Fractional Solitons in Excitonic Josephson Junctions

NASA Astrophysics Data System (ADS)

Su, Jung-Jung; Hsu, Ya-Fen

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

Quantum Dynamics of a d-wave Josephson Junction

NASA Astrophysics Data System (ADS)

Bauch, Thilo

2007-03-01

Thilo Bauch ^1, Floriana Lombardi ^1, Tobias Lindstr"om ^2, Francesco Tafuri ^3, Giacomo Rotoli ^4, Per Delsing ^1, Tord Claeson ^1 1 Quantum Device Physics Laboratory, Department of Microtechnology and Nanoscience, MC2, Chalmers University of Technology, S-412 96 G"oteborg, Sweden. 2 National Physical Laboratory, Queens Road, Teddington, Middlesex TW11 0LW, UK. 3 Istituto Nazionale per la Fisica della Materia-Dipartimento Ingegneria dell'Informazione, Seconda Universita di Napoli, Aversa (CE), Italy. 4 Dipartimento di Ingegneria Meccanica, Energetica e Gestionale, Universita of L'Aquila, Localita Monteluco, L'Aquila, Italy. We present direct observation of macroscopic quantum properties in an all high critical temperature superconductor d-wave Josephson junction. Although dissipation caused by low energy excitations is expected to strongly suppress quantum effects we demonstrate macroscopic quantum tunneling [1] and energy level quantization [2] in our d-wave Josephson junction. The results clearly indicate that the role of dissipation mechanisms in high temperature superconductors has to be revised, and may also have consequences for a new class of solid state ``quiet'' quantum bit with superior coherence time. We show that the dynamics of the YBCO grain boundary Josephson junctions fabricated on a STO substrate are strongly affected by their environment. As a first approximation we model the environment by the stray capacitance and stray inductance of the junction electrodes. The total system consisting of the junction and stray elements has two degrees of freedom resulting in two characteristic resonance frequencies. Both frequencies have to be considered to describe the quantum mechanical behavior of the Josephson circuit. [1] T. Bauch et al, Phys. Rev. Lett. 94, 087003 (2005). [2] T. Bauch et al, Science 311, 57 (2006).

Multifluxon dynamics in driven Josephson junctions

NASA Astrophysics Data System (ADS)

Lawrence, Albert; Kim, Nung Soo; McDaniel, James; Jack, Michael

1985-06-01

The dynamics of fluxons in a long Josephson junction driven by time-varying nonuniform bias currents are described by a generalization of the sine-Gordon equation. This equation has solitary wave solutions which correspond to current vortices or quantized packets of magnetic flux in the junction. As with the sine-Gordon equation, multifluxon solutions may be demonstrated for the long Josephson junction. Our numerical calculations show that several fluxons may be launched or annihilated at the end of a junction. We also show multiple steady state conditions which correspond to one or more flux quanta trapped in the junction.

Simple Electronic Analog of a Josephson Junction.

ERIC Educational Resources Information Center

Henry, R. W.; And Others

1981-01-01

Demonstrates that an electronic Josephson junction analog constructed from three integrated circuits plus an external reference oscillator can exhibit many of the circuit phenomena of a real Josephson junction. Includes computer and other applications of the analog. (Author/SK)

Four photon parametric amplification. [in unbiased Josephson junction

NASA Technical Reports Server (NTRS)

Parrish, P. T.; Feldman, M. J.; Ohta, H.; Chiao, R. Y.

1974-01-01

An analysis is presented describing four-photon parametric amplification in an unbiased Josephson junction. Central to the theory is the model of the Josephson effect as a nonlinear inductance. Linear, small signal analysis is applied to the two-fluid model of the Josephson junction. The gain, gain-bandwidth product, high frequency limit, and effective noise temperature are calculated for a cavity reflection amplifier. The analysis is extended to multiple (series-connected) junctions and subharmonic pumping.

Superconducting nanoribbon with a constriction: A quantum-confined Josephson junction

NASA Astrophysics Data System (ADS)

Flammia, L.; Zhang, L.-F.; Covaci, L.; Perali, A.; Milošević, M. V.

2018-04-01

Extended defects are known to strongly affect nanoscale superconductors. Here, we report the properties of superconducting nanoribbons with a constriction formed between two adjacent step edges by solving the Bogoliubov-de Gennes equations self-consistently in the regime where quantum confinement is important. Since the quantum resonances of the superconducting gap in the constricted area are different from the rest of the nanoribbon, such constriction forms a quantum-confined S-S'-S Josephson junction, with a broadly tunable performance depending on the length and width of the constriction with respect to the nanoribbon, and possible gating. These findings provide an intriguing approach to further tailor superconducting quantum devices where Josephson effect is of use.

Inelastic effects of Josephson junctions

NASA Astrophysics Data System (ADS)

Ranjan, Samir

We have investigated the effects of the inelastic interaction of electrons with phonons in the barrier region of S-I-S and S-N-S Josephson junctions. We find that under suitable conditions this mechanism can cause substantial modifications of the temperature dependence of the critical current jsb{c} as the inevitable loss of coherence can be more than compensated by the enhancement of the tunneling probability resulting from the phonon absorption. The effect depends strongly on the ratio qsb{TF}a of the junction width a to the screening length in the barrier region. For a S-I-S junction, a monotonic decrease in the critical current with temperature is found for qsb{TF}a ≫ 1 whereas for qsb{TF}a ≪ 1, the appearance of a peak in jsb{c}(T) near Tsb{c} is predicted. This new interesting effect is the consequence of the competition between the decrease of the superconducting gap function and the increase in the number of phonons with temperature. A wide range of parameter values has been explored and contact with relevant experimental results has been made. For an S-N-S junction, there is a large increase in the coherence length in the non-superconducting region leading to a substantial enhancement of the critical current over a wide range of temperature. It turns out that the entire temperature range can be divided broadly into two regimes. At low temperatures, the electron predominantly exchanges energy with just one phonon and it is this process that mainly determines the critical current. At higher temperatures the critical current is determined by processes in which the electrons exchange energy with many phonons during their under barrier motion.

Modeling Bloch oscillations in nanoscale Josephson junctions.

PubMed

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

2017-08-01

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

Modeling Bloch oscillations in nanoscale Josephson junctions

PubMed Central

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

2018-01-01

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

Modeling Bloch oscillations in ultra-small Josephson junctions

NASA Astrophysics Data System (ADS)

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

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

Possible resonance effect of axionic dark matter in Josephson junctions.

PubMed

Beck, Christian

2013-12-06

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

Radiation comb generation with extended Josephson junctions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Solinas, P., E-mail: paolo.solinas@spin.cnr.it; Bosisio, R., E-mail: riccardo.bosisio@nano.cnr.it; NEST, Instituto Nanoscienze-CNR and Scuola Normale Superiore, I-56127 Pisa

2015-09-21

We propose the implementation of a Josephson radiation comb generator based on an extended Josephson junction subject to a time dependent magnetic field. The junction critical current shows known diffraction patterns and determines the position of the critical nodes when it vanishes. When the magnetic flux passes through one of such critical nodes, the superconducting phase must undergo a π-jump to minimize the Josephson energy. Correspondingly, a voltage pulse is generated at the extremes of the junction. Under periodic driving, this allows us to produce a comb-like voltage pulses sequence. In the frequency domain, it is possible to generate upmore » to hundreds of harmonics of the fundamental driving frequency, thus mimicking the frequency comb used in optics and metrology. We discuss several implementations through a rectangular, cylindrical, and annular junction geometries, allowing us to generate different radiation spectra and to produce an output power up to 10 pW at 50 GHz for a driving frequency of 100 MHz.« less

Fractional Solitons in Excitonic Josephson Junctions.

PubMed

Hsu, Ya-Fen; Su, Jung-Jung

2015-10-29

The Josephson effect is especially appealing to physicists because it reveals macroscopically the quantum order and phase. In excitonic bilayers the effect is even subtler due to the counterflow of supercurrent as well as the tunneling between layers (interlayer tunneling). Here we study, in a quantum Hall bilayer, the excitonic Josephson junction: a conjunct of two exciton condensates with a relative phase ϕ0 applied. The system is mapped into a pseudospin ferromagnet then described numerically by the Landau-Lifshitz-Gilbert equation. In the presence of interlayer tunneling, we identify a family of fractional sine-Gordon solitons which resemble the static fractional Josephson vortices in the extended superconducting Josephson junctions. Each fractional soliton carries a topological charge Q that is not necessarily a half/full integer but can vary continuously. The calculated current-phase relation (CPR) shows that solitons with Q = ϕ0/2π is the lowest energy state starting from zero ϕ0 - until ϕ0 > π - then the alternative group of solitons with Q = ϕ0/2π - 1 takes place and switches the polarity of CPR.

Holographic s-wave and p-wave Josephson junction with backreaction

NASA Astrophysics Data System (ADS)

Wang, Yong-Qiang; Liu, Shuai

2016-11-01

In this paper, we study the holographic models of s-wave and p-wave Josephoson junction away from probe limit in (3+1)-dimensional spacetime, respectively. With the backreaction of the matter, we obtained the anisotropic black hole solution with the condensation of matter fields. We observe that the critical temperature of Josephoson junction decreases with increasing backreaction. In addition to this, the tunneling current and condenstion of Josephoson junction become smaller as backreaction grows larger, but the relationship between current and phase difference still holds for sine function. Moreover, condenstion of Josephoson junction deceases with increasing width of junction exponentially.

Tunable Nitride Josephson Junctions.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Missert, Nancy A.; Henry, Michael David; Lewis, Rupert M.

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 xN 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.

Fractional Solitons in Excitonic Josephson Junctions

NASA Astrophysics Data System (ADS)

Hsu, Ya-Fen; Su, Jung-Jung

2015-10-01

The Josephson effect is especially appealing to physicists because it reveals macroscopically the quantum order and phase. In excitonic bilayers the effect is even subtler due to the counterflow of supercurrent as well as the tunneling between layers (interlayer tunneling). Here we study, in a quantum Hall bilayer, the excitonic Josephson junction: a conjunct of two exciton condensates with a relative phase ϕ0 applied. The system is mapped into a pseudospin ferromagnet then described numerically by the Landau-Lifshitz-Gilbert equation. In the presence of interlayer tunneling, we identify a family of fractional sine-Gordon solitons which resemble the static fractional Josephson vortices in the extended superconducting Josephson junctions. Each fractional soliton carries a topological charge Q that is not necessarily a half/full integer but can vary continuously. The calculated current-phase relation (CPR) shows that solitons with Q = ϕ0/2π is the lowest energy state starting from zero ϕ0 - until ϕ0 > π - then the alternative group of solitons with Q = ϕ0/2π - 1 takes place and switches the polarity of CPR.

Phase Sensitive Measurements of Ferromagnetic Josephson Junctions for Cryogenic Memory Applications

NASA Astrophysics Data System (ADS)

Niedzielski, Bethany Maria

A Josephson junction is made up of two superconducting layers separated by a barrier. The original Josephson junctions, studied in the early 1960's, contained an insulating barrier. Soon thereafter, junctions with normal-metal barriers were also studied. Ferromagnetic materials were not even theoretically considered as a barrier layer until around 1980, due to the competing order between ferromagnetic and superconducting systems. However, many exciting physical phenomena arise in hybrid superconductor/ferromagnetic devices, including devices where the ground state phase difference between the two superconductors is shifted by pi. Since their experimental debut in 2001, so-called pi junctions have been demonstrated by many groups, including my own, in systems with a single ferromagnetic layer. In this type of system, the phase of the junction can be set to either 0 or pi depending on the thickness of the ferromagnetic layer. Of interest, however, is the ability to control the phase of a single junction between the 0 and pi states. This was theoretically shown to be possible in a system containing two ferromagnetic layers (spin-valve junctions). If the materials and their thicknesses are properly chosen to manipulate the electron pair correlation function, then the phase state of a spin-valve Josephson junction should be capable of switching between the 0 and ? phase states when the magnetization directions of the two ferromagnetic layers are oriented in the antiparallel and parallel configurations, respectively. Such a phase-controllable junction would have immediate applications in cryogenic memory, which is a necessary component to an ultra-low power superconducting computer. A fully superconducting computer is estimated to be orders of magnitude more energy-efficient than current semiconductor-based supercomputers. The goal of this work was to experimentally verify this prediction for a phase-controllable ferromagnetic Josephson junction. To address this

Phase-dependent noise in Josephson junctions

NASA Astrophysics Data System (ADS)

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.

Coincidence of features of emitted THz electromagnetic wave power form a single Josephson junction and different current components

NASA Astrophysics Data System (ADS)

Hamdipour, Mohammad

2017-12-01

By applying a voltage to a Josephson junction, the charge in superconducting layers (S-layers) will oscillate. Wavelength of the charge oscillations in S-layers is related to external current in junction, by increasing the external current, the wavelength will decrease which cause in some currents the wavelength be incommensurate with width of junction, so the CVC shows Fiske like steps. External current throwing along junction has some components, resistive, capacitive and superconducting current, beside these currents there is a current in lateral direction of junction, (x direction). On the other hand, the emitted electromagnetic wave power in THz region is related to AC component of electric field in junction, which itself is related to charge density in S-layers, which is related to currents in the system. So we expect that features of variation of current components reflect the features of emitted THz power form junction. Here we study in detail the superconductive current in a long Josephson junction (JJ), the current voltage characteristics (CVC) of junction and emitted THz power from the system. Then we compare the results. Comparing the results we see that there is a good qualitative coincidence in features of emitted THz power and supercurrent in junction.

Phase dynamics of single long Josephson junction in MgB2 superconductor

NASA Astrophysics Data System (ADS)

Chimouriya, Shanker Pd.; Ghimire, Bal Ram; Kim, Ju H.

2018-05-01

A system of perturbed sine Gordon equations is derived to a superconductor-insulator-superconductor (SIS) long Joseph-son junction as an extension of the Ambegaokar-Baratoff relation, following the long route of path integral formalism. A computer simulation is performed by discretizing the equations using finite difference approximation and applied to the MgB2 superconductor with SiO2 as the junction material. The solution of unperturbed sG equation is taken as the initial profile for the simulation and observed how the perturbation terms play the role to modify it. It is found initial profile deformed as time goes on. The variation of total Josephson current has also been observed. It is found that, the perturbation terms play the role for phase frustration. The phase frustration achieves quicker for high tunneling current.

Intrinsically shunted Josephson junctions for electronics applications

NASA Astrophysics Data System (ADS)

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.

Precise Heater Controller with rf-Biased Josephson Junctions

NASA Technical Reports Server (NTRS)

Green, Colin J.; Sergatskov, Dmitri A.; Duncan, R. V.

2003-01-01

Paramagnetic susceptibility thermometers used in fundamental physics experiments are capable of measuring temperature changes with a precision of a part in 2 x 10(exp 10). However, heater controllers are only able to control open-loop power dissipation to about a part in 10(exp 5). We used an array of rf-biased Josephson junctions to precisely control the electrical power dissipation in a heater resistor mounted on a thermally isolated cryogenic platform. Theoretically, this method is capable of controlling the electrical power dissipation to better than a part in 10(exp 12). However, this level has not yet been demonstrated experimentally. The experiment consists of a liquid helium cell that also functions as a high-resolution PdMn thermometer, with a heater resistor mounted on it. The cell is thermally connected to a temperature-controlled cooling stage via a weak thermal link. The heater resistor is electrically connected to the array of Josephson junctions using superconducting wire. An rf-biased array of capacitively shunted Josephson junctions drives the voltage across the heater. The quantized voltage across the resistor is Vn = nf(h/2e), where h is Planck's constant, f is the array biasing frequency, e is the charge of an electron, and n is the integer quantum state of the Josephson array. This results in an electrical power dissipation on the cell of Pn = (Vn)(sup 2/R), where R is the heater resistance. The change of the quantum state of the array changes the power dissipated in the heater, which in turn, results in the change of the cell temperature. This temperature change is compared to the expected values based on the known thermal standoff resistance of the cell from the cooling stage. We will present our initial experimental results and discuss future improvements. This work has been funded by the Fundamental Physics Discipline of the Microgravity Science Office of NASA, and supported by a no-cost equipment loan from Sandia National Laboratories.

Supercurrent and multiple Andreev reflections in micrometer-long ballistic graphene Josephson junctions.

PubMed

Zhu, Mengjian; Ben Shalom, Moshe; Mishchsenko, Artem; Fal'ko, Vladimir; Novoselov, Kostya; Geim, Andre

2018-02-08

Ballistic Josephson junctions are predicted to support a number of exotic physics processess, providing an ideal system to inject the supercurrent in the quantum Hall regime. Herein, we demonstrate electrical transport measurements on ballistic superconductor-graphene-superconductor junctions by contacting graphene to niobium with a junction length up to 1.5 μm. Hexagonal boron nitride encapsulation and one-dimensional edge contacts guarantee high-quality graphene Josephson junctions with a mean free path of several micrometers and record-low contact resistance. Transports in normal states including the observation of Fabry-Pérot oscillations and Sharvin resistance conclusively witness the ballistic propagation in the junctions. The critical current density J C is over one order of magnitude larger than that of the previously reported junctions. Away from the charge neutrality point, the I C R N product (I C is the critical current and R N the normal state resistance of junction) is nearly a constant, independent of carrier density n, which agrees well with the theory for ballistic Josephson junctions. Multiple Andreev reflections up to the third order are observed for the first time by measuring the differential resistance in the micrometer-long ballistic graphene Josephson junctions.

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

NASA Astrophysics Data System (ADS)

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.

Ferromagnetic Josephson Junctions for Cryogenic Memory

NASA Astrophysics Data System (ADS)

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

2015-03-01

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

Short Ballistic Josephson Coupling in Planar Graphene Junctions with Inhomogeneous Carrier Doping

NASA Astrophysics Data System (ADS)

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.

Conditions for synchronization in Josephson-junction arrays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chernikov, A.A.; Schmidt, G.

An effective perturbation theoretical method has been developed to study the dynamics of Josephson Junction series arrays. It is shown that the inclusion of Junction capacitances, often ignored, has a significant impact on synchronization. Comparison of analytic with computational results over a wide range of parameters shows excellent agreement.

Effect of current injection into thin-film Josephson junctions

DOE PAGES

Kogan, V. G.; Mints, R. G.

2014-11-11

New thin-film Josephson junctions have recently been tested in which the current injected into one of the junction banks governs Josephson phenomena. One thus can continuously manage the phase distribution at the junction by changing the injected current. Our method of calculating the distribution of injected currents is also proposed for a half-infinite thin-film strip with source-sink points at arbitrary positions at the film edges. The strip width W is assumed small relative to Λ=2λ 2/d;λ is the bulk London penetration depth of the film material and d is the film thickness.

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

NASA Astrophysics Data System (ADS)

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.

Overdamped Nb/Al-AlO{sub x}/Nb Josephson junctions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lacquaniti, V.; Cagliero, C.; Maggi, S.

2005-01-24

We report the fabrication and characterization of overdamped Nb/Al-AlO{sub x}/Nb superconductor-insulator-superconductor Josephson junction whose fabrication process derives from that of the well-known hysteretic junctions. These junctions are an intermediate state between the superconductor-normal metal-superconductor and the superconductor-insulator-superconductor Josephson junctions. Stable and reproducible nonhysteretic current-voltage characteristics are obtained with a proper choice of the fabrication parameters. We have measured critical current densities J{sub C} from 10{sup 3} up to 2x10{sup 4} A/cm{sup 2}, with characteristic voltages from 80 to nearly 450 {mu}V. The junctions are stable against time and repeated thermal cycling.

High temperature superconductor step-edge Josephson junctions using Ti-Ca-Ba-Cu-O

DOEpatents

Ginley, David S.; Hietala, Vincent M.; Hohenwarter, Gert K. G.; Martens, Jon S.; Plut, Thomas A.; Tigges, Chris P.; Vawter, Gregory A.; Zipperian, Thomas E.

1994-10-25

A process for formulating non-hysteretic and hysteretic Josephson junctions using HTS materials which results in junctions having the ability to operate at high temperatures while maintaining high uniformity and quality. The non-hysteretic Josephson junction is formed by step-etching a LaAlO.sub.3 crystal substrate and then depositing a thin film of TlCaBaCuO on the substrate, covering the step, and forming a grain boundary at the step and a subsequent Josephson junction. Once the non-hysteretic junction is formed the next step to form the hysteretic Josephson junction is to add capacitance to the system. In the current embodiment, this is accomplished by adding a thin dielectric layer, LaA1O.sub.3, followed by a cap layer of a normal metal where the cap layer is formed by first depositing a thin layer of titanium (Ti) followed by a layer of gold (Au). The dielectric layer and the normal metal cap are patterned to the desired geometry.

Cryogenic Memories based on Spin-Singlet and Spin-Triplet Ferromagnetic Josephson Junctions

NASA Astrophysics Data System (ADS)

Gingrich, Eric

The last several decades have seen an explosion in the use and size of computers for scientific applications. The US Department of Energy has set an ExaScale computing goal for high performance computing that is projected to be unattainable by current CMOS computing designs. This has led to a renewed interest in superconducting computing as a means of beating these projections. One of the primary requirements of this thrust is the development of an efficient cryogenic memory. Estimates of power consumption of early Rapid Single Flux Quantum (RSFQ) memory designs are on the order of MW, far too steep for any real application. Therefore, other memory concepts are required. S/F/S Josephson Junctions, a class of device in which two superconductors (S) are separated by one or more ferromagnetic layers (F) has shown promise as a memory element. Several different systems have been proposed utilizing either the spin-singlet or spin-triplet superconducting states. This talk will discuss the concepts underpinning these devices, and the recent work done to demonstrate their feasibility. This research is supported in part by the Office of the Director of National Intelligence (ODNI), Intelligence Advanced Research Projects Activity (IARPA), via U.S. Army Research Office Contract W911NF-14-C-0115.

Josephson junctions in high-T/sub c/ superconductors

DOEpatents

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

1981-01-14

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

Majorana splitting from critical currents in Josephson junctions

NASA Astrophysics Data System (ADS)

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

2017-11-01

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

High-Tc SNS Junctions: A New Generation of Proximity-Coupled Josephson Devices

NASA Technical Reports Server (NTRS)

Kleinsasser, A. W.

1997-01-01

This paper reviews this evolution of proximity - coupled Josephson jucntion from the early investigations on low temperature superconductor-normal -superconductor junctions through the introduction of hybrid superconductor-semiconductor devices and the resulting interest in mesoscopic Josephson junctions, to the recent development of high temperature devices.

Coherent quantum transport in hybrid Nb-InGaAs-Nb Josephson junctions

NASA Astrophysics Data System (ADS)

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.

Ultimately short ballistic vertical graphene Josephson junctions

PubMed Central

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

2015-01-01

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

0-π phase-controllable thermal Josephson junction

NASA Astrophysics Data System (ADS)

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| < π/2 (refs 2-4). The direction of both the Josephson charge and heat currents can be inverted by adding a π shift to ϕ. In the static electrical case, this effect has been obtained in a few systems, for example via a ferromagnetic coupling or a non-equilibrium distribution in the weak link. These structures opened new possibilities for superconducting quantum logic and ultralow-power superconducting computers. Here, we report the first experimental realization of a thermal Josephson junction whose phase bias can be controlled from 0 to π. This is obtained thanks to a superconducting quantum interferometer that allows full control of the direction of the coherent energy transfer through the junction. This possibility, in conjunction with the completely superconducting nature of our system, provides temperature modulations with an unprecedented amplitude of ∼100 mK and transfer coefficients exceeding 1 K per flux quantum at 25 mK. Then, this quantum structure represents a fundamental step towards the realization of caloritronic logic components such as thermal transistors, switches and memory devices. These elements, combined with heat interferometers and diodes, would complete the thermal conversion of the most important phase-coherent electronic devices and benefit cryogenic microcircuits requiring energy management, such as quantum computing architectures and radiation sensors.

Spin-valve Josephson junctions for cryogenic memory

NASA Astrophysics Data System (ADS)

Niedzielski, Bethany M.; Bertus, T. J.; Glick, Joseph A.; Loloee, R.; Pratt, W. P.; Birge, Norman O.

2018-01-01

Josephson junctions containing two ferromagnetic layers are being considered for use in cryogenic memory. Our group recently demonstrated that the ground-state phase difference across such a junction with carefully chosen layer thicknesses could be controllably toggled between zero and π by switching the relative magnetization directions of the two layers between the antiparallel and parallel configurations. However, several technological issues must be addressed before those junctions can be used in a large-scale memory. Many of these issues can be more easily studied in single junctions, rather than in the superconducting quantum interference device (SQUID) used for phase-sensitive measurements. In this work, we report a comprehensive study of spin-valve junctions containing a Ni layer with a fixed thickness of 2.0 nm and a NiFe layer of thickness varying between 1.1 and 1.8 nm in steps of 0.1 nm. We extract the field shift of the Fraunhofer patterns and the critical currents of the junctions in the parallel and antiparallel magnetic states, as well as the switching fields of both magnetic layers. We also report a partial study of similar junctions containing a slightly thinner Ni layer of 1.6 nm and the same range of NiFe thicknesses. These results represent the first step toward mapping out a "phase diagram" for phase-controllable spin-valve Josephson junctions as a function of the two magnetic layer thicknesses.

Josephson junction in the quantum mesoscopic electric circuits with charge discreteness

NASA Astrophysics Data System (ADS)

Pahlavani, H.

2018-04-01

A quantum mesoscopic electrical LC-circuit with charge discreteness including a Josephson junction is considered and a nonlinear Hamiltonian that describing the dynamic of such circuit is introduced. The quantum dynamical behavior (persistent current probability) is studied in the charge and phase regimes by numerical solution approaches. The time evolution of charge and current, number-difference and the bosonic phase and also the energy spectrum of a quantum mesoscopic electric LC-circuit with charge discreteness that coupled with a Josephson junction device are investigated. We show the role of the coupling energy and the electrostatic Coulomb energy of the Josephson junction in description of the quantum behavior and the spectral properties of a quantum mesoscopic electrical LC-circuits with charge discreteness.

High temperature superconductor step-edge Josephson junctions using Ti-Ca-Ba-Cu-O

DOEpatents

Ginley, D.S.; Hietala, V.M.; Hohenwarter, G.K.G.; Martens, J.S.; Plut, T.A.; Tigges, C.P.; Vawter, G.A.; Zipperian, T.E.

1994-10-25

A process is disclosed for formulating non-hysteretic and hysteretic Josephson junctions using HTS materials which results in junctions having the ability to operate at high temperatures while maintaining high uniformity and quality. The non-hysteretic Josephson junction is formed by step-etching a LaAlO[sub 3] crystal substrate and then depositing a thin film of TlCaBaCuO on the substrate, covering the step, and forming a grain boundary at the step and a subsequent Josephson junction. Once the non-hysteretic junction is formed the next step to form the hysteretic Josephson junction is to add capacitance to the system. In the current embodiment, this is accomplished by adding a thin dielectric layer, LaA1O[sub 3], followed by a cap layer of a normal metal where the cap layer is formed by first depositing a thin layer of titanium (Ti) followed by a layer of gold (Au). The dielectric layer and the normal metal cap are patterned to the desired geometry. 8 figs.

Josephson junction devices: Model quantum mechanical systems and medical applications

NASA Astrophysics Data System (ADS)

Chen, Josephine

In this dissertation, three experiments using Josephson junction devices are described. In Part I, the effect of dissipation on tunneling between charge states in a superconducting single-electron transistor (sSET) was studied. The sSET was fabricated on top of a semi-conductor heterostructure with a two-dimensional electron gas (2DEG) imbedded beneath the surface. The 2DEG acted as a dissipative ground plane. The sheet resistance of the 2DEG could be varied in situ by applying a large voltage to a gate on the back of the substrate. The zero-bias conductance of the sSET was observed to increase with increasing temperature and 2DEG resistance. Some qualitative but not quantitative agreement was found with theoretical calculations of the functional dependence of the conductance on temperature and 2DEG resistance. Part II describes a series of experiments performed on magnesium diboride point-contact junctions. The pressure between the MgB2 tip and base pieces could be adjusted to form junctions with different characteristics. With light pressure applied between the two pieces, quasiparticle tunneling in superconductor-insulator-superconductor junctions was measured. From these data, a superconducting gap of approximately 2 meV and a critical temperature of 29 K were estimated. Increasing the pressure between the MgB2 pieces formed junctions with superconductor-normal metal-superconductor characteristics. We used these junctions to form MgB2 superconducting quantum interference devices (SQUIDS). Noise levels as low as 35 fT/Hz1/2 and 4 muphi 0/Hz1/2 at 1 kHz were measured. In Part III, we used a SQUID-based instrument to acquire magnetocardiograms (MCG), the magnetic field signal measured from the human heart. We measured 51 healthy volunteers and 11 cardiac patients both at rest and after treadmill exercise. We found age and sex related differences in the MCG of the healthy volunteers that suggest that these factors should be considered when evaluating the MCG for

Processing of Superconductor-Normal-Superconductor Josephson Edge Junctions

NASA Technical Reports Server (NTRS)

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.

Measure synchronization in a spin-orbit-coupled bosonic Josephson junction

NASA Astrophysics Data System (ADS)

Wang, Wen-Yuan; Liu, Jie; Fu, Li-Bin

2015-11-01

We present measure synchronization (MS) in a bosonic Josephson junction with spin-orbit coupling. The two atomic hyperfine states are coupled by a Raman dressing scheme, and they are regarded as two orientations of a pseudo-spin-1 /2 system. A feature specific to a spin-orbit-coupled (SOC) bosonic Josephson junction is that the transition from non-MS to MS dynamics can be modulated by Raman laser intensity, even in the absence of interspin atomic interaction. A phase diagram of non-MS and MS dynamics as functions of Raman laser intensity and Josephson tunneling amplitude is presented. Taking into account interspin atomic interactions, the system exhibits MS breaking dynamics resulting from the competition between intraspin and interspin atomic interactions. When interspin atomic interactions dominate in the competition, the system always exhibits MS dynamics. For interspin interaction weaker than intraspin interaction, a window for non-MS dynamics is present. Since SOC Bose-Einstein condensates provide a powerful platform for studies on physical problems in various fields, the study of MS dynamics is valuable in researching the collective coherent dynamical behavior in a spin-orbit-coupled bosonic Josephson junction.

Fractional Josephson vortices in two-gap superconductor long Josephson junctions

NASA Astrophysics Data System (ADS)

Kim, Ju

2014-03-01

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

Magnetically-driven colossal supercurrent enhancement in InAs nanowire Josephson junctions

PubMed Central

Tiira, J.; Strambini, E.; Amado, M.; Roddaro, S.; San-Jose, P.; Aguado, R.; Bergeret, F. S.; Ercolani, D.; Sorba, L.; Giazotto, F.

2017-01-01

The Josephson effect is a fundamental quantum phenomenon where a dissipationless supercurrent is introduced in a weak link between two superconducting electrodes by Andreev reflections. The physical details and topology of the junction drastically modify the properties of the supercurrent and a strong enhancement of the critical supercurrent is expected to occur when the topology of the junction allows an emergence of Majorana bound states. Here we report charge transport measurements in mesoscopic Josephson junctions formed by InAs nanowires and Ti/Al superconducting leads. Our main observation is a colossal enhancement of the critical supercurrent induced by an external magnetic field applied perpendicular to the substrate. This striking and anomalous supercurrent enhancement cannot be described by any known conventional phenomenon of Josephson junctions. We consider these results in the context of topological superconductivity, and show that the observed critical supercurrent enhancement is compatible with a magnetic field-induced topological transition. PMID:28401951

Exact analytical solution of a classical Josephson tunnel junction problem

NASA Astrophysics Data System (ADS)

Kuplevakhsky, S. V.; Glukhov, A. M.

2010-10-01

We give an exact and complete analytical solution of the classical problem of a Josephson tunnel junction of arbitrary length W ɛ(0,∞) in the presence of external magnetic fields and transport currents. Contrary to a wide-spread belief, the exact analytical solution unambiguously proves that there is no qualitative difference between so-called "small" (W≪1) and "large" junctions (W≫1). Another unexpected physical implication of the exact analytical solution is the existence (in the current-carrying state) of unquantized Josephson vortices carrying fractional flux and located near one of the edges of the junction. We also refine the mathematical definition of critical transport current.

Simulation and measurement of a Ka-band HTS MMIC Josephson junction mixer

NASA Astrophysics Data System (ADS)

Zhang, Ting; Pegrum, Colin; Du, Jia; Guo, Yingjie Jay

2017-01-01

We report modeling and simulation results for a Ka band high-temperature superconducting (HTS) monolithic microwave integrated circuit (MMIC) Josephson junction mixer. A Verilog-A model of a Josephson junction is established and imported into the system simulator to realize a full HTS MMIC circuit simulation containing the HTS passive circuit models. Impedance matching optimization between the junction and passive devices is investigated. Junction DC I-V characteristics, current and local oscillator bias conditions and mixing performance are simulated and compared with the experimental results. Good agreement is obtained between the simulation and measurement results.

Tunable 0-π transition by interband coupling in iron-based superconductor Josephson junctions

NASA Astrophysics Data System (ADS)

Tao, Y. C.; Liu, S. Y.; Bu, N.; Wang, J.; Di, Y. S.

2016-01-01

An extended four-component Bogoliubov-de Gennes equation is applied to study the Josephson effect in ballistic limit between either two iron-based superconductors (SCs) or an iron-based SC and a conventional s-wave SC, separated by a normal metal. A 0-π transition as a function of interband coupling strength α is always exhibited, arising from the tuning of mixing between the two trajectories with opposite phases. The novel property can be experimentally used to discriminate the {s}+/- -wave pairing symmetry in the iron-based SCs from the {s}++-wave one in MgB2. The effect of interface transparency on the 0-π transition is also presented. The 0-π transition as a function of α is wholly distinct from that as a function of barrier strength or temperature in recent theories (Linder et al 2009 Phys. Rev. B 80 020503(R)). The possible experimental probe of the phase-shift effect in iron-based SC Josephson junctions is commented on as well.

Classical analogs for Rabi-oscillations, Ramsey-fringes, and spin-echo in Josephson junctions

NASA Astrophysics Data System (ADS)

Marchese, J. E.; Cirillo, M.; Grønbech-Jensen, N.

2007-08-01

We investigate the results of recently published experiments on the quantum behavior of Josephson circuits in terms of the classical modeling based on the resistively and capacitively-shunted (RCSJ) junction model. Our analysis shows evidence for a close analogy between the nonlinear behavior of a pulsed microwave-driven Josephson junction at low temperature and low dissipation and the experimental observations reported for the Josephson circuits. Specifically, we demonstrate that Rabi-oscillations, Ramsey-fringes, and spin-echo observations are not phenomena with a unique quantum interpretation. In fact, they are natural consequences of transients to phase-locking in classical nonlinear dynamics and can be observed in a purely classical model of a Josephson junction when the experimental recipe for the application of microwaves is followed and the experimental detection scheme followed. We therefore conclude that classical nonlinear dynamics can contribute to the understanding of relevant experimental observations of Josephson response to various microwave perturbations at very low temperature and low dissipation.

Is there a relationship between curvature and inductance in the Josephson junction?

NASA Astrophysics Data System (ADS)

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.

Synchronization of Large Josephson-Junction Arrays by Traveling Electromagnetic Waves

NASA Astrophysics Data System (ADS)

Galin, M. A.; Borodianskyi, E. A.; Kurin, V. V.; Shereshevskiy, I. A.; Vdovicheva, N. K.; Krasnov, V. M.; Klushin, A. M.

2018-05-01

Mutual synchronization of many Josephson junctions is required for superradiant enhancement of the emission power. However, the larger the junction array is, the more difficult is the synchronization, especially when the array size becomes much larger than the emitted wavelength. Here, we study experimentally Josephson emission from such larger-than-the-wavelength Nb /NbSi /Nb junction arrays. For one of the arrays we observe a clear superradiant enhancement of emission above a threshold number of active junctions. The arrays exhibit strong geometrical resonances, seen as steps in current-voltage characteristics. However, radiation patterns of the arrays have forward-backward asymmetry, which is inconsistent with the solely geometrical resonance (standing-wave) mechanism of synchronization. We argue that the asymmetry provides evidence for an alternative mechanism of synchronization mediated by unidirectional traveling-wave propagation along the array (such as a surface plasmon). In this case, emission occurs predominantly in the direction of propagation of the traveling wave. Our conclusions are supported by numerical modeling of Josephson traveling-wave antenna. We argue that such a nonresonant mechanism of synchronization opens a possibility for phase locking of very large arrays of oscillators.

What happens in Josephson junctions at high critical current densities

NASA Astrophysics Data System (ADS)

Massarotti, D.; Stornaiuolo, D.; Lucignano, P.; Caruso, R.; Galletti, L.; Montemurro, D.; Jouault, B.; Campagnano, G.; Arani, H. F.; Longobardi, L.; Parlato, L.; Pepe, G. P.; Rotoli, G.; Tagliacozzo, A.; Lombardi, F.; Tafuri, F.

2017-07-01

The impressive advances in material science and nanotechnology are more and more promoting the use of exotic barriers and/or superconductors, thus paving the way to new families of Josephson junctions. Semiconducting, ferromagnetic, topological insulator and graphene barriers are leading to unconventional and anomalous aspects of the Josephson coupling, which might be useful to respond to some issues on key problems of solid state physics. However, the complexity of the layout and of the competing physical processes occurring in the junctions is posing novel questions on the interpretation of their phenomenology. We classify some significant behaviors of hybrid and unconventional junctions in terms of their first imprinting, i.e., current-voltage curves, and propose a phenomenological approach to describe some features of junctions characterized by relatively high critical current densities Jc. Accurate arguments on the distribution of switching currents will provide quantitative criteria to understand physical processes occurring in high-Jc junctions. These notions are universal and apply to all kinds of junctions.

Tunable ohmic environment using Josephson junction chains

NASA Astrophysics Data System (ADS)

Rastelli, Gianluca; Pop, Ioan M.

2018-05-01

We propose a scheme to implement a tunable, wide frequency-band dissipative environment using a double chain of Josephson junctions. The two parallel chains consist of identical superconducting quantum interference devices (SQUIDs), with magnetic-flux tunable inductance, coupled to each other at each node via a capacitance much larger than the junction capacitance. Thanks to this capacitive coupling, the system sustains electromagnetic modes with a wide frequency dispersion. The internal quality factor of the modes is maintained as high as possible, and the damping is introduced by a uniform coupling of the modes to a transmission line, itself connected to an amplification and readout circuit. For sufficiently long chains, containing several thousands of junctions, the resulting admittance is a smooth function versus frequency in the microwave domain, and its effective dissipation can be continuously monitored by recording the emitted radiation in the transmission line. We show that by varying in situ the SQUIDs' inductance, the double chain can operate as a tunable ohmic resistor in a frequency band spanning up to 1 GHz, with a resistance that can be swept through values comparable to the resistance quantum Rq=h /(4 e2) ≃6.5 kΩ . We argue that the circuit complexity is within reach using current Josephson junction technology.

Underdamped long Josephson junction coupled to overdamped single-flux-quantum circuits

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Y.M.; Borzenets, V.; Kaplunenko, V.K.

1997-09-01

We report a circuit that integrates an underdamped long Josephson junction with overdamped single-flux-quantum (SFQ) circuits. We confirm that the resonant soliton modes in the long junction are not affected by SFQ cells coupled to the junction, and demonstrate that the radiation frequency and linewidth of the soliton resonances can be measured with SFQ T-flip-flops. Our experimental results also show that a 4{pi} quantum mechanical phase leap at the end of the long junction, which is due to the reflection of a soliton, creates two single flux quanta propagating in the overdamped Josephson transmission line. {copyright} {ital 1997 American Institutemore » of Physics.}« less

Fabrication of Josephson Junction without shadow evaporation

NASA Astrophysics Data System (ADS)

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

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

4π-periodic Josephson supercurrent in HgTe-based topological Josephson junctions

PubMed Central

Wiedenmann, J.; Bocquillon, E.; Deacon, R. S.; Hartinger, S.; Herrmann, O.; Klapwijk, T. M.; Maier, L.; Ames, C.; Brüne, C.; Gould, C.; Oiwa, A.; Ishibashi, K.; Tarucha, S.; Buhmann, H.; Molenkamp, L. W.

2016-01-01

The Josephson effect describes the generic appearance of a supercurrent in a weak link between two superconductors. Its exact physical nature deeply influences the properties of the supercurrent. In recent years, considerable efforts have focused on the coupling of superconductors to the surface states of a three-dimensional topological insulator. In such a material, an unconventional induced p-wave superconductivity should occur, with a doublet of topologically protected gapless Andreev bound states, whose energies vary 4π-periodically with the superconducting phase difference across the junction. In this article, we report the observation of an anomalous response to rf irradiation in a Josephson junction made of a HgTe weak link. The response is understood as due to a 4π-periodic contribution to the supercurrent, and its amplitude is compatible with the expected contribution of a gapless Andreev doublet. Our work opens the way to more elaborate experiments to investigate the induced superconductivity in a three-dimensional insulator. PMID:26792013

Effect of interjunction coupling on superconducting current and charge correlations in intrinsic Josephson junctions

NASA Astrophysics Data System (ADS)

Shukrinov, Yu. M.; Hamdipour, M.; Kolahchi, M. R.

2009-07-01

Charge formations on superconducting layers and creation of the longitudinal plasma wave in the stack of intrinsic Josephson junctions change crucially the superconducting current through the stack. Investigation of the correlations of superconducting currents in neighboring Josephson junctions and the charge correlations in neighboring superconducting layers allows us to predict the additional features in the current-voltage characteristics. The charge autocorrelation functions clearly demonstrate the difference between harmonic and chaotic behavior in the breakpoint region. Use of the correlation functions gives us a powerful method for the analysis of the current-voltage characteristics of coupled Josephson junctions.

Ballistic Graphene Josephson Junctions from the Short to the Long Junction Regimes.

PubMed

Borzenets, I V; Amet, F; Ke, C T; Draelos, A W; Wei, M T; Seredinski, A; Watanabe, K; Taniguchi, T; Bomze, Y; Yamamoto, M; Tarucha, S; Finkelstein, G

2016-12-02

We investigate the critical current I_{C} of ballistic Josephson junctions made of encapsulated graphene-boron-nitride heterostructures. We observe a crossover from the short to the long junction regimes as the length of the device increases. In long ballistic junctions, I_{C} is found to scale as ∝exp(-k_{B}T/δE). The extracted energies δE are independent of the carrier density and proportional to the level spacing of the ballistic cavity. As T→0 the critical current of a long (or short) junction saturates at a level determined by the product of δE (or Δ) and the number of the junction's transversal modes.

Resonant TMR inversion in LiF/EuS based spin-filter tunnel junctions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Fen; Chen, Aixi; Institute for Quantum Computing & Department of Electrical and Computer Engineering, University of Waterloo, Waterloo, ON N2L 3G1 Canada

Resonant tunneling can lead to inverse tunnel magnetoresistance when impurity levels rather than direct tunneling dominate the transport process. We fabricated hybrid magnetic tunnel junctions of CoFe/LiF/EuS/Ti, with an epitaxial LiF energy barrier joined with a polycrystalline EuS spin-filter barrier. Due to the water solubility of LiF, the devices were fully packaged in situ. The devices showed sizeable positive TMR up to 16% at low bias voltages but clearly inverted TMR at higher bias voltages. The TMR inversion depends sensitively on the thickness of LiF, and the tendency of inversion disappears when LiF gets thick enough and recovers its intrinsicmore » properties.« less

A semiconductor nanowire Josephson junction microwave laser

NASA Astrophysics Data System (ADS)

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

We present measurements of microwave lasing from a single Al/InAs/Al nanowire Josephson junction strongly coupled to a high quality factor superconducting cavity. Application of a DC bias voltage to the Josephson junction results in photon emission into the cavity when the bias voltage is equal to a multiple of the cavity frequency. At large voltage biases, the strong non-linearity of the circuit allows for efficient down conversion of high frequency microwave photons down to multiple photons at the fundamental frequency of the cavity. In this regime, the emission linewidth narrows significantly below the bare cavity linewidth to < 10 kHz and real time analysis of the emission statistics shows above threshold lasing with a power conversion efficiency > 50%. The junction-cavity coupling and laser emission can be tuned rapidly via an external gate, making it suitable to be integrated into a scalable qubit architecture as a versatile source of coherent microwave radiation. This work has been supported by the Netherlands Organisation for Scientific Research (NWO/OCW), Foundation for Fundamental Research on Matter (FOM), European Research Council (ERC), and Microsoft Corporation Station Q.

Measurement of Aharonov-Casher effect in a Josephson junction chain

NASA Astrophysics Data System (ADS)

Pop, Ioan Mihai; Lecocq, Florent; Pannetier, Bernard; Buisson, Olivier; Guichard, Wiebke

2011-03-01

We have recently measured the effect of superconducting phase-slips on the ground state of a Josephson junction chain and a rhombi chain. Here we report clear evidence of Aharonov-Casher effect in a chain of Josephson junctions. This phenomenon is the dual of the well known Aharonov-Bohm interference. Using a capacitively coupled gate to the islands of the chain, we induce oscillations of the supercurrent by tuning the polarization charges on the islands. We observe complex interference patterns for different quantum phase slip amplitudes, that we understand quantitatively as Aharonov-Casher vortex interferences. European STREP MIDAS.

Ultralow power artificial synapses using nanotextured magnetic Josephson junctions.

PubMed

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.

Ultralow power artificial synapses using nanotextured magnetic Josephson junctions

PubMed Central

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

Applications of Josephson Junction SQUIDs (Superconducting Quantum Interference Device) and Arrays.

DTIC Science & Technology

1982-11-01

Research, Cntract 7he transient respose is doinated by o NO. 00014-61-C-0615. and Wj. Figure 2 shows the time evolution of e a:d e M for owI, 0-1 and 5...connect a dc S 0UID "Shunted Josephson Tunel Junctions- if gh transmitter with another dc SQU D receiver by a Frequency, Self -Pvmd L Nise lifiers...resistive SQUID WVO incidentally to their self -puVzed Josepson perametric2 mplifier. Using a SQJID with 6 -2. ZmpHi, r-3xlO . and a in matching

Tunable-φ Josephson junction with a quantum anomalous Hall insulator

NASA Astrophysics Data System (ADS)

Sakurai, Keimei; Ikegaya, Satoshi; Asano, Yasuhiro

2017-12-01

We theoretically study the Josephson current in a superconductor/quantum anomalous Hall insulator/superconductor junction by using the lattice Green function technique. When an in-plane external Zeeman field is applied to the quantum anomalous Hall insulator, the Josephson current J flows without a phase difference across the junction θ . The phase shift φ appearing in the current-phase relationship J ∝sin(θ -φ ) is proportional to the amplitude of Zeeman fields and depends on the direction of Zeeman fields. A phenomenological analysis of the Andreev reflection processes explains the physical origin of φ . In a quantum anomalous Hall insulator, time-reversal symmetry and mirror-reflection symmetry are broken simultaneously. However, magnetic mirror-reflection symmetry is preserved. Such characteristic symmetry properties enable us to have a tunable φ junction with a quantum Hall insulator.

Tunneling conductance in superconductor-hybrid double quantum dots Josephson junction

NASA Astrophysics Data System (ADS)

Chamoli, Tanuj; Ajay

2018-05-01

The present work deals with the theoretical model study to analyse the tunneling conductance across a superconductor hybrid double quantum dots tunnel junction (S-DQD-S). Recently, there are many experimental works where the Josephson current across such nanoscopic junction is found to be dependent on nature of the superconducting electrodes, coupling of the hybrid double quantum dot's electronic states with the electronic states of the superconductors and nature of electronic structure of the coupled dots. For this, we have attempted a theoretical model containing contributions of BCS superconducting leads, magnetic coupled quantum dot states and coupling of superconducting leads with QDs. In order to include magnetic coupled QDs the contributions of competitive Kondo and Ruderman-Kittel- Kasuya-Yosida (RKKY) interaction terms are also introduced through many body effects in the model Hamiltonian at low temperatures (where Kondo temperature TK < superconducting transition temperature TC). Employing non-equilibrium Green's function approach within mean field approximation, we have obtained expressions for density of states (DOS) and analysed the same using numerical computation to underline the nature of DOS close to Fermi level in S-DQD-S junctions. On the basis of numerical computation, it is pointed out that indirect exchange interaction between impurities (QD) i.e. RKKY interaction suppresses the screening of magnetic QD due to Cooper pair electrons i.e. Kondo effect in the form of reduction in the magnitude of sharp DOS peak close to Fermi level which is in qualitative agreement with the experimental observations in such tunnel junctions. Tunneling conductance is proportional to DOS, hence we can analyse it's behaviour with the help of DOS.

Edge currents in frustrated Josephson junction ladders

NASA Astrophysics Data System (ADS)

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

2016-09-01

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

Ferromagnetic resonance with long Josephson junction

NASA Astrophysics Data System (ADS)

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.

Phase retrapping in a pointlike φ Josephson junction: the butterfly effect.

PubMed

Goldobin, E; Kleiner, R; Koelle, D; Mints, R G

2013-08-02

We consider a φ Josephson junction, which has a bistable zero-voltage state with the stationary phases ψ = ±φ. In the nonzero voltage state the phase "moves" viscously along a tilted periodic double-well potential. When the tilting is reduced quasistatically, the phase is retrapped in one of the potential wells. We study the viscous phase dynamics to determine in which well (-φ or +φ) the phase is retrapped for a given damping, when the junction returns from the finite-voltage state back to the zero-voltage state. In the limit of low damping, the φ Josephson junction exhibits a butterfly effect-extreme sensitivity of the destination well on damping. This leads to an impossibility to predict the destination well.

Detailed investigation of the bifurcation diagram of capacitively coupled Josephson junctions in high-Tc superconductors and its self similarity

NASA Astrophysics Data System (ADS)

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.

Current–phase relations of few-mode InAs nanowire Josephson junctions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Spanton, Eric M.; Deng, Mingtang; Vaitiekėnas, Saulius

Gate-tunable semiconductor nanowires with superconducting leads have great potential for quantum computation and as model systems for mesoscopic Josephson junctions. The supercurrent, I, versus the phase, Φ, across the junction is called the current–phase relation (CPR). It can reveal not only the amplitude of the critical current, but also the number of modes and their transmission. Here, we measured the CPR of many individual InAs nanowire Josephson junctions, one junction at a time. Both the amplitude and shape of the CPR varied between junctions, with small critical currents and skewed CPRs indicating few-mode junctions with high transmissions. In a gate-tunablemore » junction, we found that the CPR varied with gate voltage: near the onset of supercurrent, we observed behaviour consistent with resonant tunnelling through a single, highly transmitting mode. The gate dependence is consistent with modelled subband structure that includes an effective tunnelling barrier due to an abrupt change in the Fermi level at the boundary of the gate-tuned region. These measurements of skewed, tunable, few-mode CPRs are promising both for applications that require anharmonic junctions and for Majorana readout proposals.« less

Current–phase relations of few-mode InAs nanowire Josephson junctions

DOE PAGES

Spanton, Eric M.; Deng, Mingtang; Vaitiekėnas, Saulius; ...

2017-08-14

Gate-tunable semiconductor nanowires with superconducting leads have great potential for quantum computation and as model systems for mesoscopic Josephson junctions. The supercurrent, I, versus the phase, Φ, across the junction is called the current–phase relation (CPR). It can reveal not only the amplitude of the critical current, but also the number of modes and their transmission. Here, we measured the CPR of many individual InAs nanowire Josephson junctions, one junction at a time. Both the amplitude and shape of the CPR varied between junctions, with small critical currents and skewed CPRs indicating few-mode junctions with high transmissions. In a gate-tunablemore » junction, we found that the CPR varied with gate voltage: near the onset of supercurrent, we observed behaviour consistent with resonant tunnelling through a single, highly transmitting mode. The gate dependence is consistent with modelled subband structure that includes an effective tunnelling barrier due to an abrupt change in the Fermi level at the boundary of the gate-tuned region. These measurements of skewed, tunable, few-mode CPRs are promising both for applications that require anharmonic junctions and for Majorana readout proposals.« less

Investigation of properties of nanobridge Josephson junctions and superconducting tracks fabricated by FIB

NASA Astrophysics Data System (ADS)

Li, B.; Godfrey, T.; Cox, D.; Li, T.; Gallop, J.; Galer, S.; Nisbet, A.; Romans, Ed; Hao, L.

2018-02-01

An important requirement across a range of sensitive detectors is to determine accurately the energy deposited by the impact of a particle in a small volume. The particle may be anything from a visible photon through to an X-ray or massive charged particle. We have been developing nanobridge Josephson junctions based SQUIDs and nanoSQUID devices covering the entire range of particle detection energies from 1eV to MeV. In this paper we discuss some developments in nanobridge Josephson junctions fabrication using focussed ion beam (FIB) and how these developments impact future applications. We focus on tuning of the transition temperature of a superconducting thin-film absorber, with the aim to match the absorber Tc to the working temperature range of the SQUID and also on using a new Xe FIB to improve Josephson junction and superconducting film quality.

Fabrication of a Tantalum-Based Josephson Junction for an X-Ray Detector

NASA Astrophysics Data System (ADS)

Morohashi, Shin'ichi; Gotoh, Kohtaroh; Yokoyama, Naoki

2000-06-01

We have fabricated a tantalum-based Josephson junction for an X-ray detector. The tantalum layer was selected for the junction electrode because of its long quasiparticle lifetime, large X-ray absorption efficiency and stability against thermal cycling. We have developed a buffer layer to fabricate the tantalum layer with a body-centered cubic structure. Based on careful consideration of their superconductivity, we have selected a niobium thin layer as the buffer layer for fabricating the tantalum base electrode, and a tungsten thin layer for the tantalum counter electrode. Fabricated Nb/AlOx-Al/Ta/Nb and Nb/Ta/W/AlOx-Al/Ta/Nb Josephson junctions exhibited current-voltage characteristics with a low subgap leakage current.

Low-noise current amplifier based on mesoscopic Josephson junction.

PubMed

Delahaye, J; Hassel, J; Lindell, R; Sillanpää, M; Paalanen, M; Seppä, H; Hakonen, P

2003-02-14

We used the band structure of a mesoscopic Josephson junction to construct low-noise amplifiers. By taking advantage of the quantum dynamics of a Josephson junction, i.e., the interplay of interlevel transitions and the Coulomb blockade of Cooper pairs, we created transistor-like devices, Bloch oscillating transistors, with considerable current gain and high-input impedance. In these transistors, the correlated supercurrent of Cooper pairs is controlled by a small base current made up of single electrons. Our devices reached current and power gains on the order of 30 and 5, respectively. The noise temperature was estimated to be around 1 kelvin, but noise temperatures of less than 0.1 kelvin can be realistically achieved. These devices provide quantum-electronic building blocks that will be useful at low temperatures in low-noise circuit applications with an intermediate impedance level.

Low frequency critical current noise and two level system defects in Josephson junctions

NASA Astrophysics Data System (ADS)

Nugroho, Christopher Daniel

The critical current in a Josephson junction is known to exhibit a 1/falpha low frequency noise. Implemented as a superconducting qubit, this low frequency noise can lead to decoherence. While the 1/f noise has been known to arise from an ensemble of two level systems connected to the tunnel barrier, the precise microscopic nature of these TLSs remain a mystery. In this thesis we will present measurements of the 1/f alpha low frequency noise in the critical current and tunneling resistance of Al-AlOx-Al Josephson junctions. Measurements in a wide range of resistively shunted and unshunted junctions confirm the equality of critical current and tunneling resistance noise. That is the critical current fluctuation corresponds to fluctuations of the tunneling resistance. In not too small Al-AlOx-Al junctions we have found that the fractional power spectral density scales linearly with temperature. We confirmed that the 1/falpha power spectrum is the result of a large number of two level systems modulating the tunneling resistance. At small junction areas and low temperatures, the number of thermally active TLSs is insufficient to integrate out a featureless 1/ f spectral shape. By analyzing the spectral variance in small junction areas, we have been able to deduce the TLS defect density, n ≈ 2.53 per micrometer squared per Kelvin spread in the TLS energy per factor e in the TLS lifetimes. This density is consistent with the density of tunneling TLSs found in glassy insulators, as well as the density deduced from coherent TLSs interacting at qubit frequencies. The deduced TLS density combined with the magnitude of the 1/f power spectral density in large area junctions, gives an average TLS effective area, A ˜ 0.3 nanometer squared. In ultra small tunnel junctions, we have studied the time-domain dynamics of isolated TLSs. We have found a TLS whose dynamics is described by the quantum tunneling between the two localized wells, and a one-phonon absorption

Fluoride barriers in Nb/Pb Josephson junctions

NASA Astrophysics Data System (ADS)

Asano, H.; Tanabe, K.; Michikami, O.; Igarashi, M.; Beasley, M. R.

1985-03-01

Josephson tunnel junctions are fabricated using a new class of artificial barriers, metal fluorides (Al fluoride and Zr fluoride). These fluoride barriers are deposited on the surface of a Nb base electrode, which are previously cleaned using a CF4 cleaning process, and covered by a Pb counterelectrode. The junctions with both Al fluoride and Zr fluoride barriers exhibit good tunneling characteristics and have low specific capacitance. In the case of Zr fluoride, it is observed that reasonable resistances are obtained even at thickness greater than 100 A. This phenomenon might be explained by tunneling via localized states in Zr fluoride.

Thin-film metal coated insulation barrier in a Josephson tunnel junction. [Patent application

DOEpatents

Hawkins, G.A.; Clarke, J.

1975-10-31

A highly stable, durable, and reproducible Josephson tunnel junction consists of a thin-film electrode of a hard superconductor, a thin oxide insulation layer over the electrode constituting a Josephson tunnel junction barrier, a thin-film layer of stabilizing metal over the barrier, and a second thin-film hard superconductive electrode over the stabilizing film. The thin stabilizing metal film is made only thick enough to limit penetration of the electrode material through the insulation layer so as to prevent a superconductive short.

Magnetic field penetration in niobium- and vanadium-based Josephson junctions

NASA Astrophysics Data System (ADS)

Cucolo, A. M.; Pace, S.; Vaglio, R.; di Chiara, A.; Peluso, G.; Russo, M.

1983-02-01

Measurements on the temperature dependence of the magnetic field penetration in Nb-NbxOy-Pb and V-VxOy-Pb Josephson junctions have been performed. Results on the zero-temperature penetration depth in niobium films are far above the bulk values although consistent with other measurements on junctions reported in the literature. For vanadium junctions anomalously large penetration depth values are obtained at low temperatures. Nevertheless, the temperature dependence is in reasonable agreement with the local dirty limit model.

Linewidth dependence of coherent terahertz emission from Bi2Sr2CaCu2O8 intrinsic Josephson junction stacks in the hot-spot regime

NASA Astrophysics Data System (ADS)

Li, Mengyue; Yuan, Jie; Kinev, Nickolay; Li, Jun; Gross, Boris; Guénon, Stefan; Ishii, Akira; Hirata, Kazuto; Hatano, Takeshi; Koelle, Dieter; Kleiner, Reinhold; Koshelets, Valery P.; Wang, Huabing; Wu, Peiheng

2012-08-01

We report on measurements of the linewidth Δf of terahertz radiation emitted from intrinsic Josephson junction stacks, using a Nb/AlN/NbN integrated receiver for detection. Previous resolution-limited measurements indicated that Δf may be below 1 GHz—much smaller than expected from a purely cavity-induced synchronization. While at low bias we found Δf to be not smaller than ˜500 MHz, at high bias, where a hot spot coexists with regions which are still superconducting, Δf turned out to be as narrow as 23 MHz. We attribute this to the hot spot acting as a synchronizing element. Δf decreases with increasing bath temperature, a behavior reminiscent of motional narrowing in NMR or electron spin resonance (ESR), but hard to explain in standard electrodynamic models of Josephson junctions.

Majorana zero modes in Dirac semimetal Josephson junctions

NASA Astrophysics Data System (ADS)

Li, Chuan; de Boer, Jorrit; de Ronde, Bob; Huang, Yingkai; Golden, Mark; Brinkman, Alexander

We have realized proximity-induced superconductivity in a Dirac semimetal and revealed the topological nature of the superconductivity by the observation of Majorana zero modes. As a Dirac semimetal, Bi0.97Sb0.03 is used, where a three-dimensional Dirac cone exists in the bulk due to an accidental touching between conduction and valence bands. Electronic transport measurements on Hall-bars fabricated out of Bi0.97Sb0.03 flakes consistently show negative magnetoresistance for magnetic fields parallel to the current, which is associated with the chiral anomaly. In perpendicular magnetic fields, we see Shubnikov-de Haas oscillations that indicate very low carrier densities. The low Fermi energy and protection against backscattering in our Dirac semimetal Josephson junctions provide favorable conditions for a large contribution of Majorana zero modes to the supercurrent. In radiofrequency irradiation experiments, we indeed observe these Majorana zero modes in Nb-Bi0.97Sb0.03-Nb Josephson junctions as a 4 π periodic contribution to the current-phase relation.

Long Josephson tunnel junctions with doubly connected electrodes

NASA Astrophysics Data System (ADS)

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

2012-03-01

In order to mimic the phase changes in the primordial Big Bang, several cosmological solid-state experiments have been conceived, during the last decade, to investigate the spontaneous symmetry breaking in superconductors and superfluids cooled through their transition temperature. In one of such experiments, the number of magnetic flux quanta spontaneously trapped in a superconducting loop was measured by means of a long Josephson tunnel junction built on top of the loop itself. We have analyzed this system and found a number of interesting features not occurring in the conventional case with simply connected electrodes. In particular, the fluxoid quantization results in a frustration of the Josephson phase, which, in turn, reduces the junction critical current. Further, the possible stable states of the system are obtained by a self-consistent application of the principle of minimum energy. The theoretical findings are supported by measurements on a number of samples having different geometrical configuration. The experiments demonstrate that a very large signal-to-noise ratio can be achieved in the flux quanta detection.

Engineering double-well potentials with variable-width annular Josephson tunnel junctions

NASA Astrophysics Data System (ADS)

Monaco, Roberto

2016-11-01

Long Josephson tunnel junctions are non-linear transmission lines that allow propagation of current vortices (fluxons) and electromagnetic waves and are used in various applications within superconductive electronics. Recently, the Josephson vortex has been proposed as a new superconducting qubit. We describe a simple method to create a double-well potential for an individual fluxon trapped in a long elliptic annular Josephson tunnel junction characterized by an intrinsic non-uniform width. The distance between the potential wells and the height of the inter-well potential barrier are controlled by the strength of an in-plane magnetic field. The manipulation of the vortex states can be achieved by applying a proper current ramp across the junction. The read-out of the state is accomplished by measuring the vortex depinning current in a small magnetic field. An accurate one-dimensional sine-Gordon model for this strongly non-linear system is presented, from which we calculate the position-dependent fluxon rest-mass, its Hamiltonian density and the corresponding trajectories in the phase space. We examine the dependence of the potential properties on the annulus eccentricity and its electrical parameters and address the requirements for observing quantum-mechanical effects, as discrete energy levels and tunneling, in this two-state system.

Josephson junction microwave modulators for qubit control

NASA Astrophysics Data System (ADS)

Naaman, O.; Strong, J. A.; Ferguson, D. G.; Egan, J.; Bailey, N.; Hinkey, R. T.

2017-02-01

We demonstrate Josephson junction based double-balanced mixer and phase shifter circuits operating at 6-10 GHz and integrate these components to implement both a monolithic amplitude/phase vector modulator and an I/Q quadrature mixer. The devices are actuated by flux signals, dissipate no power on chip, exhibit input saturation powers in excess of 1 nW, and provide cryogenic microwave modulation solutions for integrated control of superconducting qubits.

High-efficiency thermal switch based on topological Josephson junctions

NASA Astrophysics Data System (ADS)

Sothmann, Björn; Giazotto, Francesco; Hankiewicz, Ewelina M.

2017-02-01

We propose theoretically a thermal switch operating by the magnetic-flux controlled diffraction of phase-coherent heat currents in a thermally biased Josephson junction based on a two-dimensional topological insulator. For short junctions, the system shows a sharp switching behavior while for long junctions the switching is smooth. Physically, the switching arises from the Doppler shift of the superconducting condensate due to screening currents induced by a magnetic flux. We suggest a possible experimental realization that exhibits a relative temperature change of 40% between the on and off state for realistic parameters. This is a factor of two larger than in recently realized thermal modulators based on conventional superconducting tunnel junctions.

Asymmetry of the velocity-matching steps in YBCO long Josephson junctions

NASA Astrophysics Data System (ADS)

Revin, L. S.; Pankratov, A. L.; Chiginev, A. V.; Masterov, D. V.; Parafin, A. E.; Pavlov, S. A.

2018-04-01

We carry out experimental and theoretical investigations into the effect of the vortex chain propagation on the current-voltage characteristics of YBa2Cu3O7-δ (YBCO) long Josephson junctions. Samples of YBCO Josephson junctions, fabricated on 24° [001]-tilt bicrystal substrates, have been measured. The improved technology has allowed us to observe and study the asymmetry of the current-voltage characteristics with opposite magnetic fields (Revin et al 2012 J. Appl. Phys. 114 243903), which we believe occurs due to anisotropy of bicrystal substrates (Kupriyanov et al (2013 JETP Lett. 95 289)). Specifically, we examine the flux-flow resonant steps versus the external magnetic field, and study the differential resistance and its relation to oscillation power for opposite directions of vortex propagation.

The c-axis charge traveling wave in a coupled system of Josephson junctions

NASA Astrophysics Data System (ADS)

Shukrinov, Yu. M.; Hamdipour, M.

2012-05-01

We demonstrate a manifestation of the charge traveling wave along the c axis (TW) in current voltage characteristics of coupled Josephson junctions in high- T c superconductors. The branches related to the TW with different wavelengths are found for the stacks with different number of Josephson junctions at different values of system's parameters. Transitions between the TW branches and the outermost branch are observed. The electric charge in the superconducting layers and charge-charge correlation functions for TW and outermost branches show different behavior with bias current. We propose an experimental testing of the TW branching by microwave irradiation.

Current driven transition from Abrikosov-Josephson to Josephson-like vortex in mesoscopic lateral S/S’/S superconducting weak links

PubMed Central

Carapella, G.; Sabatino, P.; Barone, C.; Pagano, S.; Gombos, M.

2016-01-01

Vortices are topological defects accounting for many important effects in superconductivity, superfluidity, and magnetism. Here we address the stability of a small number of such excitations driven by strong external forces. We focus on Abrikosov-Josephson vortex that appears in lateral superconducting S/S’/S weak links with suppressed superconductivity in S’. In such a system the vortex is nucleated and confined in the narrow S’ region by means of a small magnetic field and moves under the effect of a force proportional to an applied electrical current with a velocity proportional to the measured voltage. Our numerical simulations show that when a slow moving Abrikosov-Josephson vortex is driven by a strong constant current it becomes unstable with respect to a faster moving excitation: the Josephon-like vortex. Such a current-driven transition explains the structured dissipative branches that we observe in the voltage-current curve of the weak link. When vortex matter is strongly confined phenomena as magnetoresistance oscillations and reentrance of superconductivity can possibly occur. We experimentally observe these phenomena in our weak links. PMID:27752137

Terahertz emission from thermally-managed square intrinsic Josephson junction microstrip antennas

NASA Astrophysics Data System (ADS)

Klemm, Richard; Davis, Andrew; Wang, Qing

We show for thin square microstrip antennas that the transverse magnetic electromagnetic cavity modes are greatly restricted in number due to the point group symmetry of a square. For the ten lowest frequency emissions, we present plots of the orthonormal wave functions and of the angular distributions of the emission power obtained from the uniform Josephson current source and from the excitation of an electromagnetic cavity mode excited in the intrinsic Josephson junctions between the layers of a highly anisotropic layered superconductor.

Controllable 0–π Josephson junctions containing a ferromagnetic spin valve

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gingrich, E. C.; Niedzielski, Bethany M.; Glick, Joseph A.

Superconductivity and ferromagnetism are antagonistic forms of order, and rarely coexist. Many interesting new phenomena occur, however, in hybrid superconducting/ferromagnetic systems. For example, a Josephson junction containing a ferromagnetic material can exhibit an intrinsic phase shift of π in its ground state for certain thicknesses of the material. Such ‘π-junctions’ were first realized experimentally in 2001, and have been proposed as circuit elements for both high-speed classical superconducting computing and for quantum computing. Here we demonstrate experimentally that the phase state of a Josephson junction containing two ferromagnetic layers can be toggled between 0 and pi by changing the relativemore » orientation of the two magnetizations. These controllable 0–π junctions have immediate applications in cryogenic memory, where they serve as a necessary component to an ultralow power superconducting computer. Such a fully superconducting computer is estimated to be orders of magnitude more energy-efficient than current semiconductor-based supercomputers. Here, phase-controllable junctions also open up new possibilities for superconducting circuit elements such as superconducting ‘programmable logic’, where they could function in superconducting analogues to field-programmable gate arrays.« less

Controllable 0–π Josephson junctions containing a ferromagnetic spin valve

DOE PAGES

Gingrich, E. C.; Niedzielski, Bethany M.; Glick, Joseph A.; ...

2016-03-14

Superconductivity and ferromagnetism are antagonistic forms of order, and rarely coexist. Many interesting new phenomena occur, however, in hybrid superconducting/ferromagnetic systems. For example, a Josephson junction containing a ferromagnetic material can exhibit an intrinsic phase shift of π in its ground state for certain thicknesses of the material. Such ‘π-junctions’ were first realized experimentally in 2001, and have been proposed as circuit elements for both high-speed classical superconducting computing and for quantum computing. Here we demonstrate experimentally that the phase state of a Josephson junction containing two ferromagnetic layers can be toggled between 0 and pi by changing the relativemore » orientation of the two magnetizations. These controllable 0–π junctions have immediate applications in cryogenic memory, where they serve as a necessary component to an ultralow power superconducting computer. Such a fully superconducting computer is estimated to be orders of magnitude more energy-efficient than current semiconductor-based supercomputers. Here, phase-controllable junctions also open up new possibilities for superconducting circuit elements such as superconducting ‘programmable logic’, where they could function in superconducting analogues to field-programmable gate arrays.« less

Critical current oscillations of elliptical Josephson junctions with single-domain ferromagnetic layers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Glick, Joseph A.; Khasawneh, Mazin A.; Niedzielski, Bethany M.

We report that josephson junctions containing ferromagnetic layers are of considerable interest for the development of practical cryogenic memory and superconducting qubits. Such junctions exhibit a ground-state phase shift of π for certain ranges of ferromagnetic layer thicknesses. We present studies of Nb based micron-scale elliptically shaped Josephson junctions containing ferromagnetic barriers of Ni 81Fe 19 or Ni 65Fe 15Co 20. By applying an external magnetic field, the critical current of the junctions is found to follow characteristic Fraunhofer patterns and display sharp switching behavior suggestive of single-domain magnets. The high quality of the Fraunhofer patterns enables us to extractmore » the maximum value of the critical current even when the peak is shifted significantly outside the range of the data due to the magnetic moment of the ferromagnetic layer. The maximum value of the critical current oscillates as a function of the ferromagnetic barrier thickness, indicating transitions in the phase difference across the junction between values of zero and π. Lastly, we compare the data to previous work and to models of the 0-π transitions based on existing theories.« less

Critical current oscillations of elliptical Josephson junctions with single-domain ferromagnetic layers

DOE PAGES

Glick, Joseph A.; Khasawneh, Mazin A.; Niedzielski, Bethany M.; ...

2017-10-06

We report that josephson junctions containing ferromagnetic layers are of considerable interest for the development of practical cryogenic memory and superconducting qubits. Such junctions exhibit a ground-state phase shift of π for certain ranges of ferromagnetic layer thicknesses. We present studies of Nb based micron-scale elliptically shaped Josephson junctions containing ferromagnetic barriers of Ni 81Fe 19 or Ni 65Fe 15Co 20. By applying an external magnetic field, the critical current of the junctions is found to follow characteristic Fraunhofer patterns and display sharp switching behavior suggestive of single-domain magnets. The high quality of the Fraunhofer patterns enables us to extractmore » the maximum value of the critical current even when the peak is shifted significantly outside the range of the data due to the magnetic moment of the ferromagnetic layer. The maximum value of the critical current oscillates as a function of the ferromagnetic barrier thickness, indicating transitions in the phase difference across the junction between values of zero and π. Lastly, we compare the data to previous work and to models of the 0-π transitions based on existing theories.« less

Dissipation and traversal time in Josephson junctions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cacciari, Ilaria; Ranfagni, Anedio; Moretti, Paolo

2010-05-01

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 tau of the barrier with regard to dissipation can be established, according to which DELTAtau/tau > 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 frommore » a semiempirical analysis based on an increase in the potential barrier caused by dissipative effects.« less

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

NASA Astrophysics Data System (ADS)

Kim, Ju H.

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

Effect of inductive and capacitive coupling on the current–voltage characteristic and electromagnetic radiation from a system of Josephson junctions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rahmonov, I. R., E-mail: rahmonov@theor.jinr.ru, E-mail: ilhom-tj@inbox.ru; Shukrinov, Yu. M.; Atanasova, P. Kh.

We have studied the current–voltage characteristic of a system of long Josephson junctions taking into account the inductive and capacitive coupling. The dependence of the average time derivative of the phase difference on the bias current and spatiotemporal dependences of the phase difference and magnetic field in each junction are considered. The possibility of branching of the current–voltage characteristic in the region of zero field step, which is associated with different numbers of fluxons in individual Josephson junctions, is demonstrated. The current–voltage characteristic of the system of Josephson junctions is compared with the case of a single junction, and itmore » is shown that the observed branching is due to coupling between the junctions. The intensity of electromagnetic radiation associated with motion of fluxons is calculated, and the effect of coupling between junctions on the radiation power is analyzed.« less

Variability metrics in Josephson Junction fabrication for Quantum Computing circuits

NASA Astrophysics Data System (ADS)

Rosenblatt, Sami; Hertzberg, Jared; Brink, Markus; Chow, Jerry; Gambetta, Jay; Leng, Zhaoqi; Houck, Andrew; Nelson, J. J.; Plourde, Britton; Wu, Xian; Lake, Russell; Shainline, Jeff; Pappas, David; Patel, Umeshkumar; McDermott, Robert

Multi-qubit gates depend on the relative frequencies of the qubits. To reliably build multi-qubit devices therefore requires careful fabrication of Josephson junctions in order to precisely set their critical currents. The Ambegaokar-Baratoff relation between tunnel conductance and critical current implies a correlation between qubit frequency spread and tunnel junction resistance spread. Here we discuss measurement of large numbers of tunnel junctions to assess these resistance spreads, which can exceed 5% of mean resistance. With the goal of minimizing these spreads, we investigate process parameters such as lithographic junction area, evaporation and masking scheme, oxidation conditions, and substrate choice, as well as test environment, design and setup. In addition, trends of junction resistance with temperature are compared with theoretical models for further insights into process and test variability.

Manifestation of resonance-related chaos in coupled Josephson junctions

NASA Astrophysics Data System (ADS)

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

2012-11-01

Manifestation of chaos in the temporal dependence of the electric charge is demonstrated through the calculation of the maximal Lyapunov exponent, phase-charge and charge-charge Lissajous diagrams and correlation functions. It is found that the number of junctions in the stack strongly influences the fine structure in the current-voltage characteristics and a strong proximity effect results from the nonperiodic boundary conditions. The observed resonance-related chaos exhibits intermittency. The criteria for a breakpoint region with no chaos are obtained. Such criteria could clarify recent experimental observations of variations in the power output from intrinsic Josephson junctions in high temperature superconductors.

Some Aspects of Self-Field Effects in Large Vanadium-Based Josephson Junctions

NASA Astrophysics Data System (ADS)

Cristiano, R.; Russo, M.; Di Chiara, A.; Huang, Hesheng; Peluso, G.

1984-03-01

Experiments concerning large V-VxOy-Pb Josephson junctions have been performed. Structures having an overlap-type geometry have been considered. Preliminary experimental results are justified in the framework of the linearized current-phase model.

Frequency Combs in a Lumped-Element Josephson-Junction Circuit

NASA Astrophysics Data System (ADS)

Khan, Saeed; Türeci, Hakan E.

2018-04-01

We investigate the dynamics of a microwave-driven Josephson junction capacitively coupled to a lumped-element L C oscillator. In the regime of driving where the Josephson junction can be approximated as a Kerr oscillator, this minimal nonlinear system has been previously shown to exhibit a bistability in phase and amplitude. In the present study, we characterize the full phase diagram and show that besides a parameter regime exhibiting bistability, there is also a regime of self-oscillations characterized by a frequency comb in its spectrum. We discuss the mechanism of comb generation which appears to be different from those studied in microcavity frequency combs and mode-locked lasers. We then address the fate of the comblike spectrum in the regime of strong quantum fluctuations, reached when nonlinearity becomes the dominant scale with respect to dissipation. We find that the nonlinearity responsible for the emergence of the frequency combs also leads to its dephasing, leading to broadening and ultimate disappearance of sharp spectral peaks. Our study explores the fundamental question of the impact of quantum fluctuations for quantum systems which do not possess a stable fixed point in the classical limit.

Controllable phase transitions and novel selection rules in Josephson junctions with inherent orthogonality

NASA Astrophysics Data System (ADS)

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.

A Josephson Junction based SPDT switch

NASA Astrophysics Data System (ADS)

Zhang, Helin; Earnest, Nathan; Lu, Yao; Ma, Ruichao; Chakram, Srivatsan; Schuster, David

RF microwave switches are useful tools in cryogenic experiments, allowing for multiple experiments to be connected to a single cryogenic measurement chain. However, these switches dissipate a substantial amount of heat, preventing fast switching. Josephson junction (JJ) are a promising avenue for realizing millikelvin microwave switching. We present a JJ based single-pole-double throw (SPDT) switch that has fast switching time, no heat dissipation, large on/off contrast, and works over a wide bandwidth. The switch can be used for real-time switching between experiments, routing single photons, or even generating entanglement. We will describe the design of the switch and present experimental characterization of its performance.

Current phase relation from graphs and diagrams and application to thick ferromagnetic Josephson junctions

NASA Astrophysics Data System (ADS)

Margaris, I.; Paltoglou, V.; Flytzanis, N.

2018-05-01

In this work we present a method of representing terms in the current-phase-relation of a ballistic Josephson junction by combinations of diagrams, used in previous work to represent an equivalent of the matching condition determinant of the junction. This is accomplished by the expansion of the logarithm of this determinant in Taylor series and keeping track of surviving terms, i.e. terms that do not annihilate each other. The types of the surviving terms are represented by connected graphs, whose points represent diagrammatic terms of the determinant expansion. Then the theory is applied to obtain approximations of the current-phase relation of relatively thick ballistic ferromagnetic Josephson junctions with non-collinear magnetizations. This demonstrates the versatility of the method in developing approximations schemes and providing physical insight into the nature of contributions to the supercurrent from the available particle excitations in the junction. We also discuss the strong second harmonic contribution to the supercurrent in junctions with three mutually orthogonal magnetization vectors and a weak intermediate ferromagnet.

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

NASA Astrophysics Data System (ADS)

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

2017-09-01

We give a semiclassical analysis of the average photon number as well as photon number variance (Fano factor F ) for a Josephson junction (JJ) embedded microwave cavity system, where the JJ is subject to a fluctuating (i.e., noisy) bias voltage with finite dc average. Through the ac Josephson effect, the dc voltage bias drives the effectively nonlinear microwave cavity mode into an amplitude squeezed state (F <1 ), as has been established previously [Armour et al., Phys. Rev. Lett. 111, 247001 (2013), 10.1103/PhysRevLett.111.247001], but bias noise acts to degrade this squeezing. We find that the sensitivity of the Fano factor to bias voltage noise depends qualitatively on which stable fixed point regime the system is in for the corresponding classical nonlinear steady-state dynamics. Furthermore, we show that the impact of voltage bias noise is most significant when the cavity is excited to states with large average photon number.

The in-phase states of Josephson junctions stacks as attractors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hristov, I.; Dimova, S.; Hristova, R.

2014-11-12

The aim of this investigation is to show that the coherent, in-phase states of intrinsic Josephson junctions stacks are attractors of the stacks' states when the applied external magnetic field h{sub e} and the external current γ vary within certain domains. Mathematically the problem is to find the solutions of the system of perturbed sine-Gordon equations for fixed other parameters and zero or random initial conditions. We determine the region in the plane (h{sub e}, γ), where the in-phase states are attractors of the stack's states for arbitrary initial perturbations. This is important, because the in-phase states are required formore » achieving terahertz radiation from the Josephson stacks.« less

Testing the kibble-zurek scenario with annular josephson tunnel junctions

PubMed

Kavoussanaki; Monaco; Rivers

2000-10-16

In parallel with Kibble's description of the onset of phase transitions in the early Universe, Zurek has provided a simple picture for the onset of phase transitions in condensed matter systems, supported by agreement with experiments in 3He and superconductors. We show how experiments with annular Josephson tunnel junctions can, and do, provide further support for this scenario.

Bistability in Josephson Junction array resonator

NASA Astrophysics Data System (ADS)

Muppalla, Phani Raja; Alexandre Blais Collaboration; Christian Kraglund Andersen Collaboration; Ioan Pop, Lukas Gruenhaupt Collaboration; Michel Devoret Collaboration; Oscar Garguilo, Gerhard Kirchmair Team

``We present an experimental analysis of the Kerr effect of extended plasma resonances in a 1000 Josephson junction (JJ) chain resonator inside a rectangular waveguide. The Kerr effect manifests itself as a frequency shift that depends linearly on the number of photons in a resonant mode. We study the bistable behavior, using a pump probe scheme on two modes of the JJ array, exploiting the Cross-Kerr effect in our system. In order to understand the behavior of the bi-stability we perform continuous time measurements to observe the switching between the two metastable states. We observe a strong dependence of the switching rates on the photon number and the drive frequency.''

Readout for phase qubits without Josephson junctions

NASA Astrophysics Data System (ADS)

Steffen, Matthias; Kumar, Shwetank; DiVincenzo, David; Keefe, George; Ketchen, Mark; Rothwell, Mary Beth; Rozen, Jim

2010-03-01

We present a readout scheme for phase qubits which eliminates the read-out superconducting quantum interference device so that the entire qubit and measurement circuitry only require a single Josephson junction. Our scheme capacitively couples the phase qubit directly to a transmission line and detects its state after the measurement pulse by determining a frequency shift observable in the forward scattering parameter of the readout microwaves. This readout is extendable to multiple phase qubits coupled to a common readout line and can in principle be used for other flux biased qubits having two quasistable readout configurations.

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

PubMed

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

2016-12-23

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

Switching Dynamics of an Underdamped Josephson Junction Coupled to a Microwave Cavity

NASA Astrophysics Data System (ADS)

Oelsner, G.; Il'ichev, E.

2018-05-01

Current-biased Josephson junctions are promising candidates for the detection of single photons in the microwave frequency domain. With modern fabrication technologies, the switching properties of the junction can be adjusted to achieve quantum limited sensitivity. Namely, the width of the switching current distribution can be reduced well below the current amplitude produced by a single photon trapped inside a superconducting cavity. However, for an effective detection a strong junction cavity coupling is required, providing nonlinear system dynamics. We compare experimental findings for our prototype device with a theoretical analysis aimed to describe the switching dynamics of junctions under microwave irradiation. Measurements are found in qualitative agreement with our simulations.

Synchronization of a Josephson junction array in terms of global variables

NASA Astrophysics Data System (ADS)

Vlasov, Vladimir; Pikovsky, Arkady

2013-08-01

We consider an array of Josephson junctions with a common LCR load. Application of the Watanabe-Strogatz approach [Physica DPDNPDT0167-278910.1016/0167-2789(94)90196-1 74, 197 (1994)] allows us to formulate the dynamics of the array via the global variables only. For identical junctions this is a finite set of equations, analysis of which reveals the regions of bistability of the synchronous and asynchronous states. For disordered arrays with distributed parameters of the junctions, the problem is formulated as an integro-differential equation for the global variables; here stability of the asynchronous states and the properties of the transition synchrony-asynchrony are established numerically.

High-performance dc SQUIDs with submicrometer niobium Josephson junctions

NASA Astrophysics Data System (ADS)

de Waal, V. J.; Klapwijk, T. M.; van den Hamer, P.

1983-11-01

We report on the fabrication and performance of low-noise, all-niobium, thin-film planar dc SQUIDs with submicrometer Josephson junctions. The junctions are evaporated obliquely through a metal shadow evaporation mask, which is made using optical lithography with 0.5 µm tolerance. The Josephson junction barrier is formed by evaporating a thin silicon film and with a subsequent oxidation in a glow discharge. The junction parameters can be reproduced within a factor of two. Typical critical currents of the SQUIDs are about 3 µA and the resistances are about 100 Ω. With SQUIDs having an inductance of 1 nH the voltage modulation is at least 60 µV. An intrinsic energy resolution of 4×10-32 J/Hz has been reached. The SQUIDs are coupled to wire-wound input coils or with thin-film input coils. The thin-film input coil consists of a niobium spiral of 20 turns on a separate substrate. In both cases the coil is glued onto a 2-nH SQUID with a coupling efficiency of at least 0.5. Referred to the thin-film input coil, the best coupled energy resolution achieved is 1.2×10-30 J/Hz measured in a flux-locked loop at frequencies above 10 Hz. As far as we know, this is the best figure achieved with an all-refractory-metal thin-film SQUID. The fabrication technique used is suited for making circuits with SQUID and pickup coil on the same substrate. We describe a compact, planar, first-order gradiometer integrated with a SQUID on a single substrate. The gradient noise of this device is 3×10-12 T m-1. The gradiometer has a size of 12 mm×17 mm, is simple to fabricate, and is suitable for biomedical applications.

Experimental Studies of Josephson Effect

DTIC Science & Technology

1990-09-06

to test predictions that macroscopic variables, such as the flux through a SQUID loop, display quantum mechanical properties such as tunneling and...approximately Oo/L as flux quanta enter the loop. In the Josephson junctions used here are lead-alloy tunnel junc- linear region, for I, <<J, the rate...magnetometer. The junctions ln(F)-AU/kT+In(f/2z). (3) used were nominal I x I pm 2 Nb/AI2O3/Nb tunnel junc- As Fig. 3 shows, the observed dependence is in

Pb/InAs nanowire josephson junction with high critical current and magnetic flux focusing.

PubMed

Paajaste, J; Amado, M; Roddaro, S; Bergeret, F S; Ercolani, D; Sorba, L; Giazotto, F

2015-03-11

We have studied mesoscopic Josephson junctions formed by highly n-doped InAs nanowires and superconducting Ti/Pb source and drain leads. The current-voltage properties of the system are investigated by varying temperature and external out-of-plane magnetic field. Superconductivity in the Pb electrodes persists up to ∼7 K and with magnetic field values up to 0.4 T. Josephson coupling at zero backgate voltage is observed up to 4.5 K and the critical current is measured to be as high as 615 nA. The supercurrent suppression as a function of the magnetic field reveals a diffraction pattern that is explained by a strong magnetic flux focusing provided by the superconducting electrodes forming the junction.

Josephson junctions of candidate topological crystalline insulator Pb1-xSnxTe

NASA Astrophysics Data System (ADS)

Snyder, Rodney; Trimble, Christie; Taylor, Patrick; Williams, James

Incorporating superconducting ordering through proximity effects in topological states of matter offers potential routes to novel excitations with properties beyond that of simple electrons. Topological crystalline insulators TCI offer alternative routes to topological states of matter with surface states of distinct character to those in more common 3d topological insulators. We report on the fabrication Josephson junctions using MBE-grown candidate TCI material Pb-doped SnTe as weak links and characterize the departures from conventional junctions using combined DC and RF techniques. Opportunities to create junction weak links from materials possessing electronic interactions will be discussed.

Charge creation and nucleation of the longitudinal plasma wave in coupled Josephson junctions

NASA Astrophysics Data System (ADS)

Shukrinov, Yu. M.; Hamdipour, M.

2010-11-01

We study the phase dynamics in coupled Josephson junctions described by a system of nonlinear differential equations. Results of detailed numerical simulations of charge creation in the superconducting layers and the longitudinal plasma wave (LPW) nucleation are presented. We demonstrate the different time stages in the development of the LPW and present the results of FFT analysis at different values of bias current. The correspondence between the breakpoint position on the outermost branch of current voltage characteristics (CVC) and the growing region in time dependence of the electric charge in the superconducting layer is established. The effects of noise in the bias current and the external microwave radiation on the charge dynamics of the coupled Josephson junctions are found. These effects introduce a way to regulate the process of LPW nucleation in the stack of IJJ.

Connecting Dissipation and Phase Slips in a Josephson Junction between Fermionic Superfluids.

PubMed

Burchianti, A; Scazza, F; Amico, A; Valtolina, G; Seman, J A; Fort, C; Zaccanti, M; Inguscio, M; Roati, G

2018-01-12

We study the emergence of dissipation in an atomic Josephson junction between weakly coupled superfluid Fermi gases. We find that vortex-induced phase slippage is the dominant microscopic source of dissipation across the Bose-Einstein condensate-Bardeen-Cooper-Schrieffer crossover. We explore different dynamical regimes by tuning the bias chemical potential between the two superfluid reservoirs. For small excitations, we observe dissipation and phase coherence to coexist, with a resistive current followed by well-defined Josephson oscillations. We link the junction transport properties to the phase-slippage mechanism, finding that vortex nucleation is primarily responsible for the observed trends of conductance and critical current. For large excitations, we observe the irreversible loss of coherence between the two superfluids, and transport cannot be described only within an uncorrelated phase-slip picture. Our findings open new directions for investigating the interplay between dissipative and superfluid transport in strongly correlated Fermi systems, and general concepts in out-of-equilibrium quantum systems.

Connecting Dissipation and Phase Slips in a Josephson Junction between Fermionic Superfluids

NASA Astrophysics Data System (ADS)

Burchianti, A.; Scazza, F.; Amico, A.; Valtolina, G.; Seman, J. A.; Fort, C.; Zaccanti, M.; Inguscio, M.; Roati, G.

2018-01-01

We study the emergence of dissipation in an atomic Josephson junction between weakly coupled superfluid Fermi gases. We find that vortex-induced phase slippage is the dominant microscopic source of dissipation across the Bose-Einstein condensate-Bardeen-Cooper-Schrieffer crossover. We explore different dynamical regimes by tuning the bias chemical potential between the two superfluid reservoirs. For small excitations, we observe dissipation and phase coherence to coexist, with a resistive current followed by well-defined Josephson oscillations. We link the junction transport properties to the phase-slippage mechanism, finding that vortex nucleation is primarily responsible for the observed trends of conductance and critical current. For large excitations, we observe the irreversible loss of coherence between the two superfluids, and transport cannot be described only within an uncorrelated phase-slip picture. Our findings open new directions for investigating the interplay between dissipative and superfluid transport in strongly correlated Fermi systems, and general concepts in out-of-equilibrium quantum systems.

High Density Planar High Temperature Superconducting Josephson Junctions Arrays

DTIC Science & Technology

2006-09-01

focusing effects in magnetic field measurements and are more comparable with classical sandwich type Josephson junctions. Low temper- ature (100TC...The result is shown in Figure 4.1(b). The noise temperature calculated from the fit was 71.9 K, which is close to the measurement temperature of 63 K...The additional noise temperature is attributed to the measurement system. Both of the fits produce similar IcR,, 35 WV, and 31 MV for the RSJ and

Graphene-Based Josephson-Junction Single-Photon Detector

NASA Astrophysics Data System (ADS)

Walsh, Evan D.; Efetov, Dmitri K.; Lee, Gil-Ho; Heuck, Mikkel; Crossno, Jesse; Ohki, Thomas A.; Kim, Philip; Englund, Dirk; Fong, Kin Chung

2017-08-01

We propose to use graphene-based Josephson junctions (GJJs) to detect single photons in a wide electromagnetic spectrum from visible to radio frequencies. Our approach takes advantage of the exceptionally low electronic heat capacity of monolayer graphene and its constricted thermal conductance to its phonon degrees of freedom. Such a system could provide high-sensitivity photon detection required for research areas including quantum information processing and radio astronomy. As an example, we present our device concepts for GJJ single-photon detectors in both the microwave and infrared regimes. The dark count rate and intrinsic quantum efficiency are computed based on parameters from a measured GJJ, demonstrating feasibility within existing technologies.

Josephson junction microwave amplifier in self-organized noise compression mode

PubMed Central

Lähteenmäki, Pasi; Vesterinen, Visa; Hassel, Juha; Seppä, Heikki; Hakonen, Pertti

2012-01-01

The fundamental noise limit of a phase-preserving amplifier at frequency is the standard quantum limit . In the microwave range, the best candidates have been amplifiers based on superconducting quantum interference devices (reaching the noise temperature at 700 MHz), and non-degenerate parametric amplifiers (reaching noise levels close to the quantum limit at 8 GHz). We introduce a new type of an amplifier based on the negative resistance of a selectively damped Josephson junction. Noise performance of our amplifier is limited by mixing of quantum noise from Josephson oscillation regime down to the signal frequency. Measurements yield nearly quantum-limited operation, at 2.8 GHz, owing to self-organization of the working point. Simulations describe the characteristics of our device well and indicate potential for wide bandwidth operation. PMID:22355788

External noise-induced transitions in a current-biased Josephson junction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Qiongwei; Xue, Changfeng, E-mail: cfxue@163.com; Tang, Jiashi

We investigate noise-induced transitions in a current-biased and weakly damped Josephson junction in the presence of multiplicative noise. By using the stochastic averaging procedure, the averaged amplitude equation describing dynamic evolution near a constant phase difference is derived. Numerical results show that a stochastic Hopf bifurcation between an absorbing and an oscillatory state occurs. This means the external controllable noise triggers a transition into the non-zero junction voltage state. With the increase of noise intensity, the stationary probability distribution peak shifts and is characterised by increased width and reduced height. And the different transition rates are shown for large andmore » small bias currents.« less

Maximizing entanglement in bosonic Josephson junctions using shortcuts to adiabaticity and optimal control

NASA Astrophysics Data System (ADS)

Stefanatos, Dionisis; Paspalakis, Emmanuel

2018-05-01

In this article we consider a bosonic Josephson junction, a model system composed by two coupled nonlinear quantum oscillators which can be implemented in various physical contexts, initially prepared in a product of weakly populated coherent states. We quantify the maximum achievable entanglement between the modes of the junction and then use shortcuts to adiabaticity, a method developed to speed up adiabatic quantum dynamics, as well as numerical optimization, to find time-dependent controls (the nonlinearity and the coupling of the junction) which bring the system to a maximally entangled state.

Determination of the dissipation in superconducting Josephson junctions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mugnai, D., E-mail: d.mugnai@ifac.cnr.it; Ranfagni, A.; Cacciari, I.

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,more » 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.« less

Array of Josephson junctions with a nonsinusoidal current-phase relation as a model of the resistive transition of unconventional superconductors

NASA Astrophysics Data System (ADS)

Carbone, Anna; Gilli, Marco; Mazzetti, Piero; Ponta, Linda

2010-12-01

An array of resistively and capacitively shunted Josephson junctions with nonsinusoidal current-phase relation is considered for modeling the transition in high-Tc superconductors. The emergence of higher harmonics, besides the simple sinusoid Ic sin ϕ, is expected for dominant d-wave symmetry of the Cooper pairs, random distribution of potential drops, dirty grains, or nonstationary conditions. We show that additional cosine and sine terms act, respectively, by modulating the global resistance and by changing the Josephson coupling of the mixed superconductive-normal states. First, the approach is applied to simulate the transition in disordered granular superconductors with the weak-links characterized by nonsinusoidal current-phase relation. In granular superconductors, the emergence of higher-order harmonics affects the slope of the transition. Then, arrays of intrinsic Josephson junctions, naturally formed by the CuO2 planes in cuprates, are considered. The critical temperature suppression, observed at values of hole doping close to p =1/8, is investigated. Such suppression, related to the sign change and modulation of the Josephson coupling across the array, is quantified in terms of the intensities of the first and second sinusoids of the current-phase relation. Applications are envisaged for the design and control of quantum devices based on stacks of intrinsic Josephson junctions.

Josephson-junction array in an irrational magnetic field: A superconducting glass

DOE Office of Scientific and Technical Information (OSTI.GOV)

Halsey, T.C.

1985-08-26

A model is used to show that a Josephson junction array in an irrational magnetic field undergoes a glass transition for finite cooling rate. At zero temperature the resultant glassy state possesses a nonzero critical current. The low-temperature behavior of the system can be modeled by a spin-wave theory. The relevance of these results for real experiments on arrays is discussed.

A thin polymer insulator for Josephson tunneling applications

NASA Technical Reports Server (NTRS)

Wilmsen, C. M.

1973-01-01

The use of an organic monolayer formed from a vapor as an insulating barrier for thin film Josephson junctions is considered, and the effect of an organic monolayer on the transition temperature of a thin film superconductor is investigated. Also analyzed are the geometric factors which influence Josephson junctions and Josephson junction interferometers.

Vortex dynamics in two-dimensional Josephson junction arrays

NASA Astrophysics Data System (ADS)

Ashrafuzzaman, Md.; Capezzali, Massimiliano; Beck, Hans

2003-08-01

The dynamic response of two-dimensional Josephson junction arrays close to, but above the Berezinskii-Kosterlitz-Thouless (BKT) transition temperature is described in terms of the vortex dielectric function ɛ(ω) and the flux noise spectrum Sφ(ω). They are calculated by considering both the contributions of free vortices interacting through a screened Coulomb potential and the pair motion of vortices that are closer to each other than the BKT correlation length. This procedure allows us to understand various anomalous features in ɛ(ω) and in Sφ(ω) that have been observed both experimentally and in dynamic simulations.

Identifying the chiral d-wave superconductivity by Josephson φ0-states.

PubMed

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.

Identifying the chiral d-wave superconductivity by Josephson φ0-states

PubMed Central

Liu, Jun-Feng; Xu, Yong; Wang, Jun

2017-01-01

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 φ0-junction state where the current-phase relation is shifted by a phase φ0 from the sinusoidal relation, other than 0 and π. The ground-state phase difference φ0 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 φ0-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 φ0- junction, which is useful in superconducting electronics and superconducting quantum computation. PMID:28266582

Little-Parks oscillations in superconducting ring with Josephson junctions

NASA Astrophysics Data System (ADS)

Sharon, Omri J.; Sharoni, Amos; Berger, Jorge; Shaulov, Avner; Yeshurun, Yosi

2018-03-01

Nb nano-rings connected serially by Nb wires exhibit, at low bias currents, the typical parabolic Little-Parks magnetoresistance oscillations. As the bias current increases, these oscillations become sinusoidal. This result is ascribed to the generation of Josephson junctions caused by the combined effect of current-induced phase slips and the non-uniformity of the order parameter along each ring due to the Nb wires attached to it. This interpretation is validated by further increasing the bias current, which results in magnetoresistance oscillations typical of a SQUID.

Critical current of SF-NFS Josephson junctions

NASA Astrophysics Data System (ADS)

Soloviev, I. I.; Klenov, N. V.; Bakursky, S. V.; Kupriyanov, M. Yu.; Golubov, A. A.

2015-02-01

The properties of SF-NFS sandwiches composed of two superconducting (S) electrodes separated by a weak-link region formed by a normal-metal (N) step with the thickness d N situated on the top of a lower S electrode and a ferromagnetic (F) layer with the thickness d F deposited onto the step and the remaining free surface of the lower electrode have been studied theoretically. It has been shown in the approximation of linearized semiclassical Usadel equations that the two-dimensional problem in the weak-link region can be reduced to two one-dimensional problems in its SFS and SNFS segments. The spatial distributions of the critical current density J c in the segments as a function of the layer thickness d F have been calculated. The dependences of the critical current I c of the structure on the magnitude of the magnetization vector M of the ferromagnetic layer have been found for various directions of the magnetization within the junction plane. It has been shown that these dependences are affected considerably by both the orientation of M and the spatial distribution of J c.

Side-wall spacer passivated sub-μm Josephson junction fabrication process

NASA Astrophysics Data System (ADS)

Grönberg, Leif; Kiviranta, Mikko; Vesterinen, Visa; Lehtinen, Janne; Simbierowicz, Slawomir; Luomahaara, Juho; Prunnila, Mika; Hassel, Juha

2017-12-01

We present a structure and a fabrication method for superconducting tunnel junctions down to the dimensions of 200 nm using i-line UV lithography. The key element is a sidewall-passivating spacer structure (SWAPS) which is shaped for smooth crossline contacting and low parasitic capacitance. The SWAPS structure enables formation of junctions with dimensions at or below the lithography-limited linewidth. An additional benefit is avoiding the excessive use of amorphous dielectric materials which is favorable in sub-Kelvin microwave applications often plagued by nonlinear and lossy dielectrics. We apply the structure to niobium trilayer junctions, and provide characterization results yielding evidence on wafer-scale scalability, and critical current density tuning in the range of 0.1-3.0 kA cm-2. We discuss the applicability of the junction process in the context of different applications, such as SQUID magnetometers and Josephson parametric amplifiers.

Invariant submanifold for series arrays of Josephson junctions.

PubMed

Marvel, Seth A; Strogatz, Steven H

2009-03-01

We study the nonlinear dynamics of series arrays of Josephson junctions in the large-N limit, where N is the number of junctions in the array. The junctions are assumed to be identical, overdamped, driven by a constant bias current, and globally coupled through a common load. Previous simulations of such arrays revealed that their dynamics are remarkably simple, hinting at the presence of some hidden symmetry or other structure. These observations were later explained by the discovery of N-3 constants of motion, the choice of which confines the resulting flow in phase space to a low-dimensional invariant manifold. Here we show that the dimensionality can be reduced further by restricting attention to a special family of states recently identified by Ott and Antonsen. In geometric terms, the Ott-Antonsen ansatz corresponds to an invariant submanifold of dimension one less than that found earlier. We derive and analyze the flow on this submanifold for two special cases: an array with purely resistive loading and another with resistive-inductive-capacitive loading. Our results recover (and in some instances improve) earlier findings based on linearization arguments.

Thermally Driven Josephson Effect

NASA Technical Reports Server (NTRS)

Penanen, Konstantin; Chui, Talso

2008-01-01

A concept is proposed of the thermally driven Josephson effect in superfluid helium. Heretofore, the Josephson effect in a superfluid has been recognized as an oscillatory flow that arises in response to a steady pressure difference between two superfluid reservoirs separated by an array of submicron-sized orifices, which act in unison as a single Josephson junction. Analogously, the thermally driven Josephson effect is an oscillatory flow that arises in response to a steady temperature difference. The thermally driven Josephson effect is partly a consequence of a quantum- mechanical effect known as the fountain effect, in which a temperature difference in a superfluid is accompanied by a pressure difference. The thermally driven Josephson effect may have significance for the development of a high-resolution gyroscope based on the Josephson effect in a superfluid: If the pressure-driven Josephson effect were used, then the fluid on the high-pressure side would become depleted, necessitating periodic interruption of operation to reverse the pressure difference. If the thermally driven Josephson effect were used, there would be no net flow and so the oscillatory flow could be maintained indefinitely by maintaining the required slightly different temperatures on both sides of the junction.

Unconventional Josephson effect in hybrid superconductor-topological insulator devices.

PubMed

Williams, J R; Bestwick, A J; Gallagher, P; Hong, Seung Sae; Cui, Y; Bleich, Andrew S; Analytis, J G; Fisher, I R; Goldhaber-Gordon, D

2012-08-03

We report on transport properties of Josephson junctions in hybrid superconducting-topological insulator devices, which show two striking departures from the common Josephson junction behavior: a characteristic energy that scales inversely with the width of the junction, and a low characteristic magnetic field for suppressing supercurrent. To explain these effects, we propose a phenomenological model which expands on the existing theory for topological insulator Josephson junctions.

Advanced Concepts in Josephson Junction Reflection Amplifiers

NASA Astrophysics Data System (ADS)

Lähteenmäki, Pasi; Vesterinen, Visa; Hassel, Juha; Paraoanu, G. S.; Seppä, Heikki; Hakonen, Pertti

2014-06-01

Low-noise amplification at microwave frequencies has become increasingly important for the research related to superconducting qubits and nanoelectromechanical systems. The fundamental limit of added noise by a phase-preserving amplifier is the standard quantum limit, often expressed as noise temperature . Towards the goal of the quantum limit, we have developed an amplifier based on intrinsic negative resistance of a selectively damped Josephson junction. Here we present measurement results on previously proposed wide-band microwave amplification and discuss the challenges for improvements on the existing designs. We have also studied flux-pumped metamaterial-based parametric amplifiers, whose operating frequency can be widely tuned by external DC-flux, and demonstrate operation at pumping, in contrast to the typical metamaterial amplifiers pumped via signal lines at.

Microwave integrated circuit for Josephson voltage standards

NASA Technical Reports Server (NTRS)

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

1980-01-01

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

Modeling the Effects of Varying the Capacitance, Resistance, Temperature, and Frequency Dependence for HTS Josephson Junctions, DC SQUIDs and DC bi-SQUIDS

DTIC Science & Technology

2014-09-01

junction is a thin layer of insulating material sep- arating two superconductors that is thin enough for electrons to tunnel through. Two Josephson...can sense minute magnetic fields approaching 1015 Tesla. These SQUIDs can be arranged in arrays with different coupling schemes and parameter values to...different material and/or method on the bisecting Josephson junction for high temperature superconductor (HTS) YBa2Cu3O7 (YBCO) bi-SQUIDs. This

A closed cycle cascade Joule Thomson refrigerator for cooling Josephson junction magnetometers

NASA Technical Reports Server (NTRS)

Tward, E.; Sarwinski, R.

1985-01-01

A closed cycle cascade Joule Thomson refrigerator designed to cool Josephson Junction magnetometers to liquid helium temperature is being developed. The refrigerator incorporates 4 stages of cooling using the working fluids CF4 and He. The high pressure gases are provided by a small compressor designed for this purpose. The upper stages have been operated and performance will be described.

Josephson effects in a Bose–Einstein condensate of magnons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Troncoso, Roberto E., E-mail: r.troncoso.c@gmail.com; Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Casilla 487-3, Santiago; Núñez, Álvaro S., E-mail: alnunez@dfi.uchile.cl

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 betweenmore » the above phenomena and Josephson’s effect. •We remark the distinctive oscillations that characterize the Josephson oscillations.« less

RF assisted switching in magnetic Josephson junctions

NASA Astrophysics Data System (ADS)

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.

Devil's staircases and continued fractions in Josephson junctions

NASA Astrophysics Data System (ADS)

Shukrinov, Yu. M.; Medvedeva, S. Yu.; Botha, A. E.; Kolahchi, M. R.; Irie, A.

2013-12-01

Detailed numerical simulations of the IV characteristics of a Josephson junction under external electromagnetic radiation show the devil's staircase within different bias current intervals. We have found that the observed steps form very precisely continued fractions. Increase of the amplitude of the radiation shifts the devil's staircase to higher Shapiro steps. An algorithm for the appearance and detection of subharmonics with increasing radiation amplitude is proposed. We demonstrate that the subharmonic steps registered in the well-known experiments by Dayem and Wiegand [Phys. Rev. 155, 419 (1967), 10.1103/PhysRev.155.419] and Clarke [Phys. Rev. B 4, 2963 (1971), 10.1103/PhysRevB.4.2963] also form continued fractions.

Controlling dynamical entanglement in a Josephson tunneling junction

NASA Astrophysics Data System (ADS)

Ziegler, K.

2017-12-01

We analyze the evolution of an entangled many-body state in a Josephson tunneling junction and its dependence on the number of bosons and interaction strength. A N00N state, which is a superposition of two complementary Fock states, appears in the evolution with sufficient probability only for a moderate many-body interaction on an intermediate time scale. This time scale is inversely proportional to the tunneling rate. Many-body interaction strongly supports entanglement: The probability for creating an entangled state decays exponentially with the number of particles without many-body interaction, whereas it decays only like the inverse square root of the number of particles in the presence of many-body interaction.

Investigation of Supercurrent in the Quantum Hall Regime in Graphene Josephson Junctions

NASA Astrophysics Data System (ADS)

Draelos, Anne W.; Wei, Ming Tso; Seredinski, Andrew; Ke, Chung Ting; Mehta, Yash; Chamberlain, Russell; Watanabe, Kenji; Taniguchi, Takashi; Yamamoto, Michihisa; Tarucha, Seigo; Borzenets, Ivan V.; Amet, François; Finkelstein, Gleb

2018-06-01

In this study, we examine multiple encapsulated graphene Josephson junctions to determine which mechanisms may be responsible for the supercurrent observed in the quantum Hall (QH) regime. Rectangular junctions with various widths and lengths were studied to identify which parameters affect the occurrence of QH supercurrent. We also studied additional samples where the graphene region is extended beyond the contacts on one side, making that edge of the mesa significantly longer than the opposite edge. This is done in order to distinguish two potential mechanisms: (a) supercurrents independently flowing along both non-contacted edges of graphene mesa, and (b) opposite sides of the mesa being coupled by hybrid electron-hole modes flowing along the superconductor/graphene boundary. The supercurrent appears suppressed in extended junctions, suggesting the latter mechanism.

Traveling wave parametric amplifier with Josephson junctions using minimal resonator phase matching

DOE Office of Scientific and Technical Information (OSTI.GOV)

White, T. C.; Mutus, J. Y.; Hoi, I.-C.

Josephson parametric amplifiers have become a critical tool in superconducting device physics due to their high gain and quantum-limited noise. Traveling wave parametric amplifiers (TWPAs) promise similar noise performance, while allowing for significant increases in both bandwidth and dynamic range. We present a TWPA device based on an LC-ladder transmission line of Josephson junctions and parallel plate capacitors using low-loss amorphous silicon dielectric. Crucially, we have inserted λ/4 resonators at regular intervals along the transmission line in order to maintain the phase matching condition between pump, signal, and idler and increase gain. We achieve an average gain of 12 dB acrossmore » a 4 GHz span, along with an average saturation power of −92 dBm with noise approaching the quantum limit.« less

Penetration depth of MgB2 measured using Josephson junctions and SQUIDs

NASA Astrophysics Data System (ADS)

Cunnane, Daniel; Zhuang, Chenggang; Chen, Ke; Xi, X. X.; Yong, Jie; Lemberger, T. R.

2013-02-01

The penetration depth of MgB2 was measured using two methods of different mechanisms. The first method used MgB2 Josephson junctions and the magnetic field dependence of the junction critical current. The second method deduced the penetration depth from the inductance of a MgB2 microstrip used to modulate the voltage of a MgB2 DC SQUID. The two methods showed a consistent value of the low-temperature penetration depth for MgB2 to be about 40 nm. Both the small penetration depth value and its temperature dependence are in agreement with a microscopic theory for MgB2 in the clean limit.

Study of charge-phase diagrams for coupled system of Josephson junctions

NASA Astrophysics Data System (ADS)

Hamdipour, M.; Shukrinov, Y. U. M.

2010-11-01

Dynamics of stacked intrinsic Josephson junctions (IJJ) in the high-Tc superconductors is theoretically investigated. We calculate the current-voltage characteristics (CVC) of IJJ and study the breakpoint region on the outermost branch of the CVC for the stacks with 9 IJJ. A method for investigation of the fine structure in CVC of IJJ based on the recording the "phase-charge" diagrams is suggested. It is demonstrated that this method reflects the main features of the breakpoint region.

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

NASA Astrophysics Data System (ADS)

Rakyta, Péter; Kormányos, Andor; Cserti, József

2016-06-01

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

Controllable Quantum States Mesoscopic Superconductivity and Spintronics (MS+S2006)

NASA Astrophysics Data System (ADS)

Takayanagi, Hideaki; Nitta, Junsaku; Nakano, Hayato

2008-10-01

Mesoscopic effects in superconductors. Tunneling measurements of charge imbalance of non-equilibrium superconductors / R. Yagi. Influence of magnetic impurities on Josephson current in SNS junctions / T. Yokoyama. Nonlinear response and observable signatures of equilibrium entanglement / A. M. Zagoskin. Stimulated Raman adiabatic passage with a Cooper pair box / Giuseppe Falci. Crossed Andreev reflection-induced giant negative magnetoresistance / Francesco Giazotto -- Quantum modulation of superconducting junctions. Adiabatic pumping through a Josephson weak link / Fabio Taddei. Squeezing of superconducting qubits / Kazutomu Shiokawa. Detection of Berrys phases in flux qubits with coherent pulses / D. N. Zheng. Probing entanglement in the system of coupled Josephson qubits / A. S. Kiyko. Josephson junction with tunable damping using quasi-particle injection / Ryuta Yagi. Macroscopic quantum coherence in rf-SQUIDs / Alexey V. Ustinov. Bloch oscillations in a Josephson circuit / D. Esteve. Manipulation of magnetization in nonequilibrium superconducting nanostructures / F. Giazotto -- Superconducting qubits. Decoherence and Rabi oscillations in a qubit coupled to a quantum two-level system / Sahel Ashhab. Phase-coupled flux qubits: CNOT operation, controllable coupling and entanglement / Mun Dae Kim. Characteristics of a switchable superconducting flux transformer with a DC-SQUID / Yoshihiro Shimazu. Characterization of adiabatic noise in charge-based coherent nanodevices / E. Paladino -- Unconventional superconductors. Threshold temperatures of zero-bias conductance peak and zero-bias conductance dip in diffusive normal metal/superconductor junctions / Iduru Shigeta. Tunneling conductance in 2DEG/S junctions in the presence of Rashba spin-orbit coupling / T. Yokoyama. Theory of charge transport in diffusive ferromagnet/p-wave superconductor junctions / T. Yokoyama. Theory of enhanced proximity effect by the exchange field in FS bilayers / T. Yokoyama. Theory of

Fabrication of sapphire-based high performance step-edge HTS Josephson junctions and SQUIDs and their application to scanning SQUID microscopy

NASA Astrophysics Data System (ADS)

Ming, Bin

Josephson junctions are at the heart of any superconductor device applications. A SQUID (Superconducting Quantum Interference Device), which consists of two Josephson junctions, is by far the most important example. Unfortunately, in the case of high-Tc superconductors (HTS), the quest for a robust, flexible, and high performance junction technology is yet far from the end. Currently, the only proven method to make HTS junctions is the SrTiO3(STO)-based bicrystal technology. In this thesis we concentrate on the fabrication of YBCO step-edge junctions and SQUIDs on sapphire. The step-edge method provides complete control of device locations and facilitates sophisticated, high-density layout. We select CeO2 as the buffer layer, as the key step to make device quality YBCO thin films on sapphire. With an "overhang" shadow mask produced by a novel photolithography technique, a steep step edge was fabricated on the CeO2 buffer layer by Ar+ ion milling with optimized parameters for minimum ion beam divergence. The step angle was determined to be in excess of 80° by atomic force microscopy (AFM). Josephson junctions patterned from those step edges exhibited resistively shunted junction (RSJ) like current-voltage characteristics. IcR n values in the 200--500 mV range were measured at 77K. Shapiro steps were observed under microwave irradiation, reflecting the true Josephson nature of those junctions. The magnetic field dependence of the junction Ic indicates a uniform current distribution. These results suggest that all fabrication processes are well controlled and the step edge is relatively straight and free of microstructural defects. The SQUIDs made from the same process exhibit large voltage modulation in a varying magnetic field. At 77K, our sapphire-based step-edge SQUID has a low white noise level at 3muphi0/ Hz , as compared to typically >10muphi0/ Hz from the best bicrystal STO SQUIDS. Our effort at device fabrication is chiefly motivated by the scanning SQUID

Third order intermodulation distortion in HTS Josephson Junction downconverter at 12GHz

DOE Office of Scientific and Technical Information (OSTI.GOV)

Suzuki, Katsumi; Hayashi, Kunihiko; Fujimoto, Manabu

1994-12-31

Here the authors first report on the microwave characteristics of the third order intermodulation distortion(IMD3) in High-Tc Superconductor (HTS) Josephson Junction (JJ) Downconverter at 12GHz. They have successfully developed high quality nonlinear YBCO microbridge Josephson junctions for such an active MMIC as a mixer with RF, LO, IF and bias filters, which have been fabricated on (100) MgO substrates with 20mm x 20mm x 0.5mm dimensions. The minimum conversion loss of the JJ mixer is 11 dB at very small local microwave input power LO= {minus}20dBm which is two order less than Schottky diode mixer. Consequently, this small optimum LOmore » power gives the small RF input power at which the output IF power of the YBCO mixer saturates. Two-tone third-order intercept point(IP3) performance is a significantly important figure of merit typically used to define linearity of devices and circuits. The RF input power = {minus}15dBm at the IP3 point is obtained for the YBCO mixer at 15K and LO = 10.935GHz with {minus}22dBm. The have successfully measured the dependence of IMD3 on temperature, bias current and LO power.« less

Long-range Kitaev chains via planar Josephson junctions

NASA Astrophysics Data System (ADS)

Liu, Dillon T.; Shabani, Javad; Mitra, Aditi

2018-06-01

We show how a recently proposed solid-state Majorana platform comprising a planar Josephson junction proximitized to a 2D electron gas (2DEG) with Rashba spin-orbit coupling and Zeeman field can be viewed as an effectively one-dimensional (1D) Kitaev chain with long-range pairing and hopping terms. We highlight how the couplings of the 1D system may be tuned by changing experimentally realistic parameters. We also show that the mapping is robust to disorder by computing the Clifford pseudospectrum index in real space for the long-range Kitaev chain across several topological phases. This mapping opens up the possibility of using current experimental setups to explore 1D topological superconductors with nonstandard and tunable couplings.

Fabrication of superconductor-ferromagnet-insulator-superconductor Josephson junctions with critical current uniformity applicable to integrated circuits

NASA Astrophysics Data System (ADS)

Ito, Hiroshi; Taniguchi, Soya; Ishikawa, Kouta; Akaike, Hiroyuki; Fujimaki, Akira

2017-03-01

Nb Josephson junctions (JJs) were fabricated with a Pd89Ni11 ferromagnetic interlayer and an AlO x tunnel barrier layer for use in large-scale superconducting integrated circuits. The junctions had a small critical current (I c) spread, where the standard deviation 1σ was less than 2% at 4.2 K for junctions with the same designed size. It was observed that the electrical behavior of the junctions could be controlled by manipulating the film thickness of the PdNi interlayer. The junctions behaved as a π-JJ for thicknesses of 9 and 11 nm, showing 1σ in the I c spread of 1.2% for 9 nm.

Anomalous Josephson effect controlled by an Abrikosov vortex

NASA Astrophysics Data System (ADS)

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.

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

NASA Astrophysics Data System (ADS)

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

2018-07-01

We report theoretical and experimental work on the development of a Josephson vortex two-state system based on a confocal annular Josephson tunnel junction (CAJTJ). The key ingredient of this geometrical configuration is a periodically variable width that generates a spatial vortex potential 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 4.2 {{K}} 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 vortex two-state system based on CAJTJs is robust and workable.

Quantum resonances in a single plaquette of Josephson junctions: excitations of Rabi oscillations

NASA Astrophysics Data System (ADS)

Fistul, M. V.

2002-03-01

We present a theoretical study of a quantum regime of the resistive (whirling) state of dc driven anisotropic single plaquette containing small Josephson junctions. The current-voltage characteristics of such systems display resonant steps that are due to the resonant interaction between the time dependent Josephson current and the excited electromagnetic oscillations (EOs). The voltage positions of the resonances are determined by the quantum interband transitions of EOs. We show that in the quantum regime as the system is driven on the resonance, coherent Rabi oscillations between the quantum levels of EOs occur. At variance with the classical regime the magnitude and the width of resonances are determined by the frequency of Rabi oscillations that in turn, depends in a peculiar manner on an externally applied magnetic field and the parameters of the system.

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

NASA Astrophysics Data System (ADS)

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

2018-02-01

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

Applying the Network Simulation Method for testing chaos in a resistively and capacitively shunted Josephson junction model

NASA Astrophysics Data System (ADS)

Bellver, Fernando Gimeno; Garratón, Manuel Caravaca; Soto Meca, Antonio; López, Juan Antonio Vera; Guirao, Juan L. G.; Fernández-Martínez, Manuel

In this paper, we explore the chaotic behavior of resistively and capacitively shunted Josephson junctions via the so-called Network Simulation Method. Such a numerical approach establishes a formal equivalence among physical transport processes and electrical networks, and hence, it can be applied to efficiently deal with a wide range of differential systems. The generality underlying that electrical equivalence allows to apply the circuit theory to several scientific and technological problems. In this work, the Fast Fourier Transform has been applied for chaos detection purposes and the calculations have been carried out in PSpice, an electrical circuit software. Overall, it holds that such a numerical approach leads to quickly computationally solve Josephson differential models. An empirical application regarding the study of the Josephson model completes the paper.

Coherent Charge Transport in Ballistic InSb Nanowire Josephson Junctions

PubMed Central

Li, S.; Kang, N.; Fan, D. X.; Wang, L. B.; Huang, Y. Q.; Caroff, P.; Xu, H. Q.

2016-01-01

Hybrid InSb nanowire-superconductor devices are promising for investigating Majorana modes and topological quantum computation in solid-state devices. An experimental realisation of ballistic, phase-coherent superconductor-nanowire hybrid devices is a necessary step towards engineering topological superconducting electronics. Here, we report on a low-temperature transport study of Josephson junction devices fabricated from InSb nanowires grown by molecular-beam epitaxy and provide a clear evidence for phase-coherent, ballistic charge transport through the nanowires in the junctions. We demonstrate that our devices show gate-tunable proximity-induced supercurrent and clear signatures of multiple Andreev reflections in the differential conductance, indicating phase-coherent transport within the junctions. We also observe periodic modulations of the critical current that can be associated with the Fabry-Pérot interference in the nanowires in the ballistic transport regime. Our work shows that the InSb nanowires grown by molecular-beam epitaxy are of excellent material quality and hybrid superconducting devices made from these nanowires are highly desirable for investigation of the novel physics in topological states of matter and for applications in topological quantum electronics. PMID:27102689

The Josephson Effect and e/h

ERIC Educational Resources Information Center

Clarke, John

1970-01-01

Discusses the theory of the Josephson Effect, the derivation of the Josephson voltage-frequency relation, and methods of measuring the fundamental constatn ratio e/h. Various types of Josephson junctions are described. The impact of the measurement of e/h upin the fundamental constants and quantum electro-dynamics is briefly discussed.…

Fast generation of spin-squeezed states in bosonic Josephson junctions

NASA Astrophysics Data System (ADS)

Juliá-Díaz, B.; Torrontegui, E.; Martorell, J.; Muga, J. G.; Polls, A.

2012-12-01

We describe methods for the fast production of highly coherent-spin-squeezed many-body states in bosonic Josephson junctions. We start from the known mapping of the two-site Bose-Hubbard (BH) Hamiltonian to that of a single effective particle evolving according to a Schrödinger-like equation in Fock space. Since, for repulsive interactions, the effective potential in Fock space is nearly parabolic, we extend recently derived protocols for shortcuts to adiabatic evolution in harmonic potentials to the many-body BH Hamiltonian. A comparison with current experiments shows that our methods allow for an important reduction in the preparation times of highly squeezed spin states.

Unpaired Majorana modes in Josephson-Junction Arrays with gapless bulk excitations

DOE PAGES

Pino, M.; Tsvelik, A.; Ioffe, L. B.

2015-11-06

In this study, the search for Majorana bound states in solid-state physics has been limited to materials that display a gap in their bulk spectrum. We show that such unpaired states appear in certain quasi-one-dimensional Josephson-junction arrays with gapless bulk excitations. The bulk modes mediate a coupling between Majorana bound states via the Ruderman-Kittel-Yosida-Kasuya mechanism. As a consequence, the lowest energy doublet acquires a finite energy difference. For a realistic set of parameters this energy splitting remains much smaller than the energy of the bulk eigenstates even for short chains of length L~10.

Graphene Josephson Junction Single Photon Detector

NASA Astrophysics Data System (ADS)

Walsh, Evan D.; Lee, Gil-Ho; Efetov, Dmitri K.; Heuck, Mikkel; Crossno, Jesse; Taniguchi, Takashi; Watanabe, Kenji; Ohki, Thomas A.; Kim, Philip; Englund, Dirk; Fong, Kin Chung

Single photon detectors (SPDs) have found use across a wide array of applications depending on the wavelength to which they are sensitive. Graphene, because of its linear, gapless dispersion near the Dirac point, has a flat, wide bandwidth absorption that can be enhanced to near 100 % through the use of resonant structures making it a promising candidate for broadband SPDs. Upon absorbing a photon in the optical to mid-infrared range, a small (~10 μm2) sheet of graphene at cryogenic temperatures can experience a significant increase in electronic temperature due to its extremely low heat capacity. At 1550 nm, for example, calculations show that the temperature could rise by as much as 500 %. This temperature increase could be detected with near perfect quantum efficiency by making the graphene the weak link in a Josephson junction (JJ). We present a theoretical model demonstrating that such a graphene JJ SPD could operate at the readily achievable temperature of 3 K with near zero dark count, sub-50 ps timing jitter, and sub-5 ns dead time and report on the progress toward experimentally realizing the device.

All-spinel oxide Josephson junctions for high-efficiency spin filtering.

PubMed

Mesoraca, S; Knudde, S; Leitao, D C; Cardoso, S; Blamire, M G

2018-01-10

Obtaining high efficiency spin filtering at room temperature using spinel ferromagnetic tunnel barriers has been hampered by the formation of antiphase boundaries due to their difference in lattice parameters between barrier and electrodes. In this work we demonstrate the use of LiTi 2 O 4 thin films as electrodes in an all-spinel oxide CoFe 2 O 4 -based spin filter devices. These structures show nearly perfect epitaxy maintained throughout the structure and so minimise the potential for APBs formation. The LiTi 2 O 4 in these devices is superconducting and so measurements at low temperature have been used to explore details of the tunnelling and Josephson junction behaviour.

Microwave heating of a high-Tc YBa2Cu3O6.9 superconductor through a Josephson-junction system

NASA Astrophysics Data System (ADS)

Stankowski, J.; Czyak, B.; Martinek, J.

1990-12-01

An overheating of a Josephson-junction system (JJS) in ceramic YBa2Cu3O6.9 samples was induced by microwave irradiation in a microwave cavity. The amplitude of the Josephson microwave absorption (JMA) was used as a monitor of the local JJS temperature. The difference between the JJS temperature and a sample temperature depends linearly on the power of the microwave field. A thermal hysteresis of Tc for heating and cooling is proportional to the microwave power applied in the JMA experiment.

High-performance passive microwave survey on Josephson junctions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Denisov, A.G.; Radzikhovsky, V.N.; Kudeliya, A.M.

1994-12-31

The quasi-optical generations of image of objects with their internal structure in millimeter (MM) and submillimeter (SMM) bands is one of the prime problems of modern radioelectronics. The main advantage of passive MM imaging systems in comparison with visible and infrared (IR) systems is small attenuation of signals in fog, cloud, smoke, dust and other obscurants. However at a panoramic scanning of space the observation time lengthens and thereby the information processing rate becomes restricted. So that single-channel system cannot image in real time. Therefore we must use many radiometers in parallel to reduce the observation time. Such system mustmore » contain receiving sensors as pixels in multibeam antenna. The use of Josephson Junctions (JJ) for this purpose together with the cryoelectronic devices like GaAs FET or SQUIDS for signal amplifications after JJ is of particular interest in this case.« less

High-performance passive microwave survey on Josephson Junctions

NASA Technical Reports Server (NTRS)

Denisov, A. G.; Radzikhovsky, V. N.; Kudeliya, A. M.

1995-01-01

The quasi-optical generations of images of objects with their internal structure in millimeter (MM) and submillimeter (SMM) bands is one of prime problems of modern radioelectronics. The main advantage of passive MM imaging systems in comparison with visible and infrared (IR) systems is small attenuation of signals in fog, cloud, smoke, dust and other obscurants. However, at a panoramic scanning of space the observation time lengthens and thereby the information processing rate becomes restricted so that single-channel system cannot image in real time. Therefore we must use many radiometers in parallel to reduce the observation time. Such system must contain receiving sensors as pixels in multibeam antenna. The use of Josephson Junctions (JJ) for this purpose together with the cryoelectronic devices like GaAs FET (field effect transistors) or SQUIDS for signal amplifications after JJ is of particular interest in this case.

Direct DC 10 V comparison between two programmable Josephson voltage standards made of niobium nitride (NbN)-based and niobium (Nb)-based Josephson junctions

NASA Astrophysics Data System (ADS)

Solve, S.; Chayramy, R.; Maruyama, M.; Urano, C.; Kaneko, N.-H.; Rüfenacht, A.

2018-04-01

BIPM’s new transportable programmable Josephson voltage standard (PJVS) has been used for an on-site comparison at the National Metrology Institute of Japan (NMIJ) and the National Institute of Advanced Industrial Science and Technology (AIST) (NMIJ/AIST, hereafter called just NMIJ unless otherwise noted). This is the first time that an array of niobium-based Josephson junctions with amorphous niobium silicon Nb x Si1-x barriers, developed by the National Institute of Standards and Technology4 (NIST), has been directly compared to an array of niobium nitride (NbN)-based junctions (developed by the NMIJ in collaboration with the Nanoelectronics Research Institute (NeRI), AIST). Nominally identical voltages produced by both systems agreed within 5 parts in 1012 (0.05 nV at 10 V) with a combined relative uncertainty of 7.9  ×  10-11 (0.79 nV). The low side of the NMIJ apparatus is, by design, referred to the ground potential. An analysis of the systematic errors due to the leakage current to ground was conducted for this ground configuration. The influence of a multi-stage low-pass filter installed at the output measurement leads of the NMIJ primary standard was also investigated. The number of capacitances in parallel in the filter and their insulation resistance have a direct impact on the amplitude of the systematic voltage error introduced by the leakage current, even if the current does not necessarily return to ground. The filtering of the output of the PJVS voltage leads has the positive consequence of protecting the array from external sources of noise. Current noise, when coupled to the array, reduces the width or current range of the quantized voltage steps. The voltage error induced by the leakage current in the filter is an order of magnitude larger than the voltage error in the absence of all filtering, even though the current range of steps is significantly decreased without filtering.

Electronic decoherence of two-level systems in a Josephson junction

NASA Astrophysics Data System (ADS)

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.

Weyl nodes in Andreev spectra of multiterminal Josephson junctions: Chern numbers, conductances, and supercurrents

NASA Astrophysics Data System (ADS)

Xie, Hong-Yi; Vavilov, Maxim G.; Levchenko, Alex

2018-02-01

We consider mesoscopic four-terminal Josephson junctions and study emergent topological properties of the Andreev subgap bands. We use symmetry-constrained analysis for Wigner-Dyson classes of scattering matrices to derive band dispersions. When the scattering matrix of the normal region connecting superconducting leads is energy independent, the determinant formula for Andreev spectrum can be reduced to a palindromic equation that admits a complete analytical solution. Band topology manifests with an appearance of the Weyl nodes which serve as monopoles of finite Berry curvature. The corresponding fluxes are quantified by Chern numbers that translate into a quantized nonlocal conductance that we compute explicitly for the time-reversal-symmetric scattering matrix. The topological regime can also be identified by supercurrents as Josephson current-phase relationships exhibit pronounced nonanalytic behavior and discontinuities near Weyl points that can be controllably accessed in experiments.

An investigation of the SNS Josephson junction as a three-terminal device. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Meissner, H.; Prans, G. P.

1973-01-01

A particular phenomenon of the SNS Josephson junction was investigated; i.e., control by a current entering the normal region and leaving through one of the superconducting regions. The effect of the control current on the junction was found to be dependent upon the ration of the resistances of the two halves of the N layer. A low frequency, lumped, nonlinear model was proposed to describe the electrical characteristics of the device, and a method was developed to plot the dynamic junction resistance as a function of junction current. The effective thermal noise temperature of the sample was determined. Small signal linearized analysis of the device suggests its use as an impedance transformer, although geometric limitations must be overcome. Linear approximation indicates that it is reciprocal and no power gain is possible. It is felt that, with suitable metallurgical and geometrical improvements, the device has promise to become a superconducting transistor.

AdS and dS Entropy from String Junctions or The Function of Junction Conjunctions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Silverstein, Eva M

Flux compactifications of string theory exhibiting the possibility of discretely tuning the cosmological constant to small values have been constructed. The highly tuned vacua in this discretuum have curvature radii which scale as large powers of the flux quantum numbers, exponential in the number of cycles in the compactification. By the arguments of Susskind/Witten (in the AdS case) and Gibbons/Hawking (in the dS case), we expect correspondingly large entropies associated with these vacua. If they are to provide a dual description of these vacua on their Coulomb branch, branes traded for the flux need to account for this entropy atmore » the appropriate energy scale. In this note, we argue that simple string junctions and webs ending on the branes can account for this large entropy, obtaining a rough estimate for junction entropy that agrees with the existing rough estimates for the spacing of the discretuum. In particular, the brane entropy can account for the (A)dS entropy far away from string scale correspondence limits.« less

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

PubMed

Ghaemi, Pouyan; Nair, V P

2016-01-22

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

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

NASA Astrophysics Data System (ADS)

Ghaemi, Pouyan; Nair, V. P.

2016-01-01

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

Phase and vortex correlations in superconducting Josephson-junction arrays at irrational magnetic frustration.

PubMed

Granato, Enzo

2008-07-11

Phase coherence and vortex order in a Josephson-junction array at irrational frustration are studied by extensive Monte Carlo simulations using the parallel-tempering method. A scaling analysis of the correlation length of phase variables in the full equilibrated system shows that the critical temperature vanishes with a power-law divergent correlation length and critical exponent nuph, in agreement with recent results from resistivity scaling analysis. A similar scaling analysis for vortex variables reveals a different critical exponent nuv, suggesting that there are two distinct correlation lengths associated with a decoupled zero-temperature phase transition.

Current-voltage scaling of a Josephson-junction array at irrational frustration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Granato, E.

1996-10-01

Numerical simulations of the current-voltage characteristics of an ordered two-dimensional Josephson-junction array at an irrational flux quantum per plaquette are presented. The results are consistent with a scaling analysis that assumes a zero-temperature vortex-glass transition. The thermal-correlation length exponent characterizing this transition is found to be significantly different from the corresponding value for vortex-glass models in disordered two-dimensional superconductors. This leads to a current scale where nonlinearities appear in the current-voltage characteristics decreasing with temperature {ital T} roughly as {ital T}{sup 2} in contrast with the {ital T}{sup 3} behavior expected for disordered models. {copyright} {ital 1996 The American Physicalmore » Society.}« less

Voltage noise of current-driven vortices in disordered Josephson junction arrays.

PubMed

He, G L; Zhao, Z G; Liu, S; Yang, Y H; Liu, M; Xing, D Y

2006-08-16

Dynamical phenomena of moving vortices and voltage noise spectra are studied in disordered Josephson junction arrays (JJAs). The plastic motion of vortices, smectic flow, and moving Bragg glass phases are separated by two dynamic melting transitions driven by current. From the voltage noise spectra of moving vortices, it is found that the driving current plays an important role in the melting of pinning vortices glass and ordering of moving vortices. The features of noise spectra obtained in the disordered JJA model have been observed recently in the high-temperature superconductor Bi(2)Sr(2)CaCu(2)O(y) near the first-order melting transition, indicating that both of them are related to each other.

Photon-detections via probing the switching current shifts of Josephson junctions

NASA Astrophysics Data System (ADS)

Wang, Yiwen; Zhou, Pinjia; Wei, Lianfu; Zhang, Beihong; Wei, Qiang; Zhai, Jiquan; Xu, Weiwei; Cao, Chunhai

2015-08-01

Phenomenally, Cooper pairs can be broken up by external energy and thus the Cooper-pair density in the superconducting electrodes of a Josephson junction (JJ) under radiation can be lowered accordingly. Therefore, by probing the shift of the switching current through the junction, the radiation power absorbed by the superconductors can be detected. Here, we experimentally demonstrate weak optical detections in two types of JJs: Al/AlOx/Al junction (Al-J) and Nb/AlOx/Nb junction (Nb-J), with the superconducting transition temperatures Tc ≈ 1.2K and 6.8 K respectively. The photon-induced switching current shifts are measured at ultra-low temperature (T ≈ 16mK) in order to significantly suppress thermal noises. It is observed that the Al-J has a higher sensitivity than the Nb-J, which is expected since Al has a smaller superconducting gap energy than Nb. The minimum detectable optical powers (at 1550 nm) with the present Al-J and Nb-J are measured as 8 pW and 2 nW respectively, and the noise equivalent power (NEP) are estimated to be 7 ×10-11W /√{ Hz } (for Nb-J) and 3 ×10-12W /√{ Hz } (for Al-J). We also find that the observed switching current responses are dominated by the photon-induced thermal effects. Several methods are proposed to further improve the device sensitivity, so that the JJ based devices can be applicable in photon detections.

Charge imbalance and Josephson effects in superconductor-normal metal mesoscopic structures

NASA Astrophysics Data System (ADS)

Volkov, A. F.

2007-11-01

We consider a SBS Josephson junction the superconducting electrodes S of which are in contact with normal metal reservoirs ( B means a barrier). For temperatures near Tc we calculate an effective critical current Ic* and the resistance of the system at the currents IS wire, affects essentially the characteristics of the structure. The effective critical current Ic* is always larger than the critical current Ic in the absence of the normal reservoirs and increases with decreasing the ratio of the length of the S wire 2L to the charge imbalance relaxation length lQ . It is shown that a series of peaks arises on the I-V characteristics due to excitation of the Carlson-Goldman collective modes. We find the position of Shapiro steps which deviates from that given by the Josephson relation.

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

NASA Astrophysics Data System (ADS)

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

2018-05-01

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

Josephson flux-flow oscillator: The microscopic tunneling approach

NASA Astrophysics Data System (ADS)

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

2017-07-01

We elaborate a theoretical description of large Josephson junctions which is based on Werthamer's microscopic tunneling theory. The model naturally incorporates coupling of electromagnetic radiation to the tunnel currents and, therefore, is particularly suitable for description of the self-coupling effect in Josephson junction. In our numerical calculations we treat the arising integro-differential equation, which describes temporal evolution of the superconducting phase difference coupled to the electromagnetic field, by the Odintsov-Semenov-Zorin algorithm. This allows us to avoid evaluation of the time integrals at each time step while taking into account all the memory effects. To validate the obtained microscopic model of large Josephson junction we focus our attention on the Josephson flux-flow oscillator. The proposed microscopic model of flux-flow oscillator does not involve the phenomenological damping parameter, rather the damping is taken into account naturally in the tunnel current amplitudes calculated at a given temperature. The theoretically calculated current-voltage characteristics is compared to our experimental results obtained for a set of fabricated flux-flow oscillators of different lengths.

5. SWITCH TOWER AND JUNCTION OF S.A.R. #1 & S.A.R. ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

5. SWITCH TOWER AND JUNCTION OF S.A.R. #1 & S.A.R. #2 TRANSMISSION LINES, MARCH 7, 1916. SCE drawing no. 4932. - Santa Ana River Hydroelectric System, Transmission Lines, Redlands, San Bernardino County, CA

Time-dependent photon heat transport through a mesoscopic Josephson device

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

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

Atomic Josephson Vortex

NASA Astrophysics Data System (ADS)

Kaurov, Vitaliy; Kuklov, Anatoly

2006-03-01

We show that atomic Josephson vortices [1] in a quasi-1D atomic junction can be controllably manipulated by imposing a tunneling bias current created by a difference of chemical potentials on the atomic BEC waveguides forming the junction. This effect, which has its origin in the Berry phase structure of a vortex, turns out to be very robust in the whole range of the parameters where such vortices can exist [2]. Acceleration of the vortex up to a certain threshold speed, determined by the strength of the Josephson coupling, results in the phase slip causing switching of the vorticity. This effect is directly related to the interconversion [1], when slow variation of the coupling can cause transformation of the vortex into the dark soliton and vice verse. We also propose that a Josephson vortex can be created by the phase imprinting technique and can be identified by a specific tangential feature in the interference picture produced by expanding clouds released from the waveguides [2]. [1] V. M. Kaurov , A. B. Kuklov, Phys. Rev. A 71, 11601(R) (2005). [2] V. M. Kaurov , A. B. Kuklov cond-mat/0508342

Feynman's and Ohta's Models of a Josephson Junction

ERIC Educational Resources Information Center

De Luca, R.

2012-01-01

The Josephson equations are derived by means of the weakly coupled two-level quantum system model given by Feynman. Adopting a simplified version of Ohta's model, starting from Feynman's model, the strict voltage-frequency Josephson relation is derived. The contribution of Ohta's approach to the comprehension of the additional term given by the…

Markovian Dynamics of Josephson Parametric Amplification

NASA Astrophysics Data System (ADS)

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

2017-09-01

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

dc properties of series-parallel arrays of Josephson junctions in an external magnetic field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lewandowski, S.J.

1991-04-01

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-{ital T}{sub {ital 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 amore » 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-{ital T}{sub {ital c}} materials are pointed out as a potential source of additional noise.« less

Transport in arrays of submicron Josephson junctions over a ground plane

NASA Astrophysics Data System (ADS)

Ho, Teressa Rae

One-dimensional (1D) and two-dimensional (2D) arrays of Al islands linked by submicron Al/Alsb{x}Osb{y}/Al tunnel junctions were fabricated on an insulating layer grown on a ground plane. The arrays were cooled to temperatures as low as 20 mK where the Josephson coupling energy Esb{J} of each junction and the charging energy Esb{C} of each island were much greater than the thermal energy ksb{B}T. The capacitance Csb{g} between each island and the ground plane was much greater than the junction capacitance C. Two classes of arrays were studied. In the first class, the normal state tunneling resistance of the junctions was much larger than the resistance quantum for single electrons, Rsb{N}≫ Rsb{Qe}equiv h/esp2≈ 25.8 kOmega, and the islands were driven normal by an applied magnetic field such that Esb{J}=0 and the array was in the Coulomb blockade regime. The arrays were made on degenerately-doped Si, thermally oxidized to a thickness of approximately 100 nm. The current-voltage (I-V) characteristics of a 1D and a 2D array were measured and found to display a threshold voltage Vsb{T} below which little current flows. Above threshold the array current I scaled as (V/Vsb{T}-1)sp{zeta}; this scaling behavior was interpreted as a dynamic critical phenomenon. A 2D array with intentionally-added island area disorder was also measured and found to have a similar threshold voltage Vsb{T} but a larger scaling exponent zeta than the array with only intrinsic disorder. In the second class of arrays, the normal state tunneling resistance of the junctions was close to the resistance quantum for Cooper pairs, Rsb{N}≈ Rsb{Q}equiv h/4esp2≈ 6.45kOmega, such that Esb{J}/Esb{C}≈1. The arrays were made on GaAs/Alsb{0.3}Gasb{0.7}As heterostructures with a two-dimensional electron gas (2DEG) approximately 100 nm below the surface. The resistance per square of the 2DEG, Rsb{g}, could be varied by applying a large voltage between the 2DEG and a metallic back gate; varying Rsb

Theory of coherent quantum phase slips in Josephson junction chains with periodic spatial modulations

NASA Astrophysics Data System (ADS)

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.

Anomalous spin Josephson effect

NASA Astrophysics Data System (ADS)

Wang, Mei-Juan; Wang, Jun; Hao, Lei; Liu, Jun-Feng

2016-10-01

We report a theoretical study on the spin Josephson effect arising from the exchange coupling of the two ferromagnets (Fs), which are deposited on a two-dimensional (2D) time-reversal-invariant topological insulator. An anomalous spin supercurrent Js z˜sin(α +α0) is found to flow in between the two Fs and the ground state of the system is not limited to the magnetically collinear configuration (α =n π ,n is an integer) but determined by a controllable angle α0, where α is the crossed angle between the two F magnetizations. The angle α0 is the dynamic phase of the electrons traveling in between the two Fs and can be controlled electrically by a gate voltage. This anomalous spin Josephson effect, similar to the conventional φ0 superconductor junction, originates from the definite electron chirality of the helical edge states in the 2D topological insulator. These results indicate that the magnetic coupling in a topological system is different from the usual one in conventional materials.

Experimental studies on hybrid superconductor-topological insulator nanoribbon Josephson devices

NASA Astrophysics Data System (ADS)

Kayyalha, Morteza; Jauregui, Luis; Kazakov, Aleksander; Miotkowski, Ireneusz; Rokhinson, Leonid; Chen, Yong

The spin-helical topological surface states (TSS) of topological insulators in proximity with an s-wave superconductor are predicted to demonstrate signatures of topological superconductivity and host Majorana fermions. Here, we report on the observation of gate-tunable proximity-induced superconductivity in an intrinsic BiSbTeSe2 topological insulator nanoribbon (TINR) based Josephson junction (JJ) with Nb contacts. We observe a gate-tunable critical current (IC) with an anomalous behavior in the temperature (T) dependence of IC. We discuss various possible scenarios that could be relevant to this anomalous behavior, such as (i) the different temperature dependence of supercurrent generated by in-gap, where phase slip plays an important role, and out-of-gap Andreev bound states or (ii) the different critical temperatures associated with the top and bottom topological surface states. Our modeling of IC vs. T suggests the possible existence of one pair of in-gap Andreev bound states in our TINR. We have also studied the effects of magnetic fields on the critical current in our TINR Josephson junctions.

Low temperature properties of spin filter NbN/GdN/NbN Josephson junctions

NASA Astrophysics Data System (ADS)

Massarotti, D.; Caruso, R.; Pal, A.; Rotoli, G.; Longobardi, L.; Pepe, G. P.; Blamire, M. G.; Tafuri, F.

2017-02-01

A ferromagnetic Josephson junction (JJ) represents a special class of hybrid system where different ordered phases meet and generate novel physics. In this work we report on the transport measurements of underdamped ferromagnetic NbN/GdN/NbN JJs at low temperatures. In these junctions the ferromagnetic insulator gadolinium nitride barrier generates spin-filtering properties and a dominant second harmonic component in the current-phase relation. These features make spin filter junctions quite interesting also in terms of fundamental studies on phase dynamics and dissipation. We discuss the fingerprints of spin filter JJs, through complementary transport measurements, and their implications on the phase dynamics, through standard measurements of switching current distributions. NbN/GdN/NbN JJs, where spin filter properties can be controllably tuned along with the critical current density (Jc), turn to be a very relevant term of reference to understand phase dynamics and dissipation in an enlarged class of JJs, not necessarily falling in the standard tunnel limit characterized by low Jc values.

Parameter optimization for transitions between memory states in small arrays of Josephson junctions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rezac, Jacob D.; Imam, Neena; Braiman, Yehuda

Coupled arrays of Josephson junctions possess multiple stable zero voltage states. Such states can store information and consequently can be utilized for cryogenic memory applications. Basic memory operations can be implemented by sending a pulse to one of the junctions and studying transitions between the states. In order to be suitable for memory operations, such transitions between the states have to be fast and energy efficient. Here in this article we employed simulated annealing, a stochastic optimization algorithm, to study parameter optimization of array parameters which minimizes times and energies of transitions between specifically chosen states that can be utilizedmore » for memory operations (Read, Write, and Reset). Simulation results show that such transitions occur with access times on the order of 10–100 ps and access energies on the order of 10 -19–5×10 -18 J. Numerical simulations are validated with approximate analytical results.« less

Josephson junction as the receiving and measuring element in panoramic receiver: frequencymeter in terahertz band

NASA Astrophysics Data System (ADS)

Denisov, Alexander; Gudkov, Alexander; Qiu, Jing Hui

2014-10-01

Josephson junction (JJ) can be used as the criterion in single-block super wide band frequency-meter and as the sensitive element in the super wide band panoramic receiver. There presented the theoretical and experimental investigations and described the innovation decision about to combine both devices in one new microwave device. JJ in this case works in self-pump mode regime. New device can be especially convenient for the experimental purposes with new generation structures when radiated power is small and frequency are unknown correctly.

High-T(sub c) Superconductor-Normal-Superconductor Junctions with Polyimide-Passivated Ambient Temperature Edge Formation

NASA Technical Reports Server (NTRS)

Barner, J. B.; Kleinsasser, A. W.; Hunt, B. D.

1996-01-01

The ability to controllably fabricate High-Temperature Superconductor (HTS) S-Normal-S (SNS) Josephson Juntions (JJ's) enhances the possibilities fro many applications, including digital circuits, SQUID's, and mixers. A wide variety of approaches to fabricating SNS-like junctions has been tried and analyzed in terms of proximity effect behavior.

Jonction Josephson en couche épaisse d'oxydes supraconducteurs

NASA Astrophysics Data System (ADS)

Gunther, C.; Monfort, Y.; Sing, M. Lam Chok; Bloyet, D.; Brousse, T.; Provost, J.; Raveau, B.

1992-02-01

Constrictions engraved in YBaCuO thick films fabricated by screen printing on YSZ substrate (J_c>3 000 A/cm^2 at 77 K) have been studied. Microwave irradiation of the devices at LN2 showed distinct Shapiro steps demonstrating the presence intrinsic Josephson junctions. The latter have an I_c(T) dependence fitting (1-T/T_c)^2 characteristic of SNS junctions. Furthermore, dc SQUID effects have also been observed with a peak-to-peak response simeq 0.2 μV and with a magnetic field periodicity extending through several hundred of φ_0. An energy resolution close to 3× 10^{-29} J/Hz is estimated for our constriction operating in the white noise frequency range (f>50 Hz) at 77 K. This sensitivity is adequate to use this flux sensor in many applications : geomagnetism, magnetocardiology, ... Nous avons étudié des constrictions gravées dans des couches épaisses d'YBaCuO déposées sur substrat de YSZ (J_c>3 000 A/cm^2 à 77 K). L'observation de marches de Shapiro lors d'irradiations des échantillons à 77 K par un champ HF met clairement en évidence la présence de jonctions Josephson intrinsèques de type SNS, leur dépendance en température du courant critique étant en (1-T/T_c)^2. De plus, nous avons obtenu des réponses en champ magnétique, caractéristiques des SQUIDs dc, d'amplitude 0,2 μVcc et dont la périodicité s'étend sur plusieurs centaines de φ_0. La résolution en énergie est de l'ordre de 3× 10^{-29} J/Hz en zone de bruit blanc (f>50 Hz) à 77 K. Cette sensibilité est suffisante pour envisager son utilisation dans des applications telles que : géomagnétisme, magnétocardiologie, ...

Origin of hydrogen-inclusion-induced critical current deviation in Nb/AlOx/Al/Nb Josephson junctions

NASA Astrophysics Data System (ADS)

Hinode, Kenji; Satoh, Tetsuro; Nagasawa, Shuichi; Hidaka, Mutsuo

2010-04-01

We investigated the mechanisms that change the critical current density (Jc) of Nb/AlOx/Al/Nb Josephson junctions due to the inclusion of hydrogen in the Nb electrodes. Our investigations were performed according to three aspects: the superconductivity change, the change in thickness of the barrier layer, and the change in the barrier height due to the electronic effect. The results are as follows: (a) the hydrogen-inclusion-accompanied changes in the superconductivity parameters, such as the junction gap voltage, were much less than those of the critical current density, (b) the effect of hydrogen inclusion on Jc varied depending on the electrodes, i.e., the upper electrode above the barrier layer was the most affected, (c) the junctions with increased Ics due to hydrogen exclusion showed the identical amount of decrease in the junction resistance measured at room temperature, and (d) the hydrogen exclusion from the junction electrodes had no influence on the Nb/Al/AlOx/Al/Nb junctions, which had an extra Al layer. Based on these results we conclude that the Jc change is mainly caused by the change in junction resistance. A one order of magnitude smaller effect is caused by the superconductivity change. We believe the Jc change is caused by a Nb work function increase due to the hydrogen inclusion, resulting in an increase in barrier height.

Interactions between electrons, mesoscopic Josephson effect and asymmetric current fluctuations

NASA Astrophysics Data System (ADS)

Huard, B.

2006-07-01

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

Flux Cloning in Josephson Transmission Lines

NASA Astrophysics Data System (ADS)

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

2006-07-01

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.

Spatially inhomogeneous barrier height in graphene/MoS2 Schottky junctions

NASA Astrophysics Data System (ADS)

Tomer, Dushyant; Rajput, Shivani; Li, Lian

Graphene interfaced with a semiconductor forms a Schottky junction with rectifying properties. In this study, graphene Schottky junctions are fabricated by transferring CVD monolayer graphene on mechanically exfoliated MoS2 multilayers. The forward bias current-voltage characteristics are measured in the temperature range of 210-300 K. An increase in the zero bias barrier height and decrease in the ideality factor are observed with increasing temperature. Such behavior is attributed to Schottky barrier inhomogeneities possibly due to graphene ripples and ridges at the junction interface as suggested by atomic force microscopy. Assuming a Gaussian distribution of the barrier height, mean barrier of 0.97+/-0.10 eV is found for the graphene MoS2 junction. Our findings provide significant insight on the barrier height inhomogeneities in graphene/two dimensional semiconductor Schottky junctions. U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering Award No. DEFG02-07ER46228.

Magnetometry with Low-Resistance Proximity Josephson Junction

NASA Astrophysics Data System (ADS)

Jabdaraghi, R. N.; Peltonen, J. T.; Golubev, D. S.; Pekola, J. P.

2018-06-01

We characterize a niobium-based superconducting quantum interference proximity transistor (Nb-SQUIPT) and its key constituent formed by a Nb-Cu-Nb SNS weak link. The Nb-SQUIPT and SNS devices are fabricated simultaneously in two separate lithography and deposition steps, relying on Ar ion cleaning of the Nb contact surfaces. The quality of the Nb-Cu interface is characterized by measuring the temperature-dependent equilibrium critical supercurrent of the SNS junction. In the Nb-SQUIPT device, we observe a maximum flux-to-current transfer function value of about 55 nA/Φ_0 in the sub-gap regime of bias voltages. This results in suppression of power dissipation down to a few fW. Low-bias operation of the device with a relatively low probe junction resistance decreases the dissipation by up to two orders of magnitude compared to a conventional device based on an Al-Cu-Al SNS junction and an Al tunnel probe (Al-SQUIPT).

The gatemon: a transmon with a voltage-variable superconductor-semiconductor junction

NASA Astrophysics Data System (ADS)

Petersson, Karl

We have developed a superconducting transmon qubit with a semiconductor-based Josephson junction element. The junction is made from an InAs nanowire with in situ molecular beam epitaxy-grown superconducting Al contacts. This gate-controlled transmon, or gatemon, allows simple tuning of the qubit transition frequency using a gate voltage to vary the density of carriers in the semiconductor region. In the first generations of devices we have measured coherence times up to ~10 μs. These coherence times, combined with stable qubit operation, permit single qubit rotations with fidelities of ~99.5 % for all gates including voltage-controlled Z rotations. Towards multi-qubit operation we have also implemented a two qubit voltage-controlled cPhase gate. In contrast to flux-tuned transmons, voltage-tunable gatemons may simplify the task of scaling to multi-qubit circuits and enable new means of control for many qubit architectures. In collaboration with T.W. Larsen, L. Casparis, M.S. Olsen, F. Kuemmeth, T.S. Jespersen, P. Krogstrup, J. Nygard and C.M. Marcus. Research was supported by Microsoft Project Q, Danish National Research Foundation and a Marie Curie Fellowship.

Nonadiabatic Josephson current pumping by chiral microwave irradiation

NASA Astrophysics Data System (ADS)

Venitucci, B.; Feinberg, D.; Mélin, R.; Douçot, B.

2018-05-01

Irradiating a Josephson junction with microwaves can operate not only on the amplitude but also on the phase of the Josephson current. This requires breaking time-inversion symmetry, which is achieved by introducing a phase lapse between the microwave components acting on the two sides of the junction. General symmetry arguments and the solution of a specific single-level quantum dot model show that this induces chirality in the Cooper pair dynamics due to the topology of the Andreev bound-state wave function. Another essential condition is to break electron-hole symmetry within the junction. A shift of the current-phase relation is obtained, which is controllable in sign and amplitude with the microwave phase and an electrostatic gate, thus producing a "chiral" Josephson transistor. The dot model is solved in the infinite-gap limit by Floquet theory and in the general case with Keldysh nonequilibrium Green's functions. The chiral current is nonadiabatic: it is extremal and changes sign close to resonant chiral transitions between the Andreev bound states.

Effets Josephson generalises entre antiferroaimants et entre supraconducteurs antiferromagnetiques

NASA Astrophysics Data System (ADS)

Chasse, Dominique

L'effet Josephson est generalement presente comme le resultat de l'effet tunnel coherent de paires de Cooper a travers une jonction tunnel entre deux supraconducteurs, mais il est possible de l'expliquer dans un contexte plus general. Par exemple, Esposito & al. ont recemment demontre que l'effet Josephson DC peut etre decrit a l'aide du boson pseudo-Goldstone de deux systemes couples brisant chacun la symetrie abelienne U(1). Puisque cette description se generalise de facon naturelle a des brisures de symetries continues non-abeliennes, l'equivalent de l'effet Josephson devrait donc exister pour des types d'ordre a longue portee differents de la supraconductivite. Le cas de deux ferroaimants itinerants (brisure de symetrie 0(3)) couples a travers une jonction tunnel a deja ete traite dans la litterature Afin de mettre en evidence la generalite du phenomene et dans le but de faire des predictions a partir d'un modele realiste, nous etudions le cas d'une jonction tunnel entre deux antiferroaimants itinerants. En adoptant une approche Similaire a celle d'Ambegaokar & Baratoff pour une jonction Josephson, nous trouvons un courant d'aimantation alternee a travers la jonction qui est proportionnel a sG x sD ou fG et sD sont les vecteurs de Neel de part et d'autre de la jonction. La fonction sinus caracteristique du courant Josephson standard est donc remplacee.ici par un produit vectoriel. Nous montrons que, d'un point de vue microscopique, ce phenomene resulte de l'effet tunnel coherent de paires particule-trou de spin 1 et de vecteur d'onde net egal au vecteur d'onde antiferromagnetique Q. Nous trouvons egalement la dependance en temperature de l'analogue du courant critique. En presence d'un champ magnetique externe, nous obtenons l'analogue de l'effet Josephson AC et la description complete que nous en donnons s'applique aussi au cas d'une jonction tunnel entre ferroaimants (dans ce dernier cas, les traitements anterieurs de cet effet AC s'averent incomplets). Nous

Josephson coupling between superconducting islands on single- and bi-layer graphene

NASA Astrophysics Data System (ADS)

Mancarella, Francesco; Fransson, Jonas; Balatsky, Alexander

2016-05-01

We study the Josephson coupling of superconducting (SC) islands through the surface of single-layer graphene (SLG) and bilayer graphene (BLG) in the long-junction regime, as a function of the distance between the grains, temperature, chemical potential and external (transverse) gate-voltage. For SLG, we provide a comparison with existing literature. The proximity effect is analyzed through a Matsubara Green’s function approach. This represents the first step in a discussion of the conditions for the onset of a granular superconductivity within the film, made possible by Josephson currents flowing between superconductors. To ensure phase coherence over the 2D sample, a random spatial distribution can be assumed for the SC islands on the SLG sheet (or intercalating the BLG sheets). The tunable gate-voltage-induced band gap of BLG affects the asymptotic decay of the Josephson coupling-distance characteristic for each pair of SC islands in the sample, which results in a qualitatively strong field dependence of the relation between Berezinskii-Kosterlitz-Thouless transition critical temperature and gate voltage.

Critical Current Statistics of a Graphene-Based Josephson Junction Infrared Single Photon Detector

NASA Astrophysics Data System (ADS)

Walsh, Evan D.; Lee, Gil-Ho; Efetov, Dmitri K.; Heuck, Mikkel; Crossno, Jesse; Taniguchi, Takashi; Watanabe, Kenji; Ohki, Thomas A.; Kim, Philip; Englund, Dirk; Fong, Kin Chung

Graphene is a promising material for single photon detection due to its broadband absorption and exceptionally low specific heat. We present a photon detector using a graphene sheet as the weak link in a Josephson junction (JJ) to form a threshold detector for single infrared photons. Calculations show that such a device could experience temperature changes of a few hundred percent leading to sub-Hz dark count rates and internal efficiencies approaching unity. We have fabricated the graphene-based JJ (gJJ) detector and measure switching events that are consistent with single photon detection under illumination by an attenuated laser. We study the physical mechanism for these events through the critical current behavior of the gJJ as a function of incident photon flux.

Non-linear wave phenomena in Josephson elements for superconducting electronics

NASA Astrophysics Data System (ADS)

Christiansen, P. L.; Parmentier, R. D.; Skovgaard, O.

1985-07-01

The long and intermediate length Josephson tunnel junction oscillator with overlap geometry of linear and circular configuration, is investigated by computational solution of the perturbed sine-Gordon equation model and by experimental measurements. The model predicts the experimental results very well. Line oscillators as well as ring oscillators are treated. For long junctions soliton perturbation methods are developed and turn out to be efficient prediction tools, also providing physical understanding of the dynamics of the oscillator. For intermediate length junctions expansions in terms of linear cavity modes reduce computational costs. The narrow linewidth of the electromagnetic radiation (typically 1 kHz of a line at 10 GHz) is demonstrated experimentally. Corresponding computer simulations requiring a relative accuracy of less than 10 to the -7th power are performed on supercomputer CRAY-1-S. The broadening of linewidth due to external microradiation and internal thermal noise is determined.

Coherent and dissipative transport in a Josephson junction between fermionic superfluids of 6Li atoms

NASA Astrophysics Data System (ADS)

Neri, Elettra; Scazza, Francesco; Roati, Giacomo

2018-04-01

Quantum systems out of equilibrium offer the possibility of understanding intriguing and challenging problems in modern physics. Studying transport properties is not only valuable to unveil fundamental properties of quantum matter but it is also an excellent tool for developing new quantum devices which inherently employ quantum-mechanical effects. In this contribution, we present our experimental studies on quantum transport using ultracold Fermi gases of 6Li atoms. We realize the analogous of a Josephson junction by bisecting fermionic superfluids by a thin optical barrier. We observe coherent dynamics in both the population and in the relative phase between the two reservoirs. For critical parameters, the superfluid dynamics exhibits both coherent and resistive flow due to phase-slippage events manifesting as vortices propagating into the bulk. We uncover also a regime of strong dissipation where the junction operation is irreversibly affected by vortex proliferation. Our studies open new directions for investigating dissipation and superfluid transport in strongly correlated fermionic systems.

Time-evolution of photon heat current through series coupled two mesoscopic Josephson junction devices

NASA Astrophysics Data System (ADS)

Lu, Wen-Ting; Zhao, Hong-Kang; Wang, Jian

2018-03-01

Photon heat current tunneling through a series coupled two mesoscopic Josephson junction (MJJ) system biased by dc voltages has been investigated by employing the nonequilibrium Green’s function approach. The time-oscillating photon heat current is contributed by the superposition of different current branches associated with the frequencies of MJJs ω j (j = 1, 2). Nonlinear behaviors are exhibited to be induced by the self-inductance, Coulomb interaction, and interference effect relating to the coherent transport of Cooper pairs in the MJJs. Time-oscillating pumping photon heat current is generated in the absence of temperature difference, while it becomes zero after time-average. The combination of ω j and Coulomb interactions in the MJJs determines the concrete heat current configuration. As the external and intrinsic frequencies ω j and ω 0 of MJJs match some specific combinations, resonant photon heat current exhibits sinusoidal behaviors with large amplitudes. Symmetric and asymmetric evolutions versus time t with respect to ω 1 t and ω 2 t are controlled by the applied dc voltages of V 1 and V 2. The dc photon heat current formula is a special case of the general time-dependent heat current formula when the bias voltages are settled to zero. The Aharonov-Bohm effect has been investigated, and versatile oscillation structures of photon heat current can be achieved by tuning the magnetic fluxes threading through separating MJJs.

11. Historic American Buildings Survey S.F. Chronicle Library Collection, S.F. ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

11. Historic American Buildings Survey S.F. Chronicle Library Collection, S.F. WALLS AND TOWER AFTER DISASTER OF 1906 - St. Mary's Church, 660 California Street, San Francisco, San Francisco County, CA

Structured chaos in a devil's staircase of the Josephson junction.

PubMed

Shukrinov, Yu M; Botha, A E; Medvedeva, S Yu; Kolahchi, M R; Irie, A

2014-09-01

The phase dynamics of Josephson junctions (JJs) under external electromagnetic radiation is studied through numerical simulations. Current-voltage characteristics, Lyapunov exponents, and Poincaré sections are analyzed in detail. It is found that the subharmonic Shapiro steps at certain parameters are separated by structured chaotic windows. By performing a linear regression on the linear part of the data, a fractal dimension of D = 0.868 is obtained, with an uncertainty of ±0.012. The chaotic regions exhibit scaling similarity, and it is shown that the devil's staircase of the system can form a backbone that unifies and explains the highly correlated and structured chaotic behavior. These features suggest a system possessing multiple complete devil's staircases. The onset of chaos for subharmonic steps occurs through the Feigenbaum period doubling scenario. Universality in the sequence of periodic windows is also demonstrated. Finally, the influence of the radiation and JJ parameters on the structured chaos is investigated, and it is concluded that the structured chaos is a stable formation over a wide range of parameter values.

Structured chaos in a devil's staircase of the Josephson junction

NASA Astrophysics Data System (ADS)

Shukrinov, Yu. M.; Botha, A. E.; Medvedeva, S. Yu.; Kolahchi, M. R.; Irie, A.

2014-09-01

The phase dynamics of Josephson junctions (JJs) under external electromagnetic radiation is studied through numerical simulations. Current-voltage characteristics, Lyapunov exponents, and Poincaré sections are analyzed in detail. It is found that the subharmonic Shapiro steps at certain parameters are separated by structured chaotic windows. By performing a linear regression on the linear part of the data, a fractal dimension of D = 0.868 is obtained, with an uncertainty of ±0.012. The chaotic regions exhibit scaling similarity, and it is shown that the devil's staircase of the system can form a backbone that unifies and explains the highly correlated and structured chaotic behavior. These features suggest a system possessing multiple complete devil's staircases. The onset of chaos for subharmonic steps occurs through the Feigenbaum period doubling scenario. Universality in the sequence of periodic windows is also demonstrated. Finally, the influence of the radiation and JJ parameters on the structured chaos is investigated, and it is concluded that the structured chaos is a stable formation over a wide range of parameter values.

Structured chaos in a devil's staircase of the Josephson junction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shukrinov, Yu. M.; Botha, A. E., E-mail: bothaae@unisa.ac.za; Medvedeva, S. Yu.

2014-09-01

The phase dynamics of Josephson junctions (JJs) under external electromagnetic radiation is studied through numerical simulations. Current-voltage characteristics, Lyapunov exponents, and Poincaré sections are analyzed in detail. It is found that the subharmonic Shapiro steps at certain parameters are separated by structured chaotic windows. By performing a linear regression on the linear part of the data, a fractal dimension of D = 0.868 is obtained, with an uncertainty of ±0.012. The chaotic regions exhibit scaling similarity, and it is shown that the devil's staircase of the system can form a backbone that unifies and explains the highly correlated and structured chaotic behavior.more » These features suggest a system possessing multiple complete devil's staircases. The onset of chaos for subharmonic steps occurs through the Feigenbaum period doubling scenario. Universality in the sequence of periodic windows is also demonstrated. Finally, the influence of the radiation and JJ parameters on the structured chaos is investigated, and it is concluded that the structured chaos is a stable formation over a wide range of parameter values.« less

Discreteness-induced resonances and ac voltage amplitudes in long one-dimensional Josephson junction arrays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Duwel, A.E.; Watanabe, S.; Trias, E.

1997-11-01

New resonance steps are found in the experimental current-voltage characteristics of long, discrete, one-dimensional Josephson junction arrays with open boundaries and in an external magnetic field. The junctions are underdamped, connected in parallel, and dc biased. Numerical simulations based on the discrete sine-Gordon model are carried out, and show that the solutions on the steps are periodic trains of fluxons, phase locked by a finite amplitude radiation. Power spectra of the voltages consist of a small number of harmonic peaks, which may be exploited for possible oscillator applications. The steps form a family that can be numbered by the harmonicmore » content of the radiation, the first member corresponding to the Eck step. Discreteness of the arrays is shown to be essential for appearance of the higher order steps. We use a multimode extension of the harmonic balance analysis, and estimate the resonance frequencies, the ac voltage amplitudes, and the theoretical limit on the output power on the first two steps. {copyright} {ital 1997 American Institute of Physics.}« less

Josephson Photodetectors via Temperature-to-Phase Conversion

NASA Astrophysics Data System (ADS)

Virtanen, P.; Ronzani, A.; Giazotto, F.

2018-05-01

We theoretically investigate the temperature-to-phase conversion (TPC) process occurring in dc superconducting quantum interferometers based on superconductor-normal-metal-superconductor (S -N -S ) mesoscopic Josephson junctions. In particular, we predict the temperature-driven rearrangement of the phase gradients in the interferometer under the fixed constraints of fluxoid quantization and supercurrent conservation. This mechanism allows sizeable phase variations across the junctions for suitable structure parameters and temperatures. We show that the TPC can be a basis for sensitive single-photon sensors or bolometers. We propose a radiation detector realizable with conventional materials and state-of-the-art nanofabrication techniques. Integrated with a superconducting quantum-interference proximity transistor as a readout setup, an aluminum-based TPC calorimeter can provide a large signal-to-noise ratio >100 in the 10-GHz-10-THz frequency range and a resolving power larger than 1 02 below 50 mK for terahertz photons. In the bolometric operation, electrical noise equivalent power of approximately 10-22 W /√{Hz } is predicted at 50 mK. This device can be attractive as a cryogenic single-photon sensor operating in the giga- and terahertz regime with applications in dark-matter searches.

Josephson parametric converter saturation and higher order effects

NASA Astrophysics Data System (ADS)

Liu, G.; Chien, T.-C.; Cao, X.; Lanes, O.; Alpern, E.; Pekker, D.; Hatridge, M.

2017-11-01

Microwave parametric amplifiers based on Josephson junctions have become indispensable components of many quantum information experiments. One key limitation which has not been well predicted by theory is the gain saturation behavior which limits the amplifier's ability to process large amplitude signals. The typical explanation for this behavior in phase-preserving amplifiers based on three-wave mixing, such as the Josephson Parametric Converter, is pump depletion, in which the consumption of pump photons to produce amplification results in a reduction in gain. However, in this work, we present experimental data and theoretical calculations showing that the fourth-order Kerr nonlinearities inherent in Josephson junctions are the dominant factor. The Kerr-based theory has the unusual property of causing saturation to both lower and higher gains, depending on bias conditions. This work presents an efficient methodology for optimizing device performance in the presence of Kerr nonlinearities while retaining device tunability and points to the necessity of controlling higher-order Hamiltonian terms to make further improvements in parametric devices.

Solitonic Josephson-based meminductive systems

NASA Astrophysics Data System (ADS)

Guarcello, Claudio; Solinas, Paolo; di Ventra, Massimiliano; Giazotto, Francesco

2017-04-01

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.

Solitonic Josephson-based meminductive systems

DOE PAGES

Guarcello, Claudio; Solinas, Paolo; Di Ventra, Massimiliano; ...

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 systemsmore » belong to the general class of memelements, few of them combine these important physical features in a single component. Here in this paper, 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.« less

Solitonic Josephson-based meminductive systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guarcello, Claudio; Solinas, Paolo; Di Ventra, Massimiliano

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 systemsmore » belong to the general class of memelements, few of them combine these important physical features in a single component. Here in this paper, 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.« less

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

NASA Astrophysics Data System (ADS)

Granato, Enzo

2018-05-01

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

Vortex states in a submicron Bi2212 crystal probed by intrinsic Josephson junctions

NASA Astrophysics Data System (ADS)

Ooi, S.; Tachiki, M.; Mochiku, T.; Wang, H. B.; Komori, K.; Hirata, K.; Arisawa, S.

2018-03-01

To study the pancake-vortex states confined in a submicron Bi2Sr2CaCu2O8+y (Bi2212) crystal, we have measured the c-axis resistance and I-V characteristics of a stack of intrinsic Josephson junctions with a lateral dimension less than 1 µm. Although the stack was accidentally shunted by a parallel resistance of 7.5 kΩ, the I-V characteristics show homogeneous multiple branches after the subtraction of the component. The penetrations of single vortices into the submicron stack were clearly observed in the resistance measurements. A vortex phase diagram was constructed by mapping the c-axis resistance on an H-T plane. Temperature dependence of the first-vortex penetration field is consistent with the theoretical estimation on the formation of a pancake-vortex stack in the center of a superconducting strip.

Breakdown of autoresonance due to separatrix crossing in dissipative systems: From Josephson junctions to the three-wave problem.

PubMed

Chacón, Ricardo

2008-12-01

Optimal energy amplification via autoresonance in dissipative systems subjected to separatrix crossings is discussed through the universal model of a damped driven pendulum. Analytical expressions of the autoresonance responses and forces as well as the associated adiabatic invariants for the phase space regions separated by the underlying separatrix are derived from the energy-based theory of autoresonance. Additionally, applications to a single Josephson junction, topological solitons in Frenkel-Kontorova chains, as well as to the three-wave problem in dissipative media are discussed in detail from the autoresonance analysis.

Optimal Normal Tissue Sparing in Craniospinal Axis Irradiation Using IMRT With Daily Intrafractionally Modulated Junction(s)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kusters, Johannes M.A.M.; Louwe, Rob J.W.; Kollenburg, Peter G.M. van

2011-12-01

Purpose: To develop a treatment technique for craniospinal irradiation using intensity-modulated radiotherapy (IMRT) with improved dose homogeneity at the field junction(s), increased target volume conformity, and minimized dose to the organs at risk (OARs). Methods and Materials: Five patients with high-risk medulloblastoma underwent CT simulation in supine position. For each patient, an IMRT plan with daily intrafractionally modulated junction(s) was generated, as well as a treatment plan based on conventional three-dimensional planning (3DCRT). A dose of 39.6 Gy in 22 daily fractions of 1.8 Gy was prescribed. Dose-volume parameters for target volumes and OARs were compared for the two techniques.more » Results: The maximum dose with IMRT was <107% in all patients. V{sub <95} and V{sub >107} were <1 cm{sup 3} for IMRT compared with 3-9 cm{sup 3} for the craniospinal and 26-43 cm{sup 3} for the spinal-spinal junction with 3DCRT. These observations corresponded with a lower homogeneity index and a higher conformity index for the spinal planning target volume with IMRT. IMRT provided considerable sparing of acute and late reacting tissues. V{sub 75} for the esophagus, gastroesophageal junction, and intestine was 81%, 81%, and 22% with 3DCRT versus 5%, 0%, and 1% with IMRT, respectively. V{sub 75} for the heart and thyroid was 42% and 32% vs. 0% with IMRT. Conclusion: IMRT with daily intrafractionally modulated junction results in a superior target coverage and junction homogeneity compared with 3DCRT. A significant dose reduction can be obtained for acute as well as late-reacting tissues.« less

Wideband Isolation by Frequency Conversion in a Josephson-Junction Transmission Line

NASA Astrophysics Data System (ADS)

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.

Low Leakage Superconducting Tunnel Junctions with a Single Crystal Al2O3 Barrier

DTIC Science & Technology

2016-03-30

have recently implemented Josephson junction superconducting devices into qubits [1-6]. Before a multi -qubit quantum computer is realized, however...Low-Leakage Superconducting Tunnel Junctions with a Single-Crystal Al2O3 Barrier* S Oh1,2, K Cicak1, R McDermott3, K B Cooper3, K D Osborn1, R W...growth scheme for single-crystal Al2O3 tunnel barriers. The barriers are epitaxially grown on single-crystal rhenium (Re) base electrodes that are

Chaotic Dynamics of a Josephson Junction with a Ratchet Potential and Current-Modulating Damping

NASA Astrophysics Data System (ADS)

Li, Fei; Li, Wenwu; Xu, Lan

2018-06-01

The chaotic dynamics of a Josephson junction with a ratchet potential and current-modulating damping are studied. Under the first-order approximation, we construct the general solution of the first-order equation whose boundedness condition contains the famous Melnikov chaotic criterion. Based on the general solution, the incomputability and unpredictability of the system's chaotic behavior are discussed. For the case beyond perturbation conditions, the evolution of stroboscopic Poincaré sections shows that the system undergoes a quasi-periodic transition to chaos with an increasing intensity of the rf-current. Through a suitable feedback controlling strategy, the chaos can be effectively suppressed and the intensity of the controller can vary in a large range. It is also found that the current between the two separated superconductors increases monotonously in some specific parameter spaces.

Chaotic Dynamics of a Josephson Junction with a Ratchet Potential and Current-Modulating Damping

NASA Astrophysics Data System (ADS)

Li, Fei; Li, Wenwu; Xu, Lan

2018-04-01

The chaotic dynamics of a Josephson junction with a ratchet potential and current-modulating damping are studied. Under the first-order approximation, we construct the general solution of the first-order equation whose boundedness condition contains the famous Melnikov chaotic criterion. Based on the general solution, the incomputability and unpredictability of the system's chaotic behavior are discussed. For the case beyond perturbation conditions, the evolution of stroboscopic Poincaré sections shows that the system undergoes a quasi-periodic transition to chaos with an increasing intensity of the rf-current. Through a suitable feedback controlling strategy, the chaos can be effectively suppressed and the intensity of the controller can vary in a large range. It is also found that the current between the two separated superconductors increases monotonously in some specific parameter spaces.

Dissipation in microwave quantum circuits with hybrid nanowire Josephson elements

NASA Astrophysics Data System (ADS)

Mugnai, D.; Ranfagni, A.; Agresti, A.

2017-04-01

Recent experiments on hybrid Josephson junctions have made the argument a topical subject. However, a quantity which remains still unknown is the tunneling (or response) time, which is strictly connected to the role that dissipation plays in the dynamics of the complete system. A simple way for evaluating dissipation in microwave circuits, previously developed for describing the dynamics of conventional Josephson junctions, is now presented as suitable for application even to non-conventional junctions. The method is based on a stochastic model, as derived from the telegrapher's equation, and is particularly devoted to the case of junctions loaded by real transmission lines. When the load is constituted by lumped-constant circuits, a connection with the stochastic model is also maintained. The theoretical model demonstrated its ability to analyze both classically-allowed and forbidden processes, and has found a wide field of applicability, namely in all cases in which dissipative effects cannot be ignored.

Josephson current in ballistic graphene Corbino disk

NASA Astrophysics Data System (ADS)

Abdollahipour, Babak; Mohammadkhani, Ramin; Khalilzadeh, Mina

2018-06-01

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

Josephson Metamaterial with a Widely Tunable Positive or Negative Kerr Constant

NASA Astrophysics Data System (ADS)

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

2017-11-01

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

Characterization of NbN films and tunnel junctions

NASA Technical Reports Server (NTRS)

Stern, J. A.; Leduc, H. G.

1991-01-01

Properties of NbN films and NbN/MgO/NbN tunnel junctions are discussed. NbN junctions are being developed for use in high-frequency, SIS quasiparticle mixers. To properly design mixer circuits, junction and film properties need to be characterized. The specific capacitance of NbN/MgO/NbN junctions has been measured as a function of the product of the normal-state resistance and the junction area (RnA), and it is found to vary by more than a factor of two (35-85 fF/sq microns) over the range of RnA measured (1000-50 ohm sq microns). This variation is important because the specific capacitance determines the RC speed of the tunnel junction at a given RnA value. The magnetic penetration depth of NbN films deposited under different conditions is also measured. The magnetic penetration depth affects the design of microstrip line used in RF tuning circuits. Control of the magnetic penetration depth is necessary to fabricate reproducible tuning circuits. Additionally, the critical current uniformity for arrays of 100 junctions has been measured. Junction uniformity will affect the design of focal-plane arrays of SIS mixers. Finally, the relevance of these measurements to the design of Josephson electronics is discussed.

Spin Josephson effect in topological superconductor-ferromagnet junction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ren, C. D.; Wang, J., E-mail: jwang@seu.edu.cn

2014-03-21

The composite topological superconductor (TS), made of one-dimensional spin-orbit coupled nanowire with proximity-induced s-wave superconductivity, is not a pure p-wave superconductor but still has a suppressed s-wave pairing. We propose to probe the spin texture of the p-wave pairing in this composite TS by examining possible spin supercurrents in an unbiased TS/ferromagnet junction. It is found that both the exchange-coupling induced and spin-flip reflection induced spin currents exist in the setup and survive even in the topological phase. We showed that besides the nontrivial p-wave pairing state accounting for Majorana Fermions, there shall be a trivial p-wave pairing state thatmore » contributes to spin supercurrent. The trivial p-wave pairing state is diagnosed from the mixing effect between the suppressed s-wave pairing and the topologically nontrivial p-wave pairing. The d vector of the TS is proved not to be rigorously perpendicular to the spin projection of p-wave pairings. Our findings are also confirmed by the Kitaev's p-wave model with a nonzero s-wave pairing.« less

Altered epidermal lipid processing and calcium distribution in the KID syndrome mouse model Cx26S17F.

PubMed

Bosen, Felicitas; Celli, Anna; Crumrine, Debra; vom Dorp, Katharina; Ebel, Philipp; Jastrow, Holger; Dörmann, Peter; Winterhager, Elke; Mauro, Theodora; Willecke, Klaus

2015-07-08

The keratitis-ichthyosis-deafness (KID) syndrome is caused by mutations in the gap junctional channel protein connexin 26 (Cx26), among them the mutation Cx26S17F. Heterozygous Cx26S17F mice resemble the human KID syndrome, i.e. exhibiting epidermal hyperplasia and hearing impairments. Newborn Cx26S17F mice show a defective epidermal water barrier as well as altered epidermal lipid secretion and location. Linoleoyl ω-esterified ceramides are strongly decreased on the skin surface of Cx26S17F mice. Moreover, the epidermal calcium gradient is altered in the mutant mice. These alterations may be caused by an abnormal Cx26S17F channel function that leads to a defective epidermal water barrier, which in turn may trigger the hyperproliferation seen in the KID syndrome. Copyright © 2015 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

Origin of the Ultrafast Response of the Lateral Photovoltaic Effect in Amorphous MoS2/Si Junctions.

PubMed

Hu, Chang; Wang, Xianjie; Miao, Peng; Zhang, Lingli; Song, Bingqian; Liu, Weilong; Lv, Zhe; Zhang, Yu; Sui, Yu; Tang, Jinke; Yang, Yanqiang; Song, Bo; Xu, Ping

2017-05-31

The lateral photovoltaic (LPV) effect has attracted much attention for a long time because of its application in position-sensitive detectors (PSD). Here, we report the ultrafast response of the LPV in amorphous MoS 2 /Si (a-MoS 2 /Si) junctions prepared by the pulsed laser deposition (PLD) technique. Different orientations of the built-in field and the breakover voltages are observed for a-MoS 2 films deposited on p- and n-type Si wafers, resulting in the induction of positive and negative voltages in the a-MoS 2 /n-Si and a-MoS 2 /p-Si junctions upon laser illumination, respectively. The dependence of the LPV on the position of the illumination shows very high sensitivity (183 mV mm -1 ) and good linearity. The optical relaxation time of LPV with a positive voltage was about 5.8 μs in a-MoS 2 /n-Si junction, whereas the optical relaxation time of LPV with a negative voltage was about 2.1 μs in a-MoS 2 /p-Si junction. Our results clearly suggested that the inversion layer at the a-MoS 2 /Si interface made a good contribution to the ultrafast response of the LPV in a-MoS 2 /Si junctions. The large positional sensitivity and ultrafast relaxation of LPV may promise the a-MoS 2 /Si junction's applications in fast position-sensitive detectors.

Fabrication of NiS modified CdS nanorod p-n junction photocatalysts with enhanced visible-light photocatalytic H2-production activity.

PubMed

Zhang, Jun; Qiao, Shi Zhang; Qi, Lifang; Yu, Jiaguo

2013-08-07

Production of hydrogen from photocatalytic water splitting has become an attractive research area due to the possibility of converting solar energy into green chemical energy. In this study, novel NiS nanoparticle (NP) modified CdS nanorod (NR) p-n junction photocatalysts were prepared by a simple two-step hydrothermal method. Even without the Pt co-catalyst, the as-prepared NiS NP-CdS NR samples exhibited enhanced visible-light photocatalytic activity and good stability for H2-production. The optimal NiS loading content was determined to be 5 mol%, and the corresponding H2-production rate reached 1131 μmol h(-1) g(-1), which is even higher than that of the optimized Pt-CdS NRs. It is believed that the assembly of p-type NiS NPs on the surface of n-type CdS NRs could form a large number of p-n junctions, which could effectively reduce the recombination rates of electrons and holes, thus greatly enhancing the photocatalytic activity. This work not only shows a possibility for the utilization of low cost NiS nanoparticles as a substitute for noble metals (such as Pt) in the photocatalytic H2-production but also provides a new insight into the design and fabrication of other new p-n junction photocatalysts for enhancing H2-production activity.

Josephson junction spectrum analyzer for millimeter and submillimeter wavelengths

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

1994-12-31

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

Josephson Junction spectrum analyzer for millimeter and submillimeter wavelengths

NASA Technical Reports Server (NTRS)

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

1995-01-01

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.

F.S.V.B. Volleyball

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

2006-06-07

22me assemblée des délégués de la Fédération Suisse de Volley Ball (F.S.V.B.), en présence entre autres de Claude Delay, représentant de la société fédérale de gymnastique et Hans Gauer, représentant de l'association suisse de gymnastique féminine. Annonce d'une démonstration d'un mini match de volley ball à Meyrin dans l'après-midi.

Computed tomography image using sub-terahertz waves generated from a high-T{sub c} superconducting intrinsic Josephson junction oscillator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kashiwagi, T., E-mail: kashiwagi@ims.tsukuba.ac.jp; Minami, H.; Kadowaki, K.

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.

Spin Transport in Electric-Barrier-Modulated Ferromagnetic/Normal/Ferromagnetic Monolayer Zigzag MoS2 Nanoribbon Junction

NASA Astrophysics Data System (ADS)

Xia, Y.-Y.; Yuan, R.-Y.; Yang, Q.-J.; Sun, Q.; Zheng, J.; Guo, Y.

In this paper, with the three-band tight-binding model and non-equilibrium Green’s function technique, we investigate spin transport in electric-barrier-modulated Ferromagnetic/Normal/Ferromagnetic (F/N/F) monolayer (ML) zigzag MoS2 nanoribbon junction. The results demonstrate that once the double electric barriers structure emerges, the oscillations of spin conductances become violent, especially for spin-down conductance, the numbers of resonant peaks increase obviously, thus we can obtain 100% spin polarization in the low energy region. It is also found that with the intensity of the exchange field enhancement, the resonant peaks of spin-up and spin-down conductances move in the opposite direction in a certain energy region. As a consequence, the spin-down conductance can be filtered out completely. The findings here indicate that the present structure may be considered as a good candidate for spin filter.

Origin of intrinsic Josephson coupling in the cuprates and its relation to order parameter symmetry: An incoherent hopping model

NASA Astrophysics Data System (ADS)

Radtke, R. J.; Levin, K.

1995-02-01

Experiments on the cuprate superconductors demonstrate that these materials may be viewed as a stack of Josephson junctions along the direction normal to the CuO 2 planes (the c-axis). In this paper, we present a model which describes this intrinsic Josephson coupling in terms of incherent quasiparticle hopping along the c-axis arising from wave-function overlap, impurity-assisted hopping, and boson-assised hopping. We use this model to compute the magnitude and temperature T dependence of the resulting Josephson critical current jc( T) for s- and d-wave superconductors. Contrary to other approaches, d-wave pairing in this model is compatible with an intrinsic Josephson effect at all hole concentrations and leads to jc( T) αT at low T. By parameterizing our theory with c-axis resistivity data from YBa 2Cu 3O 7-δ (YBCO), we estimate jc( T) for optimally doped and underdoped members of this family. jc( T) can be measured either directly or indirectly through microwave penetration depth experiments, and current measurements on Bi 2Sr 2CaCu 2O 8 and La 2- xSr xCuO 4 are found to be consistent with s-wave pairing and the dominance of assisted hopping processes. The situation in YBCO is still unclear, but our estimates suggest that further experiments on this compound would be of great help in elucidating the validity of our model in general and the pairing symmetry in particular.

Josephson supercurrent through a topological insulator surface state.

PubMed

Veldhorst, M; Snelder, M; Hoek, M; Gang, T; Guduru, V K; Wang, X L; Zeitler, U; van der Wiel, W G; Golubov, A A; Hilgenkamp, H; Brinkman, A

2012-02-19

The long-sought yet elusive Majorana fermion is predicted to arise from a combination of a superconductor and a topological insulator. An essential step in the hunt for this emergent particle is the unequivocal observation of supercurrent in a topological phase. Here, direct evidence for Josephson supercurrents in superconductor (Nb)-topological insulator (Bi(2)Te(3))-superconductor electron-beam fabricated junctions is provided by the observation of clear Shapiro steps under microwave irradiation, and a Fraunhofer-type dependence of the critical current on magnetic field. Shubnikov-de Haas oscillations in magnetic fields up to 30 T reveal a topologically non-trivial two-dimensional surface state. This surface state is attributed to mediate the ballistic Josephson current despite the fact that the normal state transport is dominated by diffusive bulk conductivity. The lateral Nb-Bi(2)Te(3)-Nb junctions hence provide prospects for the realization of devices supporting Majorana fermions.

Hierarchy of Supercurrents in Multicomponent Atomic Josephson Vortices

NASA Astrophysics Data System (ADS)

Kaurov, Vitaliy

2009-03-01

We show that a quasi-1D long atomic Josephson junction [1,2] containing a mixture of BECs can sustain multi-component Josephson vortices (mJV). A new exact soliton solution is given to describe a stationary mJV in the general N-component case. Depending on system parameters (scattering lengths, tunneling strengths, and chemical potentials) Josephson supercurrents of different components form a hierarchy according to their intensity and proximity to phase slip. By tuning the parameters it is possible to turn off or on particular currents using the JV -- dark soliton interconversion effect [1,2]. Inside the mJV different components may circulate either in the same or opposite directions resulting in bulk super-counter-flow in the latter case. The weak tunneling limit can be described by a modified Sine-Gordon model. An approximate solution for mJV propagating along the junction is found for the two-component case. The degeneracy of stationary mJV with respect to co-flow or counter-flow configurations is lifted by the uniform motion of mJV. Which configuration is energetically preferable depends on the interspecies scattering length. [1] V. M. Kaurov and A. B. Kuklov, Phys. Rev. A 71, 011601(R) (2005). [2] V. M. Kaurov and A. B. Kuklov, Phys. Rev. A 73, 013627 (2006).

Four-junction superconducting circuit

PubMed Central

Qiu, Yueyin; Xiong, Wei; He, Xiao-Ling; Li, Tie-Fu; You, J. Q.

2016-01-01

We develop a theory for the quantum circuit consisting of a superconducting loop interrupted by four Josephson junctions and pierced by a magnetic flux (either static or time-dependent). In addition to the similarity with the typical three-junction flux qubit in the double-well regime, we demonstrate the difference of the four-junction circuit from its three-junction analogue, including its advantages over the latter. Moreover, the four-junction circuit in the single-well regime is also investigated. Our theory provides a tool to explore the physical properties of this four-junction superconducting circuit. PMID:27356619

Josephson Parametric Reflection Amplifier with Integrated Directionality

NASA Astrophysics Data System (ADS)

Westig, M. P.; Klapwijk, T. M.

2018-06-01

A directional superconducting parametric amplifier in the GHz frequency range is designed and analyzed, suitable for low-power read-out of microwave kinetic inductance detectors employed in astrophysics and when combined with a nonreciprocal device at its input also for circuit quantum electrodynamics. It consists of a one-wavelength-long nondegenerate Josephson parametric reflection amplifier circuit. The device has two Josephson-junction oscillators, connected via a tailored impedance to an on-chip passive circuit which directs the in- to the output port. The amplifier provides a gain of 20 dB over a bandwidth of 220 MHz on the signal as well as on the idler portion of the amplified input and the total photon shot noise referred to the input corresponds to maximally approximately 1.3 photons per second per Hertz of bandwidth. We predict a factor of 4 increase in dynamic range compared to conventional Josephson parametric amplifiers.

F.S.V.B. Volleyball

ScienceCinema

None

2017-12-09

22me assemblée des délégués de la Fédération Suisse de Volley Ball (F.S.V.B.), en présence entre autres de Claude Delay, représentant de la société fédérale de gymnastique et Hans Gauer, représentant de l'association suisse de gymnastique féminine. Annonce d'une démonstration d'un mini match de volley ball à Meyrin dans l'après-midi.

Magnetization-induced dynamics of a Josephson junction coupled to a nanomagnet

NASA Astrophysics Data System (ADS)

Ghosh, Roopayan; Maiti, Moitri; Shukrinov, Yury M.; Sengupta, K.

2017-11-01

We study the superconducting current of a Josephson junction (JJ) coupled to an external nanomagnet driven by a time-dependent magnetic field both without and in the presence of an external ac drive. We provide an analytic, albeit perturbative, solution for the Landau-Lifshitz (LL) equations governing the coupled JJ-nanomagnet system in the presence of a magnetic field with arbitrary time dependence oriented along the easy axis of the nanomagnet's magnetization and in the limit of weak dimensionless coupling ɛ0 between the JJ and the nanomagnet. We show the existence of Shapiro-type steps in the I -V characteristics of the JJ subjected to a voltage bias for a constant or periodically varying magnetic field and explore the effect of rotation of the magnetic field and the presence of an external ac drive on these steps. We support our analytic results with exact numerical solution of the LL equations. We also extend our results to dissipative nanomagnets by providing a perturbative solution to the Landau-Lifshitz-Gilbert (LLG) equations for weak dissipation. We study the fate of magnetization-induced Shapiro steps in the presence of dissipation both from our analytical results and via numerical solution of the coupled LLG equations. We discuss experiments which can test our theory.

Spin-Valve Effect in NiFe/MoS2/NiFe Junctions.

PubMed

Wang, Weiyi; Narayan, Awadhesh; Tang, Lei; Dolui, Kapildeb; Liu, Yanwen; Yuan, Xiang; Jin, Yibo; Wu, Yizheng; Rungger, Ivan; Sanvito, Stefano; Xiu, Faxian

2015-08-12

Two-dimensional (2D) layered transition metal dichalcogenides (TMDs) have been recently proposed as appealing candidate materials for spintronic applications owing to their distinctive atomic crystal structure and exotic physical properties arising from the large bonding anisotropy. Here we introduce the first MoS2-based spin-valves that employ monolayer MoS2 as the nonmagnetic spacer. In contrast with what is expected from the semiconducting band-structure of MoS2, the vertically sandwiched-MoS2 layers exhibit metallic behavior. This originates from their strong hybridization with the Ni and Fe atoms of the Permalloy (Py) electrode. The spin-valve effect is observed up to 240 K, with the highest magnetoresistance (MR) up to 0.73% at low temperatures. The experimental work is accompanied by the first principle electron transport calculations, which reveal an MR of ∼9% for an ideal Py/MoS2/Py junction. Our results clearly identify TMDs as a promising spacer compound in magnetic tunnel junctions and may open a new avenue for the TMDs-based spintronic applications.

Superconductor Electronics Fabrication Process with MoNx Kinetic Inductors and Self-Shunted Josephson Junctions

NASA Astrophysics Data System (ADS)

Tolpygo, Sergey K.; Bolkhovsky, Vladimir; Oates, Daniel E.; Rastogi, Ravi; Zarr, Scott; Day, Alexandra L.; Weir, Tarence J.; Wynn, Alex; Johnson, Leonard M.

2018-06-01

Recent progress in superconductor electronics fabrication has enabled single-flux-quantum (SFQ) digital circuits with close to one million Josephson junctions (JJs) on 1-cm$^2$ chips. Increasing the integration scale further is challenging because of the large area of SFQ logic cells, mainly determined by the area of resistively shunted Nb/AlO$_x$-Al/Nb JJs and geometrical inductors utilizing multiple layers of Nb. To overcome these challenges, we are developing a fabrication process with self-shunted high-J$_c$ JJs and compact thin-film MoN$_x$ kinetic inductors instead of geometrical inductors. We present fabrication details and properties of MoN$_x$ films with a wide range of T$_c$, including residual stress, electrical resistivity, critical current, and magnetic field penetration depth {\\lambda}$_0$. As kinetic inductors, we implemented Mo$_2$N films with T$_c$ about 8 K, {\\lambda}$_0$ about 0.51 {\\mu}m, and inductance adjustable in the range from 2 to 8 pH/sq. We also present data on fabrication and electrical characterization of Nb-based self-shunted JJs with AlO$_x$ tunnel barriers and J$_c$ = 0.6 mA/{\\mu}m$^2$, and with 10-nm thick Si$_{1-x}$Nb$_x$ barriers, with x from 0.03 to 0.15, fabricated on 200-mm wafers by co-sputtering. We demonstrate that the electron transport mechanism in Si$_{1-x}$Nb$_x$ barriers at x < 0.08 is inelastic resonant tunneling via chains of multiple localized states. At larger x, their Josephson characteristics are strongly dependent on x and residual stress in Nb electrodes, and in general are inferior to AlO$_x$ tunnel barriers.

Crossing Over from Attractive to Repulsive Interactions in a Tunneling Bosonic Josephson Junction.

PubMed

Spagnolli, G; Semeghini, G; Masi, L; Ferioli, G; Trenkwalder, A; Coop, S; Landini, M; Pezzè, L; Modugno, G; Inguscio, M; Smerzi, A; Fattori, M

2017-06-09

We explore the interplay between tunneling and interatomic interactions in the dynamics of a bosonic Josephson junction. We tune the scattering length of an atomic ^{39}K Bose-Einstein condensate confined in a double-well trap to investigate regimes inaccessible to other superconducting or superfluid systems. In the limit of small-amplitude oscillations, we study the transition from Rabi to plasma oscillations by crossing over from attractive to repulsive interatomic interactions. We observe a critical slowing down in the oscillation frequency by increasing the strength of an attractive interaction up to the point of a quantum phase transition. With sufficiently large initial oscillation amplitude and repulsive interactions, the system enters the macroscopic quantum self-trapping regime, where we observe coherent undamped oscillations with a self-sustained average imbalance of the relative well population. The exquisite agreement between theory and experiments enables the observation of a broad range of many body coherent dynamical regimes driven by tunable tunneling energy, interactions and external forces, with applications spanning from atomtronics to quantum metrology.

New quantum oscillations in current driven small junctions

NASA Technical Reports Server (NTRS)

Ben-Jacob, E.; Gefen, Y.

1985-01-01

The response of current-biased Josephson and normal tunnel junctions (JJs and NTJs) such as those fabricated by Voss and Webb (1981) is predicted from a quantum-mechanical description based on the observation that the response of a current-driven open system is equivalent to that of a closed system subject to an external time-dependent voltage bias. Phenomena expected include voltage oscillations with no dc voltage applied, inverse Shapiro steps of dc voltage in the presence of microwave radiation, voltage oscillation in a JJ and an NTJ coupled by a capacitance to a current-biased junction, JJ voltage oscillation frequency = I/e rather than I/2e, and different NTJ resistance than in the voltage-driven case. The effects require approximate experimental parameter values Ic = 15 nA, C = 1 fF, and T much less than 0.4 K for JJs and Ic = a few nA, C = 1 fF, and R = 3 kiloohms for 100-microV inverse Shapiro steps at 10 GHz in NTJs.

Josephson 4 K-bit cache memory design for a prototype signal processor. I - General overview

NASA Astrophysics Data System (ADS)

Henkels, W. H.; Geppert, L. M.; Kadlec, J.; Epperlein, P. W.; Beha, H.

1985-09-01

In the early stages of thg Josephson computer project conducted at an American computer company, it was recognized that a very fast cache memory was needed to complement Josephson logic. A subnanosecond access time memory was implemented experimentally on the basis of a 2.5-micron Pb-alloy technology. It was then decided to switch over to a Nb-base-electrode technology with the objective to alleviate problems with the long-term reliability and aging of Pb-based junctions. The present paper provides a general overview of the status of a 4 x 1 K-bit Josephson cache design employing a 2.5-micron Nb-edge-junction technology. Attention is given to the fabrication process and its implications, aspects of circuit design methodology, an overview of system environment and chip components, design changes and status, and various difficulties and uncertainties.

Comparative analysis of approaches to frequency measurement and power estimation for polyharmonic microwave signals on the basis of the ac Josephson effect

NASA Astrophysics Data System (ADS)

Larkin, Serguey Y.; Anischenko, Serguei E.; Kamyshin, Vladimir A.

1996-12-01

The frequency and power measurements technique using ac Josephson effect is founded on deviation of the voltagecurrent curve of irradiated Josephson junction from its autonomous voltage-current (V-I) curve [1]. Generally this technique, in case of harmonic incident radiation, may be characterized in the following manner: -to measure frequency of the hannonic microwave signal inadiating the Josephson junction and to estimate its intensity using functional processing of the voltage-current curves, one should identify the "Special feature existence" zone on the voltage-current curves. The "Special feature existence" zone results the junction's response to the incident radiation. As this takes place, it is necessary to define the coordinate of a central point of the "Special feature existence" zone on the curve and to estimate the deviation of the V-I curve of irradiated Josephson junction from its autonomous V-I curve. The practical implementation of this technique place at one's disposal a number of algorithms, which enable to realize frequency measurements and intensity estimation with a particular accuracy for incident radiation. This paper presents two rational algorithms to determine the aggregate of their merits and disadvantages and to choose more optimal one.

Suppression and enhancement of decoherence in an atomic Josephson junction

NASA Astrophysics Data System (ADS)

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

2016-05-01

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

Vortex motion and dynamical states in Josephson arrays

NASA Astrophysics Data System (ADS)

Trias, Enrique

Underdamped Josephson junction arrays are used as model systems to study novel nonlinear effects. A combination of experiments, numerical simulations, and analytical analysis is used to probe different nonlinear behavior such as intrinsic localized modes, resonances in fully frustrated arrays, Meissner-like states, and vortex ratchets. Circuit models of Josephson networks are also developed, and applied to the design and measurement of parallel array oscillators. Ladder arrays have been used for an experimental study of intrinsic localized modes, or discrete breathers. Measurements of breather stability indicate that the maximum allowable bias current is proportional to the array depinning current while the minimum current is related to a junction retrapping mechanism. This retrapping instability usually leads to the formation of multi-site breathers. Collisions between the two nonlinear excitations in ladder arrays, discrete breathers and vortices, have also been numerically investigated. Discrete breathers act as pinning centers to vortex motion and the collisions can be modeled by an energy barrier activation process. When vortices are thermally induced over this barrier, a two-site breather is created. Experiments also reveal remarkable similarities among the do current-voltage characteristics of several kinds of square and triangular arrays, where two resonant voltages are observed. Simulations indicate that at full frustration a dynamical checkerboard state underlies these similarities. For such a traveling solution, the governing equations of the arrays are reduced to three coupled pendulum equations that have two characteristic resonant frequencies. Finally, a kink ratchet potential has been designed using a parallel array of Josephson junctions with alternating cell inductances and junctions areas. Experiments show that the depinning current depends on the direction of the applied current. Other properties of the depinning current versus applied field

Lateral MoS2 p-n junction formed by chemical doping for use in high-performance optoelectronics.

PubMed

Choi, Min Sup; Qu, Deshun; Lee, Daeyeong; Liu, Xiaochi; Watanabe, Kenji; Taniguchi, Takashi; Yoo, Won Jong

2014-09-23

This paper demonstrates a technique to form a lateral homogeneous 2D MoS2 p-n junction by partially stacking 2D h-BN as a mask to p-dope MoS2. The fabricated lateral MoS2 p-n junction with asymmetric electrodes of Pd and Cr/Au displayed a highly efficient photoresponse (maximum external quantum efficiency of ∼7000%, specific detectivity of ∼5 × 10(10) Jones, and light switching ratio of ∼10(3)) and ideal rectifying behavior. The enhanced photoresponse and generation of open-circuit voltage (VOC) and short-circuit current (ISC) were understood to originate from the formation of a p-n junction after chemical doping. Due to the high photoresponse at low VD and VG attributed to its built-in potential, our MoS2 p-n diode made progress toward the realization of low-power operating photodevices. Thus, this study suggests an effective way to form a lateral p-n junction by the h-BN hard masking technique and to improve the photoresponse of MoS2 by the chemical doping process.

Josephson current through a quantum dot molecule with a Majorana zero mode and Andreev bound states

NASA Astrophysics Data System (ADS)

Tang, Han-Zhao; Zhang, Ying-Tao; Liu, Jian-Jun

2018-04-01

Based on the Green's function method, we investigate the interplay between Majorana zero mode (MZM) and Andreev bound states (ABSs) in a quantum dot molecule side coupled to a topological superconducting nanowire with a pair of MZMs forming a Josephson junction. Since the strong electron-hole asymmetry induced by the nanowire with a topologically non-trivial phase, the MZM suppress the ABSs. The suppression induced by the MZM is robust against the Coulomb repulsion. The interplay between the MZM and the ABSs in Josephson junction presents a feasible experimental means for distinguish between the presence of MZM and ABSs.

Josephson A/D Converter Development.

DTIC Science & Technology

1981-10-01

by Zappe and A Landman [20]. They conclude that the simple model of the Josephson effect is applicable up to frequencies at least as high (a) as 300...GHz. B. Time-Domain Experiments 4ooF so The early high - frequency experiments with Josephson devices I .O suggested their use as very fast logic switches...exactly as for the phenomenological model . The tunneling pacitive current paths dominate the circuit at high frequencies . current is the sum of two

ac Josephson effect and resonant Cooper pair tunneling emission of a single Cooper pair transistor.

PubMed

Billangeon, P-M; Pierre, F; Bouchiat, H; Deblock, R

2007-05-25

We measure the high-frequency emission of a single Cooper pair transistor (SCPT) in the regime where transport is only due to tunneling of Cooper pairs. This is achieved by coupling on chip the SCPT to a superconductor-insulator-superconductor junction and by measuring the photon assisted tunneling current of quasiparticles across the junction. This technique allows a direct detection of the ac Josephson effect of the SCPT and provides evidence of Landau-Zener transitions for proper gate voltage. The emission in the regime of resonant Cooper pair tunneling is also investigated. It is interpreted in terms of transitions between charge states coupled by the Josephson effect.

Electron-impact-ionization dynamics of S F6

NASA Astrophysics Data System (ADS)

Bull, James N.; Lee, Jason W. L.; Vallance, Claire

2017-10-01

A detailed understanding of the dissociative electron ionization dynamics of S F6 is important in the modeling and tuning of dry-etching plasmas used in the semiconductor manufacture industry. This paper reports a crossed-beam electron ionization velocity-map imaging study on the dissociative ionization of cold S F6 molecules, providing complete, unbiased kinetic energy distributions for all significant product ions. Analysis of these distributions suggests that fragmentation following single ionization proceeds via formation of S F5 + or S F3 + ions that then dissociate in a statistical manner through loss of F atoms or F2, until most internal energy has been liberated. Similarly, formation of stable dications is consistent with initial formation of S F4 2 + ions, which then dissociate on a longer time scale. These data allow a comparison between electron ionization and photoionization dynamics, revealing similar dynamical behavior. In parallel with the ion kinetic energy distributions, the velocity-map imaging approach provides a set of partial ionization cross sections for all detected ionic fragments over an electron energy range of 50-100 eV, providing partial cross sections for S2 +, and enables the cross sections for S F4 2 + from S F+ to be resolved.

Majorana ϕ0-junction in a disordered spin-orbit coupling nanowire with tilted magnetic field

NASA Astrophysics Data System (ADS)

Huang, Hong; Liang, Qi-Feng; Yao, Dao-Xin; Wang, Zhi

2017-12-01

Majorana Josephson junctions in nanowire systems exhibit a pseudo-4π period current-phase relation in the clean limit. In this work, we study how this current-phase relation responds to a tilted magnetic field in a disordered Majorana Josephson junction within the Bogoliubov-de Gennes approach. We show that the tilted magnetic field induces a ϕ0 phase shift to the current-phase relation. Most importantly, we find that this ϕ0-junction behavior is robust even in the presence of disorders.

Intrinsic Josephson junction behaviour of the low Tc superconductor (LaSe) 1.14(NbSe 2)

NASA Astrophysics Data System (ADS)

Kačmarčík, J.; Szabó, P.; Samuely, P.; Rodrigo, J. G.; Suderow, H.; Vieira, S.; Lafond, A.; Meerschaut, A.

2008-04-01

Interlayer magnetotransport measurements on the highly anisotropic (LaSe)1.14(NbSe2) superconductor with Tc ∼ 1.2 K have indicated that this layered compound represents a model system of intrinsic Josephson junctions [P. Szabó et al., Phys. Rev. Lett. 86 (2001) 5990]. Scanning tunneling microscopy at room temperature and tunneling spectroscopy measurements at very low temperatures are presented in this work. STM imaging has revealed the presence of two types of surfaces which can be attributed to the appearance of LaSe or NbSe2 layers on the surface. The use of STM tip made of superconducting lead enabled a precise measurement of the temperature dependence of the superconducting energy gap Δ(T) on the NbSe2 layer. Δ(T) obtained from the surface sensitive STS data support the scenario obtained from our previous interlayer - ergo bulk sensitive magnetotransport measurements.

Au/Ti resistors used for Nb/Pb-alloy Josephson junctions. II. Thermal stability

NASA Astrophysics Data System (ADS)

Murakami, Masanori; Kim, K. K.

1984-10-01

In the preceding paper bilayered Au/Ti resistors were found to have excellent electrical stability during storage at room temperature after preannealing at an elevated temperature, which is essential to design logic and memory circuits of Nb/Pb-alloy Josephson junction devices. The resistors could contact directly with the Pb-alloy control lines in which Pb and In atoms which are known to intermix easily with Au atoms are contained. Since Pb and In atoms in the control lines are separated from Au atoms of the resistors by thin Ti layers, thermal stability at the contacts is a major concern for use of the Au/Ti resistor material in the Josephson devices. In the present study, surface morphology change and diffusion mechanism at the resistor/control-line contacts were studied using x-ray diffraction and scanning electron microscopy for square-shaped Au/Ti resistors covered by Pb-In layers. The samples were isothermally annealed at temperatures ranging from 353 to 423 K. The diffusion did not occur immediately after annealing at these temperatures. After the incubation period, the interdiffusion was observed to initiate at the edges of the resistors facing to the center of the cathode. Significant amounts of the In atoms in the Pb-In layers were observed to diffuse into the Au layers of the resistors, forming AuIn2 compounds under the Ti layers. By measuring growth rates of the AuIn2 layers, the diffusion coefficients and the activation energy for the layer growth were determined. Also, by analyzing changes in the In concentration in the Pb-In layers during annealing, interdiffusion coefficients of In atoms in the Pb-In layers were determined using a computer simulation technique. The activation energy was about 1.1 eV. Since these diffusion coefficients were found to be very close to those determined previously in bulk materials, the diffusion kinetics is believed to be controlled by the lattice diffusion. Based on the present results, several methods to reduce the

Gate-tuned Josephson effect on the surface of a topological insulator

PubMed Central

2014-01-01

In the study, we investigate the Josephson supercurrent of a superconductor/normal metal/superconductor junction on the surface of a topological insulator, where a gate electrode is attached to the normal metal. It is shown that the Josephson supercurrent not only can be tuned largely by the temperature but also is related to the potential and the length of the weak-link region. Especially, the asymmetry excess critical supercurrent, oscillatory character, and plateau-like structure have been revealed. We except those phenomena that can be observed in the recent experiment. PMID:25249827

Josephson Circuits as Vector Quantum Spins

NASA Astrophysics Data System (ADS)

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.

Solitonic Josephson Thermal Transport

NASA Astrophysics Data System (ADS)

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.

MoRe-based tunnel junctions and their characteristics

NASA Astrophysics Data System (ADS)

Shaternik, V.; Larkin, S.; Noskov, V.; Chubatyy, V.; Sizontov, V.; Miroshnikov, A.; Karmazin, A.

2008-02-01

Perspective Josephson Mo-Re alloy-oxide-Pb, Mo-Re alloy-normal metal-oxide-Pb and Mo-Re alloy-normal metal-oxide-normal metal-Mo-Re alloy junctions have been fabricated and investigated. Thin (~50-100 nm) MoRe superconducting films are deposited on Al2O3 substrates by using a dc magnetron sputtering of MoRe target. Normal metal (Sn, Al) thin films are deposited on the MoRe films surfaces by thermal evaporation of metals in vacuum and oxidized to fabricate junctions oxide barriers. Quasiparticle I-V curves of the fabricated junctions were measured in wide range of voltages. To investigate a transparency spread for the fabricated junctions barriers the computer simulation of the measured quasiparticle I-V curves have been done in framework of the model of multiple Andreev reflections in double-barrier junction interfaces. It's demonstrated the investigated junctions can be described as highly asymmetric double-barrier Josephson junctions with great difference between the two barrier transparencies. The result of the comparison of experimental quasiparticle I-V curves and calculated ones is proposed and discussed. Also I-V curves of the fabricated junctions have been measured under microwave irradiation with 60 GHz frequency, clear Shapiro steps in the measured I-V curves were observed and discussed.

Radiation power and linewidth of a semifluxon-based Josephson oscillator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paramonov, M.; Fominsky, M. Yu.; Koshelets, V. P.

We demonstrate a high-frequency generator operating at ∼200 GHz based on flipping a semifluxon in a Josephson junction of moderate normalized length. The semifluxon spontaneously appears at the π discontinuity of the Josephson phase artificially created by means of two tiny current injectors. The radiation is detected by an on-chip detector (tunnel junction). The estimated radiation power (at the detector) is ∼8 nW and should be compared with the dc power of ∼100 nW consumed by the generator. The measured radiation linewidth, as low as 1.1 MHz, is typical for geometrical (Fiske) resonances, although we tried to suppress such resonances by placing well-matched microwavemore » transformers at its both ends. Making use of a phase-locking feedback loop, we are able to reduce the radiation linewidth to less than 1 Hz measured relative to the reference oscillator and defined just by the resolution of our measurement setup.« less

Intrinsic line shape of electromagnetic radiation from a stack of intrinsic Josephson junctions synchronized by an internal cavity resonance

NASA Astrophysics Data System (ADS)

Koshelev, Alexei

2013-03-01

Stacks of intrinsic Josephson-junctions are realized in mesas fabricated out of layered superconducting single crystals, such as Bi2Sr2CaCu2O8 (BSCCO). Synchronization of phase oscillations in different junctions can be facilitated by the coupling to the internal cavity mode leading to powerful and coherent electromagnetic radiation in the terahertz frequency range. An important characteristic of this radiation is the shape of the emission line. A finite line width appears due to different noise sources leading to phase diffusion. We investigated the intrinsic line shape caused by the thermal noise for a mesa fabricated on the top of a BSCCO single crystal. In the ideal case of fully synchronized stack the finite line width is coming from two main contributions, the quasiparticle-current noise inside the mesa and the fluctuating radiation in the base crystal. We compute both contributions and conclude that for realistic mesa's parameters the second mechanism typically dominates. The role of the cavity quality factor in the emission line spectrum is clarified. Analytical results were verified by numerical simulations. In real mesa structures part of the stack may not be synchronized and chaotic dynamics of unsynchronized junctions may determine the real line width. Work supported by UChicago Argonne, LLC, under contract No. DE-AC02-06CH11357.

Induced Superconductivity and Engineered Josephson Tunneling Devices in Epitaxial (111)-Oriented Gold/Vanadium Heterostructures.

PubMed

Wei, Peng; Katmis, Ferhat; Chang, Cui-Zu; Moodera, Jagadeesh S

2016-04-13

We report a unique experimental approach to create topological superconductors by inducing superconductivity into epitaxial metallic thin film with strong spin-orbit coupling. Utilizing molecular beam epitaxy technique under ultrahigh vacuum conditions, we are able to achieve (111) oriented single phase of gold (Au) thin film grown on a well-oriented vanadium (V) s-wave superconductor film with clean interface. We obtained atomically smooth Au thin films with thicknesses even down to below a nanometer showing near-ideal surface quality. The as-grown V/Au bilayer heterostructure exhibits superconducting transition at around 3.9 K. Clear Josephson tunneling and Andreev reflection are observed in S-I-S tunnel junctions fabricated from the epitaxial bilayers. The barrier thickness dependent tunneling and the associated subharmonic gap structures (SGS) confirmed the induced superconductivity in Au (111), paving the way for engineering thin film heterostructures based on p-wave superconductivity and nano devices exploiting Majorana Fermions for quantum computing.

Signatures of pair-density wave order via measurement of the current-phase relation in La2-xBaxCuO4 Josephson junctions

NASA Astrophysics Data System (ADS)

Hamilton, David; Weis, Adam; Gu, Genda; van Harlingen, Dale

La2-xBaxCuO4 (LBCO) exhibits a sharp drop in the transition temperature near x = 1 / 8 doping. In this regime, charge, spin and superconducting orders are intertwined and superconductivity is believed to exist in a pair-density wave (PDW) state, an ordered stripe phase characterized by sign changes in the superconducting order parameter between adjacent stripes. We present direct measurements of the current-phase relation (CPR) of Josephson junctions patterned onto crystals of LBCO at x = 1 / 8 and x = 0 . 155 (optimal doping) using a phase-sensitive Josephson interferometry technique. In contrast to the approximately sinusoidal CPR observed at optimal doping, we find the proportion of higher harmonics in the CPR increases at x = 1 / 8 doping, consistent with the formation of a PDW state. In parallel, we are carrying out measurements of the resistance noise in thin films of LBCO of various doping levels to identify features that signify the onset of charge order and changes in the dynamics of charge stripes.

Programmable Schottky Junctions Based on Ferroelectric Gated MoS2 Transistors

NASA Astrophysics Data System (ADS)

Xiao, Zhiyong; Song, Jingfeng; Drcharme, Stephen; Hong, Xia

We report a programmable Schottky junction based on MoS2 field effect transistors with a SiO2 back gate and a ferroelectric copolymer poly(vinylidene-fluoride-trifluorethylene) (PVDF) top gate. We fabricated mechanically exfoliated single layer MoS2 flakes into two point devices via e-beam lithography, and deposited on the top of the devices ~20 nm PVDF thin films. The polarization of the PVDF layer is controlled locally by conducting atomic force microscopy. The devices exhibit linear ID-VD characteristics when the ferroelectric gate is uniformly polarized in one direction. We then polarized the gate into two domains with opposite polarization directions, and observed that the ID-VD characteristics of the MoS2 channel can be modulated between linear and rectified behaviors depending on the back gate voltage. The nonlinear ID-VD relation emerges when half of the channel is in the semiconductor phase while the other half is in the metallic phase, and it can be well described by the thermionic emission model with a Schottky barrier of ~0.5 eV. The Schottky junction can be erased by re-write the entire channel in the uniform polarization state. Our study facilitates the development of programmable, multifunctional nanoelectronics based on layered 2D TMDs..

Josephson current signatures of the Majorana flat bands on the surface of time-reversal-invariant Weyl and Dirac semimetals

NASA Astrophysics Data System (ADS)

Chen, Anffany; Pikulin, Dmitry I.; Franz, Marcel

A linear Josephson junction mediated by the surface states of a time-reversal-invariant Weyl or Dirac semimetal localizes Majorana flat bands protected by the time-reversal symmetry. We show that as a result, the Josephson current exhibits a discontinuous jump at π phase difference which can serve as an experimental signature of the Majorana bands. The magnitude of the jump scales proportionally to the junction length and the momentum space distance between the Weyl nodes projected onto the junction. It also exhibits a characteristic dependence on the junction orientation. We demonstrate that the jump is robust against the effects of non-zero temperature and weak non-magnetic disorder. This work was supported by NSERC and CIfAR. In addition A.C. acknowledges support by the 2016 Boulder Summer School for Condensed Matter and Materials Physics through NSF Grant DMR-13001648.

Manifestation of hopping conductivity and granularity within phase diagrams of LaO1-x F x BiS2, Sr1-x La x FBiS2 and related BiS2-based compounds

NASA Astrophysics Data System (ADS)

Arouca, R.; Silva Neto, M. B.; Chaves, C. M.; Nagao, M.; Watauchi, S.; Tanaka, I.; ElMassalami, M.

2017-09-01

Layered BiS 2 -based series, such as LaO 1-x F x BiS 2 and Sr 1-x La x FBiS 2 , offer ideal examples for studying normal and superconducting phase diagram of a solid solution that evolves from a nonmagnetic band-insulator parent. We constructed typical x-T phase diagrams of these systems based on events occurring in thermal evolution of their electrical resistivity, ρ(x, T) . Overall evolution of these diagrams can be rationalized in terms of (i) Mott-Efros-Shklovskii scenario which, within the semiconducting x regime (x_MIT = Mott metal-insulator transition), describes the doping influence on the thermally activated hopping conductivity. (ii) A granular metal (superconductor) scenario which, within x_MIT< x < x_solubility , describes the evolution of normal and superconducting properties in terms of conductance g, Coulomb charging energy E c and Josephson coupling J; their joint influence is usually captured within a g-\\frac{gE_c}{J}-T phase diagram. Based on analysis of the granular character of ρ(x, T) , we converted the x-T diagrams into projected g - T diagrams which, being fundamental, allow a better understanding of evolution of various granular-related properties (in particular the hallmarks of normal-state \\partialρ/\\partial T<0 feature and superconductor-insulator transition) and how such properties are influenced by x, pressure or heat treatment.

Spatial inhomogeneity in Schottky barrier height at graphene/MoS2 Schottky junctions

NASA Astrophysics Data System (ADS)

Tomer, D.; Rajput, S.; Li, L.

2017-04-01

Transport properties of graphene semiconductor Schottky junctions strongly depend on interfacial inhomogeneities due to the inherent formation of ripples and ridges. Here, chemical vapor deposited graphene is transferred onto multilayer MoS2 to fabricate Schottky junctions. These junctions exhibit rectifying current-voltage behavior with the zero bias Schottky barrier height increases and ideality factor decreases with increasing temperature between 210 and 300 K. Such behavior is attributed to the inhomogeneous interface that arises from graphene ripples and ridges, as revealed by atomic force and scanning tunneling microscopy imaging. Assuming a Gaussian distribution of the barrier height, a mean value of 0.96  ±  0.14 eV is obtained. These findings indicate a direct correlation between temperature dependent Schottky barrier height and spatial inhomogeneity in graphene/2D semiconductor Schottky junctions.

Reconfigurable p-n junction diodes and the photovoltaic effect in exfoliated MoS{sub 2} films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sutar, Surajit; Agnihotri, Pratik; Comfort, Everett

2014-03-24

Realizing basic semiconductor devices such as p-n junctions are necessary for developing thin-film and optoelectronic technologies in emerging planar materials such as MoS{sub 2}. In this work, electrostatic doping by buried gates is used to study the electronic and optoelectronic properties of p-n junctions in exfoliated MoS{sub 2} flakes. Creating a controllable doping gradient across the device leads to the observation of the photovoltaic effect in monolayer and bilayer MoS{sub 2} flakes. For thicker flakes, strong ambipolar conduction enables realization of fully reconfigurable p-n junction diodes with rectifying current-voltage characteristics, and diode ideality factors as low as 1.6. The spectralmore » response of the photovoltaic effect shows signatures of the predicted band gap transitions. For the first excitonic transition, a shift of >4{sub kB}T is observed between monolayer and bulk devices, indicating a thickness-dependence of the excitonic coulomb interaction.« less

Single d-metal atoms on F(s) and F(s+) defects of MgO(001): a theoretical study across the periodic table.

PubMed

Neyman, Konstantin M; Inntam, Chan; Matveev, Alexei V; Nasluzov, Vladimir A; Rösch, Notker

2005-08-24

Single d-metal atoms on oxygen defects F(s) and F(s+) of the MgO(001) surface were studied theoretically. We employed an accurate density functional method combined with cluster models, embedded in an elastic polarizable environment, and we applied two gradient-corrected exchange-correlation functionals. In this way, we quantified how 17 metal atoms from groups 6-11 of the periodic table (Cu, Ag, Au; Ni, Pd, Pt; Co, Rh, Ir; Fe, Ru, Os; Mn, Re; and Cr, Mo, W) interact with terrace sites of MgO. We found bonding with F(s) and F(s+) defects to be in general stronger than that with O2- sites, except for Mn-, Re-, and Fe/F(s) complexes. In M/F(s) systems, electron density is accumulated on the metal center in a notable fashion. The binding energy on both kinds of O defects increases from 3d- to 4d- to 5d-atoms of a given group, at variance with the binding energy trend established earlier for the M/O2- complexes, 4d < 3d < 5d. Regarding the evolution of the binding energy along a period, group 7 atoms are slightly destabilized compared to their group 6 congeners in both the F(s) and F(s+) complexes; for later transition elements, the binding energy increases gradually up to group 10 and finally decreases again in group 11, most strongly on the F(s) site. This trend is governed by the negative charge on the adsorbed atoms. We discuss implications for an experimental detection of metal atoms on oxide supports based on computed core-level energies.

On the junction conditions in f(R) -gravity with torsion

NASA Astrophysics Data System (ADS)

Vignolo, Stefano; Cianci, Roberto; Carloni, Sante

2018-05-01

Junction conditions are discussed within the framework of f(R) -gravity with torsion. After deriving general junction conditions, the cases of coupling to a Dirac field and a spin fluid are explicitly dealt with. The main differences with respect to Einstein–Cartan–Sciama–Kibble theory ≤ft( f(R)=R\\right) are outlined.

Fragmentation of fast Josephson vortices and breakdown of ordered states by moving topological defects

DOE PAGES

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,more » 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. In conclusion, 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.« less

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

NASA Astrophysics Data System (ADS)

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.

Fluxons and Order in Long Josephson Junctions

DTIC Science & Technology

1989-02-24

device and also the energies involved. Neglecting demagnetizing effects, the formation 6 of fluxons inside the junction occurs when the external magnetic ...8217 SUPERCONDUCTING ELECTRONICS, FLUXONS; PERIOD DOUBLING BIfURCATION, SINE GORDON EQUATION; NOISE; FLUCTUATIONS 14-) C ’ 9. ABSTRACT (Continue on reverse if...made out of Niobiuny-Nitride and Niobium. Noise and fluctuations measure- ments were performed in the voltage state of the junctions biasedin a magnetic

Balanced double-loop mesoscopic interferometer based on Josephson proximity nanojunctions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ronzani, Alberto, E-mail: alberto.ronzani@nano.cnr.it; Altimiras, Carles; Giazotto, Francesco

We report on the fabrication and characterization of a two-terminal mesoscopic interferometer based on three V/Cu/V Josephson junctions having nanoscale cross-section. The junctions have been arranged in a double-ring geometry realized by metallic thin film deposition through a suspended mask defined by electron beam lithography. Although a significant amount of asymmetry between the critical current of each junction is observed, we show that the interferometer is able to suppress the supercurrent to a level lower than 6 parts per thousand, being here limited by measurement resolution. The present nano-device is suitable for low-temperature magnetometric and gradiometric measurements over the micrometricmore » scale.« less

Single Spin Superconductivity: Bulk and Junction Effects

NASA Astrophysics Data System (ADS)

Rudd, Robert E.; Pickett, Warren E.

1998-03-01

The Josephson Effect provides a primary signature of single spin superconductivity (SSS), the as yet unobserved superconducting state which was proposed recently(W.E. Pickett, Phys. Rev. Lett. 77), 3185 (1996). as a low temperature phase of half-metallic antiferromagnets.(W.E. Pickett, ``Spin Density Functional Based Search for Half-Metallic Antiferromagnets,'' cond-mat/9709100 (1997).) These materials are insulating in the spin-down channel but are metallic in the spin-up channel. The SSS state is characterized by a unique form of p-wave pairing within a single spin channel.(R.E. Rudd and W.E. Pickett, ``Single Spin Superconductivity:Formulation and Ginzburg-Landau Theory,'' Phys. Rev. B. in press) We develop the theory of a rich variety of Josephson effects that arise due to the form of the SSS order parameter. Tunneling is allowed at a SSS-SSS^' junction depending on the relative orientation of each of their order parameters (SSS and HM AFM). No current flows between an SSS and an s-wave BCS system, which provides a powerful method to distinguish SSS from other superconducting states.

76 FR 34207 - Application(s) for Duty-Free Entry of Scientific Instruments

Federal Register 2010, 2011, 2012, 2013, 2014

2011-06-13

.... Intended Use: The system will be incorporated into a superconducting quantum bit device, and will be used to deposit and grow Josephson junctions as part of students' research requirements in the physics Ph...

Transitional basal cells at the squamous-columnar junction generate Barrett’s oesophagus

PubMed Central

Jiang, Ming; Li, Haiyan; Zhang, Yongchun; Yang, Ying; Lu, Rong; Liu, Kuancan; Lin, Sijie; Lan, Xiaopeng; Wang, Haikun; Wu, Han; Zhu, Jian; Zhou, Zhongren; Xu, Jianming; Lee, Dong-Kee; Zhang, Lanjing; Lee, Yuan-Cho; Yuan, Jingsong; Abrams, Julian A.; Wang, Timothy G.; Sepulveda, Antonia R.; Wu, Qi; Chen, Huaiyong; Sun, Xin; She, Junjun; Chen, Xiaoxin; Que, Jianwen

2017-01-01

In several organ systems the transitional zone between different types of epithelia is a hotspot for pre-neoplastic metaplasia and malignancy1–3. However, the cell-of-origin for the metaplastic epithelium and subsequent malignancy, remains obscure1–3. In the case of Barrett’s oesophagus (BE), intestinal metaplasia occurs at the gastro-oesophageal junction, where stratified squamous epithelium transitions into simple columnar cells4. Based on different experimental models, several alternative cell types have been proposed as the source of the metaplasia, but in all cases the evidence is inconclusive and no model completely mimics BE with the presence of intestinal goblet cells5–8. Here, we describe a novel transitional columnar epithelium with distinct basal progenitor cells (p63+ KRT5+ KRT7+) in the squamous-columnar junction (SCJ) in the upper gastrointestinal tract of the mouse. We use multiple models and lineage tracing strategies to show that this unique SCJ basal cell population serves as a source of progenitors for the transitional epithelium. Moreover, upon ectopic expression of CDX2 these transitional basal progenitors differentiate into intestinal-like epithelium including goblet cells, thus reproducing Barrett’s metaplasia. A similar transitional columnar epithelium is present at the transitional zones of other mouse tissues, including the anorectal junction, and, importantly, at the gastro-oesophageal junction in the human gut. Acid reflux-induced oesophagitis and the multilayered epithelium (MLE) believed to be a precursor of BE are both characterized by the expansion of the transitional basal progenitor cells. Taken together our findings reveal the presence of a previously unidentified transitional zone in the epithelium of the upper gastrointestinal tract and provide evidence that the p63+ KRT7+ basal cells in this zone are the cell-of-origin for MLE and BE. PMID:29019984

Non-Abelian holonomies, charge pumping, and quantum computation with Josephson junctions.

PubMed

Faoro, Lara; Siewert, Jens; Fazio, Rosario

2003-01-17

Non-Abelian holonomies can be generated and detected in certain superconducting nanocircuits. Here we consider an example where the non-Abelian operations are related to the adiabatic charge dynamics of the Josephson network. We demonstrate that such a device can be applied both for adiabatic charge pumping and as an implementation of a quantum computer.

Size effect on the magnetic and electronic properties of the monolayer lateral hetero-junction WS2-MoS2 nanoribbon

NASA Astrophysics Data System (ADS)

Wen, Yan-Ni; Xia, Ming-Gang; Zhang, Sheng-Li

2016-05-01

By using the VASP, we studied the magnetic and electronic properties of the monolayer lateral hetero-junction WS2-MoS2-nanoribbons (WS2-MoS2-NRs). Our results show that the NRs' edge chirality and width affect significantly its magnetic and electronic properties. The monolayer lateral hetero-junction ZZ-WS2-MoS2-NRs(ZZ: zigzag) exhibitmetallic behavior and have considerable magnetic moment. Their magnetic moments decrease in the order of Nz = 2, 6 and 4 (the width of NRs). While, the magnetic moment decreases with the increased rz (the number of the Mo-S chains, rz ≠ 0 and rz ≠ Nz) at the same width Nz. The NA-AC-WS2-NR (AC: armchair) and NA-AC-WS2-MoS2-NR-1 (the number of the Mo-S chain is 1) show metallic behavior when NA = 3 (the width of NRs). The other monolayer lateral hetero-junction AC-WS2-MoS2-NRs remain the nonmagnetic and semiconductingbehavior as bulk. But they are indirect band-gap except for the NA = 3, rA = 2 (the number of the Mo-S chains) and NA = 7, rA = 0 when NA < 9. However they are direct band-gap when NA ≥ 9. Their lowest and highest band gaps are 0.150 eV and 0.581 eV, respectively. These unique magnetic and electronic properties will provide guidanceon the WS2-MoS2 hetero-junction application in nanodevice.

Generation of squeezed microwave states by a dc-pumped degenerate parametric Josephson junction oscillator

NASA Astrophysics Data System (ADS)

Kaertner, Franz X.; Russer, Peter

1990-11-01

The master equation for a dc-pumped degenerate Josephson parametric amplifier is derived. It is shown that the Wigner distribution representation of this master equation can be approximated by a Fokker-Planck equation. By using this equation, the dynamical behavior of this degenerate Josephson amplifier with respect to squeezing of the radiation field is investigated. It is shown that below threshold of parametric oscillation, a squeezed vacuum state can be generated, and above threshold a second bifurcation point exists, where the device generates amplitude squeezed radiation. Basic relations between the achievable amplitude squeezing, the output power, and the operation frequency are derived.

Zener behaviour of p-SnS/ZnO and p-SnS/ZnS heterojunctions

NASA Astrophysics Data System (ADS)

Gupta, Yashika; Arun, P.

2018-03-01

p-SnS absorbing layers were grown by thermal evaporation on layers of various Zinc compounds, like ZnO and ZnS. This present work reports the J-V characteristics of thus obtained p-SnS/ZnO and p-SnS/ZnS heterojunctions. The pn junctions of these structures did not show any photovoltaic activity, however a zener like behaviour was observed in the 3rd quadrant of the J-V characteristics. Our analysis of the diodes suggest that the reverse breakdown or zener voltage obtained from the dark J-V characteristics can be used to estimate the energy band diagram of the junction and in turn the band-alignment at the junction. This makes it an easy alternative to x-ray Photoelectron Spectroscopy method usually used.

Geometrical Effects in Two-Dimensional Arrays of Josephson Junctions

DTIC Science & Technology

1992-05-01

Iot (4.3.4.b) dyd a .. s -f sin =o0 (4.3.4.c) ~r Tdr n snadrs where a, 13, and rare the gauge-invariant phase differences denoted in Fig. 4.8. If we...Receive Slit Coils *_ * Slit Set-screw / -Tr Drive Coil IDrive Leads if Coil Fig. 8.7. Schematic drawing of the two-coil mututal-inductance apparatus we

Quasiclassical theory for the superconducting proximity effect in Dirac materials

NASA Astrophysics Data System (ADS)

Hugdal, Henning G.; Linder, Jacob; Jacobsen, Sol H.

2017-06-01

We derive the quasiclassical nonequilibrium Eilenberger and Usadel equations to first order in quantities small compared to the Fermi energy, valid for Dirac edge and surface electrons with spin-momentum locking p .σ ¯ , as relevant for topological insulators. We discuss in detail several of the key technical points and assumptions of the derivation, and provide a Riccati parametrization of the equations. Solving first the equilibrium equations for S/N and S/F bilayers and Josephson junctions, we study the superconducting proximity effect in Dirac materials. Similarly to related works, we find that the effect of an exchange field depends strongly on the direction of the field. Only components normal to the transport direction lead to attenuation of the Cooper pair wave function inside the F. Fields parallel to the transport direction lead to phase shifts in the dependence on the superconducting phase difference for both the charge current and density of states in an S/F/S junction. Moreover, we compute the differential conductance in S/N and S/F bilayers with an applied voltage bias and determine the dependence on the length of the N and F regions and the exchange field.

Photon statistics of shot noise measured using a Josephson parametric amplifier

NASA Astrophysics Data System (ADS)

Simoneau, Jean Olivier; Virally, Stéphane; Lupien, Christian; Reulet, Bertrand

2015-03-01

Quantum measurements are very sensitive to external noise sources. Such measurements require careful amplification chain design so as not to overwhelm the signal with extraneous noise. A quantum-limited amplifier, like the Josephson parametric amplifier (paramp), is thus an ideal candidate for this purpose. We used a paramp to investigate the quantum noise of a tunnel junction. This measurement scheme allowed us to improve upon previous observations of shot noise by an order of magnitude in terms of noise temperature. With this setup, we have measured the second and fourth cumulants of current fluctuations generated by the tunnel junction within a 40 MHz bandwidth around 6 GHz. From theses measurements, we deduce the variance of the photon number fluctuations for various bias schemes of the junction. In particular, we investigate the regime where the junction emits pairs of photons.

Transport properties and device-design of Z-shaped MoS2 nanoribbon planar junctions

NASA Astrophysics Data System (ADS)

Zhang, Hua; Zhou, Wenzhe; Liu, Qi; Yang, Zhixiong; Pan, Jiangling; Ouyang, Fangping; Xu, Hui

2017-09-01

Based on MoS2 nanoribbons, metal-semiconductor-metal planar junction devices were constructed. The electronic and transport properties of the devices were studied by using density function theory (DFT) and nonequilibrium Green's functions (NEGF). It is found that a band gap about 0.4 eV occurs in the planar junction. The electron and hole transmissions of the devices are mainly contributed by the Mo atomic orbitals. The electron transport channel is located at the edge of armchair MoS2 nanoribbon, while the hole transport channel is delocalized in the channel region. The I-V curve of the two-probe device shows typical transport behavior of Schottky barrier, and the threshold voltage is of about 0.2 V. The field effect transistors (FET) based on the planar junction turn out to be good bipolar transistors, the maximum current on/off ratio can reach up to 1 × 104, and the subthreshold swing is 243 mV/dec. It is found that the off-state current is dependent on the length and width of the channel, while the on-state current is almost unaffected. The switching performance of the FET is improved with increasing the length of the channel, and shows oscillation behavior with the change of the channel width.

Relaxation to a Phase-Locked Equilibrium State in a One-Dimensional Bosonic Josephson Junction

NASA Astrophysics Data System (ADS)

Pigneur, Marine; Berrada, Tarik; Bonneau, Marie; Schumm, Thorsten; Demler, Eugene; Schmiedmayer, Jörg

2018-04-01

We present an experimental study on the nonequilibrium tunnel dynamics of two coupled one-dimensional Bose-Einstein quasicondensates deep in the Josephson regime. Josephson oscillations are initiated by splitting a single one-dimensional condensate and imprinting a relative phase between the superfluids. Regardless of the initial state and experimental parameters, the dynamics of the relative phase and atom number imbalance shows a relaxation to a phase-locked steady state. The latter is characterized by a high phase coherence and reduced fluctuations with respect to the initial state. We propose an empirical model based on the analogy with the anharmonic oscillator to describe the effect of various experimental parameters. A microscopic theory compatible with our observations is still missing.

Defect Engineering and Phase Junction Architecture of Wide-Bandgap ZnS for Conflicting Visible Light Activity in Photocatalytic H₂ Evolution.

PubMed

Fang, Zhibin; Weng, Sunxian; Ye, Xinxin; Feng, Wenhui; Zheng, Zuyang; Lu, Meiliang; Lin, Sen; Fu, Xianzhi; Liu, Ping

2015-07-01

ZnS is among the superior photocatalysts for H2 evolution, whereas the wide bandgap restricts its performance to only UV region. Herein, defect engineering and phase junction architecture from a controllable phase transformation enable ZnS to achieve the conflicting visible-light-driven activities for H2 evolution. On the basis of first-principle density functional theory calculations, electron spin resonance and photoluminescence results, etc., it is initially proposed that the regulated sulfur vacancies in wurtzite phase of ZnS play the key role of photosensitization units for charge generation in visible light and active sites for effective electron utilization. The symbiotic sphalerite-wurtzite phase junctions that dominate the charge-transfer kinetics for photoexciton separation are the indispensable configuration in the present systems. Neither ZnS samples without phase junction nor those without enough sulfur vacancies conduct visible-light photocatalytic H2 evolution, while the one with optimized phase junctions and maximum sulfur vacancies shows considerable photocatalytic activity. This work will not only contribute to the realization of visible light photocatalysis for wide-bandgap semiconductors but also broaden the vision on the design of highly efficient transition metal sulfide photocatalysts.

Overlap junctions for high coherence superconducting qubits

NASA Astrophysics Data System (ADS)

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.

Gαs Relays Sphingosine-1-Phosphate Receptor 1 Signaling to Stabilize Vascular Endothelial-Cadherin at Endothelial Junctions to Control Mouse Embryonic Vascular Integrity.

PubMed

Shao, Ximing; Liu, Ke; Fan, Yi; Ding, Zhihao; Chen, Min; Zhu, Minyan; Weinstein, Lee S; Li, Hongchang; Li, Huashun

2015-11-20

Sphingosine-1-phosphate receptor 1 (S1PR1), a G protein-coupled receptor (GPCR), controls vascular stability by stabilizing vascular endothelial (VE)-cadherin junctional localization and inhibiting vascular endothelial growth factor receptor 2 (VEGFR2) signaling. However, the molecular mechanisms that link S1PR1 signaling to intracellular effectors remain unknown. In this study, we demonstrate that the heterotrimeric G protein subfamily member Gαs, encoded by GNAS, acts as a relay mediator of S1PR1 signaling to control vascular integrity by stabilizing VE-cadherin at endothelial junctions. The endothelial cell-specific deletion of Gαs in mice causes early embryonic lethality with massive hemorrhage and a disorganized vasculature. The immunostaining results revealed that Gαs deletion remarkably reduces the junctional localization of VE-cadherin, whereas the mural cell coverage of the vessels is not impaired. In addition, we found that Gαs depletion blocks the S1PR1-activation induced VE-cadherin stabilization at junctions, supporting that Gαs acts downstream of S1PR1 signaling. Thus, our results demonstrate that Gαs is an essential mediator to relay S1PR1 signaling and maintain vascular integrity. Copyright © 2015 Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, and Genetics Society of China. Published by Elsevier Ltd. All rights reserved.

PET Quantification of the Norepinephrine Transporter in Human Brain with (S,S)-18F-FMeNER-D2.

PubMed

Moriguchi, Sho; Kimura, Yasuyuki; Ichise, Masanori; Arakawa, Ryosuke; Takano, Harumasa; Seki, Chie; Ikoma, Yoko; Takahata, Keisuke; Nagashima, Tomohisa; Yamada, Makiko; Mimura, Masaru; Suhara, Tetsuya

2017-07-01

Norepinephrine transporter (NET) in the brain plays important roles in human cognition and the pathophysiology of psychiatric disorders. Two radioligands, ( S , S )- 11 C-MRB and ( S , S )- 18 F-FMeNER-D 2 , have been used for imaging NETs in the thalamus and midbrain (including locus coeruleus) using PET in humans. However, NET density in the equally important cerebral cortex has not been well quantified because of unfavorable kinetics with ( S , S )- 11 C-MRB and defluorination with ( S , S )- 18 F-FMeNER-D 2 , which can complicate NET quantification in the cerebral cortex adjacent to the skull containing defluorinated 18 F radioactivity. In this study, we have established analysis methods of quantification of NET density in the brain including the cerebral cortex using ( S , S )- 18 F-FMeNER-D 2 PET. Methods: We analyzed our previous ( S , S )- 18 F-FMeNER-D 2 PET data of 10 healthy volunteers dynamically acquired for 240 min with arterial blood sampling. The effects of defluorination on the NET quantification in the superficial cerebral cortex was evaluated by establishing a time stability of NET density estimations with an arterial input 2-tissue-compartment model, which guided the less-invasive reference tissue model and area under the time-activity curve methods to accurately quantify NET density in all brain regions including the cerebral cortex. Results: Defluorination of ( S , S )- 18 F-FMeNER-D 2 became prominent toward the latter half of the 240-min scan. Total distribution volumes in the superficial cerebral cortex increased with the scan duration beyond 120 min. We verified that 90-min dynamic scans provided a sufficient amount of data for quantification of NET density unaffected by defluorination. Reference tissue model binding potential values from the 90-min scan data and area under the time-activity curve ratios of 70- to 90-min data allowed for the accurate quantification of NET density in the cerebral cortex. Conclusion: We have established

NbN tunnel junctions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Villegier, J.C.; Goniche, M.; Renard, P.

1985-03-01

All-niobium nitride Josephson junctions have been prepared successfully using a new processing called SNOP: Selective Niobium (Nitride) Overlap Process. Such a process involves the ''trilayer'' deposition on the whole wafer before selective patterning of the electrodes by optically controlled Dry Reactive Ion Etching. Only two photomask levels are need to define an ''overlap'' or a ''cross-type'' junction with a good accuracy. The properties of the niobium nitride films deposited by DC-Magnetron sputtering and the surface oxide growth are analysed. The most critical point to obtain high quality and high gap value junctions resides in the early stage of the NbNmore » counterelectrode growth. Some possibilities to overcome such a handicap exist even if the fabrication needs substrate temperatures below 250/sup 0/C.« less

The Josephson plasma resonance as a “scattering” probe of vortex correlation in the liquid state

NASA Astrophysics Data System (ADS)

Ong, N. P.; Bayracki, Sibel P.; Tsui, Ophelia K. C.; Kishio, K.; Watauchi, S.

1997-12-01

In the vortex liquid state the Josephson plasma frequency ωp is strongly affected by fluctuations in the vortex pancakes. We have measured in detail the variation of ωp with field B and tilt angle θ in Bi 2Sr 2CaCu 2O 8. We compare the data with Koshelev's expression relating ωp to the correlation function of the local phase S1. The agreement is quite close for θ > 1°, provided f varies with B with a weak exponent ( f measures the number of pancakes within a correkated area). A scattering picture is introduced to clarify how the plasma resonance is equivalent to a Fourier transform of | S1| 2. From the fit, we fin that, at 50 K and 1 T, f ≈ 1.4 pancakes, Jc0 equals 4160 A/cm 2 and = 0.028. Deviations observed when B is aligned with the planes are discussed.

Self-Oscillating Josephson Quantum Heat Engine

NASA Astrophysics Data System (ADS)

Marchegiani, G.; Virtanen, P.; Giazotto, F.; Campisi, M.

2016-11-01

The design of a mesoscopic self-oscillating heat engine that works thanks to purely quantum effects is presented. The proposed scheme is amenable to experimental implementation with current state-of-the-art nanotechnology and materials. One of the main features of the structure is its versatility: The engine can deliver work to a generic load without galvanic contact. This versatility makes it a promising building block for low-temperature on-chip energy-management applications. The heat engine consists of a circuit featuring a thermoelectric element based on a ferromagnetic insulator-superconductor tunnel junction and a Josephson weak link that realizes a purely quantum dc-ac converter. This makeup enables the contactless transfer of work to the load (a generic RL circuit). The performance of the heat engine is investigated as a function of the thermal gradient applied to the thermoelectric junction. Power up to 1 pW can be delivered to a load RL=10 Ω .

Phase-locking transition in a chirped superconducting Josephson resonator.

PubMed

Naaman, O; Aumentado, J; Friedland, L; Wurtele, J S; Siddiqi, I

2008-09-12

We observe a sharp threshold for dynamic phase locking in a high-Q transmission line resonator embedded with a Josephson tunnel junction, and driven with a purely ac, chirped microwave signal. When the drive amplitude is below a critical value, which depends on the chirp rate and is sensitive to the junction critical current I0, the resonator is only excited near its linear resonance frequency. For a larger amplitude, the resonator phase locks to the chirped drive and its amplitude grows until a deterministic maximum is reached. Near threshold, the oscillator evolves smoothly in one of two diverging trajectories, providing a way to discriminate small changes in I0 with a nonswitching detector, with potential applications in quantum state measurement.

π and 4 π Josephson Effects Mediated by a Dirac Semimetal

NASA Astrophysics Data System (ADS)

Yu, W.; Pan, W.; Medlin, D. L.; Rodriguez, M. A.; Lee, S. R.; Bao, Zhi-qiang; Zhang, F.

2018-04-01

Cd3As2 is a three-dimensional topological Dirac semimetal with connected Fermi-arc surface states. It has been suggested that topological superconductivity can be achieved in the nontrivial surface states of topological materials by utilizing the superconductor proximity effect. Here we report observations of both π and 4 π periodic supercurrents in aluminum-Cd3As2 -aluminum Josephson junctions. The π period is manifested by both the magnetic-field dependence of the critical supercurrent and the appearance of half-integer Shapiro steps in the ac Josephson effect. Our macroscopic theory suggests that the π period arises from interference between the induced bulk superconductivity and the induced Fermi-arc surface superconductivity. The 4 π period is manifested by the missing first Shapiro steps and is expected for topological superconductivity.

Junction formation of Cu3BiS3 investigated by Kelvin probe force microscopy and surface photovoltage measurements

PubMed Central

Mesa, Fredy; Chamorro, William; Vallejo, William; Baier, Robert; Dittrich, Thomas; Grimm, Alexander; Lux-Steiner, Martha C

2012-01-01

Summary Recently, the compound semiconductor Cu3BiS3 has been demonstrated to have a band gap of ~1.4 eV, well suited for photovoltaic energy harvesting. The preparation of polycrystalline thin films was successfully realized and now the junction formation to the n-type window needs to be developed. We present an investigation of the Cu3BiS3 absorber layer and the junction formation with CdS, ZnS and In2S3 buffer layers. Kelvin probe force microscopy shows the granular structure of the buffer layers with small grains of 20–100 nm, and a considerably smaller work-function distribution for In2S3 compared to that of CdS and ZnS. For In2S3 and CdS buffer layers the KPFM experiments indicate negatively charged Cu3BiS3 grain boundaries resulting from the deposition of the buffer layer. Macroscopic measurements of the surface photovoltage at variable excitation wavelength indicate the influence of defect states below the band gap on charge separation and a surface-defect passivation by the In2S3 buffer layer. Our findings indicate that Cu3BiS3 may become an interesting absorber material for thin-film solar cells; however, for photovoltaic application the band bending at the charge-selective contact has to be increased. PMID:22497001

Junction formation of Cu(3)BiS(3) investigated by Kelvin probe force microscopy and surface photovoltage measurements.

PubMed

Mesa, Fredy; Chamorro, William; Vallejo, William; Baier, Robert; Dittrich, Thomas; Grimm, Alexander; Lux-Steiner, Martha C; Sadewasser, Sascha

2012-01-01

Recently, the compound semiconductor Cu(3)BiS(3) has been demonstrated to have a band gap of ~1.4 eV, well suited for photovoltaic energy harvesting. The preparation of polycrystalline thin films was successfully realized and now the junction formation to the n-type window needs to be developed. We present an investigation of the Cu(3)BiS(3) absorber layer and the junction formation with CdS, ZnS and In(2)S(3) buffer layers. Kelvin probe force microscopy shows the granular structure of the buffer layers with small grains of 20-100 nm, and a considerably smaller work-function distribution for In(2)S(3) compared to that of CdS and ZnS. For In(2)S(3) and CdS buffer layers the KPFM experiments indicate negatively charged Cu(3)BiS(3) grain boundaries resulting from the deposition of the buffer layer. Macroscopic measurements of the surface photovoltage at variable excitation wavelength indicate the influence of defect states below the band gap on charge separation and a surface-defect passivation by the In(2)S(3) buffer layer. Our findings indicate that Cu(3)BiS(3) may become an interesting absorber material for thin-film solar cells; however, for photovoltaic application the band bending at the charge-selective contact has to be increased.

S1 screw bending moment with posterior spinal instrumentation across the lumbosacral junction after unilateral iliac crest harvest.

PubMed

Alegre, G M; Gupta, M C; Bay, B K; Smith, T S; Laubach, J E

2001-09-15

A biomechanical study comparing fixation across the lumbosacral junction. To determine which long posterior construct across the lumbosacral junction produces the least bending moment on the S1 screw when only one ilium is available for fixation. Recent in vitro studies have demonstrated the benefit of anterior support and fixation into the ilium when instrumenting a long posterior construct across the lumbosacral junction. Four L2-sacrum constructs were tested on six synthetic models of the lumbar spine and pelvis simulating that the right ilium had been harvested. Construct 1: L2-S1 bilateral screws. Construct 2: L2-S1 + left iliac bolt. Construct 3: L2-S1 + left iliac bolt + right S2 screw. Construct 4: L2-S1 + bilateral S2 screws. The four constructs were then retested with an anterior L5-S1 strut. A flexion-extension moment was applied across each construct, and the moment at the left and right S1 pedicle screw was measured with internal strain gauges. Iliac bolt fixation was found to significantly decrease the flexion-extension moment on the ipsilateral S1 screw by 70% and the contralateral screw by 26%. An anterior L5-S1 strut significantly decreased the S1 screw flexion-extension moment by 33%. Anterior support at L5-S1 provided no statistical decrease in the flexion-extension moment when bilateral posterior fixation beyond S1 was present with either a unilateral iliac bolt and contralateral S2 screw, or bilateral S2 screws. There is a significant decrease in the flexion-extension moment on the S1 screw when extending long posterior constructs to either the ilium or S2 sacral screw. There is no biomechanical advantage of the iliac bolt over the S2 screw in decreasing the moment on the S1 screw in flexion and extension. Adding anterior support to long posterior constructs significantly decreases the moment on the S1 screw. Adding distal posterior fixation to either the ilium or S2 decreases the moment on S1 screws more than adding anterior support. Further

Anisotropic Josephson-vortex dynamics in layered organic superconductors

NASA Astrophysics Data System (ADS)

Yasuzuka, S.; Uji, S.; Satsukawa, H.; Kimata, M.; Terashima, T.; Koga, H.; Yamamura, Y.; Saito, K.; Akutsu, H.; Yamada, J.

2010-06-01

To study the anisotropic Josephson-vortex dynamics in the d-wave superconductors, the interplane resistance has been measured on layered organic superconductors κ-(ET)2Cu(NCS)2 and β-(BDA-TTP)2SbF6 under magnetic fields precisely parallel to the conducting planes. For κ-(ET)2Cu(NCS)2, in-plane angular dependence of the Josephson-vortex flow resistance is mainly described by the fourfold symmetry and dip structures appear when the magnetic field is applied parallel to the b- and c-axes. The obtained results have a relation to the d-wave superconducting gap symmetry. However, the absence of in-plane fourfold anisotropy was found for β-(BDA-TTP)2SbF6. The different anisotropic behavior is discussed in terms of the interlayer coupling strength.

Van der Waals MoS2/VO2 heterostructure junction with tunable rectifier behavior and efficient photoresponse.

PubMed

Oliva, Nicoló; Casu, Emanuele Andrea; Yan, Chen; Krammer, Anna; Rosca, Teodor; Magrez, Arnaud; Stolichnov, Igor; Schueler, Andreas; Martin, Olivier J F; Ionescu, Adrian Mihai

2017-10-27

Junctions between n-type semiconductors of different electron affinity show rectification if the junction is abrupt enough. With the advent of 2D materials, we are able to realize thin van der Waals (vdW) heterostructures based on a large diversity of materials. In parallel, strongly correlated functional oxides have emerged, having the ability to show reversible insulator-to-metal (IMT) phase transition by collapsing their electronic bandgap under a certain external stimulus. Here, we report for the first time the electronic and optoelectronic characterization of ultra-thin n-n heterojunctions fabricated using deterministic assembly of multilayer molybdenum disulphide (MoS 2 ) on a phase transition material, vanadium dioxide (VO 2 ). The vdW MoS 2 /VO 2 heterojunction combines the excellent blocking capability of an n-n junction with a high conductivity in on-state, and it can be turned into a Schottky rectifier at high applied voltage or at temperatures higher than 68 °C, exploiting the metal state of VO 2 . We report tunable diode-like current rectification with a good diode ideality factor of 1.75 and excellent conductance swing of 120 mV/dec. Finally, we demonstrate unique tunable photosensitivity and excellent junction photoresponse in the 500/650 nm wavelength range.

Determination of the Ratio of b-Quark Fragmentation Fractions f(s)/f(d) in pp Collisions at √s=7  TeV with the ATLAS Detector.

PubMed

Aad, G; Abbott, B; Abdallah, J; Abdinov, O; Aben, R; Abolins, M; AbouZeid, O S; Abramowicz, H; Abreu, H; Abreu, R; Abulaiti, Y; Acharya, B S; Adamczyk, L; Adams, D L; Adelman, J; Adomeit, S; Adye, T; Affolder, A A; Agatonovic-Jovin, T; Agricola, J; Aguilar-Saavedra, J A; Ahlen, S P; Ahmadov, F; Aielli, G; Akerstedt, H; Åkesson, T P A; Akimov, A V; Alberghi, G L; Albert, J; Albrand, S; Alconada Verzini, M J; Aleksa, M; Aleksandrov, I N; Alexa, C; Alexander, G; Alexopoulos, T; Alhroob, M; Alimonti, G; Alio, L; Alison, J; Alkire, S P; Allbrooke, B M M; Allport, P P; Aloisio, A; Alonso, A; Alonso, F; Alpigiani, C; Altheimer, A; Alvarez Gonzalez, B; Álvarez Piqueras, D; Alviggi, M G; Amadio, B T; Amako, K; Amaral Coutinho, Y; Amelung, C; Amidei, D; Amor Dos Santos, S P; Amorim, A; Amoroso, S; Amram, N; Amundsen, G; Anastopoulos, C; Ancu, L S; Andari, N; Andeen, T; Anders, C F; Anders, G; Anders, J K; Anderson, K J; Andreazza, A; Andrei, V; Angelidakis, S; Angelozzi, I; Anger, P; Angerami, A; 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Soukharev, A M; South, D; Sowden, B C; Spagnolo, S; Spalla, M; Spangenberg, M; Spanò, F; Spearman, W R; Sperlich, D; Spettel, F; Spighi, R; Spigo, G; Spiller, L A; Spousta, M; Spreitzer, T; St Denis, R D; Staerz, S; Stahlman, J; Stamen, R; Stamm, S; Stanecka, E; Stanescu, C; Stanescu-Bellu, M; Stanitzki, M M; Stapnes, S; Starchenko, E A; Stark, J; Staroba, P; Starovoitov, P; Staszewski, R; Stavina, P; Steinberg, P; Stelzer, B; Stelzer, H J; Stelzer-Chilton, O; Stenzel, H; Stewart, G A; Stillings, J A; Stockton, M C; Stoebe, M; Stoicea, G; Stolte, P; Stonjek, S; Stradling, A R; Straessner, A; Stramaglia, M E; Strandberg, J; Strandberg, S; Strandlie, A; Strauss, E; Strauss, M; Strizenec, P; Ströhmer, R; Strom, D M; Stroynowski, R; Strubig, A; Stucci, S A; Stugu, B; Styles, N A; Su, D; Su, J; Subramaniam, R; Succurro, A; Sugaya, Y; Suhr, C; Suk, M; Sulin, V V; Sultansoy, S; Sumida, T; Sun, S; Sun, X; Sundermann, J E; Suruliz, K; Susinno, G; Sutton, M R; Suzuki, S; Svatos, M; Swiatlowski, M; Sykora, I; Sykora, T; Ta, D; Taccini, C; Tackmann, K; Taenzer, J; Taffard, A; Tafirout, R; Taiblum, N; Takai, H; Takashima, R; Takeda, H; Takeshita, T; Takubo, Y; Talby, M; Talyshev, A A; Tam, J Y C; Tan, K G; Tanaka, J; Tanaka, R; Tanaka, S; Tannenwald, B B; Tannoury, N; Tapprogge, S; Tarem, S; Tarrade, F; Tartarelli, G F; Tas, P; Tasevsky, M; Tashiro, T; Tassi, E; Tavares Delgado, A; Tayalati, Y; Taylor, F E; Taylor, G N; Taylor, W; Teischinger, F A; Teixeira Dias Castanheira, M; Teixeira-Dias, P; Temming, K K; Temple, D; Ten Kate, H; Teng, P K; Teoh, J J; Tepel, F; Terada, S; Terashi, K; Terron, J; Terzo, S; Testa, M; Teuscher, R J; Theveneaux-Pelzer, T; Thomas, J P; Thomas-Wilsker, J; Thompson, E N; Thompson, P D; Thompson, R J; Thompson, A S; Thomsen, L A; Thomson, E; Thomson, M; Thun, R P; Tibbetts, M J; Ticse Torres, R E; Tikhomirov, V O; Tikhonov, Yu A; Timoshenko, S; Tiouchichine, E; Tipton, P; Tisserant, S; Todome, K; Todorov, T; Todorova-Nova, S; Tojo, J; Tokár, S; Tokushuku, K; Tollefson, K; Tolley, E; Tomlinson, L; Tomoto, M; Tompkins, L; Toms, K; Torrence, E; Torres, H; Torró Pastor, E; Toth, J; Touchard, F; Tovey, D R; Trefzger, T; Tremblet, L; Tricoli, A; Trigger, I M; Trincaz-Duvoid, S; Tripiana, M F; Trischuk, W; Trocmé, B; Troncon, C; Trottier-McDonald, M; Trovatelli, M; True, P; Truong, L; Trzebinski, M; Trzupek, A; Tsarouchas, C; Tseng, J C-L; Tsiareshka, P V; Tsionou, D; Tsipolitis, G; Tsirintanis, N; Tsiskaridze, S; Tsiskaridze, V; Tskhadadze, E G; Tsukerman, I I; Tsulaia, V; Tsuno, S; Tsybychev, D; Tudorache, A; Tudorache, V; Tuna, A N; Tupputi, S A; Turchikhin, S; Turecek, D; Turra, R; Turvey, A J; Tuts, P M; Tykhonov, A; Tylmad, M; Tyndel, M; Ueda, I; Ueno, R; Ughetto, M; Ugland, M; Ukegawa, F; Unal, G; Undrus, A; Unel, G; Ungaro, F C; Unno, Y; Unverdorben, C; Urban, J; Urquijo, P; Urrejola, P; Usai, G; Usanova, A; Vacavant, L; Vacek, V; Vachon, B; Valderanis, C; Valencic, N; Valentinetti, S; Valero, A; Valery, L; Valkar, S; Valladolid Gallego, E; Vallecorsa, S; Valls Ferrer, J A; Van Den Wollenberg, W; Van Der Deijl, P C; van der Geer, R; van der Graaf, H; van Eldik, N; van Gemmeren, P; Van Nieuwkoop, J; van Vulpen, I; van Woerden, M C; Vanadia, M; Vandelli, W; Vanguri, R; Vaniachine, A; Vannucci, F; Vardanyan, G; Vari, R; Varnes, E W; Varol, T; Varouchas, D; Vartapetian, A; Varvell, K E; Vazeille, F; Vazquez Schroeder, T; Veatch, J; Veloce, L M; Veloso, F; Velz, T; Veneziano, S; Ventura, A; Ventura, D; Venturi, M; Venturi, N; Venturini, A; Vercesi, V; Verducci, M; Verkerke, W; Vermeulen, J C; Vest, A; Vetterli, M C; Viazlo, O; Vichou, I; Vickey, T; Vickey Boeriu, O E; Viehhauser, G H A; Viel, S; Vigne, R; Villa, M; Villaplana Perez, M; Vilucchi, E; Vincter, M G; Vinogradov, V B; Vivarelli, I; Vives Vaque, F; Vlachos, S; Vladoiu, D; Vlasak, M; Vogel, M; Vokac, P; Volpi, G; Volpi, M; von der Schmitt, H; von Radziewski, H; von Toerne, E; Vorobel, V; Vorobev, K; Vos, M; Voss, R; Vossebeld, J H; Vranjes, N; Vranjes Milosavljevic, M; Vrba, V; Vreeswijk, M; Vuillermet, R; Vukotic, I; Vykydal, Z; Wagner, P; Wagner, W; Wahlberg, H; Wahrmund, S; Wakabayashi, J; Walder, J; Walker, R; Walkowiak, W; Wang, C; Wang, F; Wang, H; Wang, H; Wang, J; Wang, J; Wang, K; Wang, R; Wang, S M; Wang, T; Wang, T; Wang, X; Wanotayaroj, C; Warburton, A; Ward, C P; Wardrope, D R; Washbrook, A; Wasicki, C; Watkins, P M; Watson, A T; Watson, I J; Watson, M F; Watts, G; Watts, S; Waugh, B M; Webb, S; Weber, M S; Weber, S W; Webster, J S; Weidberg, A R; Weinert, B; Weingarten, J; Weiser, C; Weits, H; Wells, P S; Wenaus, T; Wengler, T; Wenig, S; Wermes, N; Werner, M; Werner, P; Wessels, M; Wetter, J; Whalen, K; Wharton, A M; White, A; White, M J; White, R; White, S; Whiteson, D; Wickens, F J; Wiedenmann, W; Wielers, M; Wienemann, P; Wiglesworth, C; Wiik-Fuchs, L A M; Wildauer, A; Wilkens, H G; Williams, H H; Williams, S; Willis, C; Willocq, S; Wilson, A; Wilson, J A; Wingerter-Seez, I; Winklmeier, F; Winter, B T; Wittgen, M; Wittkowski, J; Wollstadt, S J; Wolter, M W; Wolters, H; Wosiek, B K; Wotschack, J; Woudstra, M J; Wozniak, K W; Wu, M; Wu, M; Wu, S L; Wu, X; Wu, Y; Wyatt, T R; Wynne, B M; Xella, S; Xu, D; Xu, L; Yabsley, B; Yacoob, S; Yakabe, R; Yamada, M; Yamaguchi, D; Yamaguchi, Y; Yamamoto, A; Yamamoto, S; Yamanaka, T; Yamauchi, K; Yamazaki, Y; Yan, Z; Yang, H; Yang, H; Yang, Y; Yao, W-M; Yasu, Y; Yatsenko, E; Yau Wong, K H; Ye, J; Ye, S; Yeletskikh, I; Yen, A L; Yildirim, E; Yorita, K; Yoshida, R; Yoshihara, K; Young, C; Young, C J S; Youssef, S; Yu, D R; Yu, J; Yu, J M; Yu, J; Yuan, L; Yuen, S P Y; Yurkewicz, A; Yusuff, I; Zabinski, B; Zaidan, R; Zaitsev, A M; Zalieckas, J; Zaman, A; Zambito, S; Zanello, L; Zanzi, D; Zeitnitz, C; Zeman, M; Zemla, A; Zeng, Q; Zengel, K; Zenin, O; Ženiš, T; Zerwas, D; Zhang, D; Zhang, F; Zhang, H; Zhang, J; Zhang, L; Zhang, R; Zhang, X; Zhang, Z; Zhao, X; Zhao, Y; Zhao, Z; Zhemchugov, A; Zhong, J; Zhou, B; Zhou, C; Zhou, L; Zhou, L; Zhou, N; Zhu, C G; Zhu, H; Zhu, J; Zhu, Y; Zhuang, X; Zhukov, K; Zibell, A; Zieminska, D; Zimine, N I; Zimmermann, C; Zimmermann, S; Zinonos, Z; Zinser, M; Ziolkowski, M; Živković, L; Zobernig, G; Zoccoli, A; zur Nedden, M; Zurzolo, G; Zwalinski, L

2015-12-31

With an integrated luminosity of 2.47  fb(-1) recorded by the ATLAS experiment at the LHC, the exclusive decays B(s)(0)→J/ψϕ and B(d)(0)→J/ψK(*0) of B mesons produced in pp collisions at √s=7  TeV are used to determine the ratio of fragmentation fractions f(s)/f(d). From the observed B(s)(0)→J/ψϕ and B(d)(0)→J/ψK(*0) yields, the quantity (f(s)/f(d))[B(B(s)(0)→J/ψϕ)/B(B(d)(0)→J/ψK(*0))] is measured to be 0.199±0.004(stat)±0.008(syst). Using a recent theory prediction for [B(B(s)(0)→J/ψϕ)/B(B(d)(0)→J/ψK(*0))] yields (f(s)/f(d))=0.240±0.004(stat)±0.010(syst)±0.017(th). This result is based on a new approach that provides a significant improvement of the world average.

Dirac quasiparticle tunneling in a NG/ferromagnetic barrier/SG graphene junction

NASA Astrophysics Data System (ADS)

Soodchomshom, Bumned; Tang, I.-Ming; Hoonsawat, Rassmidara

2009-07-01

We study the tunneling conductance in a spin dependent barrier NG/F B/SG graphene junction, where NG, F B and SG are normal graphene, gate ferromagnetic graphene barrier with thickness d and the graphene s-wave superconductor, respectively. In our work, the quasiparticle scattering process at the interfaces is based on quasi particles governed by the Dirac Bogoliubov-de Gennes equation with effective speed of light vF ∼ 10 6 m/s. The conductance of the junction is calculated based on Blonder-Tinkham-Klapwijk (BTK) formalism. The oscillatory conductance under varying gate potential and exchange energy in F B and the conductance induced by specular Andreev reflection are studied. By taking into account both effects of barrier strengths due to the gate potential χ∼Vd/ℏv and the exchange energy χ∼Ed/ℏv in the F B region, we find that the zero bias conductance of junction depends only on the ferromagnetic barrier strength χex in F B, when the Fermi energy in SG is very much larger than that the Fermi energy in NG ( EFS ≫ EFN). The oscillatory conductance peaks can be controlled by either varying χex or χG. In the limiting case, by setting Eex = 0, the conductance in a NG/N B/SG graphene junction, where SG is the s-wave superconductor, is also studied in order to compare with two earlier contradicted data. Our result agrees with what was obtained by Linder and Sudbo [J. Linder, A. Sudbo, Phys. Rev. B 77 (2008) 64507], which confirms the contradiction to what was given by Bhattacharjee and Sengupta [S. Bhattacharjee, K. Sengupta, Phys. Rev. Lett. 97 (2006) 217001].

Realizing Controllable Quantum States

NASA Astrophysics Data System (ADS)

Takayanagi, Hideaki; Nitta, Junsaku

1. Entanglement in solid states. Orbital entanglement and violation of bell inequalities in mesoscopic conductors / M. Büttiker, P. Samuelsson and E. V. Sukhoruk. Teleportation of electron spins with normal and superconducting dots / O. Sauret, D. Feinberg and T. Martin. Entangled state analysis for one-dimensional quantum spin system: singularity at critical point / A. Kawaguchi and K. Shimizu. Detecting crossed Andreev reflection by cross-current correlations / G. Bignon et al. Current correlations and transmission probabilities for a Y-shaped diffusive conductor / S. K. Yip -- 2. Mesoscopic electronics. Quantum bistability, structural transformation, and spontaneous persistent currents in mesoscopic Aharonov-Bohm loops / I. O. Kulik. Many-body effects on tunneling of electrons in magnetic-field-induced quasi one-dimensional systems in quantum wells / T. Kubo and Y. Tokura. Electron transport in 2DEG narrow channel under gradient magnetic field / M. Hara et al. Transport properties of a quantum wire with a side-coupled quantum dot / M. Yamaguchi et al. Photoconductivity- and magneto-transport studies of single InAs quantum wires / A. Wirthmann et al. Thermoelectric transports in charge-density-wave systems / H. Yoshimoto and S. Kurihara -- 3. Mesoscopic superconductivity. Parity-restricted persistent currents in SNS nanorings / A. D. Zaikin and S. V. Sharov. Large energy dependence of current noise in superconductingh/normal metal junctions / F. Pistolesi and M. Houzet. Generation of photon number states and their superpositions using a superconducting qubit in a microcavity / Yu-Xi Liu, L. F. Wei and F. Nori. Andreev interferometry for pumped currents / F. Taddei, M. Governale and R. Fazio. Suppression of Cooper-pair breaking against high magnetic fields in carbon nanotubes / J. Haruyama et al. Impact of the transport supercurrent on the Josephson effect / S. N. Shevchenko. Josephson current through spin-polarized Luttinger liquid / N. Yokoshi and S. Kurihara

Superconducting analog-to-digital converter with a triple-junction reversible flip-flop bidirectional counter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, G.S.

1993-07-13

A high-performance superconducting analog-to-digital converter is described, comprising: a bidirectional binary counter having n stages of triple-junction reversible flip-flops connected together in a cascade arrangement from the least significant bit (LSB) to the most significant bit (MSB) where n is the number of bits of the digital output, each triple-junction reversible flip-flop including first, second and third shunted Josephson tunnel junctions and a superconducting inductor connected in a bridge circuit, the Josephson junctions and the inductor forming upper and lower portions of the flip-flop, each reversible flip-flop being a bistable logic circuit in which the direction of the circulating currentmore » determines the state of the circuit; and means for applying an analog input current to the bidirectional counter; wherein the bidirectional counter algebraically counts incremental changes in the analog input current, increasing the binary count for positive incremental changes in the analog current and decreasing the binary count for negative incremental changes in the current, and wherein the counter does not require a gate bias, thus minimizing power dissipation.« less

Grumman S2F-1 Tracker at NACA Lewis

NASA Image and Video Library

1956-08-21

The NACA’s Lewis Flight Propulsion Laboratory acquired the Grumman S2F-1 Tracker from the Navy in 1955 to study icing instrumentation. Lewis’s icing research program was winding down at the time. The use of jet engines was increasing thus reducing the threat of ice accumulation. Nonetheless Lewis continued research on the instrumentation used to detect icing conditions. The S2F-1 Tracker was a carrier-based submarine hunter for the Navy. Grumman developed the Tracker as a successor to its Korean War-era Guardian patrol aircraft. Prototypes first flew in late 1952 and battle-ready versions entered Naval service in early 1954. The Navy utilized the Trackers to protect fleets from attack.

Structural and electrical characterization of ultra-thin SrTiO3 tunnel barriers grown over YBa2Cu3O7 electrodes for the development of high Tc Josephson junctions.

PubMed

Félix, L Avilés; Sirena, M; Guzmán, L A Agüero; Sutter, J González; Vargas, S Pons; Steren, L B; Bernard, R; Trastoy, J; Villegas, J E; Briático, J; Bergeal, N; Lesueur, J; Faini, G

2012-12-14

The transport properties of ultra-thin SrTiO(3) (STO) layers grown over YBa(2)Cu(3)O(7) electrodes were studied by conductive atomic force microscopy at the nano-scale. A very good control of the barrier thickness was achieved during the deposition process. A phenomenological approach was used to obtain critical parameters regarding the structural and electrical properties of the system. The STO layers present an energy barrier of 0.9 eV and an attenuation length of 0.23 nm, indicating very good insulating properties for the development of high-quality Josephson junctions.

Integrated Advanced Microwave Sounding Unit-A (AMSU-A). Performance Verification Report: METSAT (S/N) AMSU-A1 Receiver Assemblies P/N 1356429-1 S/N F06 and P/N 1356409-1 S/N F06

NASA Technical Reports Server (NTRS)

1999-01-01

This is the Performance Verification Report, METSAT (S/N 109) AMSU-A1 Receiver Assemblies, P/N 1356429-1 S/N F06 and P/N 1356409 S/N F06, for the Integrated Advanced Microwave Sounding Unit-A (AMSU-A).

Isolation and characterization of multiple F-box genes linked to the S9- and S10-RNase in apple (Malus × domestica Borkh.).

PubMed

Okada, Kazuma; Moriya, Shigeki; Haji, Takashi; Abe, Kazuyuki

2013-06-01

Using 11 consensus primer pairs designed from S-linked F-box genes of apple and Japanese pear, 10 new F-box genes (MdFBX21 to 30) were isolated from the apple cultivar 'Spartan' (S(9)S(10)). MdFBX21 to 23 and MdFBX24 to 30 were completely linked to the S(9) -RNase and S(10-)RNase, respectively, and showed pollen-specific expression and S-haplotype-specific polymorphisms. Therefore, these 10 F-box genes are good candidates for the pollen determinant of self-incompatibility in apple. Phylogenetic analysis and comparison of deduced amino acid sequences of MdFBX21 to 30 with those of 25 S-linked F-box genes previously isolated from apple showed that a deduced amino acid identity of greater than 88.0 % can be used as the tentative criterion to classify F-box genes into one type. Using this criterion, 31 of 35 F-box genes of apple were classified into 11 types (SFBB1-11). All types included F-box genes derived from S(3-) and S(9-)haplotypes, and seven types included F-box genes derived from S(3-), S(9-), and S(10-)haplotypes. Moreover, comparison of nucleotide sequences of S-RNases and multiple F-box genes among S(3-), S(9-), and S(10-)haplotypes suggested that F-box genes within each type showed high nucleotide identity regardless of the identity of the S-RNase. The large number of F-box genes as candidates for the pollen determinant and the high degree of conservation within each type are consistent with the collaborative non-self-recognition model reported for Petunia. These findings support that the collaborative non-self-recognition system also exists in apple.

Enhancement of macroscopic quantum tunneling in the higher-order phase switches of Bi2212 intrinsic Josephson junctions

NASA Astrophysics Data System (ADS)

Kitano, Haruhisa; Yamaguchi, Ayami; Takahashi, Yusaku; Umegai, Shunpei; Watabe, Yuji; Ohnuma, Haruka; Hosaka, Kazutaka; Kakehi, Daiki

2018-03-01

The macroscopic quantum tunneling (MQT) in the current-biased intrinsic Josephson junctions (IJJs) of high-T c cuprates has attracted much attention for decades. Although the MQT for the phase switches from the zero to the first voltage state (1st SW) in the multiple-branched I-V curves is well explained by the conventional theory, the occurrence of MQT for the higher order switches such as the switch from the 1st to 2nd voltage state (2nd SW) has been still debated. Here, we present an experimental study on the phase switches of small IJJs fabricated from underdoped Bi2Sr2(Ca,Y)Cu2Oy. We observed the single photon transition between quantized energy levels in the 3rd phase switches at 59.15 GHz and 2 K. The comparison with the previous studies on the nearly optimal-doped Bi2Sr2CaCu2Oy clearly suggests a possibility that the MQT rate for the higher-order phase switches is commonly enhanced by the effective suppression of the energy barrier for the higher-order phase escape due to the phase-running state after the 1st SW, in spite of the large difference in a critical current density and T c.

Ferroelectric-Domain-Patterning-Controlled Schottky Junction State in Monolayer MoS 2

DOE PAGES

Xiao, Zhiyong; Song, Jingfeng; Ferry, David K.; ...

2017-06-08

Here, we exploit scanning probe controlled domain patterning in a ferroelectric top-layer to induce nonvolatile modulation of the conduction characteristic of monolayer MoS 2 between a transistor and a junction state. In the presence of a domain wall, MoS 2 exhibits rectified I-V that is well described by the thermionic emission model. The induced Schottky barrier height Φ eff Β varies from 0.38 eV to 0.57 eV and is tunabe by a SiO 2 global back-gate, while the tuning range of Φ eff Β the barrier height depends sensitively on the conduction band tail trapping states. Our work points tomore » a new route to achieve programmable functionalities in van der Waals materials and sheds light on the critical performance limiting factors in these hybrid systems.« less

Ferroelectric-Domain-Patterning-Controlled Schottky Junction State in Monolayer MoS 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xiao, Zhiyong; Song, Jingfeng; Ferry, David K.

Here, we exploit scanning probe controlled domain patterning in a ferroelectric top-layer to induce nonvolatile modulation of the conduction characteristic of monolayer MoS 2 between a transistor and a junction state. In the presence of a domain wall, MoS 2 exhibits rectified I-V that is well described by the thermionic emission model. The induced Schottky barrier height Φ eff Β varies from 0.38 eV to 0.57 eV and is tunabe by a SiO 2 global back-gate, while the tuning range of Φ eff Β the barrier height depends sensitively on the conduction band tail trapping states. Our work points tomore » a new route to achieve programmable functionalities in van der Waals materials and sheds light on the critical performance limiting factors in these hybrid systems.« less

A Single-Material Logical Junction Based on 2D Crystal PdS2.

PubMed

Ghorbani-Asl, Mahdi; Kuc, Agnieszka; Miró, Pere; Heine, Thomas

2016-02-03

A single-material logical junction with negligible contact resistance is designed by exploiting quantum-confinement effects in 1T PdS2 . The metallic bilayer serves as electrodes for the semiconducting channel monolayer, avoiding contact resistance. Heat dissipation is then governed by tunnel loss, which becomes negligible at channel lengths larger than 2.45 nm. This value marks the integration limit for a conventional 2D transistor. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Determination of the ratio of b -quark fragmentation fractions f s / f d in p p collisions at s = 7 TeV with the ATLAS detector

DOE PAGES

Aad, G.

2015-12-30

With an integrated luminosity of 2.47 fb -1 recorded by the ATLAS experiment at the LHC, the exclusive decays B 0 s→J/ψΦ and B 0 d→J/ψK *0 of B mesons produced in pp collisions at √s=7 TeV are used to determine the ratio of fragmentation fractions f s/f d. From the observed B 0 s→J/ψΦ and B 0 d→J/ψK *0 yields, the quantity (f s/f d)[B(B 0 s→J/ψΦ)/B(B 0 d→J/ψK *0)] is measured to be 0.199±0.004(stat)±0.008(syst). Using a recent theory prediction for [B(B 0 s→J/ψΦ)/B(B 0 d→J/ψK *0)] yields (f s/f d)=0.240±0.004(stat)±0.010(syst)±0.017(th). As a result, it is based on amore » new approach that provides a significant improvement of the world average.« less

Determination of the ratio of b -quark fragmentation fractions f s / f d in p p collisions at s = 7 TeV with the ATLAS detector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aad, G.

With an integrated luminosity of 2.47 fb -1 recorded by the ATLAS experiment at the LHC, the exclusive decays B 0 s→J/ψΦ and B 0 d→J/ψK *0 of B mesons produced in pp collisions at √s=7 TeV are used to determine the ratio of fragmentation fractions f s/f d. From the observed B 0 s→J/ψΦ and B 0 d→J/ψK *0 yields, the quantity (f s/f d)[B(B 0 s→J/ψΦ)/B(B 0 d→J/ψK *0)] is measured to be 0.199±0.004(stat)±0.008(syst). Using a recent theory prediction for [B(B 0 s→J/ψΦ)/B(B 0 d→J/ψK *0)] yields (f s/f d)=0.240±0.004(stat)±0.010(syst)±0.017(th). As a result, it is based on amore » new approach that provides a significant improvement of the world average.« less

S locus-linked F-box genes expressed in anthers of Hordeum bulbosum.

PubMed

Kakeda, Katsuyuki

2009-09-01

Diploid Hordeum bulbosum (a wild relative of cultivated barley) exhibits a two-locus self-incompatibility (SI) system gametophytically controlled by the unlinked multiallelic loci S and Z. This unique SI system is observed in the grasses (Poaceae) including the tribe Triticeae. This paper describes the identification and characterization of two F-box genes cosegregating with the S locus in H. bulbosum, named Hordeum S locus-linked F-box 1 (HSLF1) and HSLF2, which were derived from an S (3) haplotype-specific clone (HAS175) obtained by previous AMF (AFLP-based mRNA fingerprinting) analysis. Sequence analysis showed that both genes encode similar F-box proteins with a C-terminal leucine-rich repeat (LRR) domain, which are distinct from S locus (or S haplotype-specific) F-box protein (SLF/SFB), a class of F-box proteins identified as the pollen S determinant in S-RNase-based gametophytic SI systems. A number of homologous F-box genes with an LRR domain were found in the rice genome, although the functions of the gene family are unknown. One allele of the HSLF1 gene (HSLF1-S (3)) was expressed specifically in mature anthers, whereas no expression was detected from the other two alleles examined. Although the degree of sequence polymorphism among the three HSLF1 alleles was low, a frameshift mutation was found in one of the unexpressed alleles. The HSLF2 gene showed a low level of expression with no tissue specificity as well as little sequence polymorphism among the three alleles. The multiplicity of S locus-linked F-box genes is discussed in comparison with those found in the S-RNase-based SI system.

AC Josephson effect applications in microwave systems

NASA Astrophysics Data System (ADS)

Larkin, Serguey Y.

1996-12-01

analysis allow to get the picture of temperature distribution along the plasma cord diameter in accordance with dynamics of thermonuclear process development. Modem raclioastronomic research gives scientists the unique information on the world tructure. It is also necessary to analyze Space microwave radiation providing exclusive sensitivity of the equipment. In both cases equipment is required to be superwide band, to have high sensitivity and ability to operate at more than 300 GHz frequencies. Today all these requirements are met by the devices using the ac Josephson effect. The Josephson junctions are used as an active transforming element in such devices. At the end of 20 century the sphere of their utilization embraces medicine, communications, radiophysics, space exploration, ecology, military use, etc. The State Research Center "Fonon" ( SRC "Fonon") of the State Committee on Science and Technology of Ukraine was founded in 1991. The main aim of its creation was to concentrate the scientific and financial efforts for development and production of unique devices based on the results of fundamental study in physics of high T superconductivity. First of all we were interested in technological research on the obtaining of low impedance Josephson junctions out of the High T thin films. Using such junctions in combination with our original techniques developed in our Center we have succeed in creating the following new generation equipment: industrial set-up of the frequency meter in the range of 60 ... 600 GHz; experimental set-up of the spectrum analyzer operating in the range of 50 250 GHz; experimental model of radiometric receiver in 180...260 GHz range. All the above devices are based on the using ac Josephson effect for the receiving and processing mm- and submm- microwave signals.

Two-Volt Josephson Arbitrary Waveform Synthesizer Using Wilkinson Dividers.

PubMed

Flowers-Jacobs, Nathan E; Fox, Anna E; Dresselhaus, Paul D; Schwall, Robert E; Benz, Samuel P

2016-09-01

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.

Terahertz emission from the intrinsic Josephson junctions of high-symmetry thermally-managed Bi2Sr2CaCu2O8+δ microstrip antennas

NASA Astrophysics Data System (ADS)

Klemm, Richard A.; Davis, Andrew E.; Wang, Qing X.; Yamamoto, Takashi; Cerkoney, Daniel P.; Reid, Candy; Koopman, Maximiliaan L.; Minami, Hidetoshi; Kashiwagi, Takanari; Rain, Joseph R.; Doty, Constance M.; Sedlack, Michael A.; Morales, Manuel A.; Watanabe, Chiharu; Tsujimoto, Manabu; Delfanazari, Kaveh; Kadowaki, Kazuo

2017-12-01

We show for high-symmetry disk, square, or equilateral triangular thin microstrip antennas of any composition respectively obeying C ∞v , C 4v , and C 3v point group symmetries, that the transverse magnetic electromagnetic cavity mode wave functions are restricted in form to those that are one-dimensional representations of those point groups. Plots of the common nodal points of the ten lowest-energy non-radiating two-dimensional representations of each of these three symmetries are presented. For comparison with symmetry-broken disk intrinsic Josephson junction microstrip antennas constructed from the highly anisotropic layered superconductor Bi2Sr2CaCu2O8+δ (BSCCO), we present plots of the ten lowest frequency orthonormal wave functions and of their emission power angular distributions. These results are compared with previous results for square and equilateral triangular thin microstrip antennas.

Modulation of connexin expression and gap junction communication in astrocytes by the gram-positive bacterium S. aureus.

PubMed

Esen, Nilufer; Shuffield, Debbie; Syed, Mohsin M D; Kielian, Tammy

2007-01-01

Gap junctions establish direct intercellular conduits between adjacent cells and are formed by the hexameric organization of protein subunits called connexins (Cx). It is unknown whether the proinflammatory milieu that ensues during CNS infection with S. aureus, one of the main etiologic agents of brain abscess in humans, is capable of eliciting regional changes in astrocyte homocellular gap junction communication (GJC) and, by extension, influencing neuron homeostasis at sites distant from the primary focus of infection. Here we investigated the effects of S. aureus and its cell wall product peptidoglycan (PGN) on Cx43, Cx30, and Cx26 expression, the main Cx isoforms found in astrocytes. Both bacterial stimuli led to a time-dependent decrease in Cx43 and Cx30 expression; however, Cx26 levels were elevated following bacterial exposure. Functional examination of dye coupling, as revealed by single-cell microinjections of Lucifer yellow, demonstrated that both S. aureus and PGN inhibited astrocyte GJC. Inhibition of protein synthesis with cyclohexamide (CHX) revealed that S. aureus directly modulates, in part, Cx43 and Cx30 expression, whereas Cx26 levels appear to be regulated by a factor(s) that requires de novo protein production; however, CHX did not alter the inhibitory effects of S. aureus on astrocyte GJC. The p38 MAPK inhibitor SB202190 was capable of partially restoring the S. aureus-mediated decrease in astrocyte GJC to that of unstimulated cells, suggesting the involvement of p38 MAPK-dependent pathway(s). These findings could have important implications for limiting the long-term detrimental effects of abscess formation in the brain which may include seizures and cognitive deficits. Copyright 2006 Wiley-Liss, Inc.

Terahertz Josephson spectral analysis and its applications

NASA Astrophysics Data System (ADS)

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

2017-04-01

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

The Origin of the s, p, d, f Orbital Labels

ERIC Educational Resources Information Center

Jensen, William B.

2007-01-01

The theory of s, p, d and f dealing with the line spectra of the alkali metals during the period 1881 based on analogies with the harmonic ratios of sound is described. Friedrich Hund followed Bohr's practice of labelling the various shells and subshells by replacing the secondary quantum number with the series notations (s, p, d, and f), which…

A multilayered approach to superconducting tunnel junction x ray detectors

NASA Technical Reports Server (NTRS)

Rippert, E. D.; Song, S. N.; Ketterson, J. B.; Maglic, S. R.; Lomatch, S.; Thomas, C.; Cheida, M. A.; Ulmer, M. P.

1992-01-01

'First generation' superconducting tunnel junction X-ray detectors (characterized by a single tunnel junction in direct contact with its substrate, with totally external amplification) remain more than an order of magnitude away from their theoretical energy resolutions which are in the order of eV's. The difficulties that first generation devices are encountering are being attacked by a 'second generation' of superconducting X-ray detector designs including quasiparticle trapping configurations and Josephson junction arrays. A second generation design concept, the multilayered superconducting tunnel junction X-ray detector, consisting of tens to hundreds of tunnel junctions stacked on top of one another (a superlattice), is presented. Some of the possibilities of this engineered materials approach include the tuning of phonon transmission characteristics of the material, suppression of parasitic quasiparticle trapping and intrinsic amplification.

The F-ATPase operon from the oral streptococci S. mutans and S. sanguis: How structure relates to function

NASA Astrophysics Data System (ADS)

Kuhnert, Wendi Lee

1999-10-01

The oral microbe, Streptococcus mutans is known to be a primary contributor to the most common infection in humans, dental caries. In the plaque environment, resident bacteria metabolize dietary sucrose which results in the production of organic acids and a decrease in plaque pH. The proton-translocating ATPase (F-ATPase) protects the bacteria from acidification by extruding protons, at the expense of ATP, to maintain an internal pH which is more neutral than the external environment. Examination of this enzyme will help us to gain insight regarding its contribution to the aciduricity characteristics of oral bacteria. In this work, our goal was to begin the molecular dissection of the mechanism by which streptococcal ATPases are regulated and function enzymatically. Sequence analysis of the F-ATPase from the non-pathogenic S. sanguis revealed that the structural genes are homologous to S. mutans as well as other sequenced F-ATPases. Cloned subunits were functionally similar as shown by complementing E. coli ATPase mutants. S. sanguis/E. coli hybrid enzymes hydrolyzed ATP, but proton conduction was uncoupled as demonstrated with inhibition studies. Transcriptional regulation of the F-ATPase operon from S. mutans was examined using chloramphenicol acetyltransferase gene fusions. Fusions containing 136 bp of DNA upstream of the promoter showed higher levels of expression as compared to those with only 16 bp. Similar to ATPase enzymatic activity, CAT expression also increased during growth at low pH. Analysis of RNA demonstrated that ATPase mRNA levels were higher at low pH, which supported the CAT activity data. Therefore, the F-ATPase from S. mutans was regulated, at least partially, by both the DNA located upstream of the promoter as well as by pH. Examination of structural models of the F-ATPase from the pathogenic oral organisms S. mutans and Lactobacillus casei and the non- pathogenic S. sanguis showed that the differences noted in the sequence of the catalytic �

Properties of Josephson Junction Fabricated on Bicrystal Substrate with Different Misorientation Angles

NASA Astrophysics Data System (ADS)

Minotani, Tadashi; Kawakami, Satoru; Kuroki, Yukinori; Enpuku, Keiji

1998-06-01

In order to develop YBa2Cu3O7-δ bicrystal junctions suitable for high-performance superconducting quantum interference device (SQUID), the relationship between the junction properties and the misorientation angle of the bicrystal substrate is studied experimentally. Misorientation angles of 24°, 27°, 30°, 33° and 36.8° are used, and the angular dependencies of junction resistance Rs and critical current Io are investigated. It is shown that values of Rs and Io approximately follow the relation IoRs1.5=const. in these junctions. The obtained results are analyzed in terms of the direct and resonant tunneling mechanisms. It is also shown that values of Rs≈10 Ω and Io≈20 µA can be obtained rather reproducibly when we use the 30° junctions. The properties of this junction are very promising for the development of high-performance SQUID.

Macroscopic Quantum Tunneling in Superconducting Junctions of β-Ag2Se Topological Insulator Nanowire.

PubMed

Kim, Jihwan; Kim, Bum-Kyu; Kim, Hong-Seok; Hwang, Ahreum; Kim, Bongsoo; Doh, Yong-Joo

2017-11-08

We report on the fabrication and electrical transport properties of superconducting junctions made of β-Ag 2 Se topological insulator (TI) nanowires in contact with Al superconducting electrodes. The temperature dependence of the critical current indicates that the superconducting junction belongs to a short and diffusive junction regime. As a characteristic feature of the narrow junction, the critical current decreases monotonously with increasing magnetic field. The stochastic distribution of the switching current exhibits the macroscopic quantum tunneling behavior, which is robust up to T = 0.8 K. Our observations indicate that the TI nanowire-based Josephson junctions can be a promising building block for the development of nanohybrid superconducting quantum bits.

27 CFR 17.132 - U.S.P., N.F., and H.P.U.S. preparations.

Code of Federal Regulations, 2011 CFR

2011-04-01

... NONBEVERAGE PRODUCTS Formulas and Samples Approval of Formulas § 17.132 U.S.P., N.F., and H.P.U.S..., formulas for compounds in which alcohol is a prescribed quantitative ingredient, which are stated in the... formulas and may be used as formulas for drawback products without the filing of TTB Form 5154.1. (b...

27 CFR 17.132 - U.S.P., N.F., and H.P.U.S. preparations.

Code of Federal Regulations, 2010 CFR

2010-04-01

... NONBEVERAGE PRODUCTS Formulas and Samples Approval of Formulas § 17.132 U.S.P., N.F., and H.P.U.S..., formulas for compounds in which alcohol is a prescribed quantitative ingredient, which are stated in the... formulas and may be used as formulas for drawback products without the filing of TTB Form 5154.1. (b...

27 CFR 17.132 - U.S.P., N.F., and H.P.U.S. preparations.

Code of Federal Regulations, 2013 CFR

2013-04-01

... NONBEVERAGE PRODUCTS Formulas and Samples Approval of Formulas § 17.132 U.S.P., N.F., and H.P.U.S..., formulas for compounds in which alcohol is a prescribed quantitative ingredient, which are stated in the... formulas and may be used as formulas for drawback products without the filing of TTB Form 5154.1. (b...

27 CFR 17.132 - U.S.P., N.F., and H.P.U.S. preparations.

Code of Federal Regulations, 2014 CFR

2014-04-01

... NONBEVERAGE PRODUCTS Formulas and Samples Approval of Formulas § 17.132 U.S.P., N.F., and H.P.U.S..., formulas for compounds in which alcohol is a prescribed quantitative ingredient, which are stated in the... formulas and may be used as formulas for drawback products without the filing of TTB Form 5154.1. (b...

27 CFR 17.132 - U.S.P., N.F., and H.P.U.S. preparations.

Code of Federal Regulations, 2012 CFR

2012-04-01

... NONBEVERAGE PRODUCTS Formulas and Samples Approval of Formulas § 17.132 U.S.P., N.F., and H.P.U.S..., formulas for compounds in which alcohol is a prescribed quantitative ingredient, which are stated in the... formulas and may be used as formulas for drawback products without the filing of TTB Form 5154.1. (b...

Series array of highly hysteretic Josephson junctions coupled to a microstrip resonator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Costabile, G.; Andreone, D.; Lacquaniti, V.

1985-07-15

We have tested a new device based on a 12 junction array coupled to a resonator. We have explored the feasibility of the phase lock for all the junctions at the same biasing current, which yields voltage quantization across each junction, eliminating the need to individually bias the junctions. The whole rf structure has been realized by stripline technology. The resonator is fed by a 50-..cap omega.. line and is decoupled from the dc circuit by elliptical low-pass filters inserted in the bias leads.

75 FR 50688 - Special Conditions: Erickson Air-Crane Incorporated S-64E and S-64F Rotorcraft

Federal Register 2010, 2011, 2012, 2013, 2014

2010-08-17

...) model S-64E and S-64F rotorcraft. These rotorcraft have novel or unusual design features associated with being transport category rotorcraft designed only for use in heavy external-load operations. At the time...) Powerplant Instruments. At the time of original certification, the S-64 had a novel design of being powered...

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

DTIC Science & Technology

2016-09-01

to the characteristics and extract the non-ideality. These capabilities and calibration results will assist in the characterization of advanced...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

Current-phase relations in low carrier density graphene Josephson junctions

NASA Astrophysics Data System (ADS)

Kratz, Philip; Amet, Francois; Watson, Christopher; Moler, Kathryn; Ke, Chung; Borzenets, Ivan; Watanabe, Kenji; Taniguchi, Takashi; Deacon, Russell; Yamamoto, Michihisa; Bomze, Yuriy; Tarucha, Seigo; Finkelstein, Gleb

Ideal Dirac semimetals have the unique property of being gate tunable to arbitrarily low electron and hole carrier concentrations near the Dirac point, without suffering from conduction channel pinch-off or Fermi level pinning to band edges and deep-level charge traps, which are common in typical semiconductors. SNS junctions, where N is a Dirac semimetal, can provide a versatile platform for studying few-mode superconducting weak links, with potential device applications for superconducting logic and qubits. We will use an inductive readout technique, scanning superconducting quantum interference device (SQUID) magnetometry, to measure the current-phase relations of high-mobility graphene SNS junctions as a function of temperature and carrier density, complementing magnetic Fraunhofer diffraction analysis from transport measurements which previously have assumed sinusoidal current-phase relations for junction Andreev modes. Deviations from sinusoidal behavior convey information about resonant scattering processes, dissipation, and ballistic modes in few-mode superconducting weak links.

Sabers, Lances, B-17s and F-105s: An Essay on the Human Element, Napoleonic Warfare, and Air Combat.

DTIC Science & Technology

1987-04-01

AD~~AB8 SERS LAKCES 9-175 S F-1SSS: AN ESSAY ON TNE HUMAN 1/1 COMMANDAND STAFF COLL MAXWELL AFD AL. M K WELLS APR *? UNCLASSIFIED ACSC-B go69 F/0 15...available to any writer on this subject. This document is the property of the United States Government. It is available for distribution to the general...Air Command and Staff College." -- All reproduced copies must contain the name( s ) of the report’s author( s ). -- If format modification is necessary to

Van der Waals epitaxial growth and optoelectronics of large-scale WSe2/SnS2 vertical bilayer p-n junctions.

PubMed

Yang, Tiefeng; Zheng, Biyuan; Wang, Zhen; Xu, Tao; Pan, Chen; Zou, Juan; Zhang, Xuehong; Qi, Zhaoyang; Liu, Hongjun; Feng, Yexin; Hu, Weida; Miao, Feng; Sun, Litao; Duan, Xiangfeng; Pan, Anlian

2017-12-04

High-quality two-dimensional atomic layered p-n heterostructures are essential for high-performance integrated optoelectronics. The studies to date have been largely limited to exfoliated and restacked flakes, and the controlled growth of such heterostructures remains a significant challenge. Here we report the direct van der Waals epitaxial growth of large-scale WSe 2 /SnS 2 vertical bilayer p-n junctions on SiO 2 /Si substrates, with the lateral sizes reaching up to millimeter scale. Multi-electrode field-effect transistors have been integrated on a single heterostructure bilayer. Electrical transport measurements indicate that the field-effect transistors of the junction show an ultra-low off-state leakage current of 10 -14 A and a highest on-off ratio of up to 10 7 . Optoelectronic characterizations show prominent photoresponse, with a fast response time of 500 μs, faster than all the directly grown vertical 2D heterostructures. The direct growth of high-quality van der Waals junctions marks an important step toward high-performance integrated optoelectronic devices and systems.

Recognition of a wide-range of S-RNases by S locus F-box like 2, a general-inhibitor candidate in the Prunus-specific S-RNase-based self-incompatibility system.

PubMed

Matsumoto, Daiki; Tao, Ryutaro

2016-07-01

Many species in the Rosaceae, the Solanaceae, and the Plantaginaceae exhibit S-RNase-based gametophytic self-incompatibility (GSI). This system comprises S-ribonucleases (S-RNases) as the pistil S determinant and a single or multiple F-box proteins as the pollen S determinants. In Prunus, pollen specificity is determined by a single S haplotype-specific F-box protein (SFB). The results of several studies suggested that SFB exerts cognate S-RNase cytotoxicity, and a hypothetical general inhibitor (GI) is assumed to detoxify S-RNases in non-specific manner unless it is affected by SFB. Although the identity of the GI is unknown, phylogenetic and evolutionary analyses have indicated that S locus F-box like 1-3 (or S locus F-box with low allelic sequence polymorphism 1-3; SLFL1-3), which are encoded by a region of the Prunus genome linked to the S locus, are good GI candidates. Here, we examined the biochemical characteristics of SLFL1-3 to determine whether they have appropriate GI characteristics. Pull-down assays and quantitative expression analyses indicated that Prunus avium SLFL1-3 mainly formed a canonical SCF complex with PavSSK1 and PavCul1A. Binding assays with PavS(1,3,4,6)-RNases showed that PavSLFL1, PavSLFL2, and PavSLFL3 bound to PavS(3)-RNase, all PavS-RNases tested, and none of the PavS-RNases tested, respectively. Together, these results suggested that SLFL2 has the appropriate characteristics to be the GI in sweet cherry pollen, while SLFL1 may redundantly work with SLFL2 to detoxify all S-RNases. We discuss the possible roles of SLFL1-3 as the GI in the Prunus-specific S-RNase-based GSI mechanism.

Fabrication process of superconducting integrated circuits with submicron Nb/AlOx/Nb junctions using electron-beam direct writing technique

NASA Astrophysics Data System (ADS)

Aoyagi, Masahiro; Nakagawa, Hiroshi

1997-07-01

For enhancing operating speed of a superconducting integrated circuit (IC), the device size must be reduced into the submicron level. For this purpose, we have introduced electron beam (EB) direct writing technique into the fabrication process of a Nb/AlOx/Nb Josephson IC. A two-layer (PMMA/(alpha) M-CMS) resist method called the portable conformable mask (PCM) method was utilized for having a high aspect ratio. The electron cyclotron resonance (ECR) plasma etching technique was utilized. We have fabricated micron or submicron-size Nb/AlOx/Nb Josephson junctions, where the size of the junction was varied from 2 micrometer to 0.5 micrometer at 0.1 micrometer intervals. These junctions were designed for evaluating the spread of the junction critical current. We achieved minimum-to-maximum Ic spread of plus or minus 13% for 0.81-micrometer-square (plus or minus 16% for 0.67-micrometer-square) 100 junctions spreading in 130- micrometer-square area. The size deviation of 0.05 micrometer was estimated from the spread values. We have successfully demonstrated a small-scale logic IC with 0.9-micrometer-square junctions having a 50 4JL OR-gate chain, where 4JL means four junctions logic family. The circuit was designed for measuring the gate delay. We obtained a preliminary result of the OR- gate logic delay, where the minimum delay was 8.6 ps/gate.

Effect of S267F variant of NTCP on the patients with chronic hepatitis B.

PubMed

Lee, Hye Won; Park, Hye Jung; Jin, Bora; Dezhbord, Mehrangiz; Kim, Do Young; Han, Kwang-Hyub; Ryu, Wang-Shick; Kim, Seungtaek; Ahn, Sang Hoon

2017-12-15

Sodium taurocholate cotransporting polypeptide (NTCP) was identified as an entry receptor for hepatitis B virus (HBV) infection. The substitution of serine at position 267 of NTCP with phenylalanine (S267F) is an Asian-specific variation that hampers HBV entry in vitro. In this study, we aimed to evaluate the prevalence of S267F polymorphism in Korean patients with chronic hepatitis B (CHB) and its association with disease progression and potential viral evolution in the preS1 domain of HBV. We found that the frequency of the S267F variant of NTCP in CHB patients and controls was 2.7% and 5.7% (P = 0.031), respectively, and that those who had S267F variant were less susceptible to chronic HBV infection. The frequency of the S267F variant in CHB, cirrhosis and hepatocellular carcinoma (HCC) patients was 3.3%, 0.9%, and 3.5%, respectively. Thus, the S267F variant correlated significantly with a lower risk for cirrhosis (P = 0.036). Sequencing preS1 domain of HBV from the patients who had S267F variant revealed no significant sequence change compared to the wild type. In conclusion, the S267F variant of NTCP is clinically associated with a lower risk of chronic HBV infection and cirrhosis development, which implicates suppressing HBV entry could reduce the disease burden.

Synthesis, radiolabeling, and biological evaluation of ( R)- and ( S)-2-amino-5-[ 18F]fluoro-2-methylpentanoic acid (( R)-, ( S)-[ 18F]FAMPe) as potential positron emission tomography tracers for brain tumors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bouhlel, Ahlem; Zhou, Dong; Li, Aixiao

In this paper, a novel 18F-labeled α,α-disubstituted amino acid-based tracer, 2-amino-5-[ 18F]fluoro-2-methylpentanoic acid ([ 18F]FAMPe), has been developed for brain tumor imaging with a longer alkyl side chain than previously reported compounds to increase brain availability via system L amino acid transport. Both enantiomers of [ 18F]FAMPe were obtained in good radiochemical yield (24–52% n = 8) and high radiochemical purity (>99%). In vitro uptake assays in mouse DBT gliomas cells revealed that ( S)-[ 18F]FAMPe enters cells partly via sodium-independent system L transporters and also via other nonsystem A transport systems including transporters that recognize glutamine. Biodistribution and smallmore » animal PET/CT studies in the mouse DBT model of glioblastoma showed that both ( R)- and ( S)-[ 18F]FAMPe have good tumor imaging properties with the ( S)-enantiomer providing higher tumor uptake and tumor to brain ratios. Finally, comparison of the SUVs showed that ( S)-[ 18F]FAMPe had higher tumor to brain ratios compared to ( S)-[ 18F]FET, a well-established system L substrate.« less

Synthesis, radiolabeling, and biological evaluation of ( R)- and ( S)-2-amino-5-[ 18F]fluoro-2-methylpentanoic acid (( R)-, ( S)-[ 18F]FAMPe) as potential positron emission tomography tracers for brain tumors

DOE PAGES

Bouhlel, Ahlem; Zhou, Dong; Li, Aixiao; ...

2015-04-06

In this paper, a novel 18F-labeled α,α-disubstituted amino acid-based tracer, 2-amino-5-[ 18F]fluoro-2-methylpentanoic acid ([ 18F]FAMPe), has been developed for brain tumor imaging with a longer alkyl side chain than previously reported compounds to increase brain availability via system L amino acid transport. Both enantiomers of [ 18F]FAMPe were obtained in good radiochemical yield (24–52% n = 8) and high radiochemical purity (>99%). In vitro uptake assays in mouse DBT gliomas cells revealed that ( S)-[ 18F]FAMPe enters cells partly via sodium-independent system L transporters and also via other nonsystem A transport systems including transporters that recognize glutamine. Biodistribution and smallmore » animal PET/CT studies in the mouse DBT model of glioblastoma showed that both ( R)- and ( S)-[ 18F]FAMPe have good tumor imaging properties with the ( S)-enantiomer providing higher tumor uptake and tumor to brain ratios. Finally, comparison of the SUVs showed that ( S)-[ 18F]FAMPe had higher tumor to brain ratios compared to ( S)-[ 18F]FET, a well-established system L substrate.« less

Correlating quantum decoherence and material defects in a Josephson qubit

NASA Astrophysics Data System (ADS)

Hite, D. A.; McDermott, R.; Simmonds, R. W.; Cooper, K. B.; Steffen, M.; Nam, S.; Pappas, D. P.; Martinis, J. M.

2004-03-01

Superconducting tunnel junction devices are promising candidates for constructing quantum bits (qubits) for quantum computation because of their inherently low dissipation and ease of scalability by microfabrication. Recently, the Josephson phase qubit has been characterized spectroscopically as having spurious microwave resonators that couple to the qubit and act as a dominant source of decoherence. While the origin of these spurious resonances remains unknown, experimental evidence points to the material system of the tunnel barrier. Here, we focus on our materials research aimed at elucidating and eliminating these spurious resonators. In particular, we have studied the use of high quality Al films epitaxially grown on Si(111) as the base electrode of the tunnel junction. During each step in the Al/AlOx/Al trilayer growth, we have investigated the structure in situ by AES, AED and LEED. While tunnel junctions fabricated with these epitaxial base electrodes prove to be of non-uniform oxide thickness and too thin, I-V characteristics have shown a lowering of subgap currents by a factor of two. Transport measurements will be correlated with morphological structure for a number of devices fabricated with various degrees of crystalline quality.

Fabrication of interface-modified ramp-edge junction on YBCO ground plane with multilayer structure

NASA Astrophysics Data System (ADS)

Wakana, H.; Adachi, S.; Kamitani, A.; Sugiyama, H.; Sugano, T.; Horibe, M.; Ishimaru, Y.; Tarutani, Y.; Tanabe, K.

2003-10-01

We examined the fabrication conditions to obtain high-quality ramp-edge Josephson junctions on a liquid-phase-epitaxy YBa 2Cu 3O y (LPE-YBCO) ground plane, in particular, focusing on the fabrication of a suitable insulating layer on the ground plane and the post-annealing conditions to load oxygen to the ground plane. A (LaAlO 3) 0.3-(SrAl 0.5Ta 0.5O 3) 0.7 (LSAT) insulating film on the ground planes exhibited a conductance ranging from 10 -4 to 10 -8 S after deposition of an upper superconducting film, suggesting existence of some leak paths through the LSAT insulating layer. By introducing approximately 30 nm thick SrTiO 3 (STO) buffer layers on both side of the LSAT insulating layer. We reproducibly obtained a conductance lower than 10 -8 S. The dielectric constant of the STO/LSAT/STO layer was 32, which was slightly larger than that of the single LSAT layer. It was found that a very slow cooling rate of 1.0 °C/h in oxygen was needed to fully oxidize the ground plane through the STO/LSAT/STO insulating layers, while the oxidation time could be effectively reduced by introducing via holes in the insulating layer at an interval of 200 μm. Ramp-edge junctions on LPE-YBCO ground planes with STO/LSAT/STO insulating layers exhibited a 1 σ-spread in Ic of 8% for 100-junction series-arrays and a sheet inductance of 0.7 pH/□ at 4.2 K.

Analysis of trafficking, stability and function of human connexin 26 gap junction channels with deafness-causing mutations in the fourth transmembrane helix.

PubMed

Ambrosi, Cinzia; Walker, Amy E; Depriest, Adam D; Cone, Angela C; Lu, Connie; Badger, John; Skerrett, I Martha; Sosinsky, Gina E

2013-01-01

Human Connexin26 gene mutations cause hearing loss. These hereditary mutations are the leading cause of childhood deafness worldwide. Mutations in gap junction proteins (connexins) can impair intercellular communication by eliminating protein synthesis, mis-trafficking, or inducing channels that fail to dock or have aberrant function. We previously identified a new class of mutants that form non-functional gap junction channels and hemichannels (connexons) by disrupting packing and inter-helix interactions. Here we analyzed fourteen point mutations in the fourth transmembrane helix of connexin26 (Cx26) that cause non-syndromic hearing loss. Eight mutations caused mis-trafficking (K188R, F191L, V198M, S199F, G200R, I203K, L205P, T208P). Of the remaining six that formed gap junctions in mammalian cells, M195T and A197S formed stable hemichannels after isolation with a baculovirus/Sf9 protein purification system, while C202F, I203T, L205V and N206S formed hemichannels with varying degrees of instability. The function of all six gap junction-forming mutants was further assessed through measurement of dye coupling in mammalian cells and junctional conductance in paired Xenopus oocytes. Dye coupling between cell pairs was reduced by varying degrees for all six mutants. In homotypic oocyte pairings, only A197S induced measurable conductance. In heterotypic pairings with wild-type Cx26, five of the six mutants formed functional gap junction channels, albeit with reduced efficiency. None of the mutants displayed significant alterations in sensitivity to transjunctional voltage or induced conductive hemichannels in single oocytes. Intra-hemichannel interactions between mutant and wild-type proteins were assessed in rescue experiments using baculovirus expression in Sf9 insect cells. Of the four unstable mutations (C202F, I203T, L205V, N206S) only C202F and N206S formed stable hemichannels when co-expressed with wild-type Cx26. Stable M195T hemichannels displayed an increased

Observation of superconducting vortex clusters in S/F hybrids

DOE PAGES

Di Giorgio, C.; Bobba, F.; Cucolo, A. M.; ...

2016-12-09

While Abrikosov vortices repel each other and form a uniform vortex lattice in bulk type-II superconductors, strong confinement potential profoundly affects their spatial distribution eventually leading to vortex cluster formation. The confinement could be induced by the geometric boundaries in mesoscopic-size superconductors or by the spatial modulation of the magnetic field in superconductor/ ferromagnet (S/F) hybrids. Here we study the vortex confinement in S/F thin film heterostructures and we observe that vortex clusters appear near magnetization inhomogeneities in the ferromagnet, called bifurcations. We use magnetic force microscopy to image magnetic bifurcations and superconducting vortices, while high resolution scanning tunneling microscopymore » is used to obtain detailed information of the local electronic density of states outside and inside the vortex cluster. We find an intervortex spacing at the bifurcation shorter than the one predicted for the same superconductor in a uniform magnetic field equal to the thermodynamical upper critical field H c2. This result is due to a local enhanced stray field and a competition between vortex-vortex repulsion and Lorentz force. Here, our findings suggest that special magnetic topologies could result in S/F hybrids that support superconductivity even when locally the vortex density exceeds the thermodynamic critical threshold value beyond which the superconductivity is destroyed.« less

Observation of superconducting vortex clusters in S/F hybrids.

PubMed

Di Giorgio, C; Bobba, F; Cucolo, A M; Scarfato, A; Moore, S A; Karapetrov, G; D'Agostino, D; Novosad, V; Yefremenko, V; Iavarone, M

2016-12-09

While Abrikosov vortices repel each other and form a uniform vortex lattice in bulk type-II superconductors, strong confinement potential profoundly affects their spatial distribution eventually leading to vortex cluster formation. The confinement could be induced by the geometric boundaries in mesoscopic-size superconductors or by the spatial modulation of the magnetic field in superconductor/ferromagnet (S/F) hybrids. Here we study the vortex confinement in S/F thin film heterostructures and we observe that vortex clusters appear near magnetization inhomogeneities in the ferromagnet, called bifurcations. We use magnetic force microscopy to image magnetic bifurcations and superconducting vortices, while high resolution scanning tunneling microscopy is used to obtain detailed information of the local electronic density of states outside and inside the vortex cluster. We find an intervortex spacing at the bifurcation shorter than the one predicted for the same superconductor in a uniform magnetic field equal to the thermodynamical upper critical field H c2 . This result is due to a local enhanced stray field and a competition between vortex-vortex repulsion and Lorentz force. Our findings suggest that special magnetic topologies could result in S/F hybrids that support superconductivity even when locally the vortex density exceeds the thermodynamic critical threshold value beyond which the superconductivity is destroyed.

Observation of superconducting vortex clusters in S/F hybrids

PubMed Central

Di Giorgio, C.; Bobba, F.; Cucolo, A. M.; Scarfato, A.; Moore, S. A.; Karapetrov, G.; D’Agostino, D.; Novosad, V.; Yefremenko, V.; Iavarone, M.

2016-01-01

While Abrikosov vortices repel each other and form a uniform vortex lattice in bulk type-II superconductors, strong confinement potential profoundly affects their spatial distribution eventually leading to vortex cluster formation. The confinement could be induced by the geometric boundaries in mesoscopic-size superconductors or by the spatial modulation of the magnetic field in superconductor/ferromagnet (S/F) hybrids. Here we study the vortex confinement in S/F thin film heterostructures and we observe that vortex clusters appear near magnetization inhomogeneities in the ferromagnet, called bifurcations. We use magnetic force microscopy to image magnetic bifurcations and superconducting vortices, while high resolution scanning tunneling microscopy is used to obtain detailed information of the local electronic density of states outside and inside the vortex cluster. We find an intervortex spacing at the bifurcation shorter than the one predicted for the same superconductor in a uniform magnetic field equal to the thermodynamical upper critical field Hc2. This result is due to a local enhanced stray field and a competition between vortex-vortex repulsion and Lorentz force. Our findings suggest that special magnetic topologies could result in S/F hybrids that support superconductivity even when locally the vortex density exceeds the thermodynamic critical threshold value beyond which the superconductivity is destroyed. PMID:27934898

Nonreciprocal Microwave Signal Processing with a Field-Programmable Josephson Amplifier

NASA Astrophysics Data System (ADS)

Lecocq, F.; Ranzani, L.; Peterson, G. A.; Cicak, K.; Simmonds, R. W.; Teufel, J. D.; Aumentado, J.

2017-02-01

We report on the design and implementation of a field-programmable Josephson amplifier (FPJA)—a compact and lossless superconducting circuit that can be programmed in situ by a set of microwave drives to perform reciprocal and nonreciprocal frequency conversion and amplification. In this work, we demonstrate four modes of operation: frequency conversion (transmission of -0.5 dB, reflection of -30 dB), circulation (transmission of -0.5 dB, reflection of -30 dB, isolation of 30 dB), phase-preserving amplification (gain >20 dB , one photon of added noise) and directional phase-preserving amplification (reflection of -10 dB, forward gain of 18 dB, reverse isolation of 8 dB, one photon of added noise). The system exhibits quantitative agreement with the theoretical prediction. Based on a gradiometric superconducting quantum-interference device with Nb /Al -Al Ox/Nb Josephson junctions, the FPJA is first-order insensitive to flux noise and can be operated without magnetic shielding at low temperature. Owing to its flexible design and compatibility with existing superconducting fabrication techniques, the FPJA offers a straightforward route toward on-chip integration with superconducting quantum circuits such as qubits and microwave optomechanical systems.

Gas selectivity of SILAR grown CdS nano-bulk junction

NASA Astrophysics Data System (ADS)

Jayakrishnan, R.; Nair, Varun G.; Anand, Akhil M.; Venugopal, Meera

2018-03-01

Nano-particles of cadmium sulphide were deposited on cleaned copper substrate by an automated sequential ionic layer adsorption reaction (SILAR) system. The grown nano-bulk junction exhibits Schottky diode behavior. The response of the nano-bulk junction was investigated under oxygen and hydrogen atmospheric conditions. The gas response ratio was found to be 198% for Oxygen and 34% for Hydrogen at room temperature. An increase in the operating temperature of the nano-bulk junction resulted in a decrease in their gas response ratio. A logarithmic dependence on the oxygen partial pressure to the junction response was observed, indicating a Temkin isothermal behavior. Work function measurements using a Kelvin probe demonstrate that the exposure to an oxygen atmosphere fails to effectively separate the charges due to the built-in electric field at the interface. Based on the benefits like simple structure, ease of fabrication and response ratio the studied device is a promising candidate for gas detection applications.

27 CFR 21.92 - Denaturants listed as U.S.P. or N.F.

Code of Federal Regulations, 2010 CFR

2010-04-01

....P. or N.F. 21.92 Section 21.92 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND... for Denaturants § 21.92 Denaturants listed as U.S.P. or N.F. Denaturing materials and products listed in this part as “U.S.P.” or “N.F.” shall meet the specifications set forth in the current United...

27 CFR 21.92 - Denaturants listed as U.S.P. or N.F.

Code of Federal Regulations, 2014 CFR

2014-04-01

....P. or N.F. 21.92 Section 21.92 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND... for Denaturants § 21.92 Denaturants listed as U.S.P. or N.F. Denaturing materials and products listed in this part as “U.S.P.” or “N.F.” shall meet the specifications set forth in the current United...

27 CFR 21.92 - Denaturants listed as U.S.P. or N.F.

Code of Federal Regulations, 2011 CFR

2011-04-01

....P. or N.F. 21.92 Section 21.92 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND... for Denaturants § 21.92 Denaturants listed as U.S.P. or N.F. Denaturing materials and products listed in this part as “U.S.P.” or “N.F.” shall meet the specifications set forth in the current United...

27 CFR 21.92 - Denaturants listed as U.S.P. or N.F.

Code of Federal Regulations, 2013 CFR

2013-04-01

....P. or N.F. 21.92 Section 21.92 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND... for Denaturants § 21.92 Denaturants listed as U.S.P. or N.F. Denaturing materials and products listed in this part as “U.S.P.” or “N.F.” shall meet the specifications set forth in the current United...

27 CFR 21.92 - Denaturants listed as U.S.P. or N.F.

Code of Federal Regulations, 2012 CFR

2012-04-01

....P. or N.F. 21.92 Section 21.92 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND... for Denaturants § 21.92 Denaturants listed as U.S.P. or N.F. Denaturing materials and products listed in this part as “U.S.P.” or “N.F.” shall meet the specifications set forth in the current United...

77 FR 38744 - Airworthiness Directives; Sikorsky Aircraft-Manufactured Model S-64F Helicopters

Federal Register 2010, 2011, 2012, 2013, 2014

2012-06-29

... the Sikorsky Aircraft Corporation-manufactured Model S-64F helicopters, now under the Erickson Air-Crane Incorporated (Erickson) Model S-64F type certificate. That AD currently requires inspections... docket shortly after receipt. For service information identified in this proposed AD, contact Erickson...

Passive On-Chip Superconducting Circulator Using a Ring of Tunnel Junctions

NASA Astrophysics Data System (ADS)

Müller, Clemens; Guan, Shengwei; Vogt, Nicolas; Cole, Jared H.; Stace, Thomas M.

2018-05-01

We present the design of a passive, on-chip microwave circulator based on a ring of superconducting tunnel junctions. We investigate two distinct physical realizations, based on Josephson junctions (JJs) or quantum phase slip elements (QPS), with microwave ports coupled either capacitively (JJ) or inductively (QPS) to the ring structure. A constant bias applied to the center of the ring provides an effective symmetry breaking field, and no microwave or rf bias is required. We show that this design offers high isolation, robustness against fabrication imperfections and bias fluctuations, and a bandwidth in excess of 500 MHz for realistic device parameters.

Parametric Amplifier and Oscillator Based on Josephson Junction Circuitry

NASA Astrophysics Data System (ADS)

Yamamoto, T.; Koshino, K.; Nakamura, Y.

While the demand for low-noise amplification is ubiquitous, applications where the quantum-limited noise performance is indispensable are not very common. Microwave parametric amplifiers with near quantum-limited noise performance were first demonstrated more than 20 years ago. However, there had been little effort until recently to improve the performance or the ease of use of these amplifiers, partly because of a lack of any urgent motivation. The emergence of the field of quantum information processing in superconducting systems has changed this situation dramatically. The need to reliably read out the state of a given qubit using a very weak microwave probe within a very short time has led to renewed interest in these quantum-limited microwave amplifiers, which are already widely used as tools in this field. Here, we describe the quantum mechanical theory for one particular parametric amplifier design, called the flux-driven Josephson parametric amplifier, which we developed in 2008. The theory predicts the performance of this parametric amplifier, including its gain, bandwidth, and noise temperature. We also present the phase detection capability of this amplifier when it is operated with a pump power that is above the threshold, i.e., as a parametric phase-locked oscillator or parametron.

The Evolution of the Indian Ocean Triple Junction and the Finite Rotation Problem.

DTIC Science & Technology

1980-09-01

AD-AG&9 103 ~S HOLE OCEANOGRAPHIC INSTITUTION MASS F/6 6/7 THE EVOLUTION OF THE INDIAN OCEAN TRIPLE JUNCTION AND THE FINIT-ETC(U1 SEP 80 C R TAPSCOTT...1111flfl 1.4 111116 MICROCOPY RESOLUTION TEST CHART WHOI-80-37 THE EVOLUTION OF THE INDIAN OCEAN TRIPLE JUNCTION AND THE FINITE ROTATION PROBLEM by...purpose of the United States Government. This thesis should be cited as: Christopher R. Tapscott, 1979. The Evolution of the Indian Ocean Triple Junction

7. Historic American Buildings Survey Gleason Collection, S.F. College for ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

7. Historic American Buildings Survey Gleason Collection, S.F. College for Women San Francisco, California Original: 1850's Re-photo: March 1940 VIEW FROM SOUTHEAST - Mission San Antonio de Padua, Hunter Liggett Military Reservation, Jolon, Monterey County, CA

Thick Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} Films Grown by Liquid-Phase Epitaxy for Josephson THz Applications.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simsek, Y.; Vlasko-Vlasov, V.; Koshelev, A. E.

Theoretical and experimental studies of intrinsic Josephson junctions that naturally occur in high-Tc superconducting Bi2Sr2CaCu2O8+δ (Bi-2212) have demonstrated their potential for novel types of compact devices for the generation and sensing of electromagnetic radiation in the THz range. Here, we show that the THz-on-a-chip concept may be realized in liquid phase epitaxial-grown (LPE) thick Bi-2212 films. We have grown μm-thick Bi-2212 LPE films on MgO substrates. These films display excellent c-axis alignment and single crystal grains of about 650 × 150 μm2 in size. A branched current-voltage characteristic was clearly observed in c-axis transport, which is a clear signature ofmore » underdamped intrinsic Josephson junctions, and a prerequisite for THz-generation. We discuss LPE growth conditions allowing improvement of the structural quality and superconducting properties of Bi-2212 films for THz applications.« less

Blood-C.S.F. barriers dysfunction in the chronic organic brain syndrome; a R.I.A. study.

PubMed

Vardi, Y; Czerniak, P; Rabey, Y; Flechter, S; Boruchowsky, S; Streifler, M

1978-01-01

C.S.F. samples of 35 patients, who suffered from verified chronic, non-tumorous organic brain syndrome, were radioimmunoassayed for T4 and T.S.H., and were compared to C.S.F.-R.I.A. samples from a control group of patients who underwent myelography because of lumbar disc. In addition T4 and T.S.H. plasma levels were evaluated in the O.B.S. patients. C.S.F. T4 and T.S.H. levels were significantly higher in 65% of the O.B.S. group of patients than those of the control group. The average determinations for T4 were: 0.77 muh/100 ml in O.B.S. group as against 0--0.4 micrograms/100 ml in the C.S.F.'s of the control group. P greater than 0,001 T.S.H. C.S.F. levels were 1.33 microU/ml in the O.B.S. group, and 0--0.6 microU/ml in the control group (P greater than 0.005). It is suggested that the elevated R.I.A. values of these hormones in the C.S.F. of the O.B.S. patients reflect a disruption of blood-C.S.F. barriers. Therefore in the organic brain syndrome there seems to exist a pathophysiological dysfunction of brain barriers in addition of the neural damage.

Quasibound states in short SNS junctions with point defects

NASA Astrophysics Data System (ADS)

Bespalov, A. A.

2018-04-01

Using the Green functions technique, we study the subgap spectrum of short three-dimensional superconductor-normal metal-superconductor junctions containing one or two point impurities in the normal layer. We find that a single nonmagnetic or magnetic defect induces two quasibound Shiba-like states. If the defect is located close to the junction edge, the energies of these states oscillate as functions of the distance between the impurity and the edge. In the case of two nonmagnetic impurities, there are generally four quasibound states (two per spin projection). Their energies oscillate as functions of the distance between the impurities, and reach their asymptotic values when this distance becomes much larger than the Fermi wavelength. The contributions of the impurities to the Josephson current, local density of states, and to the normal-state conductance of the junction are analyzed.

78 FR 15599 - Airworthiness Directives; Sikorsky Aircraft-Manufactured Model S-64F Helicopters

Federal Register 2010, 2011, 2012, 2013, 2014

2013-03-12

... Erickson Air-Crane Incorporated (Erickson) Model S-64F type certificate. This AD supersedes an existing AD..., contact Erickson Air-Crane Incorporated, ATTN: Chris Erickson/Compliance Officer, 3100 Willow Springs Rd... Sikorsky Aircraft Corporation-manufactured Model S-64F helicopters, now under the Erickson Air-Crane...

Integrated Advanced Microwave Sounding Unit-A (AMSU-A). Performance Verification Report: METSAT (S/N 108) AMSU-A1 Receiver Assemblies, P/N 1356429-1 S/N F05 and P/N 1356409-1 S/N F05

NASA Technical Reports Server (NTRS)

Haigh, R.; Krimchansky, S. (Technical Monitor)

2000-01-01

This is the Performance Verification Report, METSAT (S/N 108) AMSU-A1 Receiver Assemblies P/N 1356429-1 S/N F05 and P/N 1356409-1 S/N F05, for the Integrated Advanced Microwave Sounding Unit-A (AMSU-A). The ATP for the AMSU-A Receiver Subsystem, AE-26002/6A, is prepared to describe in detail the configuration of the test setups and the procedures of the tests to verify that the receiver subsystem meets the specifications as required either in the AMSU-A Instrument Performance and Operation Specifications, S-480-80, or in AMSU-A Receiver Subsystem Specifications, AE-26608, derived by the Aerojet System Engineering. Test results that verify the conformance to the specifications demonstrate the acceptability of that particular receiver subsystem.

Molecular characterization of the Serratia marcescens OmpF porin, and analysis of S. marcescens OmpF and OmpC osmoregulation.

PubMed

Hutsul, J A; Worobec, E

1997-08-01

Serratia marcescens is a nosocomial pathogen with a high incidence of beta-lactam resistance. Reduced amounts of outer-membrane porins have been correlated with increased resistance to beta-lactams but only one porin, OmpC, has been characterized at the molecular level. In this study we present the molecular characterization of a second porin, OmpF, and an analysis of the expression of S. marcescens porins in response to various environmental changes. Two porins were isolated from the outer membrane using urea-SDS-PAGE and the relative amounts were shown to be influenced by the osmolarity of the medium and the presence of salicylate. From a S. marcescens genomic DNA library an 8 kb EcoRI fragment was isolated that hybridized with an oligonucleotide encoding the published N-terminal amino acid sequence of the S. marcescens 41 kDa porin. A 41 kDa protein was detected in the outer membrane of Escherichia coli NM522 carrying the cloned S. marcescens DNA. The cloned gene was sequenced and shown to code for a protein that shared 60-70% identity with other known OmpF and OmpC sequences. The upstream DNA sequence of the S. marcescens gene was similar to the corresponding E. coli ompF sequence; however, a regulatory element important in repression of E. coli ompF at high osmolarity was absent. The cloned S. marcescens OmpF in E. coli increased in expression in conditions of high osmolarity. The potential involvement of micF in the observed osmoregulation of S. marcescens porins is discussed.

Minimum entropy principle-based solar cell operation without a pn-junction and a thin CdS layer to extract the holes from the emitter

NASA Astrophysics Data System (ADS)

Böer, Karl W.

2016-10-01

The solar cell does not use a pn-junction to separate electrons from holes, but uses an undoped CdS layer that is p-type inverted when attached to a p-type collector and collects the holes while rejecting the backflow of electrons and thereby prevents junction leakage. The operation of the solar cell is determined by the minimum entropy principle of the cell and its external circuit that determines the electrochemical potential, i.e., the Fermi-level of the base electrode to the operating (maximum power point) voltage. It leaves the Fermi level of the metal electrode of the CdS unchanged, since CdS does not participate in the photo-emf. All photoelectric actions are generated by the holes excited from the light that causes the shift of the quasi-Fermi levels in the generator and supports the diffusion current in operating conditions. It is responsible for the measured solar maximum power current. The open circuit voltage (Voc) can approach its theoretical limit of the band gap of the collector at 0 K and the cell increases the efficiency at AM1 to 21% for a thin-film CdS/CdTe that is given as an example here. However, a series resistance of the CdS forces a limitation of its thickness to preferably below 200 Å to avoid unnecessary reduction in efficiency or Voc. The operation of the CdS solar cell does not involve heated carriers. It is initiated by the field at the CdS/CdTe interface that exceeds 20 kV/cm that is sufficient to cause extraction of holes by the CdS that is inverted to become p-type. Here a strong doubly charged intrinsic donor can cause a negative differential conductivity that switches-on a high-field domain that is stabilized by the minimum entropy principle and permits an efficient transport of the holes from the CdTe to the base electrode. Experimental results of the band model of CdS/CdTe solar cells are given and show that the conduction bands are connected in the dark, where the electron current must be continuous, and the valence bands are

Depth profile composition studies of thin film CdS:Cu2S solar cells using XPS and AES

NASA Astrophysics Data System (ADS)

Bhide, V. G.; Salkalachen, S.; Rastogi, A. C.; Rao, C. N. R.; Hegde, M. S.

1981-09-01

Studies of the surface composition and depth profiles of thin film CdS:Cu2S solar cells based on the techniques of X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) are reported. Specimens were fabricated by the thermal deposition of polycrystalline CdS films onto silver-backed electrodes predeposited on window glass substrates, followed by texturization in hot HCl and chemical plating in a hot CuCl(I) bath for a few seconds to achieve the topotaxial growth of CuS films. The XPS and AES studies indicate the junction to be fairly diffused in the as-prepared cell, with heat treatment in air at 210 C sharpening the junction, improving the stoichiometry of the Cu2S layer and thus improving cell performance. The top copper sulfide layer is found to contain impurities such as Cd, Cl, O and C, which may be removed by mild Ar(+) ion beam etching. The presence of copper deep in the junction is invariably detected, apparently in the grain boundary region in the form of CuS or Cu(2+) trapped in the lattice. It is also noted that the nominal valence state of copper changes abruptly from Cu(+) to Cu(2+) across the junction.

DNA double-strand break response factors influence end-joining features of IgH class switch and general translocation junctions.

PubMed

Panchakshari, Rohit A; Zhang, Xuefei; Kumar, Vipul; Du, Zhou; Wei, Pei-Chi; Kao, Jennifer; Dong, Junchao; Alt, Frederick W

2018-01-23

Ig heavy chain (IgH) class switch recombination (CSR) in B lymphocytes switches IgH constant regions to change antibody functions. CSR is initiated by DNA double-strand breaks (DSBs) within a donor IgH switch (S) region and a downstream acceptor S region. CSR is completed by fusing donor and acceptor S region DSB ends by classical nonhomologous end-joining (C-NHEJ) and, in its absence, by alternative end-joining that is more biased to use longer junctional microhomologies (MHs). Deficiency for DSB response (DSBR) factors, including ataxia telangiectasia-mutated (ATM) and 53BP1, variably impair CSR end-joining, with 53BP1 deficiency having the greatest impact. However, studies of potential impact of DSBR factor deficiencies on MH-mediated CSR end-joining have been technically limited. We now use a robust DSB joining assay to elucidate impacts of deficiencies for DSBR factors on CSR and chromosomal translocation junctions in primary mouse B cells and CH12F3 B-lymphoma cells. Compared with wild-type, CSR and c-myc to S region translocation junctions in the absence of 53BP1, and, to a lesser extent, other DSBR factors, have increased MH utilization; indeed, 53BP1-deficient MH profiles resemble those associated with C-NHEJ deficiency. However, translocation junctions between c-myc DSB and general DSBs genome-wide are not MH-biased in ATM-deficient versus wild-type CH12F3 cells and are less biased in 53BP1- and C-NHEJ-deficient cells than CSR junctions or c-myc to S region translocation junctions. We discuss potential roles of DSBR factors in suppressing increased MH-mediated DSB end-joining and features of S regions that may render their DSBs prone to MH-biased end-joining in the absence of DSBR factors.

Development of a 6LiF/ZnS-based Neutron Multiplicity Counter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stave, Sean C.; Behling, Richard S.; Bernacki, Bruce E.

2016-10-06

Abstract–Neutron multiplicity counters are used in safeguards to provide rapid assay of samples which contain an unknown amount of plutonium in a potentially unknown configuration. A project at PNNL is using regular and nickel-quenched 6LiF/ZnS neutron-scintillator sheets and wavelength shifting plastic for light pipes in place of 3He. A combination of laboratory and modeling work predicts a LiF/ZnS-based system to be able to match or exceed the performance of the best 3He-based systems available. Also, the Ni-quenched material is expected to allow for improved neutron/gamma-ray discrimination at twice the event rate relative to the non-Ni-quenched LiF/ZnS. A new system basedmore » on the LiF/ZnS material is under construction and components are being used to optimize the detection efficiency and neutron/gamma-ray discrimination properties. Components of the new system are partially constructed and undergoing performance testing utilizing high-speed digitizers with field programmable gate arrays to perform the neutron/gamma-ray discrimination. The expected performance of the full-scale system is expected to be nearly the same as for 3He-based systems and is due for completion in 2016.« less

Intrinsic Josephson junctions in mesas and ultrathin BSCCO single crystals: Ultimate control of shape and dimensions

NASA Astrophysics Data System (ADS)

Yurgens, A.; You, L. X.; Torstensson, M.; Winkler, D.

2007-09-01

We describe experiments which are only possible through an ultimate control of sample shape and dimensions down to nanometer scale whereby transport measurements can be done in various restricted geometries. We use photolithography patterning together with a flip-chip technique to isolate very thin (d ∼ 100 nm) pieces of Bi2Sr2CaCu2O8+δ (BSCCO) single crystals. Ar-ion milling allows us to further thin these crystals down to a few nanometers in a controlled way. With decreasing thickness below two to three unit cells, the superconducting transition temperature gradually decreases to zero and the in-plane resistivity increases to large values indicating the existence of a superconductor-insulator transition in these ultrathin single crystals. In a refined technique, a precise control of the etching depth from both sides of the crystal makes it possible to form stacks of intrinsic Josephson junctions (IJJs) inside the ultrathin single crystals. The stacks can be tailor-made to any microscopic height (0-9 nm < d), i.e. enclosing a specific number of IJJs (0-6). In certain geometries, by feeding current into the topmost Cu2O4-layer of a mesa on the surface of a BSCCO single crystal, we measured the critical value of this current by detecting a sharp upturn or break in the current-voltage characteristics. From this, we estimate the sheet critical current density of a single Cu2O4 plane to be ∼0.3-0.7 A/cm at 4.5 K, corresponding to a bulk current density of ∼2-5 MA/cm2. These values are among the largest ever reported for BSCCO single crystals, thin-films and tapes.

CF₃CF₂N=S(F)CF₃: vibrational spectra and conformational properties.

PubMed

Robles, Norma L; Oberhammer, Heinz; Mews, Rüdiger; Cutin, Edgardo H

2014-05-05

The structural, conformational, and configurational properties of 1,1,1-trifluoro-N-(1,1,2,2,2-pentafluoroethyl) methanesulfinimidoyl fluoride, CF3CF2N=S(F)CF3 have been studied by vibrational spectroscopy [IR (vapor) and Raman (liquid)] and quantum chemical calculations [B3LYP, MP2 and B3PW91 levels of theory (using the 6-311+G(d) and 6-311+G(2df) basis sets). According to these theoretical approximations, CF3CF2N=S(F)CF3 might be found in the gas phase as a mixture of a favoured anticlinal form (C-N bond anticlinal with respect to the C-S-F bisector angle) and a less abundant syn conformer showing C1 symmetry as well (ΔG°≈1.5 kcal mol(-1)). However, corresponding vibrational modes for these conformers show only small shifts which would not allow confidently detecting the rather small contribution of this second form in the experimental spectra. Copyright © 2014 Elsevier B.V. All rights reserved.

Reproducible fabrication and applications of superconducting scanning tunneling microscope tips

NASA Astrophysics Data System (ADS)

Naaman, Ofer; Teizer, Winfried; Dynes, Robert C.

2001-03-01

We report on a method developed in our lab, for the fabrication of superconducting scanning tunneling microscope (STM) tips in a reproducible fashion. The fabrication process relies on sequential deposition of superconducting Pb and a proximity-coupled Ag capping layer onto a Pt/Ir tip. The tips were characterized by tunneling into both normal-metal and superconducting films, and the results confirm that the tips are superconducting with Tc and Δ close to that of bulk lead. The lead phonon structure in the tunneling density of states was observed, indicating a single step tunneling process. In an attempt to form STM Josephson junctions, we used our tips to form S/I/S junctions with R_NN ~50-100 kΩ. Results from spectroscopic measurements of these junctions at 2.0 K are discussed within the framework of the Ivanchenko and Zil'berman theory (Soviet Physics JETP, vol.28, 1272; 1969) of Josephson tunneling in the presence of strong phase fluctuations.

Electron Spin Relaxation and Biochemical Characterization of the Hydrogenase Maturase HydF: Insights into [2Fe-2S] and [4Fe-4S] Cluster Communication and Hydrogenase Activation.

PubMed

Shepard, Eric M; Byer, Amanda S; Aggarwal, Priyanka; Betz, Jeremiah N; Scott, Anna G; Shisler, Krista A; Usselman, Robert J; Eaton, Gareth R; Eaton, Sandra S; Broderick, Joan B

2017-06-27

Nature utilizes [FeFe]-hydrogenase enzymes to catalyze the interconversion between H 2 and protons and electrons. Catalysis occurs at the H-cluster, a carbon monoxide-, cyanide-, and dithiomethylamine-coordinated 2Fe subcluster bridged via a cysteine to a [4Fe-4S] cluster. Biosynthesis of this unique metallocofactor is accomplished by three maturase enzymes denoted HydE, HydF, and HydG. HydE and HydG belong to the radical S-adenosylmethionine superfamily of enzymes and synthesize the nonprotein ligands of the H-cluster. These enzymes interact with HydF, a GTPase that acts as a scaffold or carrier protein during 2Fe subcluster assembly. Prior characterization of HydF demonstrated the protein exists in both dimeric and tetrameric states and coordinates both [4Fe-4S] 2+/+ and [2Fe-2S] 2+/+ clusters [Shepard, E. M., Byer, A. S., Betz, J. N., Peters, J. W., and Broderick, J. B. (2016) Biochemistry 55, 3514-3527]. Herein, electron paramagnetic resonance (EPR) is utilized to characterize the [2Fe-2S] + and [4Fe-4S] + clusters bound to HydF. Examination of spin relaxation times using pulsed EPR in HydF samples exhibiting both [4Fe-4S] + and [2Fe-2S] + cluster EPR signals supports a model in which the two cluster types either are bound to widely separated sites on HydF or are not simultaneously bound to a single HydF species. Gel filtration chromatographic analyses of HydF spectroscopic samples strongly suggest the [2Fe-2S] + and [4Fe-4S] + clusters are coordinated to the dimeric form of the protein. Lastly, we examined the 2Fe subcluster-loaded form of HydF and showed the dimeric state is responsible for [FeFe]-hydrogenase activation. Together, the results indicate a specific role for the HydF dimer in the H-cluster biosynthesis pathway.

Unconventional Superconductivity in the BiS_{2}-Based Layered Superconductor NdO_{0.71}F_{0.29}BiS_{2}.

PubMed

Ota, Yuichi; Okazaki, Kozo; Yamamoto, Haruyoshi Q; Yamamoto, Takashi; Watanabe, Shuntaro; Chen, Chuangtian; Nagao, Masanori; Watauchi, Satoshi; Tanaka, Isao; Takano, Yoshihiko; Shin, Shik

2017-04-21

We investigate the superconducting-gap anisotropy in one of the recently discovered BiS_{2}-based superconductors, NdO_{0.71}F_{0.29}BiS_{2} (T_{c}∼5  K), using laser-based angle-resolved photoemission spectroscopy. Whereas the previously discovered high-T_{c} superconductors such as copper oxides and iron-based superconductors, which are believed to have unconventional superconducting mechanisms, have 3d electrons in their conduction bands, the conduction band of BiS_{2}-based superconductors mainly consists of Bi 6p electrons, and, hence, the conventional superconducting mechanism might be expected. Contrary to this expectation, we observe a strongly anisotropic superconducting gap. This result strongly suggests that the pairing mechanism for NdO_{0.71}F_{0.29}BiS_{2} is an unconventional one and we attribute the observed anisotropy to competitive or cooperative multiple paring interactions.

Pulse-Shape Analysis of Neutron-Induced Scintillation Light in Ni-doped 6LiF/ZnS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cowles, Christian C.; Behling, Richard S.; Imel, G. R.

Abstract–Alternatives to 3He are being investigated for gamma-ray insensitive neutron detection applications, including plutonium assay. One promising material is lithium-6 fluoride with silver activated zinc sulfide 6LiF/ZnS(Ag) in conjunction with a wavelength shifting plastic. Doping the 6LiF/ZnS(Ag) with nickel (Ni) has been proposed as a means of reducing the decay time of neutron signal pulses. This research performed a pulse shape comparison between Ni-doped and non-doped 6LiF/ZnS(Ag) neutron pulses. The Ni-doped 6LiF/ZnS(Ag) had a 32.7% ± 0.3 increase in neutron pulse height and a 32.4% ± 0.3 decrease in neutron pulse time compared to the non-doped 6LiF/ZnS(Ag). Doping 6LiF/ZnS(Ag) withmore » nickel may allow neutron detector operation with improved signal to noise ratios, and reduced pulse pileup affects, increasing the accuracy and range of source activities with which such a detector could operate.« less

The Peptidoglycan-Binding Protein SjcF1 Influences Septal Junction Function and Channel Formation in the Filamentous Cyanobacterium Anabaena.

PubMed

Rudolf, Mareike; Tetik, Nalan; Ramos-León, Félix; Flinner, Nadine; Ngo, Giang; Stevanovic, Mara; Burnat, Mireia; Pernil, Rafael; Flores, Enrique; Schleiff, Enrico

2015-06-30

Filamentous, heterocyst-forming cyanobacteria exchange nutrients and regulators between cells for diazotrophic growth. Two alternative modes of exchange have been discussed involving transport either through the periplasm or through septal junctions linking adjacent cells. Septal junctions and channels in the septal peptidoglycan are likely filled with septal junction complexes. While possible proteinaceous factors involved in septal junction formation, SepJ (FraG), FraC, and FraD, have been identified, little is known about peptidoglycan channel formation and septal junction complex anchoring to the peptidoglycan. We describe a factor, SjcF1, involved in regulation of septal junction channel formation in the heterocyst-forming cyanobacterium Anabaena sp. strain PCC 7120. SjcF1 interacts with the peptidoglycan layer through two peptidoglycan-binding domains and is localized throughout the cell periphery but at higher levels in the intercellular septa. A strain with an insertion in sjcF1 was not affected in peptidoglycan synthesis but showed an altered morphology of the septal peptidoglycan channels, which were significantly wider in the mutant than in the wild type. The mutant was impaired in intercellular exchange of a fluorescent probe to a similar extent as a sepJ deletion mutant. SjcF1 additionally bears an SH3 domain for protein-protein interactions. SH3 binding domains were identified in SepJ and FraC, and evidence for interaction of SjcF1 with both SepJ and FraC was obtained. SjcF1 represents a novel protein involved in structuring the peptidoglycan layer, which links peptidoglycan channel formation to septal junction complex function in multicellular cyanobacteria. Nonetheless, based on its subcellular distribution, this might not be the only function of SjcF1. Cell-cell communication is central not only for eukaryotic but also for multicellular prokaryotic systems. Principles of intercellular communication are well established for eukaryotes, but the

2. Historic American Buildings Survey Gleason Collection S.F. College ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

2. Historic American Buildings Survey Gleason Collection - S.F. College for Women Taken about: 1870 TOWER RESTORED AFTER EARTHQUAKE OF 1868 - John Marsh House, Marsh Creek Road, Brentwood, Contra Costa County, CA

Measurement of the decay constant f(Ds+) using D(s+)-->l+ nu.

PubMed

Artuso, M; Blusk, S; Butt, J; Khalil, S; Li, J; Menaa, N; Mountain, R; Nisar, S; Randrianarivony, K; Sia, R; Skwarnicki, T; Stone, S; Wang, J C; Bonvicini, G; Cinabro, D; Dubrovin, M; Lincoln, A; Asner, D M; Edwards, K W; Naik, P; Briere, R A; Ferguson, T; Tatishvili, G; Vogel, H; Watkins, M E; Rosner, J L; Adam, N E; Alexander, J P; Cassel, D G; Duboscq, J E; Ehrlich, R; Fields, L; Gibbons, L; Gray, R; Gray, S W; Hartill, D L; Heltsley, B K; Hertz, D; Jones, C D; Kandaswamy, J; Kreinick, D L; Kuznetsov, V E; Mahlke-Krüger, H; Mohapatra, D; Onyisi, P U E; Patterson, J R; Peterson, D; Pivarski, J; Riley, D; Ryd, A; Sadoff, A J; Schwarthoff, H; Shi, X; Stroiney, S; Sun, W M; Wilksen, T; Athar, S B; Patel, R; Yelton, J; Rubin, P; Cawlfield, C; Eisenstein, B I; Karliner, I; Kim, D; Lowrey, N; Selen, M; White, E J; Wiss, J; Mitchell, R E; Shepherd, M R; Besson, D; Pedlar, T K; Cronin-Hennessy, D; Gao, K Y; Hietala, J; Kubota, Y; Klein, T; Lang, B W; Poling, R; Scott, A W; Smith, A; Zweber, P; Dobbs, S; Metreveli, Z; Seth, K K; Tomaradze, A; Ernst, J; Ecklund, K M; Severini, H; Love, W; Savinov, V; Aquines, O; Lopez, A; Mehrabyan, S; Mendez, H; Ramirez, J; Huang, G S; Miller, D H; Pavlunin, V; Sanghi, B; Shipsey, I P J; Xin, B; Adams, G S; Anderson, M; Cummings, J P; Danko, I; Hu, D; Moziak, B; Napolitano, J; He, Q; Insler, J; Muramatsu, H; Park, C S; Thorndike, E H; Yang, F

2007-08-17

We measure the decay constant f(Ds+) using the D(s+)-->l+ nu channel, where the l+ designates either a mu+ or a tau+, when the tau+ -->pi+ nu. Using both measurements we find f(Ds+)=274+/-13+/-7 MeV. Combining with our previous determination of f(D+), we compute the ratio f(Ds+)/f(D+)=1.23+/-0.11+/-0.04. We compare with theoretical estimates.

Electron Spin Relaxation and Biochemical Characterization of the Hydrogenase Maturase HydF: Insights into [2Fe-2S] and [4Fe-4S] Cluster Communication and Hydrogenase Activation

PubMed Central

2017-01-01

Nature utilizes [FeFe]-hydrogenase enzymes to catalyze the interconversion between H2 and protons and electrons. Catalysis occurs at the H-cluster, a carbon monoxide-, cyanide-, and dithiomethylamine-coordinated 2Fe subcluster bridged via a cysteine to a [4Fe-4S] cluster. Biosynthesis of this unique metallocofactor is accomplished by three maturase enzymes denoted HydE, HydF, and HydG. HydE and HydG belong to the radical S-adenosylmethionine superfamily of enzymes and synthesize the nonprotein ligands of the H-cluster. These enzymes interact with HydF, a GTPase that acts as a scaffold or carrier protein during 2Fe subcluster assembly. Prior characterization of HydF demonstrated the protein exists in both dimeric and tetrameric states and coordinates both [4Fe-4S]2+/+ and [2Fe-2S]2+/+ clusters [Shepard, E. M., Byer, A. S., Betz, J. N., Peters, J. W., and Broderick, J. B. (2016) Biochemistry 55, 3514–3527]. Herein, electron paramagnetic resonance (EPR) is utilized to characterize the [2Fe-2S]+ and [4Fe-4S]+ clusters bound to HydF. Examination of spin relaxation times using pulsed EPR in HydF samples exhibiting both [4Fe-4S]+ and [2Fe-2S]+ cluster EPR signals supports a model in which the two cluster types either are bound to widely separated sites on HydF or are not simultaneously bound to a single HydF species. Gel filtration chromatographic analyses of HydF spectroscopic samples strongly suggest the [2Fe-2S]+ and [4Fe-4S]+ clusters are coordinated to the dimeric form of the protein. Lastly, we examined the 2Fe subcluster-loaded form of HydF and showed the dimeric state is responsible for [FeFe]-hydrogenase activation. Together, the results indicate a specific role for the HydF dimer in the H-cluster biosynthesis pathway. PMID:28525271

76 FR 66617 - Airworthiness Directives; Erickson Air-Crane Incorporated Model S-64F Helicopters

Federal Register 2010, 2011, 2012, 2013, 2014

2011-10-27

... Airworthiness Directives; Erickson Air-Crane Incorporated Model S-64F Helicopters AGENCY: Federal Aviation... the Erickson Air-Crane (Erickson Air-Crane) Model S-64F helicopters. The amendment requires, at..., contact Erickson Air-Crane Incorporated, 3100 Willow Springs Road, P.O. Box 3247, Central Point, OR 97502...

Manifestation of intra-atomic 5d6s-4f exchange coupling in photoexcited gadolinium

NASA Astrophysics Data System (ADS)

Zhang, G. P.; Jenkins, T.; Bennett, M.; Bai, Y. H.

2017-12-01

Intra-atomic exchange couplings (IECs) between 5d6s and 4f electrons are ubiquitous in rare-earth metals and play a critical role in spin dynamics. However, detecting them in real time domain has been difficult. Here we show the direct evidence of IEC between 5d6s and 4f electrons in gadolinium. Upon femtosecond laser excitation, 5d6s electrons are directly excited; their majority bands shift toward the Fermi level while their minority bands do the opposite. For the first time, our first-principles minority shift now agrees with the experiment quantitatively. Excited 5d6s electrons lower the exchange potential barrier for 4f electrons, so the 4f states are also shifted in energy, a prediction that can be tested experimentally. Although a significant number of 5d6s electrons, some several eV below the Fermi level, are excited out of the Fermi sea, there is no change in the 4f states, a clear manifestation of intra-atomic exchange coupling.

Development of High Temperature Superconducting Josephson Junction Device Technology

DTIC Science & Technology

1998-07-09

neodymium gallate , cerium oxide-buffered sapphire, and lanthanum aluminate, are not ideal for an in situ thallium cuprate junction technology. Moreover...determined that the standard HTS substrates, neodymium gallate , cerium oxide-buffered sapphire, and lanthanum aluminate, are not ideal for an in situ...2.2.1. Deposition Uniformity 10 2.2.2. Radiative Element 12 2.3. SUBSTRATES 13 2.3.1. Neodymium gallate 14 2.3.2. Cerium Oxide-Buffered Sapphire 16

S-factor of 14 N (α, γ)18 F reaction at low-energies

NASA Astrophysics Data System (ADS)

Khalili, H.

2018-06-01

The astrophysical S-factor of the 14 N (α, γ)18 F reaction has been studied at range of bombarding energy 1-1.30 MeV. The 14 N (α, γ)18 F process is important in low energy astrophysics so that a possible source of energy in massive stars which have spent their hydrogen cycle. Using the Wood-saxon potential model, we have been calculated non resonances the astrophysical S-factors for the E 2 transition and our results for Eα = 0.0 MeV is S ≈ 0.5 MeV.b where from experimental is measured to Eα = 0.0 is S ≈ o . 7 MeV.b (Couch et al., 1971) that in comparison with our data good agreement is achieved for the astrophysical S-factor of this process.

Circulation and Directional Amplification in the Josephson Parametric Converter

NASA Astrophysics Data System (ADS)

Hatridge, Michael

Nonreciprocal transport and directional amplification of weak microwave signals are fundamental ingredients in performing efficient measurements of quantum states of flying microwave light. This challenge has been partly met, as quantum-limited amplification is now regularly achieved with parametrically-driven, Josephson-junction based superconducting circuits. However, these devices are typically non-directional, requiring external circulators to separate incoming and outgoing signals. Recently this limitation has been overcome by several proposals and experimental realizations of both directional amplifiers and circulators based on interference between several parametric processes in a single device. This new class of multi-parametrically driven devices holds the promise of achieving a variety of desirable characteristics simultaneously- directionality, reduced gain-bandwidth constraints and quantum-limited added noise, and are good candidates for on-chip integration with other superconducting circuits such as qubits.

Alanine and glycine conjugates of (2S,4R)-4-[18F]fluoroglutamine for tumor imaging.

PubMed

Zha, Zhihao; Ploessl, Karl; Lieberman, Brian P; Wang, Limin; Kung, Hank F

2018-05-01

Glutamine is an essential source of energy, metabolic substrates, and building block for supporting tumor proliferation. Previously, (2S,4R)-4-[ 18 F]fluoroglutamine (4F-Gln) was reported as a glutamine-related metabolic imaging agent. To improve the in vivo kinetics of this radiotracer, two new dipeptides, [ 18 F]Gly-(2S,4R)4-fluoroglutamine (Gly-4F-Gln) and [ 18 F]Ala-(2S,4R)4-fluoroglutamine (Ala-4F-Gln) were investigated. Radiolabeling was performed via 2-steps 18 F-fluorination. Cell uptake studies of Gly-4F-Gln and Ala-4F-Gln were investigated in 9 L cell lines. In vitro and in vivo metabolism studies were carried out in Fisher 344 rats. Biodistribution and microPET imaging studies were performed in 9 L tumor-bearing rats. In vitro incubation of these [ 18 F]dipeptides in rat and human blood showed a rapid conversion to (2S,4R)-4-[ 18 F]fluoroglutamine (t 1/2  = 2.3 and 0.2 min for [ 18 F]Gly-4F-Gln and [ 18 F]Ala-4F-Gln, respectively for human blood). Biodistribution and PET imaging in Fisher 344 rats bearing 9 L tumor xenografts showed that these dipeptides rapidly localized in the tumors, comparable to that of (2S,4R)-4-[ 18 F]fluoroglutamine (4F-Gln). The results support that these dipeptides, [ 18 F]Gly-4F-Gln and [ 18 F]Ala-4F-Gln, are prodrugs, which hydrolyze in the blood after an iv injection. They appear to be selectively taken up and trapped by tumor tissue in vivo. The dipeptide, [ 18 F]Ala-4F-Gln, may be suitable as a PET tracer for imaging glutaminolysis in tumors. Copyright © 2018 Elsevier Inc. All rights reserved.

Uterine inactivation of muscle segment homeobox (Msx) genes alters epithelial cell junction proteins during embryo implantation

PubMed Central

Sun, Xiaofei; Park, Craig B.; Deng, Wenbo; Potter, S. Steven; Dey, Sudhansu K.

2016-01-01

Embryo implantation requires that the uterus differentiate into the receptive state. Failure to attain uterine receptivity will impede blastocyst attachment and result in a compromised pregnancy. The molecular mechanism by which the uterus transitions from the prereceptive to the receptive stage is complex, involving an intricate interplay of various molecules. We recently found that mice with uterine deletion of Msx genes (Msx1d/d/Msx2d/d) are infertile because of implantation failure associated with heightened apicobasal polarity of luminal epithelial cells during the receptive period. However, information on Msx’s roles in regulating epithelial polarity remains limited. To gain further insight, we analyzed cell-type–specific gene expression by RNA sequencing of separated luminal epithelial and stromal cells by laser capture microdissection from Msx1d/d/Msx2d/d and floxed mouse uteri on d 4 of pseudopregnancy. We found that claudin-1, a tight junction protein, and small proline-rich (Sprr2) protein, a major component of cornified envelopes in keratinized epidermis, were substantially up-regulated in Msx1d/d/Msx2d/d uterine epithelia. These factors also exhibited unique epithelial expression patterns at the implantation chamber (crypt) in Msx1f/f/Msx2f/f females; the patterns were lost in Msx1d/d/Msx2d/d epithelia on d 5, suggesting important roles during implantation. The results suggest that Msx genes play important roles during uterine receptivity including modulation of epithelial junctional activity.—Sun, X., Park, C. B., Deng, W., Potter, S. S., Dey, S. K. Uterine inactivation of muscle segment homeobox (Msx) genes alters epithelial cell junction proteins during embryo implantation. PMID:26667042

Loss-of-function and gain-of-function phenotypes of stomatocytosis mutant RhAG F65S

PubMed Central

Stewart, Andrew K.; Shmukler, Boris E.; Vandorpe, David H.; Rivera, Alicia; Heneghan, John F.; Li, Xiaojin; Hsu, Ann; Karpatkin, Margaret; O'Neill, Allison F.; Bauer, Daniel E.; Heeney, Matthew M.; John, Kathryn; Kuypers, Frans A.; Gallagher, Patrick G.; Lux, Samuel E.; Brugnara, Carlo; Westhoff, Connie M.

2011-01-01

Four patients with overhydrated cation leak stomatocytosis (OHSt) exhibited the heterozygous RhAG missense mutation F65S. OHSt erythrocytes were osmotically fragile, with elevated Na and decreased K contents and increased cation channel-like activity. Xenopus oocytes expressing wild-type RhAG and RhAG F65S exhibited increased ouabain and bumetanide-resistant uptake of Li+ and 86Rb+, with secondarily increased 86Rb+ influx sensitive to ouabain and to bumetanide. Increased RhAG-associated 14C-methylammonium (MA) influx was severely reduced in RhAG F65S-expressing oocytes. RhAG-associated influxes of Li+, 86Rb+, and 14C-MA were pharmacologically distinct, and Li+ uptakes associated with RhAG and RhAG F65S were differentially inhibited by NH4+ and Gd3+. RhAG-expressing oocytes were acidified and depolarized by 5 mM bath NH3/NH4+, but alkalinized and depolarized by subsequent bath exposure to 5 mM methylammonium chloride (MA/MA+). RhAG F65S-expressing oocytes exhibited near-wild-type responses to NH4Cl, but MA/MA+ elicited attenuated alkalinization and strong hyperpolarization. Expression of RhAG or RhAG F65S increased steady-state cation currents unaltered by bath Li+ substitution or bath addition of 5 mM NH4Cl or MA/MA+. These oocyte studies suggest that 1) RhAG expression increases oocyte transport of NH3/NH4+ and MA/MA+; 2) RhAG F65S exhibits gain-of-function phenotypes of increased cation conductance/permeability, and loss-of-function phenotypes of decreased and modified MA/MA+ transport, and decreased NH3/NH4+-associated depolarization; and 3) RhAG transports NH3/NH4+ and MA/MA+ by distinct mechanisms, and/or the substrates elicit distinct cellular responses. Thus, RhAG F65S is a loss-of-function mutation for amine transport. The altered oocyte intracellular pH, membrane potential, and currents associated with RhAG or RhAG F65S expression may reflect distinct transport mechanisms. PMID:21849667

ZnO:Zn/6LiF scintillator-A low afterglow alternative to ZnS:Ag/6LiF for thermal neutron detection

NASA Astrophysics Data System (ADS)

Sykora, G. Jeff; Schooneveld, Erik M.; Rhodes, Nigel J.

2018-03-01

Current ZnS:Ag/6LiF based scintillation detectors are often count rate limited by the long lifetime afterglow in the scintillator. Despite this drawback, new instruments at neutron scattering facilities, like ISIS in the UK, would still like to use ZnS:Ag/6LiF detectors due to their low gamma sensitivity, high light output, simplicity of detector design and relatively inexpensive production. One particular advantage of ZnS:Ag/6LiF detectors is their ability to provide strong pulse shape discrimination between neutrons and gammas. Despite the advantages of these detectors, it is becoming clear that new and upgraded instruments will be limited by the count rate capability of ZnS:Ag/6LiF, so an alternative scintillator technology with equivalent simplicity is being sought. ZnO:Zn/6LiF is investigated here as a low afterglow alternative to ZnS:Ag/6LiF. Basic scintillation properties of ZnO:Zn are studied and are discussed. Pulse shape discrimination between neutrons and gammas is explored and taken advantage of through simple single photon counting methods. A further step toward a realistic detector for neutron scattering is also taken by fiber coupling the ZnO:Zn/6LiF to a PMT. In an initial study of this fiber coupled configuration, 60Co gamma sensitivity of ∼ 7 × 10-6 is shown and improvements in count rate capability of at least a factor of 6 over ZnS:Ag/6LiF based neutron detectors are demonstrated.

Antiferromagnetic THz-frequency Josephson-like Oscillator Driven by Spin Current.

PubMed

Khymyn, Roman; Lisenkov, Ivan; Tiberkevich, Vasyl; Ivanov, Boris A; Slavin, Andrei

2017-03-06

The development of compact and tunable room temperature sources of coherent THz-frequency signals would open a way for numerous new applications. The existing approaches to THz-frequency generation based on superconductor Josephson junctions (JJ), free electron lasers, and quantum cascades require cryogenic temperatures or/and complex setups, preventing the miniaturization and wide use of these devices. We demonstrate theoretically that a bi-layer of a heavy metal (Pt) and a bi-axial antiferromagnetic (AFM) dielectric (NiO) can be a source of a coherent THz signal. A spin-current flowing from a DC-current-driven Pt layer and polarized along the hard AFM anisotropy axis excites a non-uniform in time precession of magnetizations sublattices in the AFM, due to the presence of a weak easy-plane AFM anisotropy. The frequency of the AFM oscillations varies in the range of 0.1-2.0 THz with the driving current in the Pt layer from 10 8  A/cm 2 to 10 9  A/cm 2 . The THz-frequency signal from the AFM with the amplitude exceeding 1 V/cm is picked up by the inverse spin-Hall effect in Pt. The operation of a room-temperature AFM THz-frequency oscillator is similar to that of a cryogenic JJ oscillator, with the energy of the easy-plane magnetic anisotropy playing the role of the Josephson energy.

Antiferromagnetic THz-frequency Josephson-like Oscillator Driven by Spin Current

NASA Astrophysics Data System (ADS)

Khymyn, Roman; Lisenkov, Ivan; Tiberkevich, Vasyl; Ivanov, Boris A.; Slavin, Andrei

2017-03-01

The development of compact and tunable room temperature sources of coherent THz-frequency signals would open a way for numerous new applications. The existing approaches to THz-frequency generation based on superconductor Josephson junctions (JJ), free electron lasers, and quantum cascades require cryogenic temperatures or/and complex setups, preventing the miniaturization and wide use of these devices. We demonstrate theoretically that a bi-layer of a heavy metal (Pt) and a bi-axial antiferromagnetic (AFM) dielectric (NiO) can be a source of a coherent THz signal. A spin-current flowing from a DC-current-driven Pt layer and polarized along the hard AFM anisotropy axis excites a non-uniform in time precession of magnetizations sublattices in the AFM, due to the presence of a weak easy-plane AFM anisotropy. The frequency of the AFM oscillations varies in the range of 0.1-2.0 THz with the driving current in the Pt layer from 108 A/cm2 to 109 A/cm2. The THz-frequency signal from the AFM with the amplitude exceeding 1 V/cm is picked up by the inverse spin-Hall effect in Pt. The operation of a room-temperature AFM THz-frequency oscillator is similar to that of a cryogenic JJ oscillator, with the energy of the easy-plane magnetic anisotropy playing the role of the Josephson energy.

Fabrication of Josephson Tunnel Junctions by Reactive Ion Milling.

DTIC Science & Technology

1980-07-21

the existence of numerous oxide phases. in addition to Vb2 05 , which is the desired tunneling barrier, NbO2 , NbO, and various suboxides can form, as...interface between Nb and Vb2 0 5 in therally grown oxide films consists of RHO and RHO 2 , and poor Junction quality has been attrib- uted to such...are believed to be important in rf plasma oxidation (3), but they are not extracted by the grids of the ion mill. Beats of formation of posLtive

S-F graphic representation analysis of photoelectric facula focometer poroo-plate glass

NASA Astrophysics Data System (ADS)

Tong, Yilin; Han, Xuecai

2016-10-01

Optical system focal length is usually based on the magnification method with focal length measurement poroo-plate glass is used as base element measuring focal length of focometer. On the basis of using analysis of magnification method to measure the accuracy of optical lens focal length, an expression between the ruling span of poroo-plate glass and the focal length of measured optical system was deduced, an efficient method to work out S-F graph with AUTOCAD was developed, the selecting principle of focometer parameter was analyzed, and Applied examples for designing poroo-plate glass in S-F figure was obtained.

Structure and migration in U.S. Blumeria graminis f. sp. tritici populations

USDA-ARS?s Scientific Manuscript database

While wheat powdery mildew occurs throughout the south-central and eastern U.S.A, epidemics are especially damaging in the Mid-Atlantic states. The structure of the U.S. Blumeria graminis f. sp. tritici population was assessed based on a sample of 238 single-spored isolates. The isolates were coll...

3. Historic American Buildings Survey From the S.F. Chronicle Library ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

3. Historic American Buildings Survey From the S.F. Chronicle Library Circa 1930 OFFICERS' CLUB - NORTH ELEVATION - Presidio of San Francisco, Commandancia, Moraga Avenue, San Francisco, San Francisco County, CA

Pollen S-locus F-box proteins of Petunia involved in S-RNase-based self-incompatibility are themselves subject to ubiquitin-mediated degradation.

PubMed

Sun, Penglin; Li, Shu; Lu, Dihong; Williams, Justin S; Kao, Teh-Hui

2015-07-01

Many flowering plants show self-incompatibility, an intra-specific reproductive barrier by which pistils reject self-pollen to prevent inbreeding and accept non-self pollen to promote out-crossing. In Petunia, the polymorphic S-locus determines self/non-self recognition. The locus contains a gene encoding an S-RNase, which controls pistil specificity, and multiple S-locus F-box (SLF) genes that collectively control pollen specificity. Each SLF is a component of an SCF (Skp1/Cullin/F-box) complex that is responsible for mediating degradation of non-self S-RNase(s), with which the SLF interacts, via the ubiquitin-26S proteasome pathway. A complete set of SLFs is required to detoxify all non-self S-RNases to allow cross-compatible pollination. Here, we show that SLF1 of Petunia inflata is itself subject to degradation via the ubiquitin-26S proteasome pathway, and identify an 18 amino acid sequence in the C-terminal region of S2 -SLF1 (SLF1 of S2 haplotype) that contains a degradation motif. Seven of the 18 amino acids are conserved among all 17 SLF proteins of S2 haplotype and S3 haplotype involved in pollen specificity, suggesting that all SLF proteins are probably subject to similar degradation. Deleting the 18 amino acid sequence from S2 -SLF1 stabilized the protein but abolished its function in self-incompatibility, suggesting that dynamic cycling of SLF proteins is an integral part of their function in self-incompatibility. © 2015 The Authors The Plant Journal © 2015 John Wiley & Sons Ltd.

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