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
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 plasma resonance in superconducting multilayers
DEFF Research Database (Denmark)
Pedersen, Niels Falsig
1999-01-01
We derive an analytical solution for the josephson plasma resonance of superconducting multilayers. This analytical solution is derived mainly for low T-c systems with magnetic coupling between the superconducting layers, but many features of our results are more general, and thus an application...... to the recently derived plasma resonance phenomena for high T-c superconductors of the BSCCO type is discussed....
Josephson plasma resonance in superconducting multilayers
DEFF Research Database (Denmark)
Pedersen, Niels Falsig; Sakai, S
1998-01-01
We derive an analytical solution for the Josephson plasma resonance of superconducting multilayers. This analytical solution is derived mainly for low-T-c systems with magnetic coupling between the superconducting layers. but many features of our results are more general, and thus an application...
Josephson plasma resonance in superconducting multilayers
DEFF Research Database (Denmark)
Pedersen, Niels Falsig
1999-01-01
We derive an analytical solution for the josephson plasma resonance of superconducting multilayers. This analytical solution is derived mainly for low T-c systems with magnetic coupling between the superconducting layers, but many features of our results are more general, and thus an application...
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.
Elementary pinning force for a superconducting vortex
International Nuclear Information System (INIS)
Hyun, O.B.; Finnemore, D.K.; Schwartzkopf, L.; Clem, J.R.
1987-01-01
The elementary pinning force f/sub p/ has been measured for a single vortex trapped in one of the superconducting layers of a cross-strip Josephson junction. At temperatures close to the transition temperature the vortex can be pushed across the junction by a transport current. The vortex is found to move in a small number of discrete steps before it exits the junction. The pinning force for each site is found to be asymmetric and to have a value of about 10/sup -6/ N/m at the reduced temperature, t = T/T/sub c/ = 0.95. As a function of temperature, f/sub p/ is found to vary approximately as (1-t)/sup 3/2/. .AE
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
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.
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 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...
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...
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.
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
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...
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)
Single-Shot Readout of a Superconducting Qubit using a Josephson Parametric Oscillator
2016-01-11
Single-shot Readout of a Superconducting Qubit using a Josephson Parametric Oscillator Philip Kranz1, Andreas Bengtsson1, Michaël Simoen1, Simon...Josephson Parametric Oscillator Philip Krantz1, Andreas Bengtsson1, Michaël Simoen1, Simon Gustavsson2, Vitaly Shumeiko1, W. D. Oliver2,3, C. M...2016) We propose and demonstrate a new read-out technique for a superconducting qubit by dispersively coupling it to a Josephson parametric
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
Superconducting vortex pinning with artificial magnetic nanostructures.
Energy Technology Data Exchange (ETDEWEB)
Velez, M.; Martin, J. I.; Villegas, J. E.; Hoffmann, A.; Gonzalez, E. M.; Vicent, J. L.; Schuller, I. K.; Univ. de Oviedo-CINN; Unite Mixte de Physique CNRS/Thales; Univ. Paris-Sud; Univ.Complutense de Madrid; Univ. California at San Diego
2008-11-01
This review is dedicated to summarizing the recent research on vortex dynamics and pinning effects in superconducting films with artificial magnetic structures. The fabrication of hybrid superconducting/magnetic systems is presented together with the wide variety of properties that arise from the interaction between the superconducting vortex lattice and the artificial magnetic nanostructures. Specifically, we review the role that the most important parameters in the vortex dynamics of films with regular array of dots play. In particular, we discuss the phenomena that appear when the symmetry of a regular dot array is distorted from regularity towards complete disorder including rectangular, asymmetric, and aperiodic arrays. The interesting phenomena that appear include vortex-lattice reconfigurations, anisotropic dynamics, channeling, and guided motion as well as ratchet effects. The different regimes are summarized in a phase diagram indicating the transitions that take place as the characteristic distances of the array are modified respect to the superconducting coherence length. Future directions are sketched out indicating the vast open area of research in this field.
Superconductivity and vortex properties in various multilayers
International Nuclear Information System (INIS)
Koorevaar, P.
1994-01-01
In this thesis three qualitatively different type of superconducting multilayers are studied. We discuss the vortex lattice structure in Nb/NbZr multilayers, a system where both type of constituting layers are superconducting. At certain temperatures and for parallel fields close to H c2parallel , the Nb/NbZr system has a strongly modulated order parameter, and in this aspect resembles the high-Tc materials. By lowering the field the modulation decreases, having important consequences for the vortex lattice structure. By studying the transport critical currents we show that in the case of strong modulation the vortex lattice has a kinked structure, but at weaker modulations the vortices are straight, and the change in modulation actually results in a vortex lattice transition. Our study confirms the picture of the existence of kinked vortex lattices, but it is rather surprising that these kinked structures can exist in a system which in itself is not at all that anisotropic. It indicates the relevance of other parameters governing the vortex lattice structure. (orig.)
Direct detection of the Josephson radiation emitted from superconducting thin-film microbridges
DEFF Research Database (Denmark)
Pedersen, Niels Falsig; Sørensen, O. H.; Mygind, Jesper
1976-01-01
We report direct measurements of the Josephson radiation emitted in X band from a superconducting thin-film microbridge coupled to a resonance cavity. Power is emitted if one of the harmonics of the Josephson frequency is in the bandwidth of the receiver. The maximum power emitted during our expe...... experiment was 10−13 W. The Josephson radiation could easily be detected at frequencies off resonance. Applied Physics Letters is copyrighted by The American Institute of Physics....
Inertial mass of a superconducting vortex
Chudnovsky, E. M.; Kuklov, A. B.
2003-01-01
We show that a large contribution to the inertial mass of a moving superconducting vortex comes from transversal displacements of the crystal lattice. The corresponding part of the mass per unit length of the vortex line is $M_{l} = ({\\rm m}_e^2c^{2}/64{\\pi}{\\alpha}^{2}{\\mu}{\\lambda}_{L}^{4})\\ln({\\lambda}_{L}/{\\xi})$ , where ${\\rm m}_{e}$ is the the bare electron mass, $c$ is the speed of light, ${\\alpha}=e^{2}/{\\hbar}c {\\approx} 1/137$ is the fine structure constant, ${\\mu}$ is the shear mod...
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.
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
Vortex dynamics in superconducting transition edge sensors
Ezaki, S.; Maehata, K.; Iyomoto, N.; Asano, T.; Shinozaki, B.
2018-02-01
The temperature dependence of the electrical resistance (R-T) and the current-voltage (I-V) characteristics has been measured and analyzed in a 40 nm thick Ti thin film, which is used as a transition edge sensor (TES). The analyses of the I-V characteristics with the vortex-antivortex pair dissociation model indicate the possible existence of the Berezinskii-Kosterlitz-Thouless (BKT) transition in two-dimensional superconducting Ti thin films. We investigated the noise due to the vortices' flow in TESs. The values of the current noise spectral density in the TESs were estimated by employing the vortex dynamics caused by the BKT transition in the Ti thin films. The estimated values of the current noise spectral density induced by the vortices' flow were in respectable agreement with the values of excess noise experimentally observed in the TESs with Ti/Au bilayer.
Vortex (particle) and antivortex (hole) doping into superconducting network
International Nuclear Information System (INIS)
Ishida, Takekazu; Shimizu, Makoto; Matsushima, Yoshiaki; Hayashi, Masahiko; Ebisawa, Hiromichi; Sato, Osamu; Kato, Masaru; Satoh, Kazuo
2007-01-01
Superconducting finite-sized Pb square networks with 10 x 10 square holes fabricated by electron beam lithography have been investigated in view of particle (vortex) doping into superconducting networks. Vortex image observations were carried out by a SQUID microscope to compare with predictions from the Ginzburg-Landau theory. We found the exactly reversed pattern between the vortex-doping x and the antivortex doping 1 - x into the fully occupied network (x = 1/4)
Gallemí, A.; Guilleumas, M.; Mayol, R.; Mateo, A. Muñoz
2016-03-01
We analyze the dynamics of Josephson vortex states in two-component Bose-Einstein condensates with Rashba-Dresselhaus spin-orbit coupling by using the Gross-Pitaevskii equation. In one dimension, both in homogeneous and harmonically trapped systems, we report on stationary states containing doubly charged, static Josephson vortices. In multidimensional systems, we find stable Josephson vortices in a regime of parameters typical of current experiments with 87Rb atoms. In addition, we discuss the instability regime of Josephson vortices in disk-shaped condensates, where the snake instability operates and vortex dipoles emerge. We study the rich dynamics that they exhibit in different regimes of the spin-orbit-coupled condensate depending on the orientation of the Josephson vortices.
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...
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)
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
Vortex loops in the critical Casimir effect in superfluid and superconducting films
International Nuclear Information System (INIS)
Williams, Gary A.
2004-01-01
Vortex-loop renormalization techniques are used to calculate the magnitude of the critical Casimir forces in superfluid and superconducting thin films. The force is found to become appreciable when the size of the thermally excited vortex loops is comparable to the film thickness, and the results for T c are found to match very well with perturbative renormalization-group theories that can only be carried out for T>T c . In helium films the Casimir force leads to a change in the film thickness close to T c that has been observed experimentally. A similar effect is predicted to occur near the transition temperature of high-T c superconducting films, which is also a vortex-loop phase transition. In this case the Casimir force takes the form of a voltage difference that will appear at the junction between a thin film and a bulk sample. Estimates show that this voltage can be appreciable (tens of microvolts), and it may be possible to observe the effect by measuring the voltage across two Josephson tunnel junctions to the film and to the bulk, using a SQUID voltmeter
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.
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
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
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
Energy Technology Data Exchange (ETDEWEB)
Kimura, Hikari; Dynes, Robert; Barber Jr., Richard. P.; Ono, S.; Ando, Y.
2009-09-01
Direct measurements of the superconducting superfluid on the surface of vacuum-cleaved Bi2Sr2CaCu2O8+delta (BSCCO) samples are reported. These measurements are accomplished via Josephson tunneling into the sample using a novel scanning tunneling microscope (STM) equipped with a superconducting tip. The spatial resolution of the STM of lateral distances less than the superconducting coherence length allows it to reveal local inhomogeneities in the pair wavefunction of the BSCCO. Instrument performance is demonstrated first with Josephson measurements of Pb films followed by the layered superconductor NbSe2. The relevant measurement parameter, the Josephson ICRN product, is discussed within the context of both BCS superconductors and the high transition temperature superconductors. The local relationship between the ICRN product and the quasiparticle density of states (DOS) gap are presented within the context of phase diagrams for BSCCO. Excessive current densities can be produced with these measurements and have been found to alter the local DOS in the BSCCO. Systematic studies of this effect were performed to determine the practical measurement limits for these experiments. Alternative methods for preparation of the BSCCO surface are also discussed.
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
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 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.
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...
Study of the vortex matter in Bi2Sr2CaCu2O8+δ using the Josephson plasma resonance
International Nuclear Information System (INIS)
Colson, S.
2003-10-01
The Josephson plasma resonance (JPR) is a tool of choice to measure the inter-plane phase coherence in the layered superconductor Bi 2 Sr 2 CaCu 2 O 8+δ (BSCCO). It enables us to evaluate the wandering length r w , defined as the thermal average of the relative thermal excursions of two pancake vortices belonging to the same flux line and localized in two consecutive superconducting layers. In this work, using two experimental techniques to probe the JPR (the resonant cavity perturbation technique and the bolometric method), we have measured r w in the vortex solid in pristine or heavy-ion irradiated (dose n d = 5 x 10 10 ions.cm -2 , i.e. B φ n-dΦ 0 = 1 T) under-doped BSCCO single crystals. In the pristine samples, at low magnetic fields, the temperature dependence of r w and its increase with the applied field can only be accounted for by the dominant role of the line tension (due to Josephson coupling) and its renormalization due to thermal fluctuations. The latter are responsible for the softening of the line tension for the large-wave vector modes, which eventually leads to the first order phase transition between the vortex solid and the vortex liquid. The field and temperature dependence of r w in the irradiated crystals for B φ , is the same as observed in the pristine samples. This observation is a validation for a description in term of 'discrete superconductor' of the material. (author)
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.
Josephson current and Andreev level dynamics in nanoscale superconducting weak links
Energy Technology Data Exchange (ETDEWEB)
Brunetti, Aldo
2014-11-15
In this thesis we focus on the interplay between proximity induced superconducting correlations and Coulomb interactions in a Josephson junction: i.e., in a system where two superconductors modeled as two s-wave superconductors at a phase difference φ are contacted by means of a weak link, in our case a quantum dot located in the contact. In the first part we study the Josephson current-phase relation for a multi-level quantum dot tunnel-contacted by two conventional s-waves superconductors. We determine in detail the conditions for observing a finite anomalous Josephson current, i.e. a supercurrent flowing at zero phase difference in a two-level dot with spin-orbit interactions, a weak magnetic (Zeeman) field, and in the presence of Coulomb interactions. This leads to an onset behavior I{sub a}∝sgn(B), interpreted as the sign of an incipient spontaneous breakdown of time-reversal symmetry. Moreover, we will provide conditions for realizing spatially separated - but topologically unprotected - Majorana bound states, whose signature in the system will be detectable via the current-phase relation. In the second part of the thesis, we address the Andreev bound state population dynamics in superconducting weak links (a superconducting 'atomic contact'), in which a poisoning mechanism due to the trapping of single quasiparticles can occur. Our motivation is that quantum coherent superconducting circuits are the most promising candidates for future large-scale quantum information processing devices. Moreover, quasiparticle poisoning has recently been observed in devices which contain a short superconducting weak link with few transport channels. We discuss a novel charge imbalance effect in the continuum quasiparticle population, which is due to phase fluctuations of the environment weakly coupled to the superconducting contact. This coupling enters the system as a transition rate connecting continuum quasiparticles and the Andreev bound state system. The
Single-shot read-out of a superconducting qubit using a Josephson parametric oscillator
Krantz, Philip; Bengtsson, Andreas; Simoen, Michaël; Gustavsson, Simon; Shumeiko, Vitaly; Oliver, W. D.; Wilson, C. M.; Delsing, Per; Bylander, Jonas
2016-01-01
We propose and demonstrate a read-out technique for a superconducting qubit by dispersively coupling it with a Josephson parametric oscillator. We employ a tunable quarter wavelength superconducting resonator and modulate its resonant frequency at twice its value with an amplitude surpassing the threshold for parametric instability. We map the qubit states onto two distinct states of classical parametric oscillation: one oscillating state, with 185±15 photons in the resonator, and one with zero oscillation amplitude. This high contrast obviates a following quantum-limited amplifier. We demonstrate proof-of-principle, single-shot read-out performance, and present an error budget indicating that this method can surpass the fidelity threshold required for quantum computing. PMID:27156732
Vortex 'puddles' and magic vortex numbers in mesoscopic superconducting disks
Energy Technology Data Exchange (ETDEWEB)
Connolly, M R; Milosevic, M V; Bending, S J [Department of Physics, University of Bath - Claverton Down, Bath, BA2 7AY (United Kingdom); Clem, J R [Ames Laboratory Department of Physics and Astronomy - Iowa State University, Ames, IA 50011-3160 (United States); Tamegai, T, E-mail: mrc61@cam.ac.u [Department of Applied Physics, University of Tokyo - Hongo, Bunkyo-ku, Tokyo 113-8627 (Japan)
2009-03-01
The magnetic properties of a superconducting disk change dramatically when its dimensions become mesoscopic. Unlike large disks, where the screening currents induced by an applied magnetic field are strong enough to force vortices to accumulate in a 'puddle' at the centre, in a mesoscopic disk the interaction between one of these vortices and the edge currents can be comparable to the intervortex repulsion, resulting in a destruction of the ordered triangular vortex lattice structure at the centre. Vortices instead form clusters which adopt polygonal and shell-like structures which exhibit magic number states similar to those of charged particles in a confining potential, and electrons in artificial atoms. We have fabricated mesoscopic high temperature superconducting Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+delta} disks and investigated their magnetic properties using magneto-optical imaging (MOI) and high resolution scanning Hall probe microscopy (SHPM). The temperature dependence of the vortex penetration field measured using MOI is in excellent agreement with models of the thermal excitation of pancake vortices over edge barriers. The growth of the central vortex puddle has been directly imaged using SHPM and magic vortex numbers showing higher stability have been correlated with abrupt jumps in the measured local magnetisation curves.
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
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.
Eck peak in underdamped discrete superconducting vortex flow devices
van der Zant, H. S. J.; Orlando, T. P.
1994-12-01
We have measured vortex motion in a long one-dimensional array of small underdamped niobium tunnel junctions which are coupled in parallel by superconducting wires. In the current-voltage characteristic, a resonant step occurs similar to the Eck peak in long continuous junctions. Due to the discrete nature of our samples, the voltage of this resonant step follows a sinusoidal dependence on the magnetic field rather than the linear dependence found in long continuous junctions. With a control current applied parallel to the array of junctions, the device can be operated as a vortex-flow transistor or as a tunable vortex-flow oscillator. Compared to long continuous junctions, the performance of discrete transistors is better with regard to the threshold currrent and transresistance, but worse with regard to the output resistance. Discrete oscillators have the advantage over their continuous counterparts in that the output impedance is of the order of 10 ohms. Numerical simulations indicate power levels around 0.5 micro Watts and frequencies above 500 GHz.
DEFF Research Database (Denmark)
Hansen, Jørn Bindslev; Levinsen, M. T.; Lindelof, Poul Erik
1979-01-01
Nonresonant detection of the Josephson radiation 35 GHz from a superconducting thin-film microbridge is reported. The high frequency and the accuracy of these measurements lead to a new important observation: subharmonic energy gap structure in the detected integral power. The maximum integral po...... power measured was as large as 8×10−11 W. Applied Physics Letters is copyrighted by The American Institute of Physics....
Lin, Z. R.; Inomata, K.; Oliver, W. D.; Koshino, K.; Nakamura, Y.; Tsai, J. S.; Yamamoto, T.
2013-09-01
We report single-shot readout of a superconducting flux qubit by using a flux-driven Josephson parametric amplifier (JPA). After optimizing the readout power, gain of the JPA, and timing of the data acquisition, we observe the Rabi oscillations with a contrast of 74%, which is mainly limited by the bandwidth of the JPA and the energy relaxation of the qubit. The observation of quantum jumps between the qubit eigenstates under continuous monitoring indicates the nondestructiveness of the readout scheme.
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
Vortex kinks in superconducting films with periodically modulated thickness
International Nuclear Information System (INIS)
Facio, Jorge I; Abate, Anabella; Guimpel, J; Cornaglia, Pablo S
2013-01-01
We report magnetoresistance measurements in Nb films having a periodic thickness modulation. The cylinder shaped thicker regions of the sample, which form a square lattice, act as repulsive centers for the superconducting vortices. For low driving currents along one of the axes of the square lattice, the resistivity ρ increases monotonously with increasing magnetic field B and the ρ–B characteristics are approximately piecewise linear. The linear ρ versus B segments change their slope at matching fields where the number of vortices is an integer or a half integer times the number of protruding cylinders in the sample. Numerical simulations allow us to associate the different segments of linear magnetoresistance to different vortex-flow regimes, some of which are dominated by the propagation of discommensurations (kinks). (paper)
Energy Technology Data Exchange (ETDEWEB)
Grimaldi, G; Leo, A; Cirillo, C; Attanasio, C; Nigro, A; Pace, S [CNR-INFM Laboratorio Regionale SuperMat, Via Salvador Allende, I-84081 Baronissi (Italy)], E-mail: grimaldi@sa.infn.it
2009-06-24
We study the vortex dynamics in the instability regime induced by high dissipative states well above the critical current in Nb superconducting strips. The magnetic field and temperature behavior of the critical vortex velocity corresponding to the observed dynamic instability is ascribed to intrinsic non-equilibrium phenomena. The Larkin-Ovchinnikov (LO) theory of electronic instability in high velocity vortex motion has been applied to interpret the temperature dependence of the critical vortex velocity. The magnetic field dependence of the vortex critical velocity shows new features in the low-field regime not predicted by LO.
International Nuclear Information System (INIS)
Andersen, N.H.; Mortensen, K.
1988-12-01
This report contains lecture notes of the basic lectures presented at the 1st Topsoee Summer School on Superconductivity held at Risoe National Laboratory, June 20-24, 1988. The following lecture notes are included: L.M. Falicov: 'Superconductivity: Phenomenology', A. Bohr and O. Ulfbeck: 'Quantal structure of superconductivity. Gauge angle', G. Aeppli: 'Muons, neutrons and superconductivity', N.F. Pedersen: 'The Josephson junction', C. Michel: 'Physicochemistry of high-T c superconductors', C. Laverick and J.K. Hulm: 'Manufacturing and application of superconducting wires', J. Clarke: 'SQUID concepts and systems'. (orig.) With 10 tabs., 128 figs., 219 refs
Energy Technology Data Exchange (ETDEWEB)
Colson, S
2003-10-01
The Josephson plasma resonance (JPR) is a tool of choice to measure the inter-plane phase coherence in the layered superconductor Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} (BSCCO). It enables us to evaluate the wandering length r{sub w}, defined as the thermal average of the relative thermal excursions of two pancake vortices belonging to the same flux line and localized in two consecutive superconducting layers. In this work, using two experimental techniques to probe the JPR (the resonant cavity perturbation technique and the bolometric method), we have measured r{sub w} in the vortex solid in pristine or heavy-ion irradiated (dose n{sub d} = 5 x 10{sup 10} ions.cm{sup -2}, i.e. B{sub {phi}} n-d{phi}{sub 0} = 1 T) under-doped BSCCO single crystals. In the pristine samples, at low magnetic fields, the temperature dependence of r{sub w} and its increase with the applied field can only be accounted for by the dominant role of the line tension (due to Josephson coupling) and its renormalization due to thermal fluctuations. The latter are responsible for the softening of the line tension for the large-wave vector modes, which eventually leads to the first order phase transition between the vortex solid and the vortex liquid. The field and temperature dependence of r{sub w} in the irradiated crystals for B << B{sub {phi}}, is the same as observed in the pristine samples. This observation is a validation for a description in term of 'discrete superconductor' of the material. (author)
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-...
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....
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
Spin density wave induced disordering of the vortex lattice in superconducting La2−xSrxCuO4
DEFF Research Database (Denmark)
Chang, J.; White, J.S.; Laver, M.
2012-01-01
We use small-angle neutron scattering to study the superconducting vortex lattice in La2-xSrxCuO4 as a function of doping and magnetic field. We show that near optimally doping the vortex lattice coordination and the superconducting coherence length. are controlled by a Van Hove singularity...
Experimental evidence for vortex-glass superconductivity in Y-Ba-Cu-O
International Nuclear Information System (INIS)
Koch, R.H.; Foglietti, V.; Gallagher, W.J.; Koren, G.; Gupta, A.; Fisher, M.P.A.
1989-01-01
We demonstrate experimentally the existence of a continuous phase transition between a normal and a true superconducting phase (with zero linear resistivity) in epitaxial films of Y-Ba-Cu-O in strong magnetic fields fields, H much-gt H c1 . The nonlinear I-V curves show scaling behavior near the transition and the relevant critical exponents are extracted. These exponents are consistent with values expected for freezing into a superconducting vortex-glass phase
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
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.
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)
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.
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.
De Lange, G.; Van Heck, B.; Bruno, A.; Van Woerkom, D.J.; Geresdi, A.; Plissard, S.R.; Bakkers, E.P.A.M.; Akhmerov, A.R.; Di Carlo, L.
2015-01-01
We report the realization of quantum microwave circuits using hybrid superconductor-semiconductor Josephson elements comprised of InAs nanowires contacted by NbTiN. Capacitively shunted single elements behave as transmon circuits with electrically tunable transition frequencies. Two-element circuits
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.
Optical excitation of Josephson plasma solitons in a cuprate superconductor.
Dienst, A; Casandruc, E; Fausti, D; Zhang, L; Eckstein, M; Hoffmann, M; Khanna, V; Dean, N; Gensch, M; Winnerl, S; Seidel, W; Pyon, S; Takayama, T; Takagi, H; Cavalleri, A
2013-06-01
Josephson plasma waves are linear electromagnetic modes that propagate along the planes of cuprate superconductors, sustained by interlayer tunnelling supercurrents. For strong electromagnetic fields, as the supercurrents approach the critical value, the electrodynamics become highly nonlinear. Josephson plasma solitons (JPSs) are breather excitations predicted in this regime, bound vortex-antivortex pairs that propagate coherently without dispersion. We experimentally demonstrate the excitation of a JPS in La1.84Sr0.16CuO4, using intense narrowband radiation from an infrared free-electron laser tuned to the 2-THz Josephson plasma resonance. The JPS becomes observable as it causes a transparency window in the opaque spectral region immediately below the plasma resonance. Optical control of magnetic-flux-carrying solitons may lead to new applications in terahertz-frequency plasmonics, in information storage and transport and in the manipulation of high-Tc superconductivity.
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.
Vortex variable range hopping in a conventional superconducting film
Percher, Ilana M.; Volotsenko, Irina; Frydman, Aviad; Shklovskii, Boris I.; Goldman, Allen M.
2017-12-01
The behavior of a disordered amorphous thin film of superconducting indium oxide has been studied as a function of temperature and magnetic field applied perpendicular to its plane. A superconductor-insulator transition has been observed, though the isotherms do not cross at a single point. The curves of resistance versus temperature on the putative superconducting side of this transition, where the resistance decreases with decreasing temperature, obey two-dimensional Mott variable-range hopping of vortices over wide ranges of temperature and resistance. To estimate the parameters of hopping, the film is modeled as a granular system and the hopping of vortices is treated in a manner analogous to hopping of charges. The reason the long-range interaction between vortices over the range of magnetic fields investigated does not lead to a stronger variation of resistance with temperature than that of two-dimensional Mott variable-range hopping remains unresolved.
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.
Gate tunability and collapse of superconductivity in hybrid tin-graphene Josephson junction arrays
Bouchiat, Vincent
The accessible and surface-exposed 2D electron gas offered by graphene provides indeed an ideal platform on which to tune, via application of an electrostatic gate, the coupling between adsorbates deposited on its surface. We have experimentally studied the case of graphene transistors which channel is decorated with an array of superconducting tin nanoparticles. They induce via percolation of proximity effect a global 2D superconducting state which critical temperature Tc can be tuned by gate voltage. When the Graphene show strong disorder, it is possible to tune via the applied gate voltage the system towards an insulating state, demonstrating the possibility to trigger a superconducting to insulator transition, which features ressembles those found in granular superconductors. In this work, graphene monolayers are surface-conjugated to regular arrays of superconducting disk-shaped metal islands, whose inter-island distances were patterned to be in the quasi-ballistic limit of the underlying 2D electron gas. Arrays can be made on a large range of geometry and density, up to the highly diluted limit with less than 5% surface coverage and few micrometers in between islands. In the lower temperature limit (developed theory, and may provide a hint to the understanding of long-standing issue of ``zero-temperature'' bosonic metallic state
Charging in a Superconducting Vortex Due to the Three Force Terms in Augmented Eilenberger Equations
Ueki, Hikaru; Ohuchi, Marie; Kita, Takafumi
2018-04-01
We derive augmented Eilenberger equations that incorporate the following missing force terms: (i) the Lorentz force, (ii) the pair-potential gradient (PPG) force, and (iii) the pressure difference arising from the slope in the density of states (DOS). Recently, augmented Eilenberger equations with the Lorentz and PPG forces have been derived microscopically by studying the Hall and charging effects in superconductors, but the pressure due to the slope in the DOS has not yet been considered in augmented Eilenberger equations, despite phenomenological indications that it is a charging mechanism in a vortex of type-II superconductors. This newly added pressure is called "the SDOS pressure". We calculate the charging in an isolated vortex of an s-wave superconductor with a spherical Fermi surface using the augmented Eilenberger equations incorporating the Lorentz force, PPG force, and SDOS pressure. When we compare the charge densities due to the three force terms in the augmented Eilenberger equations, the vortex-core charging due to the SDOS pressure is larger than that due to the other forces near the superconducting transition temperature. Thus, when we calculate the charging in an isolated vortex of a superconductor with a finite slope in the DOS, we should consider not only the Lorentz and PPG forces but also the SDOS pressure.
Liang, Xiao-Meng; Zha, Guo-Qiao
2015-12-01
In this paper, based on the time-dependent Ginzburg-Landau theory, we study the dynamics of vortex-antivortex (V-Av) pairs in a mesoscopic superconducting square with a small hole under applied bias currents. For the sample with a centered hole, a V-Av pair can nucleate at the hole edges and moves in opposite directions perpendicular to applied constant DC drive. The influence of the external magnetic field on the (anti)vortex velocity and the lifetime of V-Av pairs is mainly investigated. Different modes in the dynamical process of the V-Av collision and annihilation are identified. Moreover, in the case when the hole is displaced from the center of the square, the V-Av dynamics behaves quite differently from the symmetric case due to the shift of the V-Av creation point.
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
Disorder-induced power-law response of a superconducting vortex on a plane
Shapira, N.; Lamhot, Y.; Shpielberg, O.; Kafri, Y.; Ramshaw, B. J.; Bonn, D. A.; Liang, Ruixing; Hardy, W. N.; Auslaender, O. M.
2015-09-01
We report drive-response experiments on individual superconducting vortices on a plane, a realization for a (1+1)-dimensional directed polymer in random media. For this we use magnetic force microscopy to image and manipulate individual vortices trapped on a twin boundary in YBa2Cu3O7 -δ near optimal doping. We find that when we drag a vortex with the magnetic tip, it moves in a series of jumps. As theory suggests, the jump-size distribution does not depend on the applied force and is consistent with power-law behavior. The measured power is much larger than widely accepted theoretical calculations.
Directory of Open Access Journals (Sweden)
Sophie S. Shamailov, Joachim Brand
2018-03-01
Full Text Available Superconducting Josephson vortices have direct analogues in ultracold-atom physics as solitary-wave excitations of two-component superfluid Bose gases with linear coupling. Here we numerically extend the zero-velocity Josephson vortex solutions of the coupled Gross-Pitaevskii equations to non-zero velocities, thus obtaining the full dispersion relation. The inertial mass of the Josephson vortex obtained from the dispersion relation depends on the strength of linear coupling and has a simple pole divergence at a critical value where it changes sign while assuming large absolute values. Additional low-velocity quasiparticles with negative inertial mass emerge at finite momentum that are reminiscent of a dark soliton in one component with counter-flow in the other. In the limit of small linear coupling we compare the Josephson vortex solutions to sine-Gordon solitons and show that the correspondence between them is asymptotic, but significant differences appear at finite values of the coupling constant. Finally, for unequal and non-zero self- and cross-component nonlinearities, we find a new solitary-wave excitation branch. In its presence, both dark solitons and Josephson vortices are dynamically stable while the new excitations are unstable.
Model of vortex dynamics in superconducting films in two-coil measurements of the coherence length
Lemberger, Thomas; Loh, Yen Lee
In two-coil measurements on superconducting films, a magnetic field from a small coil is applied to the center of the film. When the amplitude of the ac field is increased, the film undergoes a transition from the ``Meissner'' state to a state with vortices and antivortices. Ultimately, the vortex density matches the applied magnetic field and field screening is negligible. Experimentally, the field at the transition is related to the superconducting coherence length, although a full theory of the relationship is lacking. We show that the mutual inductance between drive and pickup coils, on opposite sides of the film, as a function of ac field amplitude is well-described by a phenomenological model in which vortices and antivortices appear together in the film at the radius where the induced supercurrent is strongest, and then they move through a landscape of moderately strong vortex pinning sites. Work at OSU supported by DOE-Basic Energy Sciences through Grant No. FG02-08ER46533.
Force-free state in a superconducting single crystal and angle-dependent vortex helical instability
del Valle, J.; Gomez, A.; Gonzalez, E. M.; Manas-Valero, S.; Coronado, E.; Vicent, J. L.
2017-06-01
Superconducting 2 H -NbS e2 single crystals show intrinsic low pinning values. Therefore, they are ideal materials with which to explore fundamental properties of vortices. (V , I ) characteristics are the experimental data we have used to investigate the dissipation mechanisms in a rectangular-shaped 2 H -NbS e2 single crystal. Particularly, we have studied dissipation behavior with magnetic fields applied in the plane of the crystal and parallel to the injected currents, i.e., in the force-free state where the vortex helical instability governs the vortex dynamics. In this regime, the data follow the elliptic critical state model and the voltage dissipation shows an exponential dependence, V ∝eα (I -IC ∥ ) , IC ∥ being the critical current in the force-free configuration and α a linear temperature-dependent parameter. Moreover, this exponential dependence can be observed for in-plane applied magnetic fields up to 40° off the current direction, which implies that the vortex helical instability plays a role in dissipation even out of the force-free configuration.
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
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.
Flux flow, pinning, and resistive behavior in superconducting networks
International Nuclear Information System (INIS)
Teitel, S.
1991-10-01
We have studied the behavior of fluctuation effects in superconducting systems using numerical simulations of XY and Coulomb gas models. Flux flow resistance in two dimensional Josephson junction arrays has been calculated, and related to correlations in vortex structure. Randomness has been introduced, and its effects on the superconducting transition, and vortex mobility, have been studied. We find that randomness destroys phase coherence, yet the randomness induced pinning reduces flux flow resistance at low temperatures. Vortex line fluctuations in high temperature superconductors have been studied using a three dimensional XY model. We have considered the melting of the vortex line lattice, and the entanglement and cutting of vortex lines in the vortex line liquid phase. Vortex line entangling and cutting appear to occur on the same length scales in the liquid phase. The vortex structure function has been calculated and from it, elastic properties of the vortex line liquid have been inferred. The two dimensional classical Coulomb gas, where charges map onto vortices in the superconducting system, has been simulated. The melting transitions of ordered charge (vortex) lattices have been studied, and we find evidence that these transitions do not have the critical behavior expected from standard symmetry analysis
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....
Controlling vortex motion and vortex kinetic friction
International Nuclear Information System (INIS)
Nori, Franco; Savel'ev, Sergey
2006-01-01
We summarize some recent results of vortex motion control and vortex kinetic friction. (1) We describe a device [J.E. Villegas, S. Savel'ev, F. Nori, E.M. Gonzalez, J.V. Anguita, R. Garcia, J.L. Vicent, Science 302 (2003) 1188] that can easily control the motion of flux quanta in a Niobium superconducting film on an array of nanoscale triangular magnets. Even though the input ac current has zero average, the resulting net motion of the vortices can be directed along either one direction, the opposite direction, or producing zero net motion. We also consider layered strongly anisotropic superconductors, with no fixed spatial asymmetry, and show [S. Savel'ev, F. Nori, Nature Materials 1 (2002) 179] how, with asymmetric drives, the ac motion of Josephson and/or pancake vortices can provide a net dc vortex current. (2) In analogy with the standard macroscopic friction, we present [A. Maeda, Y. Inoue, H. Kitano, S. Savel'ev, S. Okayasu, I. Tsukada, F. Nori , Phys. Rev. Lett. 94 (2005) 077001] a comparative study of the friction force felt by vortices in superconductors and charge density waves
Controlling vortex motion and vortex kinetic friction
Nori, Franco; Savel'ev, Sergey
2006-05-01
We summarize some recent results of vortex motion control and vortex kinetic friction. (1) We describe a device [J.E. Villegas, S. Savel'ev, F. Nori, E.M. Gonzalez, J.V. Anguita, R. Garcìa, J.L. Vicent, Science 302 (2003) 1188] that can easily control the motion of flux quanta in a Niobium superconducting film on an array of nanoscale triangular magnets. Even though the input ac current has zero average, the resulting net motion of the vortices can be directed along either one direction, the opposite direction, or producing zero net motion. We also consider layered strongly anisotropic superconductors, with no fixed spatial asymmetry, and show [S. Savel'ev, F. Nori, Nature Materials 1 (2002) 179] how, with asymmetric drives, the ac motion of Josephson and/or pancake vortices can provide a net dc vortex current. (2) In analogy with the standard macroscopic friction, we present [A. Maeda, Y. Inoue, H. Kitano, S. Savel'ev, S. Okayasu, I. Tsukada, F. Nori , Phys. Rev. Lett. 94 (2005) 077001] a comparative study of the friction force felt by vortices in superconductors and charge density waves.
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.
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.
Thorsmølle, V K; Averitt, R D; Shibauchi, T; Hundley, M F; Taylor, A J
2006-12-08
We have used terahertz spectroscopy to measure the Josephson plasma resonance in the superconductor Tl2Ba2CaCu2O8+delta. This allows us to probe the longitudinal ordering of pancake vortices as a function of applied ab-plane current in a 2.5 kG c-axis magnetic field. With increasing current in the low temperature vortex solid phase, we observe a decrease in the interlayer phase coherence consistent with a progressive misalignment of the pancake vortices in neighboring layers. In the high temperature vortex liquid phase, an increase in the longitudinal ordering occurs above a certain threshold current. Our results show evidence of a current-driven coupling-decoupling crossover in the pinned liquid phase.
Zha, Guo-Qiao; Peeters, F. M.; Zhou, Shi-Ping
2014-12-01
In the framework of the time-dependent Ginzburg-Landau formalism, we study the dynamics of vortex-antivortex (V-Av) pairs in mesoscopic symmetric and asymmetric superconducting loops under an applied ac current. In contrast to the case of a constant biasing dc current, the process of the V-Av collision and annihilation is strongly affected by the time-periodic ac signal. As the direction of the applied ac current is reversed, the existed V-Av pair moves backward and then collides with a new created Av-V pair in a symmetric loop. In the presence of an appropriate external magnetic field, a novel sinusoidal-like oscillatory mode of the magnetization curve is observed, and the periodic dynamical process of the V-Av annihilation occurs in both branches of the sample. Moreover, for the asymmetric sample with an off-centered hole the creation point of the V-Av pair shifts away from the center of the sample, and the creation and annihilation dynamics of V-Av pairs turns out to be very different from the symmetric case.
Investigations of two types of superconducting arrays
International Nuclear Information System (INIS)
Niu, M.
1993-01-01
This dissertation has two parts. Part one studies the anisotropy effect on homogeneous superconducting wire-networks, by using the Abrikosov approach. The networks assumed to have an infinite square lattice geometry. An anisotropy parameter R is defined to be the cross sectional area ratio of the vertical and horizontal strands. Many limiting behaviors of the order parameter distribution as R → ∞ are obtained. Many anisotropy-induced vortex configurational transitions are found at several Φ/Φ 0 values studied, and are investigated in detail. Part two studies the ground-state vortex configurations of the Josephson-coupled arrays of superconducting islands. The Ginzburg-Landau Josephson array model is used. With arrays of Penrose tiling geometry, the authors have found negative evidences against a proposed mechanism, and positive evidences for a new mechanism for generating commensurate states. But the mechanisms for the majority of the nontrivial commensurate states remain to be investigated. With arrays of infinite square lattice geometry, a temperature-induced vortex configurational transition at Φ/Φ 0 = 1/6 is found. The authors discover that the equilibrium vortex ground state of an infinite square-lattice array can occur in a unit cell of size other than q by q, or 2q by 2q, which has been widely accepted and commonly used so far
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...
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....
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.)
Evidence of Vortex Jamming in Abrikosov Vortex Flux Flow Regime
Karapetrov, G.; Yefremenko, V.; Mihajlović, G.; Pearson, J. E.; Iavarone, M.; Novosad, V.; Bader, S. D.
2012-01-01
We report on dynamics of non-local Abrikosov vortex flow in mesoscopic superconducting Nb channels. Magnetic field dependence of the non-local voltage induced by the flux flow shows that vortices form ordered vortex chains. Voltage asymmetry (rectification) with respect to the direction of vortex flow is evidence that vortex jamming strongly moderates vortex dynamics in mesoscopic geometries. The findings can be applied to superconducting devices exploiting vortex dynamics and vortex manipula...
Serrano, Ismael García; Sesé, Javier; Guillamón, Isabel; Suderow, Hermann; Vieira, Sebastián; Ibarra, Manuel Ricardo; De Teresa, José María
2016-01-01
We report efficient vortex pinning in thickness-modulated tungsten-carbon-based (W-C) nanostructures grown by focused ion beam induced deposition (FIBID). By using FIBID, W-C superconducting films have been created with thickness modulation properties exhibiting periodicity from 60 to 140 nm, leading to a strong pinning potential for the vortex lattice. This produces local minima in the resistivity up to high magnetic fields (2.2 T) in a broad temperature range due to commensurability effects between the pinning potential and the vortex lattice. The results show that the combination of single-step FIBID fabrication of superconducting nanostructures with built-in artificial pinning landscapes and the small intrinsic random pinning potential of this material produces strong periodic pinning potentials, maximizing the opportunities for the investigation of fundamental aspects in vortex science under changing external stimuli (e.g., temperature, magnetic field, electrical current).
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.
Vortex jamming in superconductors and granular rheology
International Nuclear Information System (INIS)
Yoshino, Hajime; Nogawa, Tomoaki; Kim, Bongsoo
2009-01-01
We demonstrate that a highly frustrated anisotropic Josephson junction array (JJA) on a square lattice exhibits a zero-temperature jamming transition, which shares much in common with those in granular systems. Anisotropy of the Josephson couplings along the horizontal and vertical directions plays roles similar to normal load or density in granular systems. We studied numerically static and dynamic response of the system against shear, i.e. injection of external electric current at zero temperature. Current-voltage curves at various strength of the anisotropy exhibit universal scaling features around the jamming point much as do the flow curves in granular rheology, shear-stress versus shear-rate. It turns out that at zero temperature the jamming transition occurs right at the isotropic coupling and anisotropic JJA behaves as exotic fragile vortex matter: it behaves as a superconductor (vortex glass) in one direction, whereas it is a normal conductor (vortex liquid) in the other direction even at zero temperature. Furthermore, we find a variant of the theoretical model for the anisotropic JJA quantitatively reproduces universal master flow-curves of the granular systems. Our results suggest an unexpected common paradigm stretching over seemingly unrelated fields-the rheology of soft materials and superconductivity.
Moreno, A. J.; Chiliotte, C. E.; Pasquini, G.; Bekeris, V.; Gomez, A.; del Valle, J.; Gonzalez, E. M.; Prieto, J. L.; Vicent, J. L.
2015-01-01
We study the dynamics of the vortex lattice driven by ac induced currents in the critical state regime, for T > 0.70 TC. The samples are superconducting films grown on top of two-fold symmetry array of magnetic dots. In these heterostructures, the induced ac currents flow parallel to the short and to the long side of the pinning array in different areas of the samples simultaneously. This behavior produces remarkable effects in the vortex lattice dynamics. First of all, periodic features are observed in the ac susceptibility versus applied magnetic field measurements which are related to matching effects between the vortex lattices and the magnetic array. However, the vortex lattice reconfiguration observed in magnetotransport experiments is absent. Some of these features are revealed as maxima instead of being minima, indicating higher mobility at certain matching fields. Competing unstable vortex configurations could lead to increase vortex mobility precluding the reconfiguration transition. At high temperatures, where the matching effects show up, the magnetic permeability of the dots is the mechanism that governs the JC(T) behavior. Moreover, the temperature dependence of the pinning force FP(T) shows a temperature crossover related to an unexpected enhancement in vortex mobility. Vortex-vortex interaction and the interplay between trapped and interstitial vortices are a hint to explain these phenomena.
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)
Superconducting digital logic amplifier
International Nuclear Information System (INIS)
Przybysz, J.X.
1989-01-01
This paper describes a superconducting digital logic amplifier for interfacing between a Josephson junction logic circuit having output current and a higher voltage semiconductor circuit input. The amplifier comprising: an input terminal for connection to a; an output terminal for connection to a semiconductor circuit input; an input, lower critical current, Josephson junction having first and second terminals; a first series string of at least three lower critical current Josephson junctions. The first series string being connected to the first terminal of the input Josephson junction such that the first series string is in series with the input Josephson junction to provide a series combination. The input terminal being connected to the first terminal of the input Josephson junction, and with the critical current of the lower critical current Josephson junctions of the input Josephson junction and the first series Josephson junctions being less than the output current of the low voltage Josephson junction circuit; a second series string of at least four higher critical current Josephson junctions. The second string being connected in parallel with the series combination to provide parallel strings having an upper common connection and a lower common connection. The lower common connection being connected to the second terminal of the input Josephson junction and the upper common connection being connected to the output terminal; and a pulsed DC current source connected the parallel strings at the upper common connection. The DC current source having a current at least equal to the critical current of the higher critical current Josephson junctions
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.
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...
Flux flow, pinning, and resistive behavior in superconducting networks
International Nuclear Information System (INIS)
Teitel, S.
1993-10-01
We have studied the behavior of fluctuation effects in superconducting systems using numerical simulations of XY and Coulomb gas models. The fluctuation of vortex lines in high temperature superconductors, in the presence of an external magnetic field, has been studied using a three dimensional XY model. We have continued earlier work and verified the existence of two distinct phase transitions in this model. As the vortex line lattice is heated, it melts first into a line liquid where superconductivity is destroyed for currents perpendicular to the applied magnetic field, but persists for currents parallel to the field. As heating continues, the thermal excitation of closed vortex line loops links all the lines together, leading to completely normal metal properties in all directions. Upon cooling of the vortex line liquid, we find that as the system width increases, one can get trapped into an entangled non-equilibrium state in which vortex line cuttings are frozen out on measurable nine scales. We have also continued simulations of the two dimensional Coulomb gas, as a model for vortex fluctuations in two dimensional arrays of Josephson junctions, and thin film superconductors. Our preliminary results support the accepted view of a Kosterlitz-Thouless melting of the vortex lattice, in the limit of a uniform continous film
Massee, Freek; Sprau, Peter Oliver; Wang, Yong-Lei; Davis, J C Séamus; Ghigo, Gianluca; Gu, Genda D; Kwok, Wai-Kwong
2015-05-01
Maximizing the sustainable supercurrent density, J C, is crucial to high-current applications of superconductivity. To achieve this, preventing dissipative motion of quantized vortices is key. Irradiation of superconductors with high-energy heavy ions can be used to create nanoscale defects that act as deep pinning potentials for vortices. This approach holds unique promise for high-current applications of iron-based superconductors because J C amplification persists to much higher radiation doses than in cuprate superconductors without significantly altering the superconducting critical temperature. However, for these compounds, virtually nothing is known about the atomic-scale interplay of the crystal damage from the high-energy ions, the superconducting order parameter, and the vortex pinning processes. We visualize the atomic-scale effects of irradiating FeSe x Te1-x with 249-MeV Au ions and find two distinct effects: compact nanometer-sized regions of crystal disruption or "columnar defects," plus a higher density of single atomic site "point" defects probably from secondary scattering. We directly show that the superconducting order is virtually annihilated within the former and suppressed by the latter. Simultaneous atomically resolved images of the columnar crystal defects, the superconductivity, and the vortex configurations then reveal how a mixed pinning landscape is created, with the strongest vortex pinning occurring at metallic core columnar defects and secondary pinning at clusters of point-like defects, followed by collective pinning at higher fields.
Poole, Charles P; Farach, Horacio A
1995-01-01
Superconductivity covers the nature of the phenomenon of superconductivity. The book discusses the fundamental principles of superconductivity; the essential features of the superconducting state-the phenomena of zero resistance and perfect diamagnetism; and the properties of the various classes of superconductors, including the organics, the buckministerfullerenes, and the precursors to the cuprates. The text also describes superconductivity from the viewpoint of thermodynamics and provides expressions for the free energy; the Ginzburg-Landau and BCS theories; and the structures of the high
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
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...
Energy Technology Data Exchange (ETDEWEB)
Checchin, Mattia [Illinois Inst. of Technology, Chicago, IL (United States)
2016-12-01
Superconducting niobium accelerating cavities are devices operating in radio-frequency and able to accelerate charged particles up to energy of tera-electron-volts. Such accelerating structures are though limited in terms of quality factor and accelerating gradient, that translates--in some cases--in higher capital costs of construction and operation of superconducting rf accelerators. Looking forward for a new generation of more affordable accelerators, the physical description of limiting mechanisms in superconducting microwave resonators is discussed. In particular, the physics behind the dissipation introduced by vortices in the superconductor, the ultimate quench limitations and the quality factor degradation mechanism after a quench are described in detail. One of the limiting factor of the quality factor is the dissipation introduced by trapped magnetic flux vortices. The radio-frequency complex response of trapped vortices in superconductors is derived by solving the motion equation for a magnetic flux line, assuming a bi-dimensional and mean free path-dependent Lorentzian-shaped pinning potential. The resulting surface resistance shows the bell-shaped trend as a function of the mean free path, in agreement with the experimental data observed. Such bell-shaped trend of the surface resistance is described in terms of the interplay of the two limiting regimes identified as pinning and flux flow regimes, for low and large mean free path values respectively. The model predicts that the dissipation regime--pinning- or flux-flow-dominated--can be tuned either by acting on the frequency or on the electron mean free path value. The effect of different configurations of pinning sites and strength on the vortex surface resistance are also discussed. Accelerating cavities are also limited by the quench of the superconductive state, which limits the maximum accelerating gradient achievable. The accelerating field limiting factor is usually associate d to the
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).
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.
Superconductivity: Phenomenology
International Nuclear Information System (INIS)
Falicov, L.M.
1988-08-01
This document discusses first the following topics: (a) The superconducting transition temperature; (b) Zero resistivity; (c) The Meissner effect; (d) The isotope effect; (e) Microwave and optical properties; and (f) The superconducting energy gap. Part II of this document investigates the Ginzburg-Landau equations by discussing: (a) The coherence length; (b) The penetration depth; (c) Flux quantization; (d) Magnetic-field dependence of the energy gap; (e) Quantum interference phenomena; and (f) The Josephson effect
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.
Peak effect and vortex dynamics in superconducting MgB2 single crystals
International Nuclear Information System (INIS)
Lee, Hyun-Sook; Jang, Dong-Jin; Kim, Heon-Jung; Kang, Byeongwon; Lee, Sung-Ik
2007-01-01
The dynamic nature of the vortex state of MgB 2 single crystals near the peak effect (PE) region, which is very different either from that of conventional low-temperature superconductors or from that of high-temperature cuprate superconductors, is introduced in this article. Relaxation from a disordered, metastable field-cooled (FC) state to an ordered, stable zero-field-cooled (ZFC) state of the MgB 2 single crystals under an applied magnetic field and current is investigated. From an analysis of the noise properties in the ZFC state, a dynamic vortex phase diagram of the MgB 2 is obtained near the PE region. Between the onset and the peak region in the critical current vs. magnetic field diagram, crossovers from a high-noise state to a noise-free state are observed with increasing current. Above the peak, however, an opposite phenomenon, crossovers from a noise-free to a high-noise state, is observed which has not been observed in any other superconductors. The hysteresis in the I-V curves and the two-level random telegraph noise in the time evolution of the voltage response under an constant applied current at the ZFC state are also studied in detail
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.
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
Vortex pinning in superconducting Nb thin films deposited on nanoporous alumina templates
DEFF Research Database (Denmark)
Vinckx, W.; Vanacken, J.; Moshchalkov, V.V.
2006-01-01
We present a study of magnetization and transport properties of superconducting Nb thin films deposited on nanoporous aluminium oxide templates. Periodic oscillations in the critical temperature vs. field, matching effects in fields up to 700 mT and strongly enhanced critical currents were observed....... These fields are considerably higher than those typical for periodic pinning arrays made by lithographic techniques, which reflects the benefits of nanostructuring superconductors by using self-organized growth. This method provides a periodic pinning potential with sub-100 nm spacing between the pinning...
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
Current distribution across type II superconducting films: a new vortex-free critical state.
Talantsev, E F; Pantoja, A E; Crump, W P; Tallon, J L
2018-01-29
The current distribution across the thickness of a current-carrying rectangular film in the Meissner state was established long ago by the London brothers. The distribution across the width is more complicated but was later shown to be highly non-uniform, diverging at the edges. Accordingly, the standard view for type II superconductors is that vortices enter at the edges and, with increasing current, are driven inwards until they self-annihilate at the centre, causing dissipation. This condition is presumed to define the critical current. However we have shown that, under self-field (no external field), the transport critical current is a London surface current where the surface current density equals the critical field divided by λ, across the entire width. The critical current distribution must therefore be uniform. Here we report studies of the current and field distribution across commercial YBa 2 Cu 3 O 7 conductors and confirm the accepted non-uniform distribution at low current but demonstrate a radical crossover to a uniform distribution at critical current. This crossover ends discontinuously at a singularity and calculations quantitatively confirm these results in detail. The onset of self-field dissipation is, unexpectedly, thermodynamic in character and the implied vortex-free critical state seems to require new physics.
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
Evidence for a vortex-glass transition in superconducting Ba(Fe0.9Co0.1)2As2.
Prando, G; Giraud, R; Aswartham, S; Vakaliuk, O; Abdel-Hafiez, M; Hess, C; Wurmehl, S; Wolter, A U B; Büchner, B
2013-12-18
Measurements of magneto-resistivity and magnetic susceptibility were performed on single crystals of superconducting Ba(Fe0.9Co0.1)2As2 close to the conditions of optimal doping. The high quality of the investigated samples allows us to reveal dynamic scaling behaviour associated with a vortex-glass phase transition in the limit of a weak degree of quenched disorder. Accordingly, the dissipative component of the ac susceptibility is reproduced well within the framework of Havriliak-Negami relaxation, assuming a critical power-law divergence for the characteristic correlation time τ of the vortex dynamics. Remarkably, the random disorder introduced by the Fe1-xCox chemical substitution is found to act on the vortices as a much weaker quenched disorder than previously reported for cuprate superconductors such as Y1-xPrxBa2Cu3O7-δ.
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.
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)
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.
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...
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
Ketterson, John B
2008-01-01
Conceived as the definitive reference in a classic and important field of modern physics, this extensive and comprehensive handbook systematically reviews the basic physics, theory and recent advances in the field of superconductivity. Leading researchers, including Nobel laureates, describe the state-of-the-art in conventional and unconventional superconductors at a particularly opportune time, as new experimental techniques and field-theoretical methods have emerged. In addition to full-coverage of novel materials and underlying mechanisms, the handbook reflects continued intense research into electron-phone based superconductivity. Considerable attention is devoted to high-Tc superconductivity, novel superconductivity, including triplet pairing in the ruthenates, novel superconductors, such as heavy-Fermion metals and organic materials, and also granular superconductors. What’s more, several contributions address superconductors with impurities and nanostructured superconductors. Important new results on...
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....
Gamble, Ronald S., Jr.
Thin film YBa2Cu3O7--delta (YBCO) samples with added non-superconducting nanodot defects of CeO 2 and BaSnO2 are the focus of recent high-temperature superconductor studies. These nanodots allow magnetic flux to penetrate at these sites of the superconducting lattice thus creating a magnetic flux vortex state. Examining the structure shows that these quantized magnetic flux vortices arrange themselves in a self-assembled lattice. The nanodots, with non-superconducting properties, serve to present structural properties to restrict motion of these vorticies under a pinning-force and to enhance the critical current density. A formulation of a new model for the system by a variation in the electron pair velocity via the virtual work from the nanodot defects in accordance to the well-known Superconductivity theories is tested. A solution to the expression for the magnetic flux, zero net force and pair velocity will generate a setting for the optimal deposition parameters of number density, growth geometry and mass density of these nanodot structures. With a calculation of pair velocities from a similar work, a comparison is made between experimental and theoretical velocity calculations using growth geometry and chemical potential. This will yield insight into how the current density for a doped high-temperature superconductor will be modified and tuned based on the dynamics and density of the nanodots themselves.
Superconductivity in La1.56Sr0.44CuO4/La2CuO4 Superlattices
International Nuclear Information System (INIS)
Bozovic, I.; Suter, A.; Morenzoni, E.; Prokscha, T.; Luetkens, H.; Wojek, B.M.; Logvenov, G.; Gozar, A.
2011-01-01
Superlattices of the repeated structure La 1.56 Sr 0.44 CuO 4 /La 2 CuO 4 (LSCO-LCO), where none of the constituents is superconducting, show a superconducting transition of T(prime) c 25 K. In order to elucidate the nature of the superconducting state we have performed a low-energy μSR study. By applying a magnetic field parallel (Meissner state) and perpendicular (vortex state) to the film planes, we could show that superconductivity is sheet like, resulting in a very anisotropic superconducting state. This result is consistent with a simple charge-transfer model, which takes into account the layered structure and the difference in the chemical potential between LCO and LSCO, as well as Sr interdiffusion. Using a pancake-vortex model we could estimate a strict upper limit of the London penetration depth to 380 nm in these superlattices. The temperature dependence of the muon depolarization rate in field cooling experiments is very similar to what is observed in intercalated BSCCO and suggests that vortex-vortex interaction is dominated by electromagnetic coupling but negligible Josephson interaction.
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....
Poole, Charles P; Creswick, Richard J; Prozorov, Ruslan
2014-01-01
Superconductivity, Third Edition is an encyclopedic treatment of all aspects of the subject, from classic materials to fullerenes. Emphasis is on balanced coverage, with a comprehensive reference list and significant graphics from all areas of the published literature. Widely used theoretical approaches are explained in detail. Topics of special interest include high temperature superconductors, spectroscopy, critical states, transport properties, and tunneling. This book covers the whole field of superconductivity from both the theoretical and the experimental point of view. This third edition features extensive revisions throughout, and new chapters on second critical field and iron based superconductors.
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.
Quantum Theory of Conducting Matter Superconductivity and Quantum Hall Effect
Fujita, Shigeji; Godoy, Salvador
2009-01-01
Explains major superconducting properties including zero resistance, Meissner effect, sharp phase change, flux quantization, excitation energy gap, and Josephson effects using quantum statistical mechanical calculations. This book covers the 2D superconductivity and the quantum Hall effects
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.
A fast Josephson SFQ shift register
International Nuclear Information System (INIS)
Kuo, F.; Whiteley, S.R.; Faris, S.M.
1989-01-01
A novel Josephson shift register has been designed and fabricated. The main data latch is DC biased; the data storage is accomplished through the transfer of a single flux quantum in or out of a SQUID superconducting loop. A two-phase sinusoidal clock with offset is used to operate the circuit. Simulations verify that the operating frequency can go beyond 70 GHz, with operating margins exceeding 20%. Preliminary measurements indicate that the circuit operates as intended
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.
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.
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.
Gambling with Superconducting Fluctuations
Foltyn, Marek; Zgirski, Maciej
2015-08-01
Josephson junctions and superconducting nanowires, when biased close to superconducting critical current, can switch to a nonzero voltage state by thermal or quantum fluctuations. The process is understood as an escape of a Brownian particle from a metastable state. Since this effect is fully stochastic, we propose to use it for generating random numbers. We present protocol for obtaining random numbers and test the experimentally harvested data for their fidelity. Our work is prerequisite for using the Josephson junction as a tool for stochastic (probabilistic) determination of physical parameters such as magnetic flux, temperature, and current.
Farid, Behnam
1998-08-01
Interpreting their experimental data in terms of an approximate solution of the Lawrence - Doniach - Clem (LDC) model in the continuum limit (describing an isolated interlayer Josephson vortex), Moler et al (1998 Science 279 1193) have estimated the penetration depth 0953-8984/10/34/003/img1 in the direction normal to the layers of the compound 0953-8984/10/34/003/img2 (Tl-2201) to have the value 0953-8984/10/34/003/img3. They thus concluded that only 0953-8984/10/34/003/img4 of the superconducting condensation energy in Tl-2201 would be due to the interlayer-tunnelling mechanism. We have studied the LDC model and found that it has no physical solution. Therefore 0953-8984/10/34/003/img1 in Tl-2201 is in need of re-examination.
International Nuclear Information System (INIS)
2007-01-01
During 2007, a large amount of the work was centred on the ITER project and related tasks. The activities based on low-temperature superconducting (LTS) materials included the manufacture and qualification of ITER full-size conductors under relevant operating conditions, the design of conductors and magnets for the JT-60SA tokamak and the manufacture of the conductors for the European dipole facility. A preliminary study was also performed to develop a new test facility at ENEA in order to test long-length ITER or DEMO full-size conductors. Several studies on different superconducting materials were also started to create a more complete database of superconductor properties, and also for use in magnet design. In this context, an extensive measurement campaign on transport and magnetic properties was carried out on commercially available NbTi strands. Work was started on characterising MgB 2 wire and bulk samples to optimise their performance. In addition, an intense experimental study was started to clarify the effect of mechanical loads on the transport properties of multi-filamentary Nb 3 Sn strands with twisted or untwisted superconducting filaments. The experimental activity on high-temperature superconducting (HTS) materials was mainly focussed on the development and characterisation of YBa 2 Cu 3 O 7-X (YBCO) based coated conductors. Several characteristics regarding YBCO deposition, current transport performance and tape manufacture were investigated. In the framework of chemical approaches for YBCO film growth, a new method, developed in collaboration with the Technical University of Cluj-Napoca (TUCN), Romania, was studied to obtain YBCO film via chemical solution deposition, which modifies the well-assessed metallic organic deposition trifluoroacetate (MOD-TFA) approach. The results are promising in terms of critical current and film thickness values. YBCO properties in films with artificially added pinning sites were characterised in collaboration with
Energy Technology Data Exchange (ETDEWEB)
Sprungmann, Dirk
2010-01-28
The combination of the Josephson and the proximity effect is possible by the introduction of a ferromagnetic barrier into a Josephson contact resulting in a so called π coupling. The supra current through these contacts is flowing in the reverse direction. Specific new electronic circuits such as phase shifting devices are possible, for instance for high-speed analog-digital transducers. In the frame of this thesis SIFS Josephson contacts were studied, with a barrier consisting of a thin insulating Al2Ox barrier layer and a ferromagnetic thin film. For the ferromagnetic material weak ferromagnetic Ni(0.6)Cu(0.4), the strong ferromagnetic Fe(0.25)Co(0.75) and the ternary Heusler alloys Co2MnSn and Cu2MnAl were used. Josephson contacts with π coupling were realized with the NiCu alloy, triplet superconductivity seems to appear with the Heusler systems.
Superconducting InSb nanowire devices
Szombati, D.B.
2017-01-01
Josephson junctions form a two-level system which is used as a building block for many types of superconducting qubits. Junctions fabricated from semiconducting nanowires are gate-tunable and offer electrostatically adjustable Josephson energy, highly desirable in qubit architecture. Studying
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
Energy Technology Data Exchange (ETDEWEB)
Polat, Ozgur [ORNL; Sinclair IV, John W [ORNL; Zuev, Yuri L [ORNL; Thompson, James R [ORNL; Christen, David K [ORNL; Cook, Sylvester W [ORNL; Kumar, Dhananjay [ORNL; Chen, Y [SuperPower Incorporated, Schenectady, New York; Selvamanickam, V. [SuperPower Incorporated, Schenectady, New York
2011-01-01
The dependence of the critical current density Jc on temperature, magnetic field, and film thickness has been investigated in (Gd-Y)BaCu-oxide materials of 0.7, 1.4, and 2.8 m thickness. Generally, the Jc decreases with film thickness at investigated temperatures and magnetic fields. The nature and strength of the pinning centers for vortices have been identified through angular and temperature measurements, respectively. These films do not exhibit c-axis correlated vortex pinning, but do have correlated defects oriented near the ab-planes. For all film thicknesses studied, strong pinning dominates at most temperatures. The vortex dynamics were investigated through magnetic relaxation studies in the temperature range of 5 77 K in 1 T and 3 T applied magnetic fields, H || surface-normal. The creep rate S is thickness dependent at high temperatures, implying that the pinning energy is also thickness dependent. Maley analyses of the relaxation data show an inverse power law variation for the effective pinning energy Ueff ~ (J0/J) . Finally, the electric field-current density (E-J) characteristics were determined over a wide range of dissipation by combining experimental results from transport, swept field magnetometry (VSM), and Superconducting Quantum Interference Device (SQUID) magnetometry. We develop a self-consistent model of the combined experimental results, leading to an estimation of the critical current density Jc0(T) in the absence of flux creep.
Josephson effect in microbridges of large dimensions
International Nuclear Information System (INIS)
Seifert, H.
1980-01-01
The possibility of the occurrence of Josephson and flux-flow effects in microbridges, being manufactured from a type I superconductor and having got dimensions that are larger than the coherence length of the superconducting material is investigated. On account of theoretical considerations the Josephson effect as well as the existence of individual flux quanta should not be possible in such geometries, but exceeding of the critical current should be characterized by formation and motion of flux tubes containing a multitude of flux quanta. Based on earlier work, it could be shown at first by using different techniques of sample preparation and manipulation that the effects shown there have to be explained to a large extent by an intermediate layer in the samples caused by the manufacture process. If the bridge has got small dimensions (10-20 μm of width) formation of a Josephson element may be possible also in the range of the bridge. The sample characteristic depending on the high-frequency current applied for demonstration and on temperature, one has to assume that the high-frequency current makes the total region of the bridge normally conductive, a SNS contact thus being formed. The RSJ model as well as the characteristic-forming mechanisms described from it are discussed in detail by means of the results of an electronic Josephson effect-simulating device constructed within the scope of this work. (orig./HP) [de
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.)
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
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.
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.
Vortex cores and vortex motion in superconductors with anisotropic Fermi surfaces
Energy Technology Data Exchange (ETDEWEB)
Galvis, J.A. [Laboratorio de Bajas Temperaturas, Departamento de Física de la Materia Condensada, Instituto de Ciencia de Materiales Nicolás Cabrera, Condensed Matter Physics Center (IFIMAC), Facultad de Ciencias, Universidad Autónoma de Madrid, E-28049 Madrid (Spain); Departamento de Ciencias Naturales, Facultad de ingeniería y Ciencias Básicas, Universidad Central, Bogotá (Colombia); National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310 (United States); Herrera, E.; Guillamón, I.; Vieira, S. [Laboratorio de Bajas Temperaturas, Departamento de Física de la Materia Condensada, Instituto de Ciencia de Materiales Nicolás Cabrera, Condensed Matter Physics Center (IFIMAC), Facultad de Ciencias, Universidad Autónoma de Madrid, E-28049 Madrid (Spain); Unidad Asociada de Altos Campos Magnéticos y Bajas Temperaturas, UAM, CSIC, Madrid (Spain); Suderow, H., E-mail: hermann.suderow@uam.es [Laboratorio de Bajas Temperaturas, Departamento de Física de la Materia Condensada, Instituto de Ciencia de Materiales Nicolás Cabrera, Condensed Matter Physics Center (IFIMAC), Facultad de Ciencias, Universidad Autónoma de Madrid, E-28049 Madrid (Spain); Unidad Asociada de Altos Campos Magnéticos y Bajas Temperaturas, UAM, CSIC, Madrid (Spain)
2017-02-15
Highlights: • The observation of vortex cores is reviewed, with emphasis in new experiments. • Vortex cores are follow superconducting gap and Fermi surface shapes. • The vortex core shape influences vortex dynamics. - Abstract: Explaning static and dynamic properties of the vortex lattice in anisotropic superconductors requires a careful characterization of vortex cores. The vortex core contains Andreev bound states whose spatial extension depends on the anisotropy of the electronic band-structure and superconducting gap. This might have an impact on the anisotropy of the superconducting properties and on vortex dynamics. Here we briefly summarize basic concepts to understand anisotropic vortex cores and review vortex core imaging experiments. We further discuss moving vortex lattices and the influence of vortex core shape in vortex motion. We find vortex motion in highly tilted magnetic fields. We associate vortex motion to the vortex entry barrier and the screening currents at the surface. We find preferential vortex motion along the main axis of the vortex lattice. After travelling integers of the intervortex distance, we find that vortices move more slowly due to the washboard potential of the vortex lattice.
Vortex cores and vortex motion in superconductors with anisotropic Fermi surfaces
International Nuclear Information System (INIS)
Galvis, J.A.; Herrera, E.; Guillamón, I.; Vieira, S.; Suderow, H.
2017-01-01
Highlights: • The observation of vortex cores is reviewed, with emphasis in new experiments. • Vortex cores are follow superconducting gap and Fermi surface shapes. • The vortex core shape influences vortex dynamics. - Abstract: Explaning static and dynamic properties of the vortex lattice in anisotropic superconductors requires a careful characterization of vortex cores. The vortex core contains Andreev bound states whose spatial extension depends on the anisotropy of the electronic band-structure and superconducting gap. This might have an impact on the anisotropy of the superconducting properties and on vortex dynamics. Here we briefly summarize basic concepts to understand anisotropic vortex cores and review vortex core imaging experiments. We further discuss moving vortex lattices and the influence of vortex core shape in vortex motion. We find vortex motion in highly tilted magnetic fields. We associate vortex motion to the vortex entry barrier and the screening currents at the surface. We find preferential vortex motion along the main axis of the vortex lattice. After travelling integers of the intervortex distance, we find that vortices move more slowly due to the washboard potential of the vortex lattice.
Energy Technology Data Exchange (ETDEWEB)
Doenitz, D.
2006-10-31
Local analysis plays an important role in many fields of scientific research. However, imaging methods are not very common in the investigation of superconductors. For more than 20 years, Low Temperature Scanning Electron Microscopy (LTSEM) has been successfully used at the University of Tuebingen for studying of condensed matter phenomena, especially of superconductivity. In this thesis LTSEM was used for imaging current distributions in different superconducting thin film structures: - Imaging of current distributions in Josephson junctions with ferromagnetic interlayer, also known as SIFS junctions, showed inhomogeneous current transport over the junctions which directly led to an improvement in the fabrication process. An investigation of improved samples showed a very homogeneous current distribution without any trace of magnetic domains. Either such domains were not present or too small for imaging with the LTSEM. - An investigation of Nb/YBCO zigzag Josephson junctions yielded important information on signal formation in the LTSEM both for Josephson junctions in the short and in the long limit. Using a reference junction our signal formation model could be verified, thus confirming earlier results on short zigzag junctions. These results, which could be reproduced in this work, support the theory of d-wave symmetry in the superconducting order parameter of YBCO. Furthermore, investigations of the quasiparticle tunneling in the zigzag junctions showed the existence of Andreev bound states, which is another indication of the d-wave symmetry in YBCO. - The LTSEM study of Hot Electron Bolometers (HEB) allowed the first successful imaging of a stable 'Hot Spot', a self-heating region in HEB structures. Moreover, the electron beam was used to induce an - otherwise unstable - hot spot. Both investigations yielded information on the homogeneity of the samples. - An entirely new method of imaging the current distribution in superconducting interference
International Nuclear Information System (INIS)
Thomas, M.; Blank, H.; Wong, K.C.; Nguyen, C.; Kroemer, H.; Hu, E.L.
1996-01-01
InAs-AlSb quantum wells contacted with periodic gratings of superconducting Nb electrodes show Josephson-junction characteristics at low temperatures. When a nonzero resistance is reestablished by a weak magnetic field, the resistance shows a strong component periodic in the magnetic field. At fields above ∼300μT, the oscillation period corresponds to one flux quantum per grating cell; but in wide arrays (≥40μm), a frequency doubling takes place at low fields, indicating the formation of a staggered vortex superlattice at twice the lithographic period. copyright 1996 The American Physical Society
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
Superconducting electronics testing
International Nuclear Information System (INIS)
Moskowitz, P.A.; Guernsey, R.W.; Stasiak, J.W.; Flint, E.B.
1983-01-01
An I/O assembly has been designed and constructed to support the operation of superconducting circuitry. A system, previously described for chip testing, has been adapted for use with a Josephson technology system level experiment. The cryoinsert assembly, constructed of non-magnetic parts, provides 80 high frequency I/O lines between room temperature and 4.2 K. (author)
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.
Superconducting phase of YBa2Cu3O7-δ films in high magnetic fields: Vortex glass or Bose glass
International Nuclear Information System (INIS)
Woeltgens, P.J.M.; Dekker, C.; Swueste, J.; de Wijn, H.W.
1993-01-01
Nonlinear current-voltage (I-V) curves are measured in laser-ablated YBa 2 Cu 3 O 7-δ films deposited onto SrTiO 3 . The measurements are performed near the glass phase transition in a magnetic field of 5 T at various angles from the c axis. From a critical scaling analysis, the angular dependencies of the glass transition temperature and the critical glass exponents are extracted. At small angles, these results distinguish between a vortex glass, caused by random pointlike disorder, and a Bose glass, caused by linelike disorder. The results can be understood in terms of the vortex-glass model only. No evidence is found for the existence of a Bose-glass phase
DEFF Research Database (Denmark)
Laver, M.; Bowell, C.J.; Forgan, E.M.
2009-01-01
High-purity niobium exhibits a surprisingly rich assortment of vortex lattice (VL) structures for fields applied parallel to a fourfold symmetry axis, with all observed VL phases made up of degenerate domains that spontaneously break some crystal symmetry. Yet a single regular hexagonal VL domain...... is intrinsically tied to the underlying crystal symmetry. We discuss how subtle anisotropies of the crystal may generate the remarkable VLs observed....
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.
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.
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...
Energy Technology Data Exchange (ETDEWEB)
Muehlbauer, Sebastian C.
2009-12-10
In this thesis, we present a comprehensive small angle neutron scattering study of the vortex lattice (VL) in an ultra-pure Nb single crystal sample, characterized by a residual resistivity ratio of {proportional_to} 10{sup 4}. We systematically investigate the morphology of vortex structures with the magnetic field applied along a four-fold left angle 100 right angle axis. We succeed to deconvolute the general morphology of the VL and its orientation to three dominant mechanisms: First, non-local contributions, second, the transition between open and closed Fermi surface sheets and, third, the intermediate mixed state (IMS) between the Meissner and the Shubnikov phase. We present first time microscopic measurements of the intrinsic bulk VL tilt modulus c{sub 44} by means of time resolved stroboscopic small angle neutron scattering in combination with a tailored magnetic field setup. In our study we find that the VL in Nb responds to an external force - in the form of a changed magnetic field - with an exponential relaxation. As expected, the relaxation process shows increasing VL stiffness with increasing magnetic field and reduced damping with increasing temperature. Besides this general trend, we observe a dramatic changeover of the relaxation process associated with the non-trivial VL morphology in the IMS and the crossover from attractive to repulsive vortex-vortex interaction. Furthermore we use small angle neutron scattering to establish the existence of a skyrmion lattice in the A-phase of MnSi. Due to a parallel alignment of the magnetic field with respect to the neutron beam, we are able to resolve the complete magnetic structure of the A-phase: The structure in the A-phase, reminiscent of a vortex lattice, consists of topological knots of the magnetization with particle-like properties, arranged in a regular six-fold lattice. The orientation of this lattice is strictly driven by the orientation of the applied magnetic field, regardless of the underlying
International Nuclear Information System (INIS)
Muehlbauer, Sebastian C.
2009-01-01
In this thesis, we present a comprehensive small angle neutron scattering study of the vortex lattice (VL) in an ultra-pure Nb single crystal sample, characterized by a residual resistivity ratio of ∝ 10 4 . We systematically investigate the morphology of vortex structures with the magnetic field applied along a four-fold left angle 100 right angle axis. We succeed to deconvolute the general morphology of the VL and its orientation to three dominant mechanisms: First, non-local contributions, second, the transition between open and closed Fermi surface sheets and, third, the intermediate mixed state (IMS) between the Meissner and the Shubnikov phase. We present first time microscopic measurements of the intrinsic bulk VL tilt modulus c 44 by means of time resolved stroboscopic small angle neutron scattering in combination with a tailored magnetic field setup. In our study we find that the VL in Nb responds to an external force - in the form of a changed magnetic field - with an exponential relaxation. As expected, the relaxation process shows increasing VL stiffness with increasing magnetic field and reduced damping with increasing temperature. Besides this general trend, we observe a dramatic changeover of the relaxation process associated with the non-trivial VL morphology in the IMS and the crossover from attractive to repulsive vortex-vortex interaction. Furthermore we use small angle neutron scattering to establish the existence of a skyrmion lattice in the A-phase of MnSi. Due to a parallel alignment of the magnetic field with respect to the neutron beam, we are able to resolve the complete magnetic structure of the A-phase: The structure in the A-phase, reminiscent of a vortex lattice, consists of topological knots of the magnetization with particle-like properties, arranged in a regular six-fold lattice. The orientation of this lattice is strictly driven by the orientation of the applied magnetic field, regardless of the underlying crystal symmetry. The
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.
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
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
Josephson effect gain and noise in SIS mixers
Wengler, Michael J.; Dubash, Noshir B.; Pance, Gordana; Miller, Ronald E.
1992-01-01
Superconducting tunnel diode (SIS) mixers are used for radio astronomy from 100 to 500 GHz. They are being considered for NASA spaceborne astronomy at frequencies near 1000 GHz. Measurements of gain and noise in SIS mixers at 230 and 492 GHz are reported. Relatively high gain and noise associated with Josephson currents are measured that have not been previously reported. These measurements show that Josephson currents are increasingly important as operating frequencies are raised. The techniques used to make these measurements are discussed. Measurements made with hot and cold black-bodies are shown to be inaccurate at high frequencies.
Energy Technology Data Exchange (ETDEWEB)
Abrahamsen, Asger Bech
2003-11-01
The compound TmNi{sub 2}B{sub 2}C has previously been studied by Small Angle Neutron Scattering(SANS) with the applied field along the crystalline c-axis and a very rich phase diagram in terms of flux line lattices(FLL) with different symmetries have been observed. One of the FLL transitions is coincident with a magnetic phase transition between two spin density waves. In this thesis additional SANS studies of the FLL phases in TmNi{sub 2}B{sub 2}C are reported and an interpretation of the phase diagram in the paramagnetic region is presented. It is suggested that the square FLL observed is stable in between two transition lines determined by two different length scales. The lower transition field is reached when the distance between the flux lines becomes comparable to the non-locality radius resulting from non-local electrodynamics, whereas the upper transition field is determined from the crossover from intermediate to high flux line density where the vortex cores start to overlap and the superconducting order parameter is suppressed in between the flux lines. A detailed examination of the intensity of the neutron diffraction spots caused by scattering on the flux line lattice in TmNi{sub 2}B{sub 2}C is presented and analyzed on the basis of the form factor of an isolated flux line. This analysis can not provide a good explanation for the observed scattering and it is suggested that the scattering from the Tm ions must be considered. One can argue that the moments of the Tm ions are modulated by the flux line lattice, because the Ruderman-Kittel- Kasuya-Yosida(RKKY) interaction between the Tm ions might be different inside the vortex cores than outside in the superconducting phase. A calculation of the neutron scattering cross section of such a magnetic flux line lattice has been performed and compared to the SANS data. This offers a qualitative explanation of some of the observations, but future work is needed to perform a more quantitative comparison. (au)
International Nuclear Information System (INIS)
Hebard, A.F.; Fiory, A.T.; Siegal, M.P.; Phillips, J.M.; Haddon, R.C.
1991-01-01
Low-field ac screening measurements on YBa 2 Cu 3 O 7-δ films and (BEDT-TTF) 2 Cu(SCN) 2 crystals [where BEDT-TTF is bis(ethylenedithio)tetrathiafulvalene], both thought to contain a high density of defects, reveal a diminution of screening and a common extrinsic temperature dependence of the screening length λ. Vortex-core pinning at the defects is shown to give a low-temperature T 2 power-law temperature dependence to λ that, in contrast to the exponential behavior expected from s-wave pairing, can be mistaken as evidence for lines or nodes of the energy gap on the Fermi surface
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...
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.
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.
Introduction to superconductivity
Darriulat, Pierre
1998-01-01
The lecture series will address physicists, such as particle and nuclear physicists, familiar with non-relativistic quantum mechanics but not with solid state physics. The aim of this introduction to low temperature superconductivity is to give sufficient bases to the student for him/her to be able to access the scientific literature on this field. The five lectures will cover the following topics : 1. Normal metals, free electron gas, chambers equation. 2. Cooper pairs, the BCS ground state, quasi particle excitations. 3. DC superconductivity, Meissner state, dirty superconductors.4. Self consistent approach, Ginsburg Landau equations, Abrikosov fluxon lattice. 5. Josephson effects, high temperature superconductivity.
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
The Josephson effect in atomic contacts; Effect Josephson dans les contacts atomiques
Energy Technology Data Exchange (ETDEWEB)
Chauvin, M
2005-11-15
The Josephson effect appears when a weak-link establishes phase coherence between two superconductors. A unifying theory of this effect emerged in the 90's within the framework of mesoscopic physics. Based on two cornerstone concepts, conduction channels and Andreev reflection, it predicts the current-phase relation for the most basic weak-link: a single conduction channel of arbitrary transmission. This thesis illustrates this mesoscopic point of view with experiments on superconducting atomic size contacts. In particular, we have focused on the supercurrent peak around zero voltage, put into evidence the ac Josephson currents in a contact under constant bias voltage (Shapiro resonances and photon assisted multiple Andreev reflections), and performed direct measurements of the current-phase relation. (author)
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.
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
Signatures of topological superconductivity
Energy Technology Data Exchange (ETDEWEB)
Peng, Yang
2017-07-19
The prediction and experimental discovery of topological insulators brought the importance of topology in condensed matter physics into the limelight. Topology hence acts as a new dimension along which more and more new states of matter start to emerge. One of these topological states of matter, namely topological superconductors, comes into the focus because of their gapless excitations. These gapless excitations, especially in one dimensional topological superconductors, are Majorana zero modes localized at the ends of the superconductor and exhibit exotic nonabelian statistics, which can be potentially applied to fault-tolerant quantum computation. Given their highly interesting physical properties and potential applications to quantum computation, both theorists and experimentalists spend great efforts to realize topological supercondoctors and to detect Majoranas. In two projects within this thesis, we investigate the properties of Majorana zero modes in realistic materials which are absent in simple theoretical models. We find that the superconducting proximity effect, an essential ingredient in all existing platforms for topological superconductors, plays a significant role in determining the localization property of the Majoranas. Strong proximity coupling between the normal system and the superconducting substrate can lead to strongly localized Majoranas, which can explain the observation in a recent experiment. Motivated by experiments in Molenkamp's group, we also look at realistic quantum spin Hall Josephson junctions, in which charge puddles acting as magnetic impurities are coupled to the helical edge states. We find that with this setup, the junction generically realizes an exotic 8π periodic Josephson effect, which is absent in a pristine Josephson junction. In another two projects, we propose more pronounced signatures of Majoranas that are accessible with current experimental techniques. The first one is a transport measurement, which uses
Resistive transition of superconducting-wire networks. Influence of pinning and fluctuations
International Nuclear Information System (INIS)
Giroud, M.; Buisson, O.; Wang, Y.Y.; Pannetier, B.; Mailly, D.
1992-01-01
The authors studied the resistive transition of several 2-D superconducting-wire networks of various coupling strengths, which they characterize in terms of the Kosterlitz-Thouless transition temperature and the ratio ξ/a of the coherence length to the array period. In the extreme strong-coupling limit where the mesh size is of the order of the zero-temperature coherence length, the superconducting behavior is well described by the mean-field properties of the superconducting wave function. Extending to 2-D array, the 1-D phase-slippage model explains the dissipative regime observed above the Ginzburg-Landau depairing critical current. On the other hand, when the coupling is weak, phase fluctuations below the Ginzburg-Landau transition and vortex depinning dominate the resistive behavior. An activated dissipation is observed even below the depairing critical current. Results obtained in this regime for critical temperature, magnetoresistance, or critical current versus temperature, and magnetic field are shown; their periodic oscillations are discussed in terms of depinning of vortices on the array. A simple periodic pinning potential for a vortex in a wire network is calculated, and compared with the case of pinning in Josephson junction arrays. It is shown that this model explains qualitatively the experimental results observed for small ξ/a
Second international Israeli conference on High Tc Superconductivity
International Nuclear Information System (INIS)
1993-01-01
The superconductivity fields covered in this conference are: theory, applications, devices, flux properties high frequencies, Josephson junctions, magnetism, material sciences and physical properties of superconductors, spectroscopy and resonances and thin films
Khan, Hasan; Gazit, Snir; Randeria, Mohit; Trivedi, Nandini
The superconductor-insulator transition (SIT) in two dimensions is a paradigm for quantum criticality that has been observed experimentally in Josephson junction arrays, superconducting thin films, and cold atoms trapped in an optical lattice. The conventional picture of the transition is in terms of the condensation of bosonic degrees of freedom (Cooper pairs in superconductors). Interestingly, the transition has a dual description, where the insulating phase is a Bose condensate of vortices. We study the SIT numerically by means of a large-scale quantum Monte Carlo (QMC) simulation in the vortex representation. This provides direct access to both the boson and vortex degrees of freedom and allows us to numerically test the duality and quantify deviations from self-duality. Our main focus is on critical properties such as the vortex and the boson phase stiffness. We compare our results to previous studies in the bosonic representation. We acknowledge support from Grant DOE-BES DE-FG02-07ER46423 (HK, NT).
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.
A. Xu; L. Delgado; N. Khatri; Y. Liu; V. Selvamanickam; D. Abraimov; J. Jaroszynski; F. Kametani; D. C. Larbalestier
2014-01-01
Applications of REBCO coated conductors are now being developed for a very wide range of temperatures and magnetic fields and it is not yet clear whether vortex pinning strategies aimed for high temperature, low field operation are equally valid at lower temperatures and higher fields. A detailed characterization of the superconducting properties of a 15 mol. % Zr-added REBCO thin film made by metal organic chemical vapor deposition, from 4.2 to 77 K under magnetic fields up to 31 T is presen...
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.
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)
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
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.
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.
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.
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).
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...
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.
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.
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
Quantum Computing Using Superconducting Qubits
2006-04-01
terahertz out-of-plane radiation using Josephson vortices in modulated layered superconductors ", Phys. Rev. B, in press (2005) 68. J.Q. You, J.S...Program Review, Florida, USA (2004) 95. F. Nor, " Terahertz generation and vortex motion control in superconductors ", 2005 APS March Meeting, Los Angeles...magnetic flux effects on superconductors . 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF 18. NUMBER 19a. NAME OF RESPONSIBLE PERSON a. REPORT b
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 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.
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
International Nuclear Information System (INIS)
Akerman, Johan J.; Venturini, E. L.; Siegal, M. P.; Yun, S. H.; Karlsson, U. O.; Rao, K. V.
2001-01-01
The thermal-to-quantum flux creep crossover at low vortex densities has been studied in YBa 2 Cu 3 O 7 , TlBa 2 CaCu 2 O 7-δ , and HgBa 2 CaCu 2 O 6+δ thin films using ac susceptibility. The crossover temperatures T cr are 10--11, 17, and 30 K, respectively. Both thermal and quantum flux creep is suppressed as the vortex density is decreased. We observe a two-stage nature in the crossover behavior which appears to be a general property of all the three materials studied
Directory of Open Access Journals (Sweden)
A. Xu
2014-04-01
Full Text Available Applications of REBCO coated conductors are now being developed for a very wide range of temperatures and magnetic fields and it is not yet clear whether vortex pinning strategies aimed for high temperature, low field operation are equally valid at lower temperatures and higher fields. A detailed characterization of the superconducting properties of a 15 mol. % Zr-added REBCO thin film made by metal organic chemical vapor deposition, from 4.2 to 77 K under magnetic fields up to 31 T is presented in this article. Even at a such high level of Zr addition, Tc depression has been avoided (Tc = 91 K, while at the same time an exceptionally high irreversibility field Hirr ≈ 14.8 T at 77 K and a remarkably high vortex pinning force density Fp ≈ 1.7 TN/m3 at 4.2 K have been achieved. We ascribe the excellent pinning performance at high temperatures to the high density (equivalent vortex matching field ∼7 T of self-assembled BZO nanorods, while the low temperature pinning force is enhanced by large additional pinning which we ascribe to strain-induced point defects induced in the REBCO matrix by the BZO nanorods. Our results suggest even more room for further performance enhancement of commercial REBCO coated conductors and point the way to REBCO coil applications at liquid nitrogen temperatures since the critical current density Jc(H//c characteristic at 77 K are now almost identical to those of fully optimized Nb-Ti at 4 K.
Energy Technology Data Exchange (ETDEWEB)
Xu, A; Delgado, L; Khatri, N; Liu, Y; Selvamanickam, V; Abraimov, D; Jaroszynski, J; Kametani, F; Larbalestier, DC
2014-04-01
Applications of REBCO coated conductors are now being developed for a very wide range of temperatures and magnetic fields and it is not yet clear whether vortex pinning strategies aimed for high temperature, low field operation are equally valid at lower temperatures and higher fields. A detailed characterization of the superconducting properties of a 15 mol.% Zr-added REBCO thin film made by metal organic chemical vapor deposition, from 4.2 to 77 K under magnetic fields up to 31 T is presented in this article. Even at a such high level of Zr addition, T-c depression has been avoided (T-c = 91 K), while at the same time an exceptionally high irreversibility field H-irr approximate to 14.8 T at 77 K and a remarkably high vortex pinning force density F-p approximate to 1.7 TN/m(3) at 4.2 K have been achieved. We ascribe the excellent pinning performance at high temperatures to the high density (equivalent vortex matching field similar to 7 T) of self-assembled BZO nanorods, while the low temperature pinning force is enhanced by large additional pinning which we ascribe to strain-induced point defects induced in the REBCO matrix by the BZO nanorods. Our results suggest even more room for further performance enhancement of commercial REBCO coated conductors and point the way to REBCO coil applications at liquid nitrogen temperatures since the critical current density J(c)(H//c) characteristic at 77 K are now almost identical to those of fully optimized Nb-Ti at 4 K. (C) 2014 Author(s).
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
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.
Akhmetov, D G
2009-01-01
This text on vortex rings covers their theoretical foundation, systematic investigations, and practical applications such as the extinction of fires at gushing oil wells. It pays special attention to the formation and motion of turbulent vortex rings.
The study of superconducting order parameter dynamics
International Nuclear Information System (INIS)
Goldman, A.M.
1988-01-01
Flux quantization experiments have demonstrated the importance of long range phase coherence in the description of the superconducting state, an idea originally proposed as an integral part of the phenomenological theory of the Meissner-Ochsenfeld effect. The most striking experimental demonstration of the phase coherence of the superconducting state is that the maximum dc Josephson current in a thin-film tunneling junction exhibits a Fraunhofer-like dependence on magnetic field
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.
Guarcello, Claudio; Solinas, Paolo; Braggio, Alessandro; Di Ventra, Massimiliano; Giazotto, Francesco
2018-01-01
We propose a superconducting thermal memory device that exploits the thermal hysteresis in a flux-controlled temperature-biased superconducting quantum-interference device (SQUID). This system reveals a flux-controllable temperature bistability, which can be used to define two well-distinguishable thermal logic states. We discuss a suitable writing-reading procedure for these memory states. The time of the memory writing operation is expected to be on the order of approximately 0.2 ns for a Nb-based SQUID in thermal contact with a phonon bath at 4.2 K. We suggest a noninvasive readout scheme for the memory states based on the measurement of the effective resonance frequency of a tank circuit inductively coupled to the SQUID. The proposed device paves the way for a practical implementation of thermal logic and computation. The advantage of this proposal is that it represents also an example of harvesting thermal energy in superconducting circuits.
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
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.
Emergent Higgsless Superconductivity
Directory of Open Access Journals (Sweden)
Cristina Diamantini M.
2017-01-01
Full Text Available We present a new Higgsless model of superconductivity, inspired from anyon superconductivity but P- and T-invariant and generalizable to any dimension. While the original anyon superconductivity mechanism was based on incompressible quantum Hall fluids as average field states, our mechanism involves topological insulators as average field states. In D space dimensions it involves a (D-1-form fictitious pseudovector gauge field which originates from the condensation of topological defects in compact lowenergy effective BF theories. There is no massive Higgs scalar as there is no local order parameter. When electromagnetism is switched on, the photon acquires mass by the topological BF mechanism. Although the charge of the gapless mode (2 and the topological order (4 are the same as those of the standard Higgs model, the two models of superconductivity are clearly different since the origins of the gap, reflected in the high-energy sectors are totally different. In 2D thi! s type of superconductivity is explicitly realized as global superconductivity in Josephson junction arrays. In 3D this model predicts a possible phase transition from topological insulators to Higgsless superconductors.
Energy Technology Data Exchange (ETDEWEB)
Akerman, Johan J.; Venturini, E. L.; Siegal, M. P.; Yun, S. H.; Karlsson, U. O.; Rao, K. V.
2001-09-01
The thermal-to-quantum flux creep crossover at low vortex densities has been studied in YBa{sub 2}Cu{sub 3}O{sub 7}, TlBa{sub 2}CaCu{sub 2}O{sub 7-{delta}}, and HgBa{sub 2}CaCu{sub 2}O{sub 6+{delta}} thin films using ac susceptibility. The crossover temperatures T{sub cr} are 10--11, 17, and 30 K, respectively. Both thermal and quantum flux creep is suppressed as the vortex density is decreased. We observe a two-stage nature in the crossover behavior which appears to be a general property of all the three materials studied.
Diamagnetism in quasicrystalline superconducting networks
International Nuclear Information System (INIS)
Qian Niu; Nori, F.
1990-01-01
In this paper, we review recent results on superconducting structures with quasicrystalline geometry. Specifically, we consider the superconducting-normal phase boundaries of a variety of wire networks and Josephson junction arrays. We have computed the mean field phase diagrams for a number of geometries and compared them to the corresponding experimental data. We have introduced an analytical approach to the analysis of the structures present in the phase boundaries. Furthermore, we have shown in great detail how the gross structure is determined by the statistical distributions of the cell areas, and how the fine structures are determined by correlations among neighboring cells in the lattices. (author). 12 refs, 2 figs
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
Three-dimensional superconductivity and vortex glass transition in La1.87Y0.13CuO4
International Nuclear Information System (INIS)
Lee, Hyun-Sook; Kim, Heon-Jung; Kim, Hyun-Jung; Jung, Myung-Hwa; Jo, Younghun; Lee, Sung-Ik; Tsukada, Akio; Naito, Michio
2006-01-01
The angular dependence of the critical current density (J c (θ)) and the vortex glass transition temperature (T g (θ)) in La 1.87 Y 0.13 CuO 4 were measured at different fields and temperatures. Both J c (θ) and T g (θ) showed a strong angular variation, which is typical for anisotropic superconductors. The angular variation could be described by using the anisotropic three-dimensional Ginzburg-Landau theory. From our analysis, we were able to estimate the anisotropy ratio
Hybrid superconducting-magnetic memory device using competing order parameters.
Baek, Burm; Rippard, William H; Benz, Samuel P; Russek, Stephen E; Dresselhaus, Paul D
2014-05-28
In a hybrid superconducting-magnetic device, two order parameters compete, with one type of order suppressing the other. Recent interest in ultra-low-power, high-density cryogenic memories has spurred new efforts to simultaneously exploit superconducting and magnetic properties so as to create novel switching elements having these two competing orders. Here we describe a reconfigurable two-layer magnetic spin valve integrated within a Josephson junction. Our measurements separate the suppression in the superconducting coupling due to the exchange field in the magnetic layers, which causes depairing of the supercurrent, from the suppression due to the stray magnetic field. The exchange field suppression of the superconducting order parameter is a tunable and switchable behaviour that is also scalable to nanometer device dimensions. These devices demonstrate non-volatile, size-independent switching of Josephson coupling, in magnitude as well as phase, and they may enable practical nanoscale superconducting memory devices.
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
2003-01-01
Understanding the nature of vortices in high-Tc superconductors is a crucial subject for research on superconductive electronics, especially for superconducting interference devices (SQUIDs), it is also a fundamental problem in condensed-matter physics. Recent technological progress in methods for both direct and indirect observation of vortices, e.g. scanning SQUID, terahertz imaging, and microwave excitation, has led to new insights into vortex physics, the dynamic behavior of vortices in junctions and related questions of noise. This book presents the current status of research activity and provides new information on the applications of SQUIDs, including magnetocardiography, immunoassays, and laser-SQUID microscopes, all of which are close to being commercially available.
Coherence properties in superconducting flux qubits
Energy Technology Data Exchange (ETDEWEB)
Spilla, Samuele
2015-02-16
The research work discussed in this thesis deals with the study of superconducting Josephson qubits. Superconducting qubits are solid-state artificial atoms which are based on lithographically defined Josephson tunnel junctions properties. When sufficiently cooled, these superconducting devices exhibit quantized states of charge, flux or junction phase depending on their design parameters. This allows to observe coherent evolutions of their states. The results presented can be divided into two parts. In a first part we investigate operations of superconducting qubits based on the quantum coherence in superconducting quantum interference devices (SQUID). We explain experimental data which has been observed in a SQUID subjected to fast, large-amplitude modifications of its effective potential shape. The motivations for this work come from the fact that in the past few years there have been attempts to interpret the supposed quantum behavior of physical systems, such as Josephson devices, within a classical framework. Moreover, we analyze the possibility of generating GHZ states, namely maximally entangled states, in a quantum system made out of three Josephson qubits. In particular, we investigate the possible limitations of the GHZ state generation due to coupling to bosonic baths. In the second part of the thesis we address a particular cause of decoherence of flux qubits which has been disregarded until now: thermal gradients, which can arise due to accidental non equilibrium quasiparticle distributions. The reason for these detrimental effects is that heat currents flowing through Josephson tunnel junctions in response to a temperature gradient are periodic functions of the phase difference between the electrodes. The phase dependence of the heat current comes from Andreev reflection, namely an interplay between the quasiparticles which carry heat and the superconducting condensate which is sensitive to the superconducting phase difference. Generally speaking
Applied superconductivity. Handbook on devices and applications. Vol. 1 and 2
Energy Technology Data Exchange (ETDEWEB)
Seidel, Paul (ed.) [Jena Univ. (Germany). Inst. fuer Festkoerperphysik, AG Tieftemperaturphysik
2015-07-01
The both volumes contain the following 12 chapters: 1. Fundamentals; 2. Superconducting Materials; 3. Technology, Preparation, and Characterization (bulk materials, thin films, multilayers, wires, tapes; cooling); 4, Superconducting Magnets; 5. Power Applications (superconducting cables, superconducting current leads, fault current limiters, transformers, SMES and flywheels; rotating machines; SmartGrids); 6. Superconductive Passive Devices (superconducting microwave components; cavities for accelerators; superconducting pickup coils; magnetic shields); 7. Applications in Quantum Metrology (superconducting hot electron bolometers; transition edge sensors; SIS Mixers; superconducting photon detectors; applications at Terahertz frequency; detector readout); 8. Superconducting Radiation and Particle Detectors; 9. Superconducting Quantum Interference (SQUIDs); 10. Superconductor Digital Electronics; 11. Other Applications (Josephson arrays as radiation sources. Tunable microwave devices) and 12. Summary and Outlook (of the superconducting devices).
DC Transformer and DC Josephson(-like) Effects in Quantum Hall Bilayers
Girvin, S. M.
2002-01-01
In the early days of superconductivity, Ivar Giaver discovered that it was possible to make a novel DC transformer by using one superconductor to drag vortices through another. An analogous effect was predicted to exist in quantum Hall bilayers and has recently been discovered experimentally by Eisenstein's group at Caltech. Similarly, new experiments from the Caltech group have demonstrated the existence of a Josephson-like `supercurrent' branch for electrons coherently tunnelling between th...
Derevyanko, V. V.; Sukhareva, T. V.; Finkel', V. A.
2018-03-01
The temperature dependences of the resistivity of granular high-temperature superconductor YBa2Cu3O7-δ ρ( T) are measured at various transverse external magnetic fields 0 ≤ H ext ≤ 100 Oe in the temperature range from the resistivity onset temperature T ρ = 0 to the superconducting transition critical temperature T c at the transport current density from 50 to 2000 mA/cm2. The effect of the external magnetic field and transport current density on the kinetics of phase transitions in both subsystems of granular two-level HTSC ( T = T c2J, T c1g, T c ) is determined. The feasibility of the topological phase transition, i.e., the Berezinsky-Kosterlitz-Thouless transition, in the Josephson medium at T c2J < T BKT < T c1g "in transport current" is established, and its feasibility conditions are studied.
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)
Rudner, Mark; Levitov, Leonid
2009-03-01
We analyze a quantum walk on a bipartite one-dimensional lattice, in which the particle can decay whenever it visits one of the two sublattices. The corresponding non-Hermitian tight-binding problem with complex potential for the decaying sites exhibits two distinct phases, distinguished by a winding number defined in terms of the Bloch eigenstates in the Brillouin zone [1]. We find that the mean displacement of a particle initially localized on one of the non-decaying sites is quantized as an integer, changing from zero to one at the critical point. By mapping this problem onto a Jaynes-Cummings-type model with decay, we find that the topological transition is relevant for a variety of experimental settings, in particular for superconducting qubits coupled to high quality resonators [2]. The quantized behavior stands in contrast with the smooth dependence expected for a classical random walk, and can serve as a hallmark of coherent quantum dynamics in ladder-like multilevel systems. A real-space implementation of the quantum walk may help to verify quantum coherence in vortex transport in Josephson arrays [3]. [1] M. S. Rudner, L. S. Levitov, arXiv:0807.2048. [2] A. Wallraff et al., Nature 431, 162-167 (2004). [3] A. van Oudenaarden, S. J. K. Vardy, and J. E. Mooij, Phys. Rev. Lett. 77, 4257 (1996).
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.
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).
Challenges to high-Tc superconductivity in cuprates by exploring condensate properties
Maeda, A.
2008-03-01
In this paper, I introduce recent our results on superconductivity fluctuation measurement of high-Tc cuprate both for the hole-doped La2-xSrxCuO4 (LSCO) and the electron-doped La2-xCexCuO4 (LCCO). In hole doped LSCO, the universality class was found to change twice as a function of doping, starting from the 2D-XY, changing to the 3D XY and another 2D 'unknown' behavior. The results favors theoretical interpretations of the phase diagram of high-Tc cuprate which assume the existence of an additional hidden quantum critical point around at the optimum doping. In electron doped cuprate, the superconductivity fluctuation is 3D XY for all samples with different hole doping, which is in sharp contrast to the hole doped cuprate. Thus, the asymmetry of the phase diagram between the hole doped and the electron doped materials is another important key factor to judge the applicability of various theories on high-Tc superconductivity. Under finite magnetic fields, the scaling relation was valid only for weak fields, and for higher fields, aspects as vortices appeared. However, even at low temperatures, just above the first order phase transition, vortex picture alone cannot describe the data satisfactory. Thus, we need a unified theory for the description of a large superconductivity fluctuation under finite magnetic fields for high-Tc cuprates. Finally, I showed that our novel technique of fabricating high-Tc Josephson bridge junction using a small island of Fe was turned out to be very promising.
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)
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
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).
Coherent suppression of quasiparticle dissipation in a superconducting artificial atom
Energy Technology Data Exchange (ETDEWEB)
Pop, Ioan [Physikalisches Institut, Karlsruhe Institute of Technology, 76131 Karlsruhe (Germany); Department of Applied Physics, Yale University, New Haven, CT 06520 (United States)
2016-07-01
We demonstrate immunity to quasiparticle dissipation in a Josephson junction. At the foundation of this protection rests a prediction by Brian Josephson from fifty years ago: the particle-hole interference of superconducting quasiparticles when tunneling across a Josephson junction. The junction under study is the central element of a fluxonium artificial atom, which we place in an extremely low loss environment and measure using radio-frequency dispersive techniques. Furthermore, by using a quantum limited amplifier (a Josephson Parametric Converter) we can observe quantum jumps between the 0 and 1 states of the qubit in thermal equilibrium with the environment. The distribution of the times in-between the quantum jumps reveals quantitative information about the population and dynamics of quasiparticles. The data is entirely consistent with the hypothesis that our system is sensitive to single quasiparticle excitations, which opens new perspectives for quasiparticle monitoring in low temperature devices.
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...
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...
Distinct magnetic signatures of fractional vortex configurations in multiband superconductors
Energy Technology Data Exchange (ETDEWEB)
Silva, R. M. da [Programa de Pós-Graduação em Ciência dos Materiais, Universidade Federal de Pernambuco, Av. Prof. Luiz Freire, s/n, 50670-901 Recife-PE (Brazil); Milošević, M. V.; Peeters, F. M. [Departement Fysica, Universiteit Antwerpen, Groenenborgerlaan 171, B-2020 Antwerpen (Belgium); Domínguez, D. [Centro Atómico Bariloche, 8400 San Carlos de Bariloche, Río Negro (Argentina); Aguiar, J. Albino, E-mail: albino@df.ufpe.br [Departamento de Física, Universidade Federal de Pernambuco, Av. Prof. Luiz Freire, s/n, 50670-901 Recife-PE (Brazil); Programa de Pós-Graduação em Ciência dos Materiais, Universidade Federal de Pernambuco, Av. Prof. Luiz Freire, s/n, 50670-901 Recife-PE (Brazil)
2014-12-08
Vortices carrying fractions of a flux quantum are predicted to exist in multiband superconductors, where vortex core can split between multiple band-specific components of the superconducting condensate. Using the two-component Ginzburg-Landau model, we examine such vortex configurations in a two-band superconducting slab in parallel magnetic field. The fractional vortices appear due to the band-selective vortex penetration caused by different thresholds for vortex entry within each band-condensate, and stabilize near the edges of the sample. We show that the resulting fractional vortex configurations leave distinct fingerprints in the static measurements of the magnetization, as well as in ac dynamic measurements of the magnetic susceptibility, both of which can be readily used for the detection of these fascinating vortex states in several existing multiband superconductors.
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.)
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.
Superconducting emitters of THz radiation
Energy Technology Data Exchange (ETDEWEB)
Welp, Ulrich; Kadowaki, Kazuo; Kleiner, Reinhold
2013-08-29
Layered superconductors such as the copper-oxide high-temperature superconductor Bi2Sr2CaCu2O8+δ are emerging as compact sources of coherent continuous-wave electromagnetic radiation in the subterahertz and terahertz frequency ranges. The basis of their operation is the Josephson effect, which intrinsically occurs between the superconducting layers. The Josephson effect naturally converts a direct-current voltage into a high-frequency electric current. Therefore, a unique property of the devices reviewed here is the wide tunability of their frequency by varying the bias voltage. Recently, emission powers of free-space radiation of several hundreds of microwatts and emission linewidths as low as 6 MHz at 600 GHz have been achieved. These devices are promising for new applications in imaging, medical diagnostics, spectroscopy and security.
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.)
Spontaneous symmetry breaking in vortex systems with two repulsive lengthscales.
Curran, P J; Desoky, W M; Milosević, M V; Chaves, A; Laloë, J-B; Moodera, J S; Bending, S J
2015-10-23
Scanning Hall probe microscopy (SHPM) has been used to study vortex structures in thin epitaxial films of the superconductor MgB2. Unusual vortex patterns observed in MgB2 single crystals have previously been attributed to a competition between short-range repulsive and long-range attractive vortex-vortex interactions in this two band superconductor; the type 1.5 superconductivity scenario. Our films have much higher levels of disorder than bulk single crystals and therefore both superconducting condensates are expected to be pushed deep into the type 2 regime with purely repulsive vortex interactions. We observe broken symmetry vortex patterns at low fields in all samples after field-cooling from above Tc. These are consistent with those seen in systems with competing repulsions on disparate length scales, and remarkably similar structures are reproduced in dirty two band Ginzburg-Landau calculations, where the simulation parameters have been defined by experimental observations. This suggests that in our dirty MgB2 films, the symmetry of the vortex structures is broken by the presence of vortex repulsions with two different lengthscales, originating from the two distinct superconducting condensates. This represents an entirely new mechanism for spontaneous symmetry breaking in systems of superconducting vortices, with important implications for pinning phenomena and high current density applications.
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}.
Electromagnetic Radiation from Vortex Flow in Type-II Superconductors
International Nuclear Information System (INIS)
Bulaevskii, L. N.; Chudnovsky, E. M.
2006-01-01
We show that a moving vortex lattice, as it comes to a crystal edge, radiates into a free space the harmonics of the washboard frequency, ω 0 =2πv/a, up to a superconducting gap, Δ/(ℎ/2π). Here v is the velocity of the vortex lattice and a is the intervortex spacing. We compute radiation power and show that this effect can be used for the generation of terahertz radiation and for characterization of moving vortex lattices
Electromagnetic radiation from vortex flow in type-II superconductors
Bulaevskii, L. N.; Chudnovsky, E. M.
2006-01-01
We show that a moving vortex lattice, as it comes to a crystal edge, radiates into a free space the harmonics of the washboard frequency, $\\omega_0=2\\pi v/a$, up to a superconducting gap, $\\Delta/\\hbar$. Here $v$ is the velocity of the vortex lattice and $a$ is the intervortex spacing. We compute radiation power and show that this effect can be used for generation of terahertz radiation and for characterization of moving vortex lattices.
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
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.)
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.
Influence of preparation conditions on superconducting properties of ...
Indian Academy of Sciences (India)
... large broadening of resistivity curve in magnetic field suggests that this phenomenon is directly related to the intrinsic superconducting properties of the copper oxide superconductors. The sudden drop in c at relatively low magnetic field ( < 0.5 tesla) is due to the effect of Josephson weak-links at the grain boundaries.
Vortex methods and vortex statistics
International Nuclear Information System (INIS)
Chorin, A.J.
1993-05-01
Vortex methods originated from the observation that in incompressible, inviscid, isentropic flow vorticity (or, more accurately, circulation) is a conserved quantity, as can be readily deduced from the absence of tangential stresses. Thus if the vorticity is known at time t = 0, one can deduce the flow at a later time by simply following it around. In this narrow context, a vortex method is a numerical method that makes use of this observation. Even more generally, the analysis of vortex methods leads, to problems that are closely related to problems in quantum physics and field theory, as well as in harmonic analysis. A broad enough definition of vortex methods ends up by encompassing much of science. Even the purely computational aspects of vortex methods encompass a range of ideas for which vorticity may not be the best unifying theme. The author restricts himself in these lectures to a special class of numerical vortex methods, those that are based on a Lagrangian transport of vorticity in hydrodynamics by smoothed particles (''blobs'') and those whose understanding contributes to the understanding of blob methods. Vortex methods for inviscid flow lead to systems of ordinary differential equations that can be readily clothed in Hamiltonian form, both in three and two space dimensions, and they can preserve exactly a number of invariants of the Euler equations, including topological invariants. Their viscous versions resemble Langevin equations. As a result, they provide a very useful cartoon of statistical hydrodynamics, i.e., of turbulence, one that can to some extent be analyzed analytically and more importantly, explored numerically, with important implications also for superfluids, superconductors, and even polymers. In the authors view, vortex ''blob'' methods provide the most promising path to the understanding of these phenomena
Superconductivity an introduction
Mangin, Philippe
2017-01-01
This book proposes a thorough introduction for a varied audience. The reader will master London theory and the Pippard equations, and go on to understand type I and type II superconductors (their thermodynamics, magnetic properties, vortex dynamics, current transport…), Cooper pairs and the results of BCS theory. By studying coherence and flux quantization he or she will be lead to the Josephson effect which, with the SQUID, is a good example of the applications. The reader can make up for any gaps in his knowledge with the use of the appendices, follow the logic behind each model, and assimilate completely the underlying concepts. Approximately 250 illustrations help in developing a thorough understanding. This volume is aimed towards masters and doctoral students, as well as advanced undergraduates, teachers and researchers at all levels coming from a broad range of subjects (chemistry, physics, mechanical and electrical engineering, materials science…). Engineers working in industry will have a useful ...
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
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
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.
An inhomogeneous Josephson phase in thin-film and high- Tc superconductors
Imry, Y.; Strongin, M.; Homes, C. C.
2008-02-01
In many cases inhomogeneities are known to exist near the metal (or superconductor)-insulator transition, as follows from well-known domain-wall arguments. If the conducting regions are large enough (i.e. when the T = 0 superconducting gap is much larger than the single-electron level spacing), and if they have superconducting correlations, it becomes energetically favorable for the system to go into a Josephson-coupled zero-resistance state before (i.e. at higher resistance than) becoming a “real” metal. We show that this is plausible by a simple comparison of the relevant coupling constants. For small grains in the above sense, the electronic grain structure is washed out by delocalization and thus becomes irrelevant. When the proposed “Josephson state” is quenched by a magnetic field, an insulating, rather than a metallic, state should appear. This has been shown [J. Tu, M. Strongin, Y. Imry, cond-mat/0405625 (2004)] to be consistent with the existing data on oxide materials as well as ultra-thin-films. We discuss the Uemura correlations versus Homes’ law, and derive the former for the large-grain Josephson array (inhomogenous superconductor) model. The small-grain case behaves like a dirty homogenous metal. It should obey Homes’ law provided that the system is in the dirty supeconductivity limit. A speculation as to why that is typically the case for d-wave superconductors is presented.
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 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
International Nuclear Information System (INIS)
1994-01-01
Thesis of reporsts of the 30th Conference on low-temperature physics are presented. Fundamental problems of superconductivity are discussed including HTSC in bulk crystals, in thin films of Josephson junctions, ceramics and heterostructures. Specific features of superconductor structure and magnetic properties and also different mechanisms of superconductivity are analyzed
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....
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...
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
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.
Newhouse, Vernon L
1975-01-01
Applied Superconductivity, Volume II, is part of a two-volume series on applied superconductivity. The first volume dealt with electronic applications and radiation detection, and contains a chapter on liquid helium refrigeration. The present volume discusses magnets, electromechanical applications, accelerators, and microwave and rf devices. The book opens with a chapter on high-field superconducting magnets, covering applications and magnet design. Subsequent chapters discuss superconductive machinery such as superconductive bearings and motors; rf superconducting devices; and future prospec
Transport properties in a superconducting proximity sandwich, Kondo effect
International Nuclear Information System (INIS)
Mori, N.
1981-01-01
Temperature-dependent properties are evaluated in a superconducting Kondo alloy induced by the proximity effect. These include (i) the order parameter, (ii) the dc Josephson current, and (iii) the thermal conductivity and ultrasonic attenuation, in the case when there is reentance of superconductivity. The calculations are based on the theory given by Kaiser, in which the McMillan tunneling model and the Mueller-Hartmann-Zittartz theory are combined. The temperature dependence of pair-breaking is reflected directly in the above properties in much the same way as in an intrinsic Kondo superconductor, indicating that proximity-effect studies may provide detailed information on the Kondo effect in superconductivity
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
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
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...
Coherence and Chaos Phenomena in Josephson Oscillators for Superconducting Electronics.
1989-01-25
Army through Contract No. DAJA- truzione (Italy). 45-85-C-0042, the Thomas B. Thriges Fond (Denmark), l’re~ent address: Istituto di Cibernetica del CNR...qiiesto articolo ai applica la teoria di ’Mclnikov per predire analiticarnonto la pre- seimi di caost (SmIale-horscghoc) inl uii pendolo cuitlutigliczza...Istituto di Cibernetica del Consiglio Na. 1 FFT2C routine, IMSL Inc., International Mathematical and zionale delle Ricerche, via Toiano 6, 1-80072
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
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.
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
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.
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?.
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
NATO Advanced Study Institute on Superconducting Electronics
Nisenhoff, Martin; Superconducting Electronics
1989-01-01
The genesis of the NATO Advanced Study Institute (ASI) upon which this volume is based, occurred during the summer of 1986 when we came to the realization that there had been significant progress during the early 1980's in the field of superconducting electronics and in applications of this technology. Despite this progress, there was a perception among many engineers and scientists that, with the possible exception of a limited number of esoteric fundamental studies and applications (e.g., the Josephson voltage standard or the SQUID magnetometer), there was no significant future for electronic systems incorporating superconducting elements. One of the major reasons for this perception was the aversion to handling liquid helium or including a closed-cycle helium liquefier. In addition, many critics felt that IBM's cancellation of its superconducting computer project in 1983 was "proof" that superconductors could not possibly compete with semiconductors in high-speed signal processing. From our persp...
Geometrically controlled ratchet effect with collective vortex motion
International Nuclear Information System (INIS)
Rouco, V; Palau, A; Obradors, X; Puig, T; Monton, C; Del-Valle, N; Navau, C; Sanchez, A
2015-01-01
Rectified flux motion arising from the collective effect of many interacting vortices is obtained in a specially designed superconducting device. Ratchet structures with different asymmetric pinning potentials are generated by tuning the size, depth, and distribution of triangular blind-antidots in a high-temperature superconducting film. We experimentally and theoretically demonstrate that the amplitude and sign of the rectified vortex motion can be finely tuned with the pattern geometry. Two different dynamical regimes depending on the nature of vortices initiating the dissipation are identified, which can control the rectified vortex motion. (paper)
Superconducting qubits can be coupled and addressed as trapped ions
Liu, Y. X.; Wei, L. F.; Johansson, J. R.; Tsai, J. S.; Nori, F.
2009-03-01
Exploiting the intrinsic nonlinearity of superconducting Josephson junctions, we propose a scalable circuit with superconducting qubits (SCQs) which is very similar to the successful one now being used for trapped ions. The SCQs are coupled to the ``vibrational'' mode provided by a superconducting LC circuit or its equivalent (e.g., a superconducting quantum interference device). Both single-qubit rotations and qubit-LC-circuit couplings and/or decouplings can be controlled by the frequencies of the time-dependent magnetic fluxes. The circuit is scalable since the qubit-qubit interactions, mediated by the LC circuit, can be selectively performed, and the information transfer can be realized in a controllable way. [4pt] Y.X. Liu, L.F. Wei, J.R. Johansson, J.S. Tsai, F. Nori, Superconducting qubits can be coupled and addressed as trapped ions, Phys. Rev. B 76, 144518 (2007). URL: http://link.aps.org/abstract/PRB/v76/e144518
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.
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....
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...
A cryogen-free dilution refrigerator based Josephson qubit measurement system
Tian, Ye; Yu, H. F.; Deng, H.; Xue, G. M.; Liu, D. T.; Ren, Y. F.; Chen, G. H.; Zheng, D. N.; Jing, X. N.; Lu, Li; Zhao, S. P.; Han, Siyuan
2012-03-01
We develop a small-signal measurement system on cryogen-free dilution refrigerator which is suitable for superconducting qubit studies. Cryogen-free refrigerators have several advantages such as less manpower for system operation and large sample space for experiment, but concern remains about whether the noise introduced by the coldhead can be made sufficiently low. In this work, we demonstrate some effective approaches of acoustic isolation to reduce the noise impact. The electronic circuit that includes the current, voltage, and microwave lines for qubit coherent state measurement is described. For the current and voltage lines designed to have a low pass of dc-100 kHz, we show that the measurements of Josephson junction's switching current distribution with a width down to 1 nA, and quantum coherent Rabi oscillation and Ramsey interference of the superconducting qubit can be successfully performed.
Adiabatic superconducting cells for ultra-low-power artificial neural networks
Directory of Open Access Journals (Sweden)
Andrey E. Schegolev
2016-10-01
Full Text Available We propose the concept of using superconducting quantum interferometers for the implementation of neural network algorithms with extremely low power dissipation. These adiabatic elements are Josephson cells with sigmoid- and Gaussian-like activation functions. We optimize their parameters for application in three-layer perceptron and radial basis function networks.
Perturbation theory of a superconducting 0−π impurity quantum phase transition
Czech Academy of Sciences Publication Activity Database
Žonda, M.; Pokorný, Vladislav; Janiš, Václav; Novotný, T.
2015-01-01
Roč. 5, Mar (2015), s. 8821 ISSN 2045-2322 R&D Projects: GA ČR GCP204/11/J042 Institutional support: RVO:68378271 Keywords : quantum dot * superconductivity * Josephson current * quantum phase transition * perturbation expansion Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 5.228, year: 2015
Czech Academy of Sciences Publication Activity Database
Yurchenko, Vitaliy; Jirsa, Miloš; Stupakov, Oleksandr; Wördenweber, R.
2005-01-01
Roč. 139, 1/2 (2005), s. 331-338 ISSN 0022-2291. [NATO Advanced Research Workshop. Yalta Crimea , 13.09.2004-17.09.2004] Institutional research plan: CEZ:AV0Z1010914 Keywords : superconducting thin films * antidots * vortex dynamics * vortex pinning * relaxation Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.753, year: 2005
Geneva University - Superconducting flux quantum bits: fabricated quantum objects
2007-01-01
Ecole de physique Département de physique nucléaire et corspusculaire 24, Quai Ernest-Ansermet 1211 GENEVE 4 Tél: (022) 379 62 73 Fax: (022) 379 69 92 Lundi 29 janvier 2007 COLLOQUE DE LA SECTION DE PHYSIQUE 17 heures - Auditoire Stueckelberg Superconducting flux quantum bits: fabricated quantum objects Prof. Hans Mooij / Kavli Institute of Nanoscience, Delft University of Technology The quantum conjugate variables of a superconductor are the charge or number of Cooper pairs, and the phase of the order parameter. In circuits that contain small Josephson junctions, these quantum properties can be brought forward. In Delft we study so-called flux qubits, superconducting rings that contain three small Josephson junctions. When a magnetic flux of half a flux quantum is applied to the loop, there are two states with opposite circulating current. For suitable junction parameters, a quantum superposition of those macroscopic states is possible. Transitions can be driven with resonant microwaves. These quantum ...
Electromagnetic radiation from vortex flow in Type-II superconductors.
Bulaevskii, L N; Chudnovsky, E M
2006-11-10
We show that a moving vortex lattice, as it comes to a crystal edge, radiates into a free space the harmonics of the washboard frequency, omega(0)=2pi v/a, up to a superconducting gap, Delta/variant Planck's over 2pi. Here v is the velocity of the vortex lattice and a is the intervortex spacing. We compute radiation power and show that this effect can be used for the generation of terahertz radiation and for characterization of moving vortex lattices.
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)
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)
Toward a superconducting quantum computer. Harnessing macroscopic quantum coherence.
Tsai, Jaw-Shen
2010-01-01
Intensive research on the construction of superconducting quantum computers has produced numerous important achievements. The quantum bit (qubit), based on the Josephson junction, is at the heart of this research. This macroscopic system has the ability to control quantum coherence. This article reviews the current state of quantum computing as well as its history, and discusses its future. Although progress has been rapid, the field remains beset with unsolved issues, and there are still many new research opportunities open to physicists and engineers.
Review of 2D superconductivity: the ultimate case of epitaxial monolayers
Brun, Christophe; Cren, Tristan; Roditchev, Dimitri
2017-01-01
order to illustrate their specific properties related to quantum-size effects. In the next section 3 we review the growth methods and structural properties of the presented 2DEG surface-confined superconductors. In section 4, we review the electronic structure and Fermi surface properties as measured by macroscopic ARPES and confront them to ab initio DFT calculations based on the characterized atomic structures of the monolayers. The following section 5 reviews the macroscopic properties inferred from in situ electrical transport measurements methods, including attempts to study the Berezinsky-Kosterlitz-Thouless 2D regime. In the last section 6, we summarize the emerging local spectroscopic properties measured by STS. These latter demonstrate variations of the local superconducting properties at a scale much shorter than the superconducting coherence length due to a combined effect of non-magnetic disorder and two-dimensionality. Further peculiar local spectroscopic effects are presented giving evidence for the presence of a mixed singlet-triplet superconducting order parameter induced by the presence of a strong Rashba spin-orbit coupling term at the surface. These local signatures will be discussed along with ARPES and transport measurements in parallel high magnetic field on closely related systems. Finally, we present in anisotropic Pb and In monolayers the peculiar role played by atomic steps on vortex properties, leading to the observation by STS of mixed Abrikosov-Josephson vortices in agreement with in situ macroscopic transport measurements. From the overview of all recent experimental and theoretical results it appears that these surface 2D superconductors, such as one monolayer of Pb on Si(111), are ideal templates to engineer and realize topological superconductivity.
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...
Phase locking between Josephson soliton oscillators
DEFF Research Database (Denmark)
Holst, T.; Hansen, Jørn Bindslev; Grønbech-Jensen, N.
1990-01-01
We report observations of phase-locking phenomena between two Josephson soliton (fluxon) oscillators biased in self-resonant modes. The locking strength was measured as a function of bias conditions. A frequency tunability of the phase-locked oscillators up to 7% at 10 GHz was observed. Two coupled...
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.
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.
Black-Box Superconducting Circuit Quantization
Nigg, Simon E.; Paik, Hanhee; Vlastakis, Brian; Kirchmair, Gerhard; Shankar, S.; Frunzio, Luigi; Devoret, M. H.; Schoelkopf, R. J.; Girvin, S. M.
2012-06-01
We present a semiclassical method for determining the effective low-energy quantum Hamiltonian of weakly anharmonic superconducting circuits containing mesoscopic Josephson junctions coupled to electromagnetic environments made of an arbitrary combination of distributed and lumped elements. A convenient basis, capturing the multimode physics, is given by the quantized eigenmodes of the linearized circuit and is fully determined by a classical linear response function. The method is used to calculate numerically the low-energy spectrum of a 3D transmon system, and quantitative agreement with measurements is found.
Josephson frequency meter for millimeter and submillimeter wavelengths
International Nuclear Information System (INIS)
Anischenko, S.E.; Larkin, S.Y.; Chaikovsky, V.I.
1994-01-01
Frequency measurements of electromagnetic oscillations of millimeter and submillimeter wavebands with frequency growth due to a number of reasons become more and more difficult. First, these frequencies are considered to be cutoff for semiconductor converting devices and one has to use optical measurement methods instead of traditional ones with frequency transfer. Second, resonance measurement methods are characterized by using relatively narrow bands and optical ones are limited in frequency and time resolution due to the limited range and velocity of movement of their mechanical elements as well as the efficiency of these optical techniques decreases with the increase of wavelength due to diffraction losses. That requires the apriori information on the radiation frequency band of the source involved. Method of measuring frequency of harmonic microwave signals in millimeter and submillimeter wavebands based on the ac Josephson effect in superconducting contacts is devoid of all the above drawbacks. This approach offers a number of major advantages over the more traditional measurement methods, that is the one based on frequency conversion, resonance and interferrometric techniques. It can be characterized by high potential accuracy, wide range of frequencies measured, prompt measurement and the opportunity to obtain panoramic display of the results as well as full automation of the measuring process
Foley, C. P.
2007-11-01
The main theme at ISEC 2007 for superconducting materials, fabrication and analogue electronics was the description of incremental developments, including a few new directions that indicate breakthroughs in this area of research. The work on applications focused on their cost-benefit analysis (in order to improve their appeal), the development of simpler systems, making more of the data collected, improving packaging and being responsive to the power handling requirements for commercial systems. All papers presenting this level of research highlighted the importance of obtaining all the necessary details in order to investigate analogue devices and the effectiveness and commercial viability of their systems. This stage of development is important if we are to achieve the transition of superconducting electronics from the laboratory to commercial use. There were some exciting disruptive breakthroughs reported. These were in the areas of nano-SQUIDs, rotating gradiometers, superconducting scanning tunnelling microscopy (Hayashi et al) and the potential of superconducting photonics using optical interfaces with superconducting vortex flow transistors, for example. The materials research in low (LTS), high (HTS) and medium (MTS) critical temperature superconductors was reported. In LTS, nitrides emerged as important materials for use as new tunnel barriers, either insulating or semiconducting. Papers on BaN, NbN, TaN, GaN and Nb-Si superconducting materials were also presented. The MTS material of MgB2 is still under development (Zhao et al). There were also new research groups from South Africa and Turkey attending the conference. The fabrication research presented covered the areas of critical current Ic spread, which is still an issue in reducing the reproducibility of Josephson junctions, a 150 mm process for Nb/Al-AlOx/Nb and methods to improve barrier layers using both new materials and smooth surfaces at thin film interfaces (Du et al). New methods to make sub
Localized excitations in superconducting point contacts: probing the Andreev doublet
International Nuclear Information System (INIS)
Bretheau, L.
2013-01-01
The Josephson effect describes the coherent coupling between superconductors and the resulting supercurrent. Microscopically, it arises from the existence of discrete quasiparticle states, localized at the weak link, the Andreev bound states. They come in doublets in each conduction channel of the weak link, with energies symmetric about the Fermi energy and opposite supercurrents. Each Andreev doublet gives rise to four states: the ground state |-> and the excited state |+>, with even parity, and the excited odd states |↑> and |↓>. Is it possible to address and control Andreev doublets? This thesis describes two sets of experiments designed to answer this question using the most basic Josephson element, a one-atom contact between two superconducting electrodes. In a first experiment, we have observed and characterized the excited odd states |↑> and |↓>. As expected for a spin-degenerate system, they do not carry supercurrent. In this experiment the excitation was uncontrolled and resulted from trapping of spurious quasiparticles. We have measured the lifetime of the odd states: under some condition, it is found to exceed 100 μs. The second experiment is a photon-absorption spectroscopy of the Andreev doublet. It was performed by using a Josephson junction as an integrated on-chip microwave emitter and detector. The observed Andreev transitions correspond to excitation from the ground state |->to the excited even state |+>, and are well accounted for by our quantum model. This result opens the way to coherent manipulation of this two level system. The direct observation of the excited Andreev state, either by quasiparticle-injection or photon-absorption, strongly supports the mesoscopic theory of the Josephson effect. It shows that in addition to the phase difference, each channel of a Josephson weak link possesses an internal fermionic degree of freedom. It could be used to code information in a novel type of superconducting qubit. (author) [fr
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
Spontaneous vortex phase (SVP) of ruthenocuprate high Tc ...
Indian Academy of Sciences (India)
RuSr2(RE1.5Ce0.5)Cu2O10, has given rise to the concept of spontaneous vortex phase (SVP). In these compounds, the magnetic ordering temperature (Tmag >. 100 K) is higher than the superconducting transition temperature (Tc ~ 30 K). Hence, due to internal magnetic fields, these compounds remain in a spontaneous.
Spontaneous vortex phase (SVP) of ruthenocuprate high Tc ...
Indian Academy of Sciences (India)
plots show that both the superconducting and ferromagnetic components are present in the compound at 5 K. At low temperatures, the compound though remains in spontaneous vortex phase, its vs. hysteresis loop is symmetric instead of the theoretically expected asymmetric one. Our results cast doubts on either ...
Freilich, Daniel; Llewellyn Smith, Stefan
2014-11-01
A Sadovskii vortex is a patch of fluid with uniform vorticity surrounded by a vortex sheet. Using a boundary element type method, we investigate the steady states of this flow in an incompressible, inviscid straining flow. Outside the vortex, the fluid is irrotational. In the limiting case where the entire circulation is due to the vortex patch, this is a patch vortex (Moore & Saffman, Aircraft wake turbulence and its detection 1971). In the other limiting case, where all the circulation is due to the vortex sheet, this is a hollow vortex (Llewellyn Smith and Crowdy, J. Fluid Mech. 691, 2012). This flow has two governing nondimensional parameters, relating the strengths of the straining field, vortex sheet, and patch vorticity. We study the relationship between these two parameters, and examine the shape of the resulting vortices. We also work towards a bifurcation diagram of the steady states of the Sadovskii vortex in an attempt to understand the connection between vortex sheet and vortex patch desingularizations of the point vortex. Support from NSF-CMMI-0970113.
Observation of Caroli-de Gennes-Matricon Vortex States in YBa2Cu3O7 -δ
Berthod, Christophe; Maggio-Aprile, Ivan; Bruér, Jens; Erb, Andreas; Renner, Christoph
2017-12-01
The copper oxides present the highest superconducting temperature and properties at odds with other compounds, suggestive of a fundamentally different superconductivity. In particular, the Abrikosov vortices fail to exhibit localized states expected and observed in all clean superconductors. We have explored the possibility that the elusive vortex-core signatures are actually present but weak. Combining local tunneling measurements with large-scale theoretical modeling, we positively identify the vortex states in YBa2Cu3O7 -δ . We explain their spectrum and the observed variations thereof from one vortex to the next by considering the effects of nearby vortices and disorder in the vortex lattice. We argue that the superconductivity of copper oxides is conventional, but the spectroscopic signature does not look so because the superconducting carriers are a minority.
Vortex profiles and vortex interactions at the electroweak crossover
Chernodub, M. N.; Ilgenfritz, E. -M.; Schiller, A.
1999-01-01
Local correlations of Z-vortex operators with gauge and Higgs fields (lattice quantum vortex profiles) as well as vortex two-point functions are studied in the crossover region near a Higgs mass of 100 GeV within the 3D SU(2) Higgs model. The vortex profiles resemble certain features of the classical vortex solutions in the continuum. The vortex-vortex interactions are analogous to the interactions of Abrikosov vortices in a type-I superconductor.
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.)
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)
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
Towards a 16 kilobit, subnanosecond Josephson RAM
International Nuclear Information System (INIS)
Herr, Q.P.; Eaton, L.
1999-01-01
A critical component of ultrahigh-speed Josephson logic systems is compatible memory. We are developing a fast Josephson memory that could be used as a small memory or first-level cache. Performance goals include sub-ns access and cycle time, 16 kbit cm -2 integration scale, low power consumption and appreciable yield. Initial test results on circuits fabricated in TRW's standard Nb integrated circuit process indicate that all these goals may be achieved. A 5 bit parallel decoder and 1 kbit memory array have been tested at 0.5 GHz. The maximum operating frequency of the memory array was limited by the test equipment. Circuit density is consistent with 16 kbit cm -2 . The top-level architecture has been chosen to achieve high throughput and low skew. The architecture is word organized, multiported and interleaved. (author)
Phase-locked Josephson soliton oscillators
DEFF Research Database (Denmark)
Holst, T.; Hansen, Jørn Bindslev; Grønbech-Jensen, N.
1991-01-01
Detailed experimental characterization of the phase-locking at both DC and at microwave frequencies is presented for two closely spaced Josephson soliton (fluxon) oscillators. In the phase-locked state, the radiated microwave power exhibited an effective gain. With one common bias source, a frequ......Detailed experimental characterization of the phase-locking at both DC and at microwave frequencies is presented for two closely spaced Josephson soliton (fluxon) oscillators. In the phase-locked state, the radiated microwave power exhibited an effective gain. With one common bias source......, a frequency tunability of the phase-locked oscillators up to 7% at 10 GHz was observed. The interacting soliton oscillators were modeled by two inductively coupled nonlinear transmission lines...
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...
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...
Dougherty, Ralph
2013-01-01
While the macroscopic phenomenon of superconductivity is well known and in practical use worldwide in many industries, including MRIs in medical diagnostics, the current theoretical paradigm for superconductivity (BCS theory) suffers from a number of limitations, not the least of which is an adequate explanation of high temperature superconductivity. This book reviews the current theory and its limitations and suggests new ideas and approaches in addressing these issues. The central objective of the book is to develop a new, coherent, understandable theory of superconductivity directly based on molecular quantum mechanics.
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....
The North American Josephson Voltage Interlaboratory Comparison
Energy Technology Data Exchange (ETDEWEB)
Parks, Harold V. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Tang, Yi-hua [National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States); Reese, Paul [Bionetics Corporation, Patrick Air Force Base, Brevard County, FL (United States); Gust, Jeff [Fluke Corporation, Everett, WA (United States); Novak, James J. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)
2013-01-23
The ninth North American Josephson voltage standard (JVS) interlaboratory comparison (ILC) at 10 V was completed in 2011. An on-site comparison was conducted between the National Institute of Standards and Technology compact JVS and the pivot laboratory system. A set of four traveling Zener voltage standards was then shipped from the pivot laboratory to the other participants. Here, we give the results from the 2011 ILC and review recent comparisons which have used the same traveling standards and similar procedures.
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...
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.
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.
Why superconducting vortices follow to moving hot sport?
Sergeev, Andrei; Michael, Reizer
Recent experiments reported in Nature Comm. 7, 12801, 2016 show that superconducting vortices follow to the moving hot sport created by a focused laser beam, i.e. vortices move from the cold area to the moving hot area. This behavior is opposite to the vortex motion observed in numerous measurements of the vortex Nernst effect, where vortices always move against the temperature gradient. Taking into account that superconducting magnetization currents do not transfer entropy, we analyze the balance of forces acting on a vortex in stationary and dynamic temperature gradients. We show that the dynamic measurements may be described by a single vortex approximation, while in stationary measurements interaction between vortices is critical. Supported by NRC.
Strong enhancement of superconductivity in a nanosized Pb bridge
Misko, V. R.; Fomin, V. M.; Devreese, J. T.
2001-07-01
In recent experiments with a superconducting nanosized Pb bridge formed between a scanning tunneling microscope tip and a substrate, superconductivity has been detected at magnetic fields, that are a few times larger than the third (surface) critical field. We describe the observed phenomenon on the basis of a numerical solution of the Ginzburg-Landau equations in a model structure consisting of six conoids. The spatial distribution of the superconducting phase is shown to be strongly inhomogeneous, with a concentration of the superconducting phase near the narrowest part (the ``neck'') of the bridge. We show that suppression of superconductivity in the bridge by applied magnetic field or by temperature first occurs near the bases and then in the neck region, what leads to a continuous superconducting-to-normal resistive transition. A position of the transition midpoint depends on temperature and, typically, is by one order of magnitude higher than the second critical field Hc2. We find that the vortex states can be realized in the bridge at low temperatures T/Tc<=0.6. The vortex states lead to a fine structure of the superconducting-to-normal resistive transition. We also analyze vortex states in the bridge that are characterized by a varying vorticity as a function of the bridge's height.
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
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.
Phase-preserving amplification near the quantum limit with a Josephson ring modulator.
Bergeal, N; Schackert, F; Metcalfe, M; Vijay, R; Manucharyan, V E; Frunzio, L; Prober, D E; Schoelkopf, R J; Girvin, S M; Devoret, M H
2010-05-06
Recent progress in solid-state quantum information processing has stimulated the search for amplifiers and frequency converters with quantum-limited performance in the microwave range. Depending on the gain applied to the quadratures of a single spatial and temporal mode of the electromagnetic field, linear amplifiers can be classified into two categories (phase sensitive and phase preserving) with fundamentally different noise properties. Phase-sensitive amplifiers use squeezing to reduce the quantum noise, but are useful only in cases in which a reference phase is attached to the signal, such as in homodyne detection. A phase-preserving amplifier would be preferable in many applications, but such devices have not been available until now. Here we experimentally realize a proposal for an intrinsically phase-preserving, superconducting parametric amplifier of non-degenerate type. It is based on a Josephson ring modulator, which consists of four Josephson junctions in a Wheatstone bridge configuration. The device symmetry greatly enhances the purity of the amplification process and simplifies both its operation and its analysis. The measured characteristics of the amplifier in terms of gain and bandwidth are in good agreement with analytical predictions. Using a newly developed noise source, we show that the upper bound on the total system noise of our device under real operating conditions is three times the quantum limit. We foresee applications in the area of quantum analog signal processing, such as quantum non-demolition single-shot readout of qubits, quantum feedback and the production of entangled microwave signal pairs.
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.
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.
Qubit lattice coherence induced by electromagnetic pulses in superconducting metamaterials.
Ivić, Z; Lazarides, N; Tsironis, G P
2016-07-12
Quantum bits (qubits) are at the heart of quantum information processing schemes. Currently, solid-state qubits, and in particular the superconducting ones, seem to satisfy the requirements for being the building blocks of viable quantum computers, since they exhibit relatively long coherence times, extremely low dissipation, and scalability. The possibility of achieving quantum coherence in macroscopic circuits comprising Josephson junctions, envisioned by Legett in the 1980's, was demonstrated for the first time in a charge qubit; since then, the exploitation of macroscopic quantum effects in low-capacitance Josephson junction circuits allowed for the realization of several kinds of superconducting qubits. Furthermore, coupling between qubits has been successfully achieved that was followed by the construction of multiple-qubit logic gates and the implementation of several algorithms. Here it is demonstrated that induced qubit lattice coherence as well as two remarkable quantum coherent optical phenomena, i.e., self-induced transparency and Dicke-type superradiance, may occur during light-pulse propagation in quantum metamaterials comprising superconducting charge qubits. The generated qubit lattice pulse forms a compound "quantum breather" that propagates in synchrony with the electromagnetic pulse. The experimental confirmation of such effects in superconducting quantum metamaterials may open a new pathway to potentially powerful quantum computing.
Hydrodynamic Vortex on Surfaces
Ragazzo, Clodoaldo Grotta; de Barros Viglioni, Humberto Henrique
2017-10-01
The equations of motion for a system of point vortices on an oriented Riemannian surface of finite topological type are presented. The equations are obtained from a Green's function on the surface. The uniqueness of the Green's function is established under hydrodynamic conditions at the surface's boundaries and ends. The hydrodynamic force on a point vortex is computed using a new weak formulation of Euler's equation adapted to the point vortex context. An analogy between the hydrodynamic force on a massive point vortex and the electromagnetic force on a massive electric charge is presented as well as the equations of motion for massive vortices. Any noncompact Riemann surface admits a unique Riemannian metric such that a single vortex in the surface does not move ("Steady Vortex Metric"). Some examples of surfaces with steady vortex metric isometrically embedded in R^3 are presented.
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.
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.
Terahertz Generation & Vortex Motion Control in Superconductors
Nori, Franco
2005-03-01
A grand challenge is to controllably generate electromagnetic waves in layered superconducting compounds because of its Terahertz frequency range. We propose [1] four experimentally realizable devices for generating continuous and pulsed THz radiation in a controllable frequency range. We also describe [2-4] several novel devices for controlling the motion of vortices in superconductors, including a reversible rectifier made of a magnetic-superconducting hybrid structure [4]. Finally, we summarize a study [5] of the friction force felt by moving vortices. 1) S. Savel'ev, V. Yampol'skii, A. Rakhmanov, F. Nori, Tunable Terahertz radiation from Josephson vortices, preprint 2) S. Savel'ev and F. Nori, Experimentally realizable devices for controlling the motion of magnetic flux quanta, Nature Mat. 1, 179 (2002) 3) S. Savel'ev, F. Marchesoni, F. Nori, Manipulating small particles, PRL 92, 160602 (2004); B. Zhu, F. Marchesoni, F. Nori, Controlling the motion of magnetic flux quanta, PRL 92, 180602 (2004) 4) J.E. Villegas, et al., Reversible Rectifier that Controls the Motion of Magnetic Flux Quanta, Science 302, 1188 (2003) 5) A. Maeda, et al., Nano-scale friction: kinetic friction of magnetic flux quanta and charge density waves, preprint
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.
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)
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.
Xue, C.; Ge, J.-Y.; He, A.; Zharinov, V. S.; Moshchalkov, V. V.; Zhou, Y. H.; Silhanek, A. V.; Van de Vondel, J.
2017-07-01
We investigate the degeneracy of the superconducting vortex matter ground state by directly visualizing the vortex configurations in a kagome lattice of elongated antidots via scanning Hall probe microscopy. The observed vortex patterns, at specific applied magnetic fields, are in good agreement with the configurations obtained using time-dependent Ginzburg-Landau simulations. Both results indicate that the long-range interaction in this nanostructured superconductor is unable to lift the degeneracy between different vortex states and the pattern formation is mainly ruled by the nearest-neighbor interaction. This simplification makes it possible to identify a set of simple rules characterizing the vortex configurations. We demonstrate that these rules can explain both the observed vortex distributions and the magnetic-field-dependent degree of degeneracy.
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)
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.)
Vortex cutting in superconductors
Vlasko-Vlasov, Vitalii K.; Koshelev, Alexei E.; Glatz, Andreas; Welp, Ulrich; Kwok, Wai-K.
2015-03-01
Unlike illusive magnetic field lines in vacuum, magnetic vortices in superconductors are real physical strings, which interact with the sample surface, crystal structure defects, and with each other. We address the complex and poorly understood process of vortex cutting via a comprehensive set of magneto-optic experiments which allow us to visualize vortex patterns at magnetization of a nearly twin-free YBCO crystal by crossing magnetic fields of different orientations. We observe a pronounced anisotropy in the flux dynamics under crossing fields and the filamentation of induced supercurrents associated with the staircase vortex structure expected in layered cuprates, flux cutting effects, and angular vortex instabilities predicted for anisotropic superconductors. At some field angles, we find formation of the vortex domains following a type-I phase transition in the vortex state accompanied by an abrupt change in the vortex orientation. To clarify the vortex cutting scenario we performed time-dependent Ginzburg-Landau simulations, which confirmed formation of sharp vortex fronts observed in the experiment and revealed a left-handed helical instability responsible for the rotation of vortices. This work was supported by the U.S. Department of Energy, Office of Science, Materials Sciences and Engineering Division.
International Nuclear Information System (INIS)
Jerome, D.
1980-01-01
We present the experimental evidences for the existence of a superconducting state in the Quasi One Dimensional organic conductor (TMTSF) 2 PF 6 . Superconductivity occuring at 1 K under 12 kbar is characterized by a zero resistance diamagnetic state. The anistropy of the upper critical field of this type II superconductor is consistent with the band structure anistropy. We present evidences for the existence of large superconducting precursor effects giving rise to a dominant paraconductive contribution below 40 K. We also discuss the anomalously large pressure dependence of T sb(s), which drops to 0.19 K under 24 kbar in terms of the current theories. (author)
Vortex Flipping in Superconductor-Ferromagnet Spin Valve Structures
Patino, Edgar J.; Aprili, Marco; Blamire, Mark; Maeno, Yoshiteru
2014-03-01
We report in plane magnetization measurements on Ni/Nb/Ni/CoO and Co/Nb/Co/CoO spin valve structures with one of the ferromagnetic layers pinned by an antiferromagnetic layer. In samples with Ni, below the superconducting transition Tc, our results show strong evidence of vortex flipping driven by the ferromagnets magnetization. This is a direct consequence of proximity effect that leads to vortex supercurrents leakage into the ferromagnets. Here the polarized electron spins are subject to vortices magnetic field occasioning vortex flipping. Such novel mechanism has been made possible for the first time by fabrication of the F/S/F/AF multilayered spin valves with a thin-enough S layer to barely confine vortices inside as well as thin-enough F layers to align and control the magnetization within the plane. When Co is used there is no observation of vortex flipping effect. This is attributed to Co shorter coherence length. Interestingly instead a reduction in pinning field of about 400 Oe is observed when the Nb layer is in superconducting state. This effect cannot be explained in terms of vortex fields. In view of these facts any explanation must be directly related to proximity effect and thus a remarkable phenomenon that deserves further investigation. Programa Nacional de Ciencias Basicas COLCIENCIAS (No. 120452128168).
Vortex-antivortex patterns in mesoscopic superconductors
International Nuclear Information System (INIS)
Teniers, Gerd; Moshchalkov, V.V.; Chibotaru, L.F.; Ceulemans, Arnout
2003-01-01
We have studied the nucleation of superconductivity in mesoscopic structures of different shape (triangle, square and rectangle). This was made possible by using an analytical gauge transformation for the vector potential A which gives A n =0 for the normal component along the boundary line of the rectangle. As a consequence the superconductor-vacuum boundary condition reduces to the Neumann boundary condition. By solving the linearized Ginzburg-Landau equation with this boundary condition we have determined the field-temperature superconducting phase boundary and the corresponding vortex patterns. The comparison of these patterns for different structures demonstrates that the critical parameters of a superconductor can be manipulated and fine-tuned through nanostructuring
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...
Line width of Josephson flux flow oscillators
DEFF Research Database (Denmark)
Koshelets, V.P.; Dmitriev, P.N.; Sobolev, A.S.
2002-01-01
spacing of about 20 nV and extremely low differential resistance, recently observed in the IVC of the standard rectangular geometry. The obtained results have been compared with existing theories and FFO models in order to understand and possibly eliminate excess noise in the FFO. The intrinsic line width...... increases considerably at voltages above the boundary voltage because of the abrupt increase of the internal damping due to Josephson self-coupling. The influence of FFO parameters, in particular the differential resistances associated both with the bias current and with the applied magnetic field...
A Josephson ternary associative memory cell
International Nuclear Information System (INIS)
Morisue, M.; Suzuki, K.
1989-01-01
This paper describes a three-valued content addressable memory cell using a Josephson complementary ternary logic circuit named as JCTL. The memory cell proposed here can perform three operations of searching, writing and reading in ternary logic system. The principle of the memory circuit is illustrated in detail by using the threshold-characteristics of the JCTL. In order to investigate how a high performance operation can be achieved, computer simulations have been made. Simulation results show that the cycle time of memory operation is 120psec, power consumption is about 0.5 μW/cell and tolerances of writing and reading operation are +-15% and +-24%, respectively
International Nuclear Information System (INIS)
Bollinger, L.M.; Shepard, K.W.; Wangler, T.P.
1978-01-01
This project has two goals: to design, build, and test a small superconducting linac to serve as an energy booster for heavy ions from an FN tandem electrostatic accelerator, and to investigate various aspects of superconducting rf technology. The main design features of the booster are described, a status report on various components (resonators, rf control system, linac control system, cryostats, buncher) is given, and plans for the near future are outlined. Investigations of superconducting-linac technology concern studies on materials and fabrication techniques, resonator diagnostic techniques, rf-phase control, beam dynamics computer programs, asymmetry in accelerating field, and surface-treatment techniques. The overall layout of the to-be-proposed ATLAS, the Argonne Tandem-Linac Accelerator System, is shown; the ATLAS would use superconducting technology to produce beams of 5 to 25 MeV/A. 6 figures
International Nuclear Information System (INIS)
Kormann, R.; Loiseau, R.; Marcilhac, B.
1989-01-01
The invention concerns superconducting ceramics containing essentially barium, calcium and copper fluorinated oxides with close offset and onset temperatures around 97 K and 100 K and containing neither Y nor rare earth [fr
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
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.
Strand, J. D.; Bahr, D. J.; van Harlingen, D. J.; Davis, J. P.; Gannon, W. J.; Halperin, W. P.
2010-03-01
The heavy fermion superconductor UPt3 provides a rich system for studying the competition between superconductivity and other forms of electronic order because it has an unconventional pairing mechanism, coexistence of anti-ferromagnetism and superconductivity, and two distinct superconducting phases characterized by different order parameter symmetries. We have fabricated Josephson tunnel junctions on the as-grown surfaces of UPt3 single crystals at a series of angles in the basal plane. By measuring their critical current, we map out the magnitude of the superconducting order parameter as a function of k-space direction and temperature. We observe a sharp node in the superconducting gap at 45^o with respect to the a-axis in the high temperature phase and the onset of an out-of-phase component creating a complex order parameter in the low temperature phase.
DEFF Research Database (Denmark)
Aumasson, Jean-Philippe; Dunkelman, Orr; Mendel, Florian
2009-01-01
Vortex is a hash function that was first presented at ISC'2008, then submitted to the NIST SHA-3 competition after some modifications. This paper describes several attacks on both versions of Vortex, including collisions, second preimages, preimages, and distinguishers. Our attacks exploit flaws...
Houck, Edward D.
1994-01-01
A fluid transfer system that combines a vortex diode with a jet ejector to transfer liquid from one tank to a second tank by a gas pressurization method having no moving mechanical parts in the fluid system. The vortex diode is a device that has a high resistance to flow in one direction and a low resistance to flow in the other.
Aerodynamically shaped vortex generators
DEFF Research Database (Denmark)
Hansen, Martin Otto Laver; Velte, Clara Marika; Øye, Stig
2016-01-01
An aerodynamically shaped vortex generator has been proposed, manufactured and tested in a wind tunnel. The effect on the overall performance when applied on a thick airfoil is an increased lift to drag ratio compared with standard vortex generators. Copyright © 2015 John Wiley & Sons, Ltd....
Stellinga, Daan; Pietrzyk, Monika E; Glackin, James M E; Wang, Yue; Bansal, Ashu K; Turnbull, Graham A; Dholakia, Kishan; Samuel, Ifor D W; Krauss, Thomas F
2018-03-27
Optical vortex beams are at the heart of a number of novel research directions, both as carriers of information and for the investigation of optical activity and chiral molecules. Optical vortex beams are beams of light with a helical wavefront and associated orbital angular momentum. They are typically generated using bulk optics methods or by a passive element such as a forked grating or a metasurface to imprint the required phase distribution onto an incident beam. Since many applications benefit from further miniaturization, a more integrated yet scalable method is highly desirable. Here, we demonstrate the generation of an azimuthally polarized vortex beam directly by an organic semiconductor laser that meets these requirements. The organic vortex laser uses a spiral grating as a feedback element that gives control over phase, handedness, and degree of helicity of the emitted beam. We demonstrate vortex beams up to an azimuthal index l = 3 that can be readily multiplexed into an array configuration.
Dynamics and heat diffusion of Abrikosov's vortex-antivortex pairs during an annihilation process.
Duarte, E C S; Sardella, E; Ortiz, W A; Zadorosny, R
2017-10-11
The manipulation and control of vortex states in superconducting systems are of great interest in view of possible applications, for which mesoscopic materials are good candidates. In this work, we studied the annihilation dynamics and the dissipative aspects of an Abrikosov's vortex-antivortex pair in a mesoscopic superconducting system with a concentric hole. The generalized time-dependent Ginzburg-Landau equations were numerically solved. The main result is the appearance of a phase slip-like line due to the elongation of the vortex and antivortex cores. Under specific circumstances, thermal dissipation might be associated with a sizeable relaxation of the order parameter, so that the energy released in the annihilation of a vortex-antivortex pair might become detectable in measurements of the magnetization as a function of time.
Realization and Modeling of Metamaterials Made of rf Superconducting Quantum-Interference Devices
Directory of Open Access Journals (Sweden)
M. Trepanier
2013-12-01
Full Text Available We have prepared meta-atoms based on radio-frequency superconducting quantum-interference devices (rf SQUIDs and examined their tunability with dc magnetic field, rf current, and temperature. rf SQUIDs are superconducting split-ring resonators in which the usual capacitance is supplemented with a Josephson junction, which introduces strong nonlinearity in the rf properties. We find excellent agreement between the data and a model that regards the Josephson junction as the resistively and capacitively shunted junction. A magnetic field tunability of 80 THz/G at 12 GHz is observed, a total tunability of 56% is achieved, and a unique electromagnetically induced transparency feature at intermediate excitation powers is demonstrated for the first time. An rf SQUID metamaterial is shown to have qualitatively the same behavior as a single rf SQUID with regard to dc flux and temperature tuning.
International Nuclear Information System (INIS)
Minnhagen, P.; Weber, H.
1985-01-01
A Monte Carlo simulation of the Ginsburg-Landau Coulomb-gas model for vortex fluctuations is described and compared to the measured resistance scaling function for two-dimensional superconductors. This constitutes a new, more direct way of confirming the vortex-fluctuation explanation for the resistive tail of high-sheet-resistance superconducting films. The Monte Carlo data obtained indicate a striking accordance between theory and experiments
The ac effect of vortex pinning in the arrays of defect sites on Nb films
Czech Academy of Sciences Publication Activity Database
Wu, T.C.; Horng, L.; Wu, J.C.; Hsiao, C.W.; Koláček, Jan; Yang, T.-J.
2006-01-01
Roč. 99, č. 8 (2006), 08M515/1-08M515/3 ISSN 0021-8979 R&D Projects: GA ČR(CZ) GA202/05/0173 Institutional research plan: CEZ:AV0Z10100521 Keywords : superconducting vortex dynamics * flux pinning * vortex-motion control device Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.316, year: 2006
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
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...
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
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
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
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.
Cryotrons based on a simultaneously distributed Josephson contact
Energy Technology Data Exchange (ETDEWEB)
Bakhtin, P.A.; Lapir, G.M.; Makhov, V.I.; Samus, A.N.; Semenov, V.K.; Tyablikov, A.V.
1982-01-01
The features of the construction of cryotrons based on an evenly distributed Josephson contact are examined. The possibility is demonstrated of producing cryotrons with an assigned form of the controlling characteristic through the spatial isolation of the transport and controlling streams. The theoretical and experimental controlling characteristics of cryotrons based on bridges of variable thickness with connectors of normal metal are cited. The proposed principles of cryotron production are also suitable for other types of Josephson contacts.
D'Ambrosio, S.; Meissner, M.; Blanc, C.; Ronzani, A.; Giazotto, F.
2015-01-01
We report the fabrication and characterization of an alternative design for a superconducting quantum interference proximity transistor (SQUIPT) based on a normal metal (N) probe. The absence of direct Josephson coupling between the proximized metal nanowire and the N probe allows us to observe the full modulation of the wire density of states around zero voltage and current \\textit{via} the application of an external magnetic field. This results into a drastic suppression of power dissipatio...
Surface deformation caused by the Abrikosov vortex lattice
Czech Academy of Sciences Publication Activity Database
Lipavský, Pavel; Morawetz, K.; Koláček, Jan; Brandt, E. H.
2008-01-01
Roč. 77, č. 18 (2008), 184509/1-184509/7 ISSN 1098-0121 R&D Projects: GA ČR GA202/08/0326; GA AV ČR IAA100100712 Grant - others:GA ČR(CZ) GA202/07/0597 Institutional research plan: CEZ:AV0Z10100521 Keywords : superconductivity * magneto-elastic effect * vortex lattice Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.322, year: 2008
Higgsless superconductivity from topological defects in compact BF terms
Directory of Open Access Journals (Sweden)
M. Cristina Diamantini
2015-02-01
Full Text Available We present a new Higgsless model of superconductivity, inspired from anyon superconductivity but P- and T-invariant and generalisable to any dimension. While the original anyon superconductivity mechanism was based on incompressible quantum Hall fluids as average field states, our mechanism involves topological insulators as average field states. In D space dimensions it involves a (D−1-form fictitious pseudovector gauge field which originates from the condensation of topological defects in compact low-energy effective BF theories. In the average field approximation, the corresponding uniform emergent charge creates a gap for the (D−2-dimensional branes via the Magnus force, the dual of the Lorentz force. One particular combination of intrinsic and emergent charge fluctuations that leaves the total charge distribution invariant constitutes an isolated gapless mode leading to superfluidity. The remaining massive modes organise themselves into a D-dimensional charged, massive vector. There is no massive Higgs scalar as there is no local order parameter. When electromagnetism is switched on, the photon acquires mass by the topological BF mechanism. Although the charge of the gapless mode (2 and the topological order (4 are the same as those of the standard Higgs model, the two models of superconductivity are clearly different since the origins of the gap, reflected in the high-energy sectors are totally different. In 2D this type of superconductivity is explicitly realised as global superconductivity in Josephson junction arrays. In 3D this model predicts a possible phase transition from topological insulators to Higgsless superconductors.
Higgsless superconductivity from topological defects in compact BF terms
Diamantini, M. Cristina; Trugenberger, Carlo A.
2015-02-01
We present a new Higgsless model of superconductivity, inspired from anyon superconductivity but P- and T-invariant and generalisable to any dimension. While the original anyon superconductivity mechanism was based on incompressible quantum Hall fluids as average field states, our mechanism involves topological insulators as average field states. In D space dimensions it involves a (D - 1)-form fictitious pseudovector gauge field which originates from the condensation of topological defects in compact low-energy effective BF theories. In the average field approximation, the corresponding uniform emergent charge creates a gap for the (D - 2)-dimensional branes via the Magnus force, the dual of the Lorentz force. One particular combination of intrinsic and emergent charge fluctuations that leaves the total charge distribution invariant constitutes an isolated gapless mode leading to superfluidity. The remaining massive modes organise themselves into a D-dimensional charged, massive vector. There is no massive Higgs scalar as there is no local order parameter. When electromagnetism is switched on, the photon acquires mass by the topological BF mechanism. Although the charge of the gapless mode (2) and the topological order (4) are the same as those of the standard Higgs model, the two models of superconductivity are clearly different since the origins of the gap, reflected in the high-energy sectors are totally different. In 2D this type of superconductivity is explicitly realised as global superconductivity in Josephson junction arrays. In 3D this model predicts a possible phase transition from topological insulators to Higgsless superconductors.
Flux Flow, Pinning, and Resistive Behavior in Superconducting Networks
International Nuclear Information System (INIS)
Stephen Teitel
2005-01-01
Numerical simulators are used to study the behavior of interacting quantized vortices and vortex lines in superconducting networks, films, and three dimensional bulk samples. An emphasis is on the explanation of the phenomenological behavior of the ''high-Tc'' copper-oxide superconductors and related model systems
The physics of nanowire superconducting single-photon detectors
Renema, Jelmer Jan
2015-01-01
We investigate the detection mechanism in superconducting single photon detectors via quantum detector tomography. We find that the detection event is caused by diffusion of quasiparticles from the absorption spot, combined with entrance of a vortex. Moreover, we investigate the behaviour of
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.
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.
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.
Line width of Josephson flux flow oscillators
DEFF Research Database (Denmark)
Koshelets, V.P.; Dmitriev, P.N.; Sobolev, A.S.
2002-01-01
A combination of wide-band electronic tunability and moderate free-running line width makes the Josephson flux flow oscillator (FFO) a perfect on-chip local oscillator for integrated submillimeter-wave SIS receivers. The possibility of FFO phase locking at all frequencies of interest has...... to be proven before one initiates real FFO applications. To achieve this goal a comprehensive set of line width measurements of the FFO operating in different regimes has been performed. FFOs with tapered shape have been successfully implemented in order to avoid the superfine resonant structure with voltage...... spacing of about 20 nV and extremely low differential resistance, recently observed in the IVC of the standard rectangular geometry. The obtained results have been compared with existing theories and FFO models in order to understand and possibly eliminate excess noise in the FFO. The intrinsic line width...
Vortex lattice disorder in YBa2Cu3O studied with β-NMR
Saadaoui, H.; MacFarlane, W. A.; Morris, G. D.; Salman, Z.; Chow, K. H.; Fan, I.; Hossain, M. D.; Liang, R.; Mansour, A. I.; Parolin, T. J.; Smadella, M.; Song, Q.; Wang, D.; Kiefl, R. F.
2009-04-01
In this paper, we report Li+8β-NMR measurements in thin Ag films deposited on the surface of YBa2Cu3O (YBCO) in the vortex state. The resonance in the Ag overlayer broadens dramatically below the superconducting transition temperature Tc, as expected from the underlying vortex lattice in the YBCO. However, the lineshape is much broader and more symmetric than expected for an ideal vortex lattice. These results indicate the observed field distribution in the Ag overlayer is dominated by extrinsic, long length scale disorder.
Wells, Frederick S.; Pan, Alexey V.; Wang, X.; Fedoseev, Sergey A.; Hilgenkamp, Hans
2015-01-01
The glass-like vortex distribution in pulsed laser deposited YBa2Cu3O7-x thin films is observed by scanning superconducting quantum interference device microscopy and analysed for ordering after cooling in magnetic fields significantly smaller than the Earth's field. Autocorrelation calculations on
Superconducting tunable flux qubit with direct readout scheme
International Nuclear Information System (INIS)
Chiarello, Fabio; Castellano, Maria Gabriella; Leoni, Roberto; Torrioli, Guido; Carelli, Pasquale; Cosmelli, Carlo; Gangemi, Lorenzo; Poletto, Stefano; Simeone, Daniela
2005-01-01
We describe a simple and efficient scheme for the readout of a tunable flux qubit, and present preliminary experimental tests for the preparation, manipulation and final readout of the qubit state, performed in the incoherent regime at liquid helium temperature. The tunable flux qubit is realized by a double SQUID with an extra Josephson junction inserted in the large superconducting loop, and the readout is performed by applying a current ramp to the junction and recording the value for which there is a voltage response, depending on the qubit state. This preliminary work indicates the feasibility and efficiency of the scheme
Atomic physics and quantum optics using superconducting circuits.
You, J Q; Nori, Franco
2011-06-29
Superconducting circuits based on Josephson junctions exhibit macroscopic quantum coherence and can behave like artificial atoms. Recent technological advances have made it possible to implement atomic-physics and quantum-optics experiments on a chip using these artificial atoms. This Review presents a brief overview of the progress achieved so far in this rapidly advancing field. We not only discuss phenomena analogous to those in atomic physics and quantum optics with natural atoms, but also highlight those not occurring in natural atoms. In addition, we summarize several prospective directions in this emerging interdisciplinary field.
National Aeronautics and Space Administration — To overcome the communication gap to Venus, TUI proposes to develop the Venus or Titan Exploratory (VORTEX) Gimbal to point a meter scale diameter, high gain...
Arndt, R.; Pennings, P.; Bosschers, J.; van Terwisga, T.
2015-01-01
Marine propellers display several forms of cavitation. Of these, propeller-tip vortex cavitation is one of the important factors in propeller design. The dynamic behaviour of the tip vortex is responsible for hull vibration and noise. Thus, cavitation in the vortices trailing from tips of propeller blades has been studied extensively. Under certain circumstances cavitating vortices have been observed to have wave-like disturbances on the surfaces of vapour cores. Intense sound at discrete frequencies can result from a coupling between tip vortex disturbances and oscillating sheet cavitation on the surfaces of the propeller blades. This research article focuses on the dynamics of vortex cavitation and more in particular on the energy and frequency content of the radiated pressures. PMID:26442147
Arndt, R; Pennings, P; Bosschers, J; van Terwisga, T
2015-10-06
Marine propellers display several forms of cavitation. Of these, propeller-tip vortex cavitation is one of the important factors in propeller design. The dynamic behaviour of the tip vortex is responsible for hull vibration and noise. Thus, cavitation in the vortices trailing from tips of propeller blades has been studied extensively. Under certain circumstances cavitating vortices have been observed to have wave-like disturbances on the surfaces of vapour cores. Intense sound at discrete frequencies can result from a coupling between tip vortex disturbances and oscillating sheet cavitation on the surfaces of the propeller blades. This research article focuses on the dynamics of vortex cavitation and more in particular on the energy and frequency content of the radiated pressures.
Efficient one- and two-qubit pulsed gates for an oscillator-stabilized Josephson qubit
International Nuclear Information System (INIS)
Brito, Frederico; DiVincenzo, David P; Koch, Roger H; Steffen, Matthias
2008-01-01
We present theoretical schemes for performing high-fidelity one- and two-qubit pulsed gates for a superconducting flux qubit. The 'IBM qubit' consists of three Josephson junctions, three loops and a superconducting transmission line. Assuming a fixed inductive qubit-qubit coupling, we show that the effective qubit-qubit interaction is tunable by changing the applied fluxes, and can be made negligible, allowing one to perform high-fidelity single qubit gates. Our schemes are tailored to alleviate errors due to 1/f noise; we find gates with only 1% loss of fidelity due to this source, for pulse times in the range of 20-30 ns for one-qubit gates (Z rotations, Hadamard) and 60 ns for a two-qubit gate (controlled-Z). Our relaxation and dephasing time estimates indicate a comparable loss of fidelity from this source. The control of leakage plays an important role in the design of our shaped pulses, preventing shorter pulse times. However, we have found that imprecision in the control of the quantum phase plays a major role in the limitation of the fidelity of our gates
Observing quantum jumps of a transmon qubit with a Josephson parametric converter
Shankar, S.; Hatridge, M.; Schackert, F.; Geerlings, K.; Brecht, T.; Sliwa, K.; Abdo, B.; Frunzio, L.; Schoelkopf, R. J.; Devoret, M. H.
2012-02-01
A high fidelity linear quantum non-demolition (QND) readout of a superconducting qubit opens up the possibility of observing quantum jumps and is a prerequisite for quantum feedback and error correction. This readout is challenging since the qubit, the readout resonator and the following amplifier chain have to be simultaneously optimized to achieve the desired performance. We fabricated a superconducting transmon qubit at 5.7 GHz coupled to a compact resonator at 7.5 GHz, designed to produce a dispersive shift (χ) of 6 MHz of the resonator frequency when the qubit is excited. The resonator linewidth matches χ to produce maximum readout contrast in a transmission measurement, while maintaining a Purcell limited T1 of about 3 μs. Using a Josephson parametric converter that is tuned to match the resonator frequency, we achieved a system noise temperature of the following amplifier chain of about 0.5 K, roughly thrice the standard quantum limit. Using these optimized parameters, we measured the qubit state with about 5 photons in the readout resonator and observed quantum jumps with fidelity above 90 %. Further, by looking at the statistics of the jumps and the evolution of the qubit population in single shot traces, we find that the average qubit T1 during the readout matches the Purcell limited T1, as expected for a QND measurement.
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.
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.
Yerin, Y.; Omelyanchouk, A. N.
2017-09-01
Emerging in the 1950s, the multiband superconductivity has been considered for a long time as an approximate model in the form of a generalization of the BCS theory to the case of two bands for a more accurate quantitative description of the properties and characteristics of such superconductors as cuprates, heavy fermions compounds, metal boron carbides, fullerides, strontium ruthenate etc. due to their complex piecewise-continuous Fermi surfaces. However the discovery of the multiband structure of the superconducting state in magnesium diboride in 2001 and iron oxypnictides and halides in 2008 led to the appearance of many papers in which effects and different dependences well known for usual one-band s-wave superconductors were re-examined. The main purpose of these studies was to reveal the symmetry type of the order parameter, which provides an important information about the mechanism of Cooper pairing in these superconductors. One of the most effective methods of obtaining information on the symmetry properties of the order parameter in the multiband superconductors is phase-sensitive techniques. This review summarizes the results of theoretical and experimental studies of the proximity and Josephson effects in systems based on multiband superconductors in contact with normal metals, insulators and other superconductors.
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.
Superconducting rotating electronic machine
International Nuclear Information System (INIS)
Cheon, Hui Yeong
1989-04-01
This book is divided into ten chapters, which handles summary of superconducting electronic machine, aspect of using of superconductor, superconducting direct current : Homopolar D. C. Machines, Drum machines, segmented slip-ring principle and carbon fibre brushes, superconducting alternating current turbine generator, design of superconducting alternating current machine, performance of superconducting alternating current machine, superconducting turbo generator by new rotor design, basic design of superconducting current generator, generator and power model, design of rotor and information of material property.
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
Introduction to superconductivity
Tinkham, Michael
1975-01-01
Introductory survey ; the BCS theory ; magnetic properties of type I superconductors ; Ginzburg-Landau theory ; magnetic properties of type II superconductors ; Josephson effect and macroscopic quantum phenomena ; fluctuation effects ; concluding topics.
DEFF Research Database (Denmark)
Branlard, Emmanuel Simon Pierre
2017-01-01
The velocity field, vector potential and velocity gradient of a vortex ring is derived in this chapter. The Biot-Savart law for the vector potential and velocity is expressed in a first section. Then, the flow is derived at specific locations: on the axis, near the axis and in the far field where...... is dedicated to vortex rings. Source rings are only briefly mentioned....
International Nuclear Information System (INIS)
Gray, K.E.
1978-01-01
A three film superconducting tunneling device, analogous to a semiconductor transistor, is presented, including a theoretical description and experimental results showing a current gain of four. Much larger current gains are shown to be feasible. Such a development is particularly interesting because of its novelty and the striking analogies with the semiconductor junction transistor
International Nuclear Information System (INIS)
Ruvalds, J.
1990-01-01
This report discusses the following topics: Fermi liquid nesting in high temperature superconductors; optical properties of high temperature superconductors; Hall effect in superconducting La 2-x Sr x CuO 4 ; source of high transition temperatures; and prospects for new superconductors
International Nuclear Information System (INIS)
1994-08-01
This report discusses the following topics on superconducting magnets: D19B and -C: The next steps for a record-setting magnet; D20: The push beyond 10 T: Beyond D20: Speculations on the 16-T regime; other advanced magnets for accelerators; spinoff applications; APC materials development; cable and cabling-machine development; and high-T c superconductor at low temperature
International Nuclear Information System (INIS)
Pankratov, S.G.
1987-01-01
A model of bipolaron superconductivity suggested by Soviet scientist Alexandrov A.S. and French scientist Ranninger is presentes in a popular way. It is noted that the bipolaron theory gives a good explanation of certain properties of new superconductors, high critical temperature, in particular
High transition temperature superconducting integrated circuit
International Nuclear Information System (INIS)
DiIorio, M.S.
1985-01-01
This thesis describes the design and fabrication of the first superconducting integrated circuit capable of operating at over 10K. The primary component of the circuit is a dc SQUID (Superconducting QUantum Interference Device) which is extremely sensitive to magnetic fields. The dc SQUID consists of two superconductor-normal metal-superconductor (SNS) Josephson microbridges that are fabricated using a novel step-edge process which permits the use of high transition temperature superconductors. By utilizing electron-beam lithography in conjunction with ion-beam etching, very small microbridges can be produced. Such microbridges lead to high performance dc SQUIDs with products of the critical current and normal resistance reaching 1 mV at 4.2 K. These SQUIDs have been extensively characterized, and exhibit excellent electrical characteristics over a wide temperature range. In order to couple electrical signals into the SQUID in a practical fashion, a planar input coil was integrated for efficient coupling. A process was developed to incorporate the technologically important high transition temperature superconducting materials, Nb-Sn and Nb-Ge, using integrated circuit techniques. The primary obstacles were presented by the metallurgical idiosyncrasies of the various materials, such as the need to deposit the superconductors at elevated temperatures, 800-900 0 C, in order to achieve a high transition temperature
Random frequency modulation of a superconducting qubit
Silveri, Matti; Li, Jian; Sampath, Karthikeyan; Pirkkalainen, Juha-Matti; Vepsäläinen, Antti; Chien, Wei-Cheng; Tuorila, Jani; Sillanpää, Mika; Hakonen, Pertti; Thuneberg, Erkki; Paraoanu, Gheorghe
2013-03-01
Superconducting circuits with Josephson junctions are a promising platform not only for developing quantum technologies, but, importantly, also for the study of effects that typically occur in complex condensed-matter systems. Here, we employ a transmon qubit to conduct an analog simulation of motional averaging, a phenomenon initially observed in nuclear magnetic resonance spectroscopy. To realize this effect, the flux bias of the transmon is modulated by a controllable pseudo-random telegraph noise, which results in stochastic jumping of the energy separation (frequency) between two discrete values. This can also be seen as a simulated fast-fluctuation environment under direct experimental control. Additionally, we discuss the population dynamics using an analytical master equation, and apply the motional averaging analysis on phenomena where the fluctuation of the energy is due to quasiparticles or to photon shot noise.
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.
Transport through hybrid superconducting/normal nanostructures
Energy Technology Data Exchange (ETDEWEB)
Futterer, David
2013-01-29
We mainly investigate transport through interacting quantum dots proximized by superconductors. For this purpose we extend an existing theory to describe transport through proximized quantum dots coupled to normal and superconducting leads. It allows us to study the influence of a strong Coulomb interaction on Andreev currents and Josephson currents. This is a particularly interesting topic because it combines two competing properties: in superconductors Cooper pairs are formed by two electrons which experience an attractive interaction while two electrons located on a quantum dot repel each other due to the Coulomb interaction. It seems at first glance that transport processes involving Cooper pairs should be suppressed because of the two competing interactions. However, it is possible to proximize the dot in nonequilibrium situations. At first, we study a setup composed of a quantum dot coupled to one normal, one ferromagnetic, and one superconducting lead in the limit of an infinitely-large superconducting gap. Within this limit the coupling between dot and superconductor is described exactly by the presented theory. It leads to the formation of Andreev-bound states (ABS) and an additional bias scheme opens in which a pure spin current, i.e. a spin current with a vanishing associated charge current, can be generated. In a second work, starting from the infinite-gap limit, we perform a systematic expansion of the superconducting gap around infinity and investigate Andreev currents and Josephson currents. This allows us to estimate the validity of infinite-gap calculations for real systems in which the superconducting gap is usually a rather small quantity. We find indications that a finite gap renormalizes the ABS and propose a resummation approach to explore the finite-gap ABS. Despite the renormalization effects the modifications of transport by finite gaps are rather small. This result lets us conclude that the infinite-gap calculation is a valuable tool to
Energy Technology Data Exchange (ETDEWEB)
Berry, St
2000-07-01
This experimental study of the magnetic field-temperature phase diagram and of the vortex dynamics in high- T{sub c} superconductors focuses on Bismuth-based cuprates: Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8}. In type-II superconductors, mixed state characterized by the presence of vortices (quanta of magnetic flux) is divided by a transition line determined by two features of magnetization loops. For T > 40 K, magnetization loops vs applied field show a step evidence of a first order transition. From 20 to 40 K, a second peak replacing the step correspond to an abrupt increase of irreversibility interpreted as a bulk current. We want to understand the nature of the second peak (thermodynamic or nonequilibrium property) and separate phenomena contributing to irreversibility (flux pinning, geometrical or surface effects). Magnetic measurement techniques are nondestructive and have a resolution of few microns. Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} single crystals are optimized by localizing defectives regions with a magneto-optic technique for flux imaging and elimination of these regions with a wire saw. Local magnetization loops and relaxation measurements performed with a microscopic Hall probe array allow to distinguish irreversibility sources. The shape of induction profiles indicates which current dominate between surface current and bulk pinning induced current. Two crossover with time and a direct observation of two phases coexistence in induction profiles enlighten phenomena in play. The measured electric field-current density characteristics lead to barrier energy U(j) controlling thermally activated flux motion. Three relations (U(j) (surface, bulk low and high field) explain second peak. (author)
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
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.
Energy Technology Data Exchange (ETDEWEB)
Wilczek, F. [Institute for Advanced Study, Princeton, NJ (United States)
1997-09-22
The asymptotic freedom of QCD suggests that at high density - where one forms a Fermi surface at very high momenta - weak coupling methods apply. These methods suggest that chiral symmetry is restored and that an instability toward color triplet condensation (color superconductivity) sets in. Here I attempt, using variational methods, to estimate these effects more precisely. Highlights include demonstration of a negative pressure in the uniform density chiral broken phase for any non-zero condensation, which we take as evidence for the philosophy of the MIT bag model; and demonstration that the color gap is substantial - several tens of MeV - even at modest densities. Since the superconductivity is in a pseudoscalar channel, parity is spontaneously broken.
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.
Inertial Josephson relation for FIR frequencies
Czech Academy of Sciences Publication Activity Database
Lin, P.J.; Lipavský, Pavel; Matlock, P.
2012-01-01
Roč. 376, 6-7 (2012), s. 883-885 ISSN 0375-9601 R&D Projects: GA ČR(CZ) GAP204/11/0015 Institutional support: RVO:68378271 Keywords : non-equilibrium superconductivity * time-dependent Ginzburg-Landau theory Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.766, year: 2012
Vortex Apparatus and Demonstrations
Shakerin, Said
2010-05-01
Vortex flow, from millimeter to kilometer in scale, is important in many scientific and technological areas. Examples are seen in water strider locomotion, from industrial pipe flow (wastewater treatment) to air traffic control (safe distance between aircrafts on a runway ready for takeoff) to atmospheric studies.2-5 In this paper, we focus on a particular vortex known as bathtub vortex (BTV). It occurs when water is drained from a hole at the bottom of a container such as a bathtub or a sink under the action of gravity. The vortex has a funnel shape with a central air core, resembling a tornado. We have designed a portable apparatus to demonstrate bathtub vortex on a continual basis. The apparatus consists of a clear cylinder supported by a frame over a water reservoir and a submersible pump. Young and old have been equally amazed by watching the demonstrations at various public presentations held at the University of the Pacific recently. With material cost of less than 100, the apparatus can be easily fabricated and used at other universities. With a short set-up time, it is an ideal device for promoting science to the general public, and it can be used to enhance lectures in physics courses as well.
Quasi-hexagonal vortex-pinning lattice using anodized aluminum oxide nanotemplates
DEFF Research Database (Denmark)
Hallet, X.; Mátéfi-Tempfli, M.; Michotte, S.
2009-01-01
The bottom barrier layer of well-ordered nanoporous alumina membranes reveals a previously unexploited nanostructured template surface consisting of a triangular lattice of hemispherical nanoscale bumps. Quasi-hexagonal vortex-pinning lattice arrays are created in superconducting Nb films deposit...
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.
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.
Semiconductor-inspired design principles for superconducting quantum computing.
Shim, Yun-Pil; Tahan, Charles
2016-03-17
Superconducting circuits offer tremendous design flexibility in the quantum regime culminating most recently in the demonstration of few qubit systems supposedly approaching the threshold for fault-tolerant quantum information processing. Competition in the solid-state comes from semiconductor qubits, where nature has bestowed some very useful properties which can be utilized for spin qubit-based quantum computing. Here we begin to explore how selective design principles deduced from spin-based systems could be used to advance superconducting qubit science. We take an initial step along this path proposing an encoded qubit approach realizable with state-of-the-art tunable Josephson junction qubits. Our results show that this design philosophy holds promise, enables microwave-free control, and offers a pathway to future qubit designs with new capabilities such as with higher fidelity or, perhaps, operation at higher temperature. The approach is also especially suited to qubits on the basis of variable super-semi junctions.
Longitudinal Proximity Effects in Superconducting Transition-Edge Sensors
Sadleir, John E.; Smith, Stephen J.; Bandler, Simon R.; Chervenak, James A.; Clem, John R.
2010-01-01
We have found experimentally that the critical current of a square thin-film superconducting transition-edge sensor (TES) depends exponentially upon the side length L and the square root of the temperature T, a behavior that has a natural theoretical explanation in terms of longitudinal proximity effects if the TES is regarded as a weak link between superconducting leads. As a consequence, the effective transition temperature T(sub c) of the TES is current-dependent and at fixed current scales as 1/L(sup 2). We also have found that the critical current can show clear Fraunhofer-like oscillations in an applied magnetic field, similar to those found in Josephson junctions. We have observed the longitudinal proximity effect in these devices over extraordinarily long lengths up to 290 micrometers, 1450 times the mean-free path.
Wu, Jie-Zhi; Zhou, M-D
2006-01-01
The importance of vorticity and vortex dynamics has now been well rec- nized at both fundamental and applied levels of ?uid dynamics, as already anticipatedbyTruesdellhalfcenturyagowhenhewrotethe?rstmonograph onthesubject, The Kinematics of Vorticity(1954);andasalsoevidencedby the appearance of several books on this ?eld in 1990s. The present book is characterizedbythefollowingfeatures: 1. A basic physical guide throughout the book. The material is directed by a basic observation on the splitting and coupling of two fundamental processes in ?uid motion, i.e., shearing (unique to ?uid) and compre- ing/expanding.Thevorticityplaysakeyroleintheformer,andavortex isnothingbuta?uidbodywithhighconcentrationofvorticitycompared to its surrounding ?uid. Thus, the vorticity and vortex dynamics is - cordinglyde?nedasthetheoryofshearingprocessanditscouplingwith compressing/expandingprocess. 2. A description of the vortex evolution following its entire life.Thisbegins from the generation of vorticity to the formation of thi...
Neural dynamics in superconducting networks
Segall, Kenneth; Schult, Dan; Crotty, Patrick; Miller, Max
2012-02-01
We discuss the use of Josephson junction networks as analog models for simulating neuron behaviors. A single unit called a ``Josephson Junction neuron'' composed of two Josephson junctions [1] displays behavior that shows characteristics of single neurons such as action potentials, thresholds and refractory periods. Synapses can be modeled as passive filters and can be used to connect neurons together. The sign of the bias current to the Josephson neuron can be used to determine if the neuron is excitatory or inhibitory. Due to the intrinsic speed of Josephson junctions and their scaling properties as analog models, a large network of Josephson neurons measured over typical lab times contains dynamics which would essentially be impossible to calculate on a computer We discuss the operating principle of the Josephson neuron, coupling Josephson neurons together to make large networks, and the Kuramoto-like synchronization of a system of disordered junctions.[4pt] [1] ``Josephson junction simulation of neurons,'' P. Crotty, D. Schult and K. Segall, Physical Review E 82, 011914 (2010).
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.
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
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.
International Nuclear Information System (INIS)
Garcia, M.
1995-01-01
An electric vortex is the circulation of electron space charge about a magnetic field line that is transported by ion momentum. In cold, or low β flow the vortex diameter is the minimum length scale of charge neutrality. The distinctive feature of the vortex is its radial electric field which manifests the interplay of electrostatics, magnetism, and motion
Vortex Dynamics in Superconductors with Different Types of Pinning Potentials
International Nuclear Information System (INIS)
Laguna, Maria Fabiana
2001-01-01
In this work we study the behavior of the vortex system in the mixed state of a type II superconductor when it interacts with different kinds of pinning potentials. To do this, we perform numerical simulations in the presence of an external magnetic field, by making use of two different approaches.One corresponds to a Langevin simulation of the three dimensional XY model or Josephson-junction network, whereas the other corresponds to a Molecular dynamics simulation of two dimensional point-like vortices.We analyze the transport properties of highly anisotropic superconductors with different kinds of topological disorder in the configuration in which the external field is applied perpendicular to the CuO planes.We found that for systems with point defects the activation energy is the same for the two components of the resistivity, while in systems with columnar defects the activation energies can be different.We also study the structure, phase transitions and transport properties of the vortex system when the external magnetic field lies parallel to the planes in layered superconductors. We analyze the stability of different phases at low temperatures and show under which conditions the smectic phase is stable.Our results indicate the presence of the smectic phase in an intermediate range of temperatures.We have studied a vortex array in a periodic pinning potential with triangular and kagome geometries.We obtain the ground state vortex configurations and calculate some thermodynamic quantities for different magnetic fields.We observe several stages of lattice pinning and melting and we characterize different phases and transitions between them.Finally, simulating the Bitter pinning effect over the vortex system, we study static and dynamic properties of the vortex system in the presence of the surface Bitter pinning and the bulk pinning.We found low temperature structures similar to those obtained experimentally.We analyze the dynamics of the nucleation and growth
Quasiclassical studies of phase-coherent transport in superconducting nanostructures
International Nuclear Information System (INIS)
Seviour, R.F.
1999-07-01
In chapter two we introduce the quasiclassical technique and analysis the subgap conductance in S/N structures with barriers (zero bias and finite bias anomalies). We also analyse an Andreev interferometer. Also we present the results of studies on the Josephson effect in 4 terminal S/N/S contacts and on the possible sign reversal of the Josephson critical current (Published in Superlattices and Microstructures, Vol. 25, No. 5/6, p. 647 (1999)). In chapters three and four using the quasiclassical technique in conjunction with a numerical scattering approach (see Appendix) we consider a normal-superconducting-normal structure. In these chapters we consider the effects of the interface resistance between the Normal reservoirs and the normal film and the interface resistance between the superconductor and the normal film. This work has been published in J.Phys.Conds.Mat. 10 (1998), L615 and PHYS REV B 1 Nov 98. In Chapter 5 using the techniques discussed above we shown that for normal-superconducting-normal structure a new peek may arise in the temperature dependence of the conductance when the temperature is approximately equal to the transition temperature of the superconducting (Published PHYS. Rev.13, 1999, v.59, No.9, p. 6031). In chapter 6 we analyse the first ever experimental results showing the new peak in the conductance as discussed in chapter 5 (Submitted to PRL). Chapter 7 uses the numerical technique discussed in the appendix. to examine the phenomena of conductance suppression in 4 probe normal superconducting structures (Published Superlattices and Microstructures, Vol. 25, No.5, p. 640 (1999)). (author)
Decoherence of superconducting qubits caused by quasiparticle tunneling
Catelani, G.; Nigg, S. E.; Girvin, S. M.; Schoelkopf, R. J.; Glazman, L. I.
2012-11-01
In superconducting qubits, the interaction of the qubit degree of freedom with quasiparticles defines a fundamental limitation for the qubit coherence. We develop a theory of the pure dephasing rate Γϕ caused by quasiparticles tunneling through a Josephson junction and of the inhomogeneous broadening due to changes in the occupations of Andreev states in the junction. To estimate Γϕ, we derive a master equation for the qubit dynamics. The tunneling rate of free quasiparticles is enhanced by their large density of states at energies close to the superconducting gap. Nevertheless, we find that Γϕ is small compared to the rates determined by extrinsic factors in most of the current qubit designs (phase and flux qubits, transmon, fluxonium). The split transmon, in which a single junction is replaced by a SQUID loop, represents an exception that could make possible the measurement of Γϕ. Fluctuations of the qubit frequency leading to inhomogeneous broadening may be caused by the fluctuations in the occupation numbers of the Andreev states associated with a phase-biased Josephson junction. This mechanism may be revealed in qubits with small-area junctions, since the smallest relative change in frequency it causes is of the order of the inverse number of transmission channels in the junction.
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
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...
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...
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....
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...
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...
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
THz detectors using surface Josephson plasma waves in layered superconductors
International Nuclear Information System (INIS)
Savel'ev, Sergey; Yampol'skii, Valery; Nori, Franco
2006-01-01
We describe a proposal for THz detectors based on the excitation of surface waves, in layered superconductors, at frequencies lower than the Josephson plasma frequency ω J . These waves propagate along the vacuum-superconductor interface and are attenuated in both transverse directions out of the surface (i.e., towards the superconductor and towards the vacuum). The surface Josephson plasma waves are also important for the complete suppression of the specular reflection from a sample (Wood's anomalies, used for gratings) and produce a huge enhancement of the wave absorption, which can be used for the detection of THz waves
Implementation of the Grover search algorithm with Josephson charge qubits
International Nuclear Information System (INIS)
Zheng Xiaohu; Dong Ping; Xue Zhengyuan; Cao Zhuoliang
2007-01-01
A scheme of implementing the Grover search algorithm based on Josephson charge qubits has been proposed, which would be a key step to scale more complex quantum algorithms and very important for constructing a real quantum computer via Josephson charge qubits. The present scheme is simple but fairly efficient, and easily manipulated because any two-charge-qubit can be selectively and effectively coupled by a common inductance. More manipulations can be carried out before decoherence sets in. Our scheme can be realized within the current technology
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
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.)
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.
Periodic vortex pinning by regular structures in Nb thin films: magnetic vs. structural effects
Montero, Maria Isabel; Jonsson-Akerman, B. Johan; Schuller, Ivan K.
2001-03-01
The defects present in a superconducting material can lead to a great variety of static and dynamic vortex phases. In particular, the interaction of the vortex lattice with regular arrays of pinning centers such as holes or magnetic dots gives rise to commensurability effects. These commensurability effects can be observed in the magnetoresistance and in the critical current dependence with the applied field. In recent years, experimental results have shown that there is a dependence of the periodic pinning effect on the properties of the vortex lattice (i.e. vortex-vortex interactions, elastic energy and vortex velocity) and also on the dots characteristics (i.e. dot size, distance between dots, magnetic character of the dot material, etc). However, there is not still a good understanding of the nature of the main pinning mechanisms by the magnetic dots. To clarify this important issue, we have studied and compared the periodic pinning effects in Nb films with rectangular arrays of Ni, Co and Fe dots, as well as the pinning effects in a Nb film deposited on a hole patterned substrate without any magnetic material. We will discuss the differences on pinning energies arising from magnetic effects as compared to structural effects of the superconducting film. This work was supported by NSF and DOE. M.I. Montero acknowledges postdoctoral fellowship by the Secretaria de Estado de Educacion y Universidades (Spain).
Modern aspects of superconductivity theory of superconductivity
Kruchinin, Sergei; Aono, Shigeyuki
2011-01-01
Superconductivity remains one of the most interesting research areas in physics and stood as a major scientific mystery for a large part of this century. This book, written for graduate students and researchers in the field of superconductivity, discusses important aspects of the experiment and theory surrounding superconductivity. New experimental investigations of magnetic and thermodynamic superconducting properties of mesoscopic samples are explored with the help of recent developments in nanotechnologies and measurement techniques, and the results are predicted based upon theoretical mode
International Nuclear Information System (INIS)
Ohnuma, Toshiro; Ohno, J.
1994-01-01
Superconducting (SC) plasmas are proposed and investigated. The SC plasmas are not yet familiar and have not yet been studied. However, the existence and the importance of SC plasmas are stressed in this report. The existence of SC plasmas are found as follows. There is a fundamental property of Meissner effect in superconductors, which shows a repulsive effect of magnetic fields. Even in that case, in a microscopic view, there is a region of magnetic penetration. The penetration length λ is well-known as London's penetration depth, which is expressed as δ = (m s /μ 0 n s q s 2 ) 1/2 where m s , n s , q s and μ o show the mass, the density, the charge of SC electron and the permeability in free space, respectively. Because this expression is very simple, no one had tried it into more simple and meaningful form. Recently, one of the authors (T.O.) has found that the length can be expressed into more simple and understandable fundamental form as λ = c/ω ps where c = (ε 0 μ 0 ) -1/2 and ω ps = (n s q s 2 /m s ε 0 ) 1/2 are the light velocity and the superconducting plasma frequency. From this simple expression, the penetration depth of the magnetic field to SC is found as a SC plasma skin depth, that is, the fundamental property of SC can be expressed by the SC plasmas. This discovery indicates an importance of the studies of superconducting plasmas. From these points, several properties (propagating modes et al) of SC plasmas, which consist of SC electrons, normal electrons and lattice ions, are investigated in this report. Observations of SC plasma frequency is also reported with a use of Terahertz electromagnet-optical waves
Dynamical phase transition in a fully frustrated Josephson array on a square lattice
International Nuclear Information System (INIS)
Fisher, K. D.; Stroud, D.; Janin, L.
1999-01-01
We study dynamical phase transitions at temperature T=0 in a fully frustrated square Josephson junction array subject to a driving current density, which has nonzero components i x , i y parallel to both axes of the lattice. Our numerical results show clear evidence for three dynamical phases: a pinned vortex lattice characterized by zero time-averaged voltages x > t and y > t , a ''plastic'' phase in which both x > t and y > t are nonzero, and a moving lattice phase in which only one of the time-average voltage components is nonzero. The last of these has a finite transverse critical current: if a current is applied in the x direction, a nonzero transverse current density i y is required before y > t becomes nonzero. The voltage traces in the moving lattice phase are periodic in time. By contrast, the voltages in the plastic phase have continuous power spectra that are weakly dependent on frequency. This phase diagram is found numerically to be qualitatively unchanged by the presence of weak disorder. We also describe two simple analytical models that recover some, but not all, the characteristics of the three dynamical phases, and of the phase diagram calculated numerically. (c) 1999 The American Physical Society
Magnetic vortex racetrack memory
International Nuclear Information System (INIS)
Geng, Liwei D.; Jin, Yongmei M.
2017-01-01
We report a new type of racetrack memory based on current-controlled movement of magnetic vortices in magnetic nanowires with rectangular cross-section and weak perpendicular anisotropy. Data are stored through the core polarity of vortices and each vortex carries a data bit. Besides high density, non-volatility, fast data access, and low power as offered by domain wall racetrack memory, magnetic vortex racetrack memory has additional advantages of no need for constrictions to define data bits, changeable information density, adjustable current magnitude for data propagation, and versatile means of ultrafast vortex core switching. By using micromagnetic simulations, current-controlled motion of magnetic vortices in cobalt nanowire is demonstrated for racetrack memory applications. - Highlights: • Advance fundamental knowledge of current-driven magnetic vortex phenomena. • Report appealing new magnetic racetrack memory based on current-controlled magnetic vortices in nanowires. • Provide a novel approach to adjust current magnitude for data propagation. • Overcome the limitations of domain wall racetrack memory.
Jin, D. Z.; Dubin, D. H. E.
1997-11-01
We discuss the linear and nonlinear 2D dynamics of vortex crystals observed in experiments on pure electron plasmas [1]. Vortex crystals are rods of intense vorticity that form stable geometrical patterns in a low vorticity background. We consider a system consisting of several point vortices inside an initially circular background of constant vorticity. When the point vorticities have sufficiently small circulation compared to the background, there exist two time scales in the dynamics: a slow time scale associated with the motion of the point vortices and the driven response in the background; and a fast time scale associated with freely streaming Kelvin waves on the edge of the background vorticity profile. On the slow time scale, we show that the linear dynamics of the point vortices is equivalent to the classical problem of point vortices inside a circular conducting boundary, with the boundary radius equal to that of the background. However, filamentation involving both slow and fast time scales and subsequent wave breaking eventually occurs due to the nonlinear processes. This causes turbulent mixing of the background, and may be responsible for the irreversible ``cooling'' of the point vortex motions toward the vortex crystal state. Supported by NSF grant PHY94-21318. [1] K.S. Fine et al., Phys. Rev. Lett. 75, 3277 (1995).
Vortex Apparatus and Demonstrations
Shakerin, Said
2010-01-01
Vortex flow, from millimeter to kilometer in scale, is important in many scientific and technological areas. Examples are seen in water strider locomotion, from industrial pipe flow (wastewater treatment) to air traffic control (safe distance between aircrafts on a runway ready for takeoff) to atmospheric studies. In this paper, we focus on a…
Vortex core properties in iron pnictides
Directory of Open Access Journals (Sweden)
Zakharchuk I.
2014-07-01
Full Text Available The mechanism of unconventional superconductivity in recently discovered Fe-based superconductors has been intensively discussed. A plausible candidate is the superconducting (SC pairing mediated by antiferromagnetic (AFM interactions. There are two different approaches predicting the s± pairing state, in which the SC gap shows an s-wave symmetry that changes sign between different Fermi-surface (FS sheets. The first one is based on the itinerant spin ﬂuctuations promoted by FS nesting, and the second is based on the local AFM exchange couplings. We apply quasiclassical Eilenberger approach to the vortex state to calculate the cutoff parameter, ξh, at different levels of impurity scattering rates and to compare results with experimental data for iron pnictides. The s±-wave pairing symmetry is considered as a presumable state for these materials. Magnetic field dependence of ξh/ξc2 is found to be nonuniversal for s± pairing: depending on the chosen parameter set it can reside both below and above analytical Ginzburg-Landau curve. It is also found that normalized ξ2/ξc2(B/Bc2 dependence is increasing with pair-breaking (interband impurity scattering, and the intraband scattering results in decreasing of the ξ2/ξc2 value. Here, ξ2 is the vortex core size and ξc2 is the Ginzburg-Landau coherence length determined from the upper critical field. The ξ2/ξc2(B/Bc2 curve has a minimum at low temperatures and small scattering evolving into monotonously decreasing function at strong scattering and high temperatures.
Investigation of the Vortex States of Sr2RuO4-Ru Eutectic Microplates Using DC-SQUIDs
Sakuma, Daisuke; Nago, Yusuke; Ishiguro, Ryosuke; Kashiwaya, Satoshi; Nomura, Shintaro; Kono, Kimitoshi; Maeno, Yoshiteru; Takayanagi, Hideaki
2017-11-01
We investigated the magnetic properties of a Sr2RuO4-Ru eutectic microplate containing a single Ru-inclusion using micrometer-sized DC-SQUIDs (direct-current superconducting quantum interference devices). A phase frustration at the interface between chiral p-wave superconducting Sr2RuO4 and s-wave superconducting Ru is expected to cause novel magnetic vortex states such as the spontaneous Ru-center vortex under zero magnetic field [as reported by H. Kaneyasu and M. Sigrist, https://doi.org/10.1143/JPSJ.79.053706" xlink:type="simple">J. Phys. Soc. Jpn. 79, 053706 (2010)]. Our experimental results show no positive evidence for such a spontaneous vortex state. However, in an applied field, an abrupt change in the magnetic flux distribution was observed at a superconducting transition of Ru. The flux distribution is clarified by comparing our experimental results with electromagnetic field simulations in our sample geometry. We discuss the transition of the vortex states and the superconducting coupling at the Sr2RuO4/Ru interface.
DEFF Research Database (Denmark)
Aarøe, Morten; Monaco, R.; Koshelet, V.
2009-01-01
Superconducting shields are commonly used to suppress external magnetic interference. We show, that an error of almost an order of magnitude can occur in the coil factor in realistic configurations of the solenoid and the shield. The reason is that the coil factor is determined by not only...... the geometry of the solenoid, but also the nearby magnetic environment. This has important consequences for many cryogenic experiments involving magnetic fields such as the determination of the parameters of Josephson junctions, as well as other superconducting devices. It is proposed to solve the problem...
International Nuclear Information System (INIS)
Kambara, H.; Kashiwaya, S.; Yaguchi, H.; Asano, Y.; Tanaka, Y.; Maeno, Y.
2010-01-01
We report on novel local transport characteristics of naturally formed p-wave superconducting junctions of Sr 2 RuO 4 -Ru eutectic system by using microfabrication technique. We observed quite anomalous voltage-current (differential resistance-current) characteristics for both I//ab and I//c directions, which are not seen in conventional Josephson junctions. The anomalous features suggest the internal degrees of freedom of the superconducting state, possibly due to chiral p-wave domain. The dc current acts as a driving force to move chiral p-wave domain walls and form larger critical current path to cause the anomalous hysteresis.
Enhanced vortex damping by eddy currents in superconductor-semiconductor hybrids
Danckwerts; Goni; Thomsen; Eberl; Rojo
2000-04-17
An enhancement of vortex-motion damping in thin Pb/In superconducting films is obtained through coupling to an adjacent two-dimensional electron gas formed in a modulation-doped GaAs/AlGaAs heterostructure. This effect is observed by monitoring the power dissipation in the superconductor in the vortex state while increasing the density of the electron gas using a gate voltage. Quantitative agreement is found with calculations based on a viscous damping model which considers generation of eddy currents in the electron gas by moving flux lines. In the regime of filamentary vortex flow, eddy-current damping leads to a striking dissipation breakdown due to the stopping of entire vortex channels.
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...
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....
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...
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.
Josephson current through a molecular transistor in a dissipative environment
DEFF Research Database (Denmark)
Novotny, T; Rossini, Gianpaolo; Flensberg, Karsten
2005-01-01
We study the Josephson coupling between two superconductors through a single correlated molecular level, including Coulomb interaction on the level and coupling to a bosonic environment. All calculations are done to the lowest, i.e., the fourth, order in the tunneling coupling and we find a suppr...
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...
Nonresonant detection of Josephson radiation from thin-film microbridges
DEFF Research Database (Denmark)
Sørensen, O. H.; Mygind, Jesper; Pedersen, Niels Falsig
1977-01-01
Measurements are reported of the Josephson radiation from microbridges coupled to an X-band receiver via a nonresonant microwave transformer. Although closely coupled to the bridge, the transformer does not modify the bridge properties. We find that near the transition temperature the radiation l...
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 ...
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
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).
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
Josephson flux-flow oscillators in nonuniform microwave fields
DEFF Research Database (Denmark)
Salerno, Mario; Samuelsen, Mogens Rugholm
2000-01-01
We present a simple theory for Josephson flux-flow oscillators in the presence of nonuniform microwave fields. In particular we derive an analytical expression for the I-V characteristic of the oscillator from which we show that satellite steps are spaced around the main flux-flow resonance by only...
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...
100 years of superconductivity
Rogalla, Horst
2011-01-01
Even a hundred years after its discovery, superconductivity continues to bring us new surprises, from superconducting magnets used in MRI to quantum detectors in electronics. 100 Years of Superconductivity presents a comprehensive collection of topics on nearly all the subdisciplines of superconductivity. Tracing the historical developments in superconductivity, the book includes contributions from many pioneers who are responsible for important steps forward in the field.The text first discusses interesting stories of the discovery and gradual progress of theory and experimentation. Emphasizi
Superconducting accelerator technology
International Nuclear Information System (INIS)
Grunder, H.A.; Hartline, B.K.
1986-01-01
Modern and future accelerators for high energy and nuclear physics rely increasingly on superconducting components to achieve the required magnetic fields and accelerating fields. This paper presents a practical overview of the phenomenon of superconductivity, and describes the design issues and solutions associated with superconducting magnets and superconducting rf acceleration structures. Further development and application of superconducting components promises increased accelerator performance at reduced electric power cost
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)
Forgan; Kealey; Johnson; Pautrat; Simon; Lee; Aegerter; Cubitt; Farago; Schleger
2000-10-16
We have used the neutron spin-echo technique to measure the small energy change of neutrons which are diffracted by a moving vortex lattice in a low-pinning Nb-Ta superconducting sample. A transport current was passed in the mixed state to cause flux line movement. In the case of uniform motion, the flux velocity v(L) was given as expected by the values of electric and magnetic fields, via E = -v(L)wedgeB. We show that with a nonuniformly moving vortex lattice, one can measure the dispersion of the velocities, opening up new possibilities for investigating moving vortex lines.
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)
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
Silveri, M.; Zalys-Geller, E.; Hatridge, M.; Leghtas, Z.; Devoret, M. H.; Girvin, S. M.
2015-03-01
In the remote entanglement process, two distant stationary qubits are entangled with separate flying qubits and the which-path information is erased from the flying qubits by interference effects. As a result, an observer cannot tell from which of the two sources a signal came and the probabilistic measurement process generates perfect heralded entanglement between the two signal sources. Notably, the two stationary qubits are spatially separated and there is no direct interaction between them. We study two transmon qubits in superconducting cavities connected to a Josephson Parametric Converter (JPC). The qubit information is encoded in the traveling wave leaking out from each cavity. Remarkably, the quantum-limited phase-preserving amplification of two traveling waves provided by the JPC can work as a which-path information eraser. By using a stochastic master approach we demonstrate the probabilistic production of heralded entangled states and that unequal qubit-cavity pairs can be made indistinguishable by simple engineering of driving fields. Additionally, we will derive measurement rates, measurement optimization strategies and discuss the effects of finite amplification gain, cavity losses, and qubit relaxations and dephasing. Work supported by IARPA, ARO and NSF.
Superconducting fluctuations in molybdenum nitride thin films
Baskaran, R.; Thanikai Arasu, A. V.; Amaladass, E. P.; Vaidhyanathan, L. S.; Baisnab, D. K.
2018-02-01
MoN thin films have been deposited using reactive sputtering. The change in resistance near superconducting transition temperature at various magnetic fields has been analyzed based on superconducting fluctuations in the system. The Aslamazov and Larkin scaling theory has been utilized to analyze the conductance change. The results indicate that most of the measurements show two dimensional (2D) nature and exhibit scaling behavior at lower magnetic fields (7T). We have also analyzed our data based on the model in which there is no explicit dependence of Tc. These analyses also substantiate a crossover from a 2D nature to a 3D at larger fields. Analysis using lowest Landau level scaling theory for a 2D system exhibit scaling behavior and substantiate our observations. The broadening at low resistance part has been explained based on thermally activated flux flow model and show universal behavior. The dependence of Uo on magnetic field indicates both single and collective vortex behavior.
Segmented trapped vortex cavity
Grammel, Jr., Leonard Paul (Inventor); Pennekamp, David Lance (Inventor); Winslow, Jr., Ralph Henry (Inventor)
2010-01-01
An annular trapped vortex cavity assembly segment comprising includes a cavity forward wall, a cavity aft wall, and a cavity radially outer wall there between defining a cavity segment therein. A cavity opening extends between the forward and aft walls at a radially inner end of the assembly segment. Radially spaced apart pluralities of air injection first and second holes extend through the forward and aft walls respectively. The segment may include first and second expansion joint features at distal first and second ends respectively of the segment. The segment may include a forward subcomponent including the cavity forward wall attached to an aft subcomponent including the cavity aft wall. The forward and aft subcomponents include forward and aft portions of the cavity radially outer wall respectively. A ring of the segments may be circumferentially disposed about an axis to form an annular segmented vortex cavity assembly.
Wang, Luyang; Vafek, Oskar
2014-02-01
We investigate the superconducting instability of a two-dimensional repulsive Fermi gas with Rashba spin-orbit coupling αR. Using renormalization group approach, we find the superconducting transition temperature as a function of the dimensionless ratio Θ=1}/{2}mαR2/EF where EF = 0 when the smaller Fermi surface shrinks to a (Dirac) point. The general trend is that superconductivity is enhanced as Θ increases, but in an intermediate regime Θ ∼ 0.1, a dome-like behavior appears. At a very small value of Θ, the angular momentum channel jz in which superconductivity occurs is quite high. With increasing Θ, jz decreases with a step of 2 down to jz = 6, after which we find the sequence jz = 6, 4, 6, 2, the last value of which continues to Θ → ∞. In an extended range of Θ, the superconducting gap predominantly resides on the large Fermi surface, while Josephson coupling induces a much smaller gap on the small Fermi surface. Below the superconducting transition temperature, we apply mean field theory to derive the self-consistent equations and find the condensation energies. The state with the lowest condensation energy is an unconventional superconducting state which breaks time-reversal symmetry, and in which singlet and triplet pairings are mixed. In general, these states are topologically nontrivial, and the Chern number of the state with total angular momentum jz is C = 2jz.
Type-I superconductivity and neutron star precession
International Nuclear Information System (INIS)
Sedrakian, Armen
2005-01-01
Type-I proton superconducting cores of neutron stars break up in a magnetic field into alternating domains of superconducting and normal fluids. We examine two channels of superfluid-normal fluid friction where (i) rotational vortices are decoupled from the nonsuperconducting domains and the interaction is due to the strong force between protons and neutrons; (ii) the nonsuperconducting domains are dynamically coupled to the vortices and the vortex motion generates transverse electric fields within them, causing electronic current flow and Ohmic dissipation. The obtained dissipation coefficients are consistent with the Eulerian precession of neutron stars
Magnetic response of superconducting mesoscopic-size YBCO powder
Energy Technology Data Exchange (ETDEWEB)
Deimling, C.V. [Grupo de Supercondutividade e Magnetismo, Departamento de Fisica, Universidade Federal de Sao Carlos, Sao Carlos, SP (Brazil)], E-mail: cesard@df.ufscar.br; Motta, M.; Lisboa-Filho, P.N. [Laboratorio de Materiais Supercondutores, Departamento de Fisica, Universidade Estadual Paulista, Bauru, SP Brazil (Brazil); Ortiz, W.A. [Grupo de Supercondutividade e Magnetismo, Departamento de Fisica, Universidade Federal de Sao Carlos, Sao Carlos, SP (Brazil)
2008-07-15
In this work it is reported the magnetic behavior of submicron and mesoscopic-size superconducting YBCO powders, prepared by a modified polymeric precursors method. The grain size and microstructure were analyzed using scanning electron microscopy (SEM). Measurements of magnetization and AC-susceptibility as a function of temperature were performed with a quantum design SQUID magnetometer. Our results indicated significant differences on the magnetic propreties, in connection with the calcination temperature and the pressure used to pelletize the samples. This contribution is part of an effort to study vortex dynamics and magnetic properties of submicron and mesoscopic-size superconducting samples.
Jin, D. Z.; Dubin, D. H. E.
1997-11-01
This poster discusses the linear and nonlinear dynamics of vortex crystals observed in experiments on pure electron plasmas [1]. Vortex crystals are rods of intense density that form stable geometrical patterns in a low density background. We consider a system consisting of several line charges inside an initially circular background of constant density. When the line charges have sufficiently small charge per unit length compared to the background, there exist two time scales in the dynamics: a slow time scale associated with the motion of the line charges and the driven response in the background; and a fast time scale associated with freely streaming diocotron waves on the edge of the background density profile. On the slow time scale, we show that the linear dynamics of the line charges is equivalent to the classical problem of line charges inside a circular conducting wall, with the wall radius equal to that of the background. However, filamentation involving both slow and fast time scales and subsequent wave breaking eventually occurs due to the nonlinear processes. This causes turbulent mixing of the background, and may be responsible for the irreversible ``cooling'' of the line charge motions toward the vortex crystal state. Supported by NSF grant PHY94-21318. [1] K.S. Fine et al., Phys. Rev. Lett. 75, 3277 (1995).
Controllable 0-π transition in a zigzag superconducting graphene-nanoribbon junction
International Nuclear Information System (INIS)
Liang Qifeng; Yu Yong; Dong Jinming; Wang Qianghua
2009-01-01
The supercurrent in a Josephson junction composed of a zigzag-edged graphene nanoribbon (ZGNR) lying between two superconducting leads [superconductor-graphene-superconductor (SGS) junction] has been studied by the Green's function method. It is found that applying a small transverse electric field can reverse the supercurrent direction, leading to a so-called 0-π phase transition. This transition can also happen periodically with a given change in the ZGNR's length, and, more importantly, can be easily and electrically controllable by a gate voltage, which is not possible in conventional superconducting π junctions and makes the SGS junction very promising for future application in superconducting electronics, as well as in quantum information and computation. (authors)
Quantum Statistical Approach to Superconductivity
Nam, Eunsoo
The Frohlich Hamiltonian representing an interaction between electron and phonon is derived. By exchanging a virtual phonon, a system of two electrons can lower the system's total energy if the difference of their kinetic energies is less than the energy of the phonon exchanged. This is shown by using quantum mechanical perturbation theory, which is fully developed. A general theory of superconductivity is developed, starting with a BCS Hamiltonian in which the interaction strengths (V_{11}, V_{22 }, V_{12}) among and between "electron" (1) and "hole" (2) Cooper pairs are differentiated. The supercondensate is shown to be composed of equal numbers of "electron" and "hole" ground (zero-momentum) Cooper pairs with charges mp 2e.. Based on the Hamiltonian, the normal-to-super phase transition is investigated, approaching the critical temperature T_{c} from the high temperature side. Non zero momentum Cooper pairs, that is, pairs of electrons (holes) with antiparallel spins and nearly opposite momenta above T_{c } in the bulk limit, are shown to move like independent bosons with the energy momentum relation varepsilon = (1/2)upsilon_ {F}p, where upsilon_ {F} represents the Fermi velocity. We have investigated the Bose-Einstein condensation of pairons. The system of free Cooper pairs in a 3D superconductors undergoes a phase transition of the second order with the critical temperature T_{c} given byk_{B}T_{c } = (1/2)(pi^2hbar^3v_sp {F}{3}n/1.20257)^{1over3 }where n is the number density of Cooper pairs. We calculate various properties associated with superconductivity at finite temperature. We derive general expressions for the energy gaps for both quasi electrons and pairons. Based on the independent pairon model, we explain the flux quantization, London's equation and the Josephson effects, stressing the importance of the macroscopic wave -function which represents the supercondensate in motion. We derived the basic equations governing the behavior of the
Evidence of weak superconductivity at the room-temperature grown LaAlO3/SrTiO3 interface
DEFF Research Database (Denmark)
Prawiroatmodjo, G. E. D. K.; Trier, Felix; Christensen, Dennis Valbjørn
2016-01-01
The two-dimensional electron gas at the crystalline LaAlO3/SrTiO3 (c-LAO/STO) interface has sparked large interest due to its exotic properties, including an intriguing gate-tunable superconducting phase. While there is growing evidence of pronounced spatial inhomogeneity in the conductivity at STO......-based interfaces, the consequences for superconductivity remain largely unknown. We study interfaces based on amorphous LAO top layers grown at room temperature (a-LAO/STO) and demonstrate a superconducting phase similar to c-LAO/STO, however, with a gate-tunable critical temperature of 460 mK. The dependence...... of the superconducting critical current on temperature, magnetic field, and back-gate-controlled doping is found to be consistently described by a model of a random array of Josephson-coupled superconducting domains....
Pautrat, A; Brûlet, A
2014-06-11
We investigated the intermediate mixed state of a superconducting niobium sample using very small angle neutron scattering. We show that this state is stabilized through a sequence where a regular vortex lattice appears, which then coexists with vortex clusters before vanishing at low temperature. Vortices in clusters have a constant periodicity regardless of the applied field and exhibit a temperature dependence close to the one of the penetration depth. The clusters disappear in the high temperature limit. All the results agree with an explanation in terms of vortex attraction due to non-local effects and indicate a negligible role for pinning. Phase coexistence between the Abrikosov vortex lattice and vortex clusters is reported, showing the first-order nature of the boundary line.
Interferometric optical vortex array generator.
Vyas, Sunil; Senthilkumaran, P
2007-05-20
Two new interferometric configurations for optical vortex array generation are presented. These interferometers are different from the conventional interferometers in that they are capable of producing a large number of isolated zeros of intensity, and all of them contain optical vortices. Simulation and theory for optical vortex array generation using three-plane-wave interference is presented. The vortex dipole array produced this way is noninteracting, as there are no attraction or repulsion forces between them, leading to annihilation or creation of vortex pairs.
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 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.
Aircraft Wake Vortex Deformation in Turbulent Atmosphere
Hennemann, Ingo; Holzaepfel, Frank
2007-01-01
Large-scale distortion of aircraft wake vortices appears to play a crucial role for aircraft safety during approach and landing. Vortex distortion is investigated based on large eddy simulations of wake vortex evolution in a turbulent atmosphere. A vortex identification method is developed that can be adapted to the vortex scales of interest. Based on the identified vortex center tracks, a statistics of vortex curvature radii is established. This statistics constitutes the basis for understan...
Melting of heterogeneous vortex matter: The vortex 'nanoliquid'
Indian Academy of Sciences (India)
Home; Journals; Pramana – Journal of Physics; Volume 66; Issue 1. Melting of heterogeneous vortex matter: The vortex `nanoliquid'. S S Banerjee S Goldberg Y Myasoedov M Rappaport E Zeldov A Soibel F de la Cruz C J van der Beek M Konczykowski T Tamegai V Vinokur. Volume 66 Issue 1 January 2006 pp 43-54 ...
Vortex-Surface Interactions: Vortex Dynamics and Instabilities
2015-10-16
Crow instability (see for example Leweke & Williamson, 2012). (b) Short-wave cooperative elliptic instability (Leweke & Williamson 1998). (c...vortex generators. Of interest in such studies would be the formation of secondary vorticity from the surface, the downstream vortex trajectories , and
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).
Comparing the dynamics of skyrmions and superconducting vortices
Olson Reichhardt, C. J.; Lin, S. Z.; Ray, D.; Reichhardt, C.
2014-08-01
Vortices in type-II superconductors have attracted enormous attention as ideal systems in which to study nonequilibrium collective phenomena, since the self-ordering of the vortices competes with quenched disorder and thermal effects. Dynamic effects found in vortex systems include depinning, nonequilibrium phase transitions, creep, structural order-disorder transitions, and melting. Understanding vortex dynamics is also important for applications of superconductors which require the vortices either to remain pinned or to move in a controlled fashion. Recently, topological defects called skyrmions have been realized experimentally in chiral magnets. Here we highlight similarities and differences between skyrmion dynamics and vortex dynamics. Many of the previous ideas and experimental setups that have been applied to superconducting vortices can also be used to study skyrmions. We also discuss some of the differences between the two systems, such as the potentially large contribution of the Magnus force in the skyrmion system that can dramatically alter the dynamics and transport properties.
WORKSHOPS: Radiofrequency superconductivity
International Nuclear Information System (INIS)
Anon.
1992-01-01
In the continual push towards higher energy particle beams, superconducting radiofrequency techniques now play a vital role, highlighted in the fifth workshop on radiofrequency superconductivity, held at DESY from 19 - 24 August 1991
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
A Josephson systolic array processor for multiplication/addition operations
International Nuclear Information System (INIS)
Morisue, M.; Li, F.Q.; Tobita, M.; Kaneko, S.
1991-01-01
A novel Josephson systolic array processor to perform multiplication/addition operations is proposed. The systolic array processor proposed here consists of a set of three kinds of interconnected cells of which main circuits are made by using SQUID gates. A multiplication of 2 bits by 2 bits is performed in the single cell at a time and an addition of three data with two bits is simultaneously performed in an another type of cell. Furthermore, information in this system flows between cells in a pipeline fashion so that a high performance can be achieved. In this paper the principle of Josephson systolic array processor is described in detail and the simulation results are illustrated for the multiplication/addition of (4 bits x 4 bits + 8 bits). The results show that these operations can be executed in 330ps
Vortex lattices in layered superconductors
International Nuclear Information System (INIS)
Prokic, V.; Davidovic, D.; Dobrosavljevic-Grujic, L.
1995-01-01
We study vortex lattices in a superconductor--normal-metal superlattice in a parallel magnetic field. Distorted lattices, resulting from the shear deformations along the layers, are found to be unstable. Under field variation, nonequilibrium configurations undergo an infinite sequence of continuous transitions, typical for soft lattices. The equilibrium vortex arrangement is always a lattice of isocell triangles, without shear
The Acoustically Driven Vortex Cannon
Perry, Spencer B.; Gee, Kent L.
2014-01-01
Vortex cannons have been used by physics teachers for years, mostly to teach the continuity principle. In its simplest form, a vortex cannon is an empty coffee can with a hole cut in the bottom and the lid replaced. More elaborate models can be purchased through various scientific suppliers under names such as "Air Cannon" and…
Compressibility effect in vortex identification
Czech Academy of Sciences Publication Activity Database
Kolář, Václav
2009-01-01
Roč. 47, č. 2 (2009), s. 473-475 ISSN 0001-1452 R&D Projects: GA AV ČR IAA200600801 Institutional research plan: CEZ:AV0Z20600510 Keywords : vortex * vortex identification * compressible flows * compressibility effect Subject RIV: BK - Fluid Dynamics Impact factor: 0.990, year: 2009
Magnetic vortex filament flows
International Nuclear Information System (INIS)
Barros, Manuel; Cabrerizo, Jose L.; Fernandez, Manuel; Romero, Alfonso
2007-01-01
We exhibit a variational approach to study the magnetic flow associated with a Killing magnetic field in dimension 3. In this context, the solutions of the Lorentz force equation are viewed as Kirchhoff elastic rods and conversely. This provides an amazing connection between two apparently unrelated physical models and, in particular, it ties the classical elastic theory with the Hall effect. Then, these magnetic flows can be regarded as vortex filament flows within the localized induction approximation. The Hasimoto transformation can be used to see the magnetic trajectories as solutions of the cubic nonlinear Schroedinger equation showing the solitonic nature of those
Mark Josephson and the ICD: A Personal Perspective
Swerdlow, Charles D
2017-01-01
Mark Josephson dedicated his career to the prevention of premature sudden cardiac death (SCD). Toward that goal, he was an early adopter of the implantable cardioverter defibrillator (ICD) and indefatigable advocate for better ICD technology,[1] both as a clinical tool and as living laboratory to study SCD in ambulatory patients. With characteristic intellectual integrity and analytical rigour, he sought an honest and balanced appraisal of the life-saving benefits and serious complications of...
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....
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