0 from the sinusoidal relation, other than 0 and π. The ground-state phase difference φ 0 and the critical current can be used to definitely confirm and read the information about the d + id superconductivity. A smooth evolution from conventional 0-π transitions to tunable φ 0 -states can be observed by changing the relative magnitude of two types of d-wave components in the d + id pairing. On the other hand, the Josephson junction involving the d + id superconductor is also the simplest model to realize a φ 0 - junction, which is useful in superconducting electronics and superconducting quantum computation.
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.
Takayasu, M; Minervini, J V; 10.1109/TASC.2003.812854
2003-01-01
Voltage-current characteristics of mechanical pressure contact junctions between superconducting wires are investigated using a voltage-driving method. It is found that the switching regions at low voltages result from negative resistance of the contact junction. The current transport of the contact junctions is discussed from the perspective of two existing models: the multiple Andreev reflections at the two SN interfaces of a SNS (Superconductor/Normal metal /Superconductor) junction and the inhomogeneous multiple Josephson weak-link array. (13 refs).
International Nuclear Information System (INIS)
Ledvij, M.; Klemm, R.A.
1994-01-01
The Josephson coupling between a conventional and an unconventional superconductor is investigated as a function of the properties of the tunneling barrier. A simple model is adopted for the tunneling probability and it is shown that its variation dramatically affects the I c R n product of an s-d, as opposed to an s-s junction. Based on these conclusions, experiments are proposed to probe the symmetry of the order parameter in high temperature superconductors
Self-organization of the critical state in Josephson lattices and granulated superconductors
International Nuclear Information System (INIS)
Ginzburg, S.L.
1994-01-01
A number of models of a Josephson medium and granulated superconductors are studied. It is shown that an important parameter is the quantity V∼j c a 3 /Φ 0 , where j c is the Josephson-current density, a is the granule size, and Φ 0 is the quantum of flux. In the limit V>>1 the continuum approximation is inapplicable. In this case the Josephson medium is transformed into a system in which pinning is realized on elementary loops that incorporate Josephson junctions. Here, nonlinear properties of these junctions obtain. The equations obtained for the currents of the Josephson lattice are identical to the standard formulation in the problem of self-organized criticality, while in granulated superconductors a problem of self-organized criticality with a different symmetry arises-a problem not of sites, but of loop. From the point of view of the critical state in granulated superconductors the concept of self-organized criticality radically changes the entire customary picture. The usual equations of the critical state describe only the average values of the magnetic field in the hydrodynamic approximation. However, it follows from the concept of self-organized criticality that the critical state has an extremely complicated structure, much more complicated than that which follows from the equation of the critical state. In particular, the fluctuations of various quantities in the critical state are much stronger than the ordinary statistical fluctuations, since there are large-scale fluctuations of the currents and fields, with a power-law (scaling) behavior that extends up to scales of the order of the size of the system, as in a turbulent medium. On the other hand, the basic equations in it reflect all the features of pinning - hysteresis and threshold behavior. Therefore, the self-organization of the critical state of a superconductor is a natural realization of this extremely general problem. 15 refs., 4 figs
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)
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.
Overlap junctions for high coherence superconducting qubits
Wu, X.; Long, J. L.; Ku, H. S.; Lake, R. E.; Bal, M.; Pappas, D. P.
2017-07-01
Fabrication of sub-micron Josephson junctions is demonstrated using standard processing techniques for high-coherence, superconducting qubits. These junctions are made in two separate lithography steps with normal-angle evaporation. Most significantly, this work demonstrates that it is possible to achieve high coherence with junctions formed on aluminum surfaces cleaned in situ by Ar plasma before junction oxidation. This method eliminates the angle-dependent shadow masks typically used for small junctions. Therefore, this is conducive to the implementation of typical methods for improving margins and yield using conventional CMOS processing. The current method uses electron-beam lithography and an additive process to define the top and bottom electrodes. Extension of this work to optical lithography and subtractive processes is discussed.
Two-Volt Josephson Arbitrary Waveform Synthesizer Using Wilkinson Dividers
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
Josephson quartic oscillator as a superconducting phase qubit
Energy Technology Data Exchange (ETDEWEB)
Zorin, Alexander [Physikalisch-Technische Bundesanstalt, 38116 Braunschweig (Germany); Chiarello, Fabio [Istituto di Fotonica e Nanotecnologie, CNR, 00156 Rome (Italy)
2010-07-01
Due to interplay between the cosine Josephson potential and parabolic magnetic-energy potential the radio-frequency SQUID with the screening parameter value {beta}{sub L} {identical_to}(2{pi}/{phi}{sub 0})LI{sub c} {approx}1 presents an oscillator circuit which energy well can dramatically change its shape. Ultimately, the magnetic flux bias of half flux quantum {phi}{sub e}={phi}{sub 0}/2 leads to the quartic polynomial shape of the well and, therefore, to significant anharmonicity of oscillations (> 30%). We show that the two lowest eigenstates in this symmetric global minimum perfectly suit for designing the qubit which is inherently insensitive to the charge variable, always biased in the optimal point and allows efficient dispersive and bifurcation-based readouts. Moreover, in the case of a double-SQUID configuration (dc SQUID instead of a single junction) the transition frequency in this Josephson phase qubit can be easy tuned within an appreciable range allowing variable qubit-qubit and qubit-resonator couplings.
Dynamics of underdamped Josephson arrays in a magnetic field
International Nuclear Information System (INIS)
Octavio, M.; Whan, C.B.; Geigenmueller, U.; Lobb, C.J.
1994-01-01
We present simulations of the dynamics of underdamped classical Josephson arrays for values of the flux quanta per unit cell f=1/2. We find the dynamics of this system to be quite rich. The I-V characteristics are found to have two distinct regime as the damping is increased. At low voltages the current-voltage characteristics exhibit a regime which we characterize as flux-flow-like since it is dominated by the motion of the vortex superlattice. This regime may exhibit chaotic-like behavior as the damping parameter is increased. At high voltages the characteristics jump to an ohmic-like state in which the junctions are all oscillating. We present a potential model which is quite useful in understanding the dynamics of the system. (orig.)
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
with bistable states. This intrinsic vortex potential can be tuned by an externally applied magnetic field and tilted by a bias current. The two-state system is accurately modeled by a one-dimensional sine-Gordon like equation by means of which one can numerically calculate both the magnetic field needed to set...... the vortex in a given state as well as the vortex-depinning currents. Experimental data taken at on high-quality Nb/Al–AlOx/Nb CAJTJs with an individual trapped fluxon advocate the presence of a robust and finely tunable double-well potential for which reliable manipulation of the vortex state has been...... classically demonstrated. The vortex is prepared in a given potential by means of an externally applied magnetic field, while the state readout is accomplished by measuring the vortex-depinning current in a small magnetic field. Our proof of principle experiment convincingly demonstrates that the proposed...
Polaritonic Rabi and Josephson Oscillations.
Rahmani, Amir; Laussy, Fabrice P
2016-07-25
The dynamics of coupled condensates is a wide-encompassing problem with relevance to superconductors, BECs in traps, superfluids, etc. Here, we provide a unified picture of this fundamental problem that includes i) detuning of the free energies, ii) different self-interaction strengths and iii) finite lifetime of the modes. At such, this is particularly relevant for the dynamics of polaritons, both for their internal dynamics between their light and matter constituents, as well as for the more conventional dynamics of two spatially separated condensates. Polaritons are short-lived, interact only through their material fraction and are easily detuned. At such, they bring several variations to their atomic counterpart. We show that the combination of these parameters results in important twists to the phenomenology of the Josephson effect, such as the behaviour of the relative phase (running or oscillating) or the occurence of self-trapping. We undertake a comprehensive stability analysis of the fixed points on a normalized Bloch sphere, that allows us to provide a generalized criterion to identify the Rabi and Josephson regimes in presence of detuning and decay.
Aspects of stochastic resonance in Josephson junction, bimodal ...
Indian Academy of Sciences (India)
the noise amplitude helps to define maximum SNR or peak SNR for an optimum amplitude of input noise. Although .... Here we consider a typical 2-parameter bimodal cubic map defined by. Xn+1 = b + aXn − X3 n. (2) ... due to shuttling with chaotic input of a logistic map (called chaotic resonance) have been reported earlier ...
Tunneling spectroscopy in NbN based Josephson junctions
International Nuclear Information System (INIS)
Chicault, R.; Villegier, J.C.
1984-08-01
Tunneling spectroscopy in high quality NbN-oxide-Pb(In) diodes offers a direct observation of various NbN and Pb phonon frequences as other vibrating modes existing near the tunnel barrier. The large number of peaks attribuated to dips in the transverses and longitudinal acoustic branches of NbN dispersion curves are found to confirm the previous theory developing the contribution of these modes to the strong coupling and high Tc behavior of NbN
Fluxon dynamics in long annular Josephson tunnel junctions
DEFF Research Database (Denmark)
Martucciello, N.; Mygind, Jesper; Koshelets, V.P.
1998-01-01
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...
Macroscopic quantum tunnelling in a current biased Josephson junction
International Nuclear Information System (INIS)
Martinis, J.M.; Devoret, M.H.; Clarke, J.; Urbina, C.
1984-11-01
We discuss in this work an attempt to answer experimentally the question: do macroscopic variables obey quantum mechanics. More precisely, this experiment deals with the question of quantum-mechanical tunnelling of a macroscopic variable, a subject related to the famous Schrodinger's cat problem in the theory of measurement
Spontaneous fluxon formation in annular Josephson tunnel junctions
DEFF Research Database (Denmark)
Monaco, R.; Mygind, Jesper; Rivers, R.
2003-01-01
It has been argued by Zurek and Kibble that the likelihood of producing defects in a continuous phase transition depends in a characteristic way on the quench rate. In this paper we discuss our experiment for measuring the Zurek-Kibble (ZK) scaling exponent sigma for the production of fluxons...
Experiments on spontaneous vortex formation in Josephson tunnel junctions
DEFF Research Database (Denmark)
Monaco, R.; Aarøe, Morten; Mygind, Jesper
2006-01-01
It has been argued by Zurek and Kibble that the likelihood of producing defects in a continuous phase transition depends in a characteristic way on the quench rate. In this paper we discuss an improved experiment for measuring the scaling exponent sigma for the production of single fluxons...
Fluxon interaction with external rf radiation in Josephson junctions
DEFF Research Database (Denmark)
Kivshar, Yuri S.; Olsen, Ole H.; Samuelsen, Mogens Rugholm
1993-01-01
. It is shown that due to excitation of a standing linear wave by the driving force, the fluxon motion is strongly influenced by a periodic (averaged) potential similar to the Peierls-Nabarro potential in a discrete chain. This effective potential decreases in the direction of the boundary where the external rf...
Aspects of stochastic resonance in Josephson junction, bimodal ...
Indian Academy of Sciences (India)
1Department of Physics, Maharaja's College, Cochin 682 011, India. 2Department of Physics, The Cochin College, Cochin 682 002, India. E-mail: ambika@iucaa.ernet.in; kp hk2002@yahoo.co.in .... signal and noise (top left), with signal alone (top right), with noise alone. (bottom left) and with noise and signal together ...
High Density Planar High Temperature Superconducting Josephson Junctions Arrays
2006-09-01
stacked on top of each other. the Cu(2)O planes and the Cu(1)O(1) chains act like a charge reservoir, which pro- vides carriers to the CuO planes. With...the 16 bridge region (Figure 3.5). Following development, YBa 2 Cu 3 0 7- samples were etched in NaI/I+ filtered semiconductor grade gold etch for 45...40] was used. It is a common tool used in semiconductor processing for the simulation of implants, annealing and etching. The model used for the
Long Josephson tunnel junctions with doubly connected electrodes
DEFF Research Database (Denmark)
Monaco, R.; Mygind, J.; Koshelets, V. P.
2012-01-01
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...
Spatial splay states in coupled map lattices and Josephson junction ...
Indian Academy of Sciences (India)
JOYDEEP SINGHA1,*, VALERIE TCHUYANG2, PATRICK LOUODOP2,3, ROBERT TCHITNGA2,. HILDA A. CERDEIRA3 and NEELIMA GUPTE1. 1 Department of Physics, Indian Institute of Technology Madras, Chennai 600036, India. 2 Department of Physics, University of Dschang Cameroon. 3 São Paulo State University ...
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.
Design and Characterization of a millikelvin dual-tip Josephson STM
Roychowdhury, A.; Dreyer, M.; Anderson, J. R.; Lobb, C. J.; Wellstood, F. C.
2014-03-01
We describe the design and characterization of a dual-tip Josephson STM that operates at millikelvin temperatures. We report an effective noise temperature for the STM on the order of 200 mK. In addition to the expected phase diffusive super current in the ultra-small Nb-Nb junction formed by one tip and the sample, our high resolution spectroscopy at mK temperatures reveals resonant coupling between the STM junction and the electromagnetic environment it is embedded in, as predicted by P(E) theory. We have for the first time, observed Shapiro-like steps in this limit by measuring the response of the P(E) supercurrent to microwave radiation as a function of amplitude. Fits to theory indicate that the coupling of an ultra-small Josephson junction to its environment/circuit may be used to a) directly measure dissipation channels associated with circuit resonances and b) calibrate the frequency dependent microwave attenuation in cryogenic circuits as seen by the junction.
Yokoyama, Tomohiro; Eto, Mikio; Nazarov, Yuli
2014-03-01
We theoretically investigate the Josephson junction using quasi-one dimensional semiconductor nanowires with strong spin-orbit (SO) interaction, e.g., InSb. First, we examine a simple model using a single scatterer to describe the elastic scattering due to impurities and SO interaction in the normal region.[1] The Zeeman effect is taken into account by the spin-dependent phase shift of electron and hole through the system. The interplay between SO interaction and Zeeman effect results in a finite supercurrent even when the phase difference between two superconductors is zero. Moreover, the critical current depends on its current direction if more than one conduction channel is present in the nanowire. Next, we perform a numerical simulation by the tight-binding model for the nanowire to confirm our simple model. Then, we show that a spin-dependent Fermi velocity due to the SO interaction causes the anomalous Josephson effect.
Time-resolved statistics of photon pairs in two-cavity Josephson photonics
Energy Technology Data Exchange (ETDEWEB)
Dambach, Simon; Kubala, Bjoern; Ankerhold, Joachim [Institute for Complex Quantum Systems and IQST, Ulm University (Germany)
2017-06-15
We analyze the creation and emission of pairs of highly nonclassical microwave photons in a setup where a voltage-biased Josephson junction is connected in series to two electromagnetic oscillators. Tuning the external voltage such that the Josephson frequency equals the sum of the two mode frequencies, each tunneling Cooper pair creates one additional photon in both of the two oscillators. The time-resolved statistics of photon emission events from the two oscillators is investigated by means of single- and cross-oscillator variants of the second-order correlation function g{sup (2)}(τ) and the waiting-time distribution w(τ). They provide insight into the strongly correlated quantum dynamics of the two oscillator subsystems and reveal a rich variety of quantum features of light including strong antibunching and the presence of negative values in the Wigner function. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Quantum state engineering with flux-biased Josephson phase qubits by rapid adiabatic passages
Nie, W.; Huang, J. S.; Shi, X.; Wei, L. F.
2010-09-01
In this article, the scheme of quantum computing based on the Stark-chirped rapid adiabatic passage (SCRAP) technique [L. F. Wei, J. R. Johansson, L. X. Cen, S. Ashhab, and F. Nori, Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.100.113601 100, 113601 (2008)] is extensively applied to implement quantum state manipulations in flux-biased Josephson phase qubits. The broken-parity symmetries of bound states in flux-biased Josephson junctions are utilized to conveniently generate the desirable Stark shifts. Then, assisted by various transition pulses, universal quantum logic gates as well as arbitrary quantum state preparations can be implemented. Compared with the usual π-pulse operations widely used in experiments, the adiabatic population passages proposed here are insensitive to the details of the applied pulses and thus the desirable population transfers can be satisfyingly implemented. The experimental feasibility of the proposal is also discussed.
Quantum state engineering with flux-biased Josephson phase qubits by rapid adiabatic passages
International Nuclear Information System (INIS)
Nie, W.; Huang, J. S.; Shi, X.; Wei, L. F.
2010-01-01
In this article, the scheme of quantum computing based on the Stark-chirped rapid adiabatic passage (SCRAP) technique [L. F. Wei, J. R. Johansson, L. X. Cen, S. Ashhab, and F. Nori, Phys. Rev. Lett. 100, 113601 (2008)] is extensively applied to implement quantum state manipulations in flux-biased Josephson phase qubits. The broken-parity symmetries of bound states in flux-biased Josephson junctions are utilized to conveniently generate the desirable Stark shifts. Then, assisted by various transition pulses, universal quantum logic gates as well as arbitrary quantum state preparations can be implemented. Compared with the usual π-pulse operations widely used in experiments, the adiabatic population passages proposed here are insensitive to the details of the applied pulses and thus the desirable population transfers can be satisfyingly implemented. The experimental feasibility of the proposal is also discussed.
Schottky barriers at metal-finite semiconducting carbon nanotube interfaces
Xue, Yongqiang; Ratner, Mark A.
2003-01-01
Electronic properties of metal-finite semiconducting carbon nanotube interfaces are studied as a function of the nanotube length using a self-consistent tight-binding theory. We find that the shape of the potential barrier depends on the long-range tail of the charge transfer, leading to an injection barrier thickness comparable to half of the nanotube length until the nanotube reaches the bulk limit. The conductance of the nanotube junction shows a transition from tunneling to thermally-acti...
Dissipation-driven phase transition in two-dimensional Josephson arrays
International Nuclear Information System (INIS)
Capriotti, Luca; Cuccoli, Alessandro; Fubini, Andrea; Tognetti, Valerio; Vaia, Ruggero
2005-01-01
We analyze the interplay of dissipative and quantum effects in the proximity of a quantum phase transition. The prototypical system is a resistively shunted two-dimensional Josephson junction array, studied by means of an advanced Fourier path-integral Monte Carlo algorithm. The reentrant superconducting-to-normal phase transition driven by quantum fluctuations, recently discovered in the limit of infinite shunt resistance, persists for moderate dissipation strength but disappears in the limit of small resistance. For large quantum coupling our numerical results show that, beyond a critical dissipation strength, the superconducting phase is always stabilized at sufficiently low temperature. Our phase diagram explains recent experimental findings
Nanomembrane-based mesoscopic superconducting hybrid junctions.
Thurmer, Dominic J; Bof Bufon, Carlos Cesar; Deneke, Christoph; Schmidt, Oliver G
2010-09-08
A new method for combining top-down and bottom-up approaches to create superconductor-normal metal-superconductor niobium-based Josephson junctions is presented. Using a rolled-up semiconductor nanomembrane as scaffolding, we are able to create mesoscopic gold filament proximity junctions. These are created by electromigration of gold filaments after inducing an electric field mediated breakdown in the semiconductor nanomembrane, which can generate nanometer sized structures merely using conventional optical lithography techniques. We find that the created point contact junctions exhibit large critical currents of a few milliamps at 4.2 K and an I(c)R(n) product placing their characteristic frequency in the terahertz region. These nanometer-sized filament devices can be further optimized and integrated on a chip for their use in superconductor hybrid electronics circuits.
Energy Technology Data Exchange (ETDEWEB)
Barnes, S.E.; Mehran, F.
1986-10-01
The elementary theory of in situ measurements of the wave-vector-dependent dynamic susceptibility chi(q,..omega..) in superconductor-insulator-superconductor (SIS) and superconductor--normal-metal--superconductor (SNS) Josephson junctions is presented in some detail. The theory for more complicated SISN and SINS junctions is also described. In addition, the theory of point-contact and superconducting quantum interference device geometries, relevant to the recent experiments of Baberschke, Bures, and Barnes is developed. Involved is a detailed application of the Maxwell and London equations along with the distributed Josephson effect. In a measurement of chi(q,..omega..), the frequency ..omega.. is determined by the relation 2eV/sub 0/ = h-dash-bar..omega.. where V/sub 0/ is the voltage applied across the junction, and the wave vector q is determined by the relation 2edB/sub 0/ = h-dash-barq where d is the effective width of the junction and B/sub 0/ is the magnetic field applied perpendicular to the direction of the current. The relative merits of the different types of junctions are discussed and the expected signal strengths are estimated. The limitations for the maximum measurable frequency and wave vector are also given. It seems probable that the proposed technique can be used to measure spin-wave branches from zero wave vector up to about 10% of the way to the Brillouin zone edge.
Hybrid Josephson-CMOS memory: a solution for the Josephson memory problem
Duzer, T V; Meng Xiao Fan; Whiteley, S R; Yoshikawa, N
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.
Hybrid Josephson-CMOS memory: a solution for the Josephson memory problem
Energy Technology Data Exchange (ETDEWEB)
Duzer, Theodore van [Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, CA (United States); Feng Yijun [Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, CA (United States); Meng Xiaofan [Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, CA (United States); Whiteley, Stephen R [Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, CA (United States); Yoshikawa, Nobuyuki [Department of Electrical and Computer Engineering, Yokohama National University (Japan)
2002-12-01
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.
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
Superconducting junctions and method of making same
International Nuclear Information System (INIS)
Kapituinik, A.
1993-01-01
A method of making Josephson junctions in high critical temperature superconductors is described comprising the consecutive steps of: first forming a layer of high Tc copper oxide superconductor on a substrate by forming the constituent components of the superconductor onto the substrate so as to epitaxially grow the superconductor on the substrate with copper-oxygen planes parallel to the surface of the substrate, said layer formed in a pattern to create a desired electronic circuit; then narrowing selected portions of the superconductor circuit at locations where Josephson junctions are desired; then creating weak link areas at said selected portions by moving an electrode across the surface of said selected portions, generally from one side of the selected portion to the other side of the selected portion, at a distance from the surface suitable to maintain a tunnel current between the electrode and the selected portion and maintaining said tunnel current directly into said junction locations while the electrode is proximate to the selected portions and sustaining said tunnel current through the electrodes long enough to physically remove superconducting material from the selected portion; and then depositing a noble metal in the selected portion by evaporating an electrode made from the noble metal
Energy conversion efficiency in nanotube optoelectronics.
Energy Technology Data Exchange (ETDEWEB)
Leonard, Francois Leonard; Stewart, Derek A.
2004-09-01
We present theoretical performance estimates for nanotube optoelectronic devices under bias. Current-voltage characteristics of illuminated nanotube p-n junctions are calculated using a self-consistent nonequilibrium Green's function approach. Energy conversion rates reaching tens of percent are predicted for incident photon energies near the band gap energy. In addition, the energy conversion rate increases as the diameter of the nanotube is reduced, even though the quantum efficiency shows little dependence on nanotube radius. These results indicate that the quantum efficiency is not a limiting factor for use of nanotubes in optoelectronics.