Virtual Journal of Applications of Superconductivity

Study of second generation, high-temperature superconducting coils: Determination of critical current

Min Zhang, Jae-Ho Kim, Sastry Pamidi, Michal Chudy, Weijia Yuan et al.
This paper presents the modeling of second generation (2 G) high-temperature superconducting (HTS) pancake coils using finite element method. The axial symmetric model can be used to calculate current and magnetic field distribution inside the coil. The anisotropic characteristics of 2 G tapes are i ... [J. Appl. Phys. 111, 083902 (2012)] published Mon Apr 16, 2012.

Development of a Compact Moving-Sample Magnetometer Using High-T_{\text{c}} Superconducting Quantum Interference Device

Mohd Mawardi Saari, Kenji Sakai, Toshihiko Kiwa, Akira Tsukamoto, Seiji Adachi et al.
We developed a compact moving-sample magnetometer that uses a high-temperature superconductor--superconducting quantum interference device (high-T_{\text{c}} SQUID) to directly measure the flux coupled to a normal detection coil from a sample's magnetic moment in the presence of an external DC magne ... [Jpn. J. Appl. Phys. 51, 046601 (2012)] published Fri Apr 20, 2012.

Specific heat and upper critical fields in KFeAs single crystals

M. Abdel-Hafiez, S. Aswartham, S. Wurmehl, V. Grinenko, C. Hess et al.
We report low-temperature specific heat measurements for high-quality single crystalline KFeAs (T[approximate]3.5 K). The investigated zero-field specific heat data yields an unusually large nominal Sommerfeld coefficient, gamma=94(3) mJ/mol K, which is, however, affected by extrinsic contributions ... [Phys. Rev. B 85, 134533 ] published .

ac susceptibility investigation of vortex dynamics in nearly optimally doped RFeAsOF superconductors (R = La, Ce, Sm)

G. Prando, P. Carretta, R. De Renzi, S. Sanna, H.-J. Grafe et al.
Ac susceptibility and static magnetization measurements were performed in the nearly optimally doped LaFeAsOF and CeFeAsOF superconductors, complementing earlier results on SmFeAsOF [Phys. Rev. B 83, 174514 (2011)]. The magnetic field-temperature phase diagram of the mixed superconducting state is d ... [Phys. Rev. B 85, 144522 ] published .

Temperature and time scaling of the peak-effect vortex configuration in FeTeSe

Marco Bonura, Enrico Giannini, Romain Viennois, and Carmine Senatore
An extensive study of the magnetic properties of FeTeSe crystals in the superconducting state is presented. We show that weak collective pinning, originating from spatial variations of the charge carrier mean free path (deltal pinning), rules in this superconductor. Our results are compatible with t ... [Phys. Rev. B 85, 134532 ] published .

Ab initio investigation of FeAs/GaAs heterostructures for potential spintronic and superconducting applications

Sinead M. Griffin and Nicola A. Spaldin
Ultrathin FeAs is of interest both as the active component in the recently identified pnictide superconductors and in spintronic applications at the interface between ferromagnetic Fe and semiconducting GaAs. Here we use first-principles density-functional theory to investigate the properties of FeA ... [Phys. Rev. B 85, 155126 ] published .

Topographic power spectral density study of the effect of surface treatment processes on niobium for superconducting radio frequency accelerator cavities

Chen Xu, Hui Tian, Charles E. Reece, and Michael J. Kelley
Microroughness is viewed as a critical issue for attaining optimum performance of superconducting radio frequency accelerator cavities. The principal surface smoothing methods are buffered chemical polish (BCP) and electropolish (EP). The resulting topography is characterized by atomic force microsc ... [Phys. Rev. ST Accel. Beams 15, 043502 ] published .

Frequency control in the process of a multicell superconducting cavity production

Valery Shemelin and Paul Carriere
Modifications in the geometry of a superconducting RF cavity due to various processing procedures are presented in a convenient matrix formulation. Specifically, the effect of chemical etching, cooling down, and preloading are characterized, while the corresponding frequency shifts are calculated wi ... [Rev. Sci. Instrum. 83, 043304 (2012)] published Thu Apr 26, 2012.

Design and system integration of the superconducting wiggler magnets for the Compact Linear Collider damping rings

Daniel Schoerling, Fanouria Antoniou, Axel Bernhard, Alexey Bragin, Mikko Karppinen et al.
To achieve high luminosity at the collision point of the Compact Linear Collider (CLIC), the normalized horizontal and vertical emittances of the electron and positron beams must be reduced to 500 and 4 nm before the beams enter the 1.5 TeV linear accelerators. An effective way to accomplish ultralo ... [Phys. Rev. ST Accel. Beams 15, 042401 ] published .

Unconventional rf photoresponse from a superconducting spiral resonator

Alexander P. Zhuravel, Cihan Kurter, Alexey V. Ustinov, and Steven M. Anlage
Superconducting thin film resonators employing strip geometries show great promise in rf/microwave applications due to their low loss and compact nature. However, their functionality is limited by nonlinear effects at elevated rf/microwave powers. Here, we show that by using a planar spiral geometry ... [Phys. Rev. B 85, 134535 ] published .

Superconducting phase transistor in diffusive four-terminal ferromagnetic Josephson junctions

Mohammad Alidoust, Granville Sewell, and Jacob Linder
We study diffusive magnetic Josephson junctions with four superconducting terminals in the weak proximity limit where the leads are arranged in cross form. Employing the linearized Keldysh-Usadel technique, the anomalous Green's function and Josephson current are analytically obtained based on a qua ... [Phys. Rev. B 85, 144520 ] published .

Application of SQUIDs for registration of biomagnetic signals

I. D. Voitovych, M. A. Primin, and V. N. Sosnytskyy
Supersensitive magnetometric systems based on low-temperature SQUIDs have been designed to conduct research in cardiology (magnetocardiography) and to examine distribution of magnetic nanoparticles in biologic objects. Such SQUID magnetometric systems are distinguished by their noise immunity enabli ... [Low Temp. Phys. 38, 311 (2012)] published Fri Apr 27, 2012.

Driven Dynamics and Rotary Echo of a Qubit Tunably Coupled to a Harmonic Oscillator

S. Gustavsson, J. Bylander, F. Yan, P. Forn-Diaz, V. Bolkhovsky et al.
We have investigated the driven dynamics of a superconducting flux qubit that is tunably coupled to a microwave resonator. We find that the qubit experiences an oscillating field mediated by off-resonant driving of the resonator, leading to strong modifications of the qubit Rabi frequency. This open ... [Phys. Rev. Lett. 108, 170503 ] published .

Resonatorzero-qubit architecture for superconducting qubits

Andrei Galiautdinov, Alexander N. Korotkov, and John M. Martinis
We analyze the performance of the resonatorzero-qubit (RezQu) architecture in which the qubits are complemented by memory resonators and coupled via a resonator bus. Separating the stored information from the rest of the processing circuit by at least two coupling steps and the zero qubit state resu ... [Phys. Rev. A 85, 042321 ] published .

Engineered two-dimensional Ising interactions in a trapped-ion quantum simulator with hundreds of spins

Joseph W. Britton, Brian C. Sawyer, Adam C. Keith, C.-C. Joseph Wang, James K. Freericks et al.
The presence of long-range quantum spin correlations underlies a variety of physical phenomena in condensed-matter systems, potentially including high-temperature superconductivity. However, many properties of exotic, strongly correlated spin systems, such as spin liquids, have proved difficult to ... [Nature 484, 489 (2012)] published Thu Apr 26, 2012.

Coherent quantum phase slip

O. V. Astafiev, L. B. Ioffe, S. Kafanov, Yu. A. Pashkin, K. Yu. Arutyunov et al.
A hundred years after the discovery of superconductivity, one fundamental prediction of the theory, coherent quantum phase slip (CQPS), has not been observed. CQPS is a phenomenon exactly dual to the Josephson effect; whereas the latter is a coherent transfer of charges between superconducting lead ... [Nature 484, 355 (2012)] published Fri Apr 20, 2012.

Improved characteristics of mesa-type intrinsic Josephson junctions by vacuum cleavage process for BiSrCaCuO/Au contacts

Hiroki Ishida, Takahiro Kato, Atsushi Saito, and Kanji Yasui
Improvement in the quality of stacked intrinsic Josephson junctions (IJJs) was attempted using BiSrCaCuO (Bi-2212) single crystals. The introduction of a clean Bi-2212/Au interface reduced contact resistivity (rho), decreased low frequency noise, and suppressed the drop in the maximum Josephson curr ... [J. Vac. Sci. Technol. A 30, 031101 (2012)] published Fri Apr 27, 2012.

Josephson effect in cuprate superconducting structures

G. A. Ovsyannikov and K. Y. Constantinian
Electron transport and microwave properties of cuprate superconducting structures (bicrystal junctions and hybrid mesa heterostructures) are discussed here. Superconducting current in junctions from cuprate superconductors with the dominant d-wave symmetry is determined by the barrier properties, ch ... [Low Temp. Phys. 38, 333 (2012)] published Fri Apr 27, 2012.

Coupled superconductors and beyond

Brian D. Josephson
This paper describes the events leading to the discovery of coupled superconductors, the author's move in the 1970s to a perspective where mind plays a role comparable to matter, and the remarkable hostility sometimes encountered by those who venture into unconventional areas. ... [Low Temp. Phys. 38, 260 (2012)] published Fri Apr 27, 2012.

Superposition of states in flux qubits with a Josephson junction of the ScS type (Review Article)

V. I. Shnyrkov, A. A. Soroka, A. M. Korolev, and O. G. Turutanov
The consequences of the transition to a quantum description of magnetic flux motion in the superconducting ring closed by an ScS type Josephson junction are considered. Here we review the principal results regarding macroscopic quantum tunneling (MQT) of Bose condensate consisting of a macroscopical ... [Low Temp. Phys. 38, 301 (2012)] published Fri Apr 27, 2012.

Multiphoton transitions in Josephson-junction qubits (Review Article)

S. N. Shevchenko, A. N. Omelyanchouk, and E. Il'ichev
Two basic physical models, a two-level system and a harmonic oscillator, are realized on the mesoscopic scale as coupled qubit and resonator. The realistic system includes moreover the electronics for controlling the distance between the qubit energy levels and their populations and to read out the ... [Low Temp. Phys. 38, 283 (2012)] published Fri Apr 27, 2012.

Nanoelectromechanics of superconducting weak links (Review Article)

A. V. Parafilo, I. V. Krive, R. I. Shekhter, and M. Jonson
Nanoelectromechanical effects in superconducting weak links are considered. Three different superconducting devices are studied: (i) a single-Cooper-pair transistor, (ii) a transparent SNS junction, and (iii) a single-level quantum dot coupled to superconducting electrodes. The electromechanical cou ... [Low Temp. Phys. 38, 273 (2012)] published Fri Apr 27, 2012.

Escape dynamics in moderately damped Josephson junctions (Review Article)

D. Massarotti, L. Longobardi, L. Galletti, D. Stornaiuolo, D. Montemurro et al.
The Josephson effect is a privileged access to the macroscopic quantum nature of superconductors. We review some ideas and experimental techniques on macroscopic quantum decay phenomena occurring in Josephson structures. The attention is mainly addressed to intermediate levels of dissipation which c ... [Low Temp. Phys. 38, 263 (2012)] published Fri Apr 27, 2012.