Virtual Journal of Applications of Superconductivity

Magnetic flux pinning in superconductors with hyperbolic-tesselation arrays of pinning sites

V. R. Misko and Franco Nori
We study magnetic flux interacting with arrays of pinning sites (APSs) placed on vertices of hyperbolic tesselations (HTs). We show that, due to the gradient in the density of pinning sites, HT APSs are capable of trapping vortices for a broad range of applied magnetic fluxes. Thus, the penetration ... [Phys. Rev. B 85, 184506 ] published .

Critical-current reduction in thin superconducting wires due to current crowding

H. L. Hortensius, E. F. C. Driessen, T. M. Klapwijk, K. K. Berggren, and J. R. Clem
We demonstrate experimentally that the critical current in superconducting NbTiN wires is dependent on their geometrical shape, due to current-crowding effects. Geometric patterns such as 90 corners and sudden expansions of wire width are shown to result in the reduction of critical currents. The re ... [Appl. Phys. Lett. 100, 182602 (2012)] published Thu May 3, 2012.

One-step synthesis of KFeSe single crystal for high critical current density

Toshinori Ozaki, Hiroyuki Takeya, Hiroyuki Okazaki, Keita Deguchi, Satoshi Demura et al.
We have established a simple process that allows for the one-step synthesis of KFeSe single crystals, which exhibit high critical current density J. The post annealing and quenching technique has improved the homogeneity of as-grown crystals, resulting in full shielding of the external magnetic fiel ... [EPL 98, 27002 (2012)] published Wed May 2, 2012.

High-temperature change of the creep rate in YBaCuO films with different pinning landscapes

N. Haberkorn, M. Miura, J. Baca, B. Maiorov, I. Usov et al.
Magnetic relaxation measurements in YBaCuO (YBCO) films at intermediate and high temperatures show that the collective vortex creep based on the elastic motion of the vortex lattice has a crossover to fast creep that significantly reduces the superconducting critical current density (J). This crosso ... [Phys. Rev. B 85, 174504 ] published .

Controlling flux flow dissipation by changing flux pinning in superconducting films

G. Grimaldi, A. Leo, A. Nigro, A. V. Silhanek, N. Verellen et al.
We study the flux flow state in superconducting materials characterized by rather strong intrinsic pinning, such as Nb, NbN, and nanostructured Al thin films, in which we drag the superconducting dissipative state into the normal state by current biasing. We modify the vortex pinning strength either ... [Appl. Phys. Lett. 100, 202601 (2012)] published Mon May 14, 2012.

Nonthermal response of YBaCuO thin films to picosecond THz pulses

P. Probst, A. Semenov, M. Ries, A. Hoehl, P. Rieger et al.
The photoresponse of YBaCuO thin film microbridges with thicknesses between 15 and 50 nm was studied in the optical and terahertz frequency range. The voltage transients in response to short radiation pulses were recorded in real time with a resolution of a few tens of picoseconds. The bridges were ... [Phys. Rev. B 85, 174511 ] published .

Minimum quench power dissipation and current non-uniformity in international thermonuclear experimental reactor type NbTi cable-in-conduit conductor samples under direct current conditions

G. Rolando, E. P. A. van Lanen, and A. Nijhuis
The level of current non-uniformity in NbTi cable-in-conduit conductors (CICCs) sections near the joints in combination with the magnetic field profile needs attention in view of proper joint design. The strand joule power and current distribution at quench under DC conditions of two samples of ITER ... [J. Appl. Phys. 111, 093904 (2012)] published Wed May 2, 2012.

Digital holographic microscopy long-term and real-time monitoring of cell division and changes under simulated zero gravity

Feng Pan, Shuo Liu, Zhe Wang, Peng Shang, and Wen Xiao
The long-term and real-time monitoring the cell division and changes of osteoblasts under simulated zero gravity condition were succeed by combing a digital holographic microscopy (DHM) with a superconducting magnet (SM). The SM could generate different magnetic force fields in a cylindrical cavity, ... [Opt. Express 20, 11496 (2012)] published Thu May 10, 2012.

Complete tailor-made inverse filter for image processing of scanning SQUID microscope

Masahiko Hayashi, Hiromichi Ebisawa, Ho Thanh Huy, and Takekazu Ishida
By introducing a numerical image processing technique, the resolution of scanning SQUID microscope (SSM) has been improved beyond the naive limit determined by the size of the pickup (sensor) coil. Our image processing is developed by taking account of the specific characteristics of SSM apparatus, ... [Appl. Phys. Lett. 100, 182601 (2012)] published Tue May 1, 2012.

Voltage response of non-uniform arrays of bi-superconductive quantum interference devices

Patrick Longhini, Susan Berggren, Anna Leese de Escobar, Antonio Palacios, Sarah Rice et al.
Multi-loop arrays of Josephson junctions (JJs) with non-uniform area distributions, which are known as superconducting quantum interference filters (SQIFs), are the most highly sensitive sensors of changes in applied magnetic field as well as the absolute magnitude of magnetic fields. The non-unifor ... [J. Appl. Phys. 111, 093920 (2012)] published Fri May 11, 2012.

Control of the radiative level shift and linewidth of a superconducting artificial atom through a variable boundary condition

Kazuki Koshino and Yasunobu Nakamura
We investigate the dynamics of a superconducting qubit strongly coupled to a semi-infinite one-dimensional microwave field having a variable boundary condition. The radiative level shift and linewidth of the qubit are controllable through the boundary condition of the field, and the spectral propert ... [New J. Phys. 14, 043005 (2012)] published Wed May 2, 2012.

Strong Coupling of Spin Qubits to a Transmission Line Resonator

Pei-Qing Jin, Michael Marthaler, Alexander Shnirman, and Gerd Schon
We propose a mechanism for coupling spin qubits formed in double quantum dots to a superconducting transmission line resonator. Coupling the resonator to the gate controlling the interdot tunneling creates a spin qubit-resonator interaction with a strength of tens of MHz. This mechanism allows opera ... [Phys. Rev. Lett. 108, 190506 ] published .

Improving the quality factor of microwave compact resonators by optimizing their geometrical parameters

K. Geerlings, S. Shankar, E. Edwards, L. Frunzio, R. J. Schoelkopf et al.
Applications in quantum information processing and photon detectors are stimulating a race to produce the highest possible quality factor on-chip superconducting microwave resonators. We have tested the surface-dominated loss hypothesis by systematically studying the role of geometrical parameters o ... [Appl. Phys. Lett. 100, 192601 (2012)] published Mon May 7, 2012.

Superconductivity with excitons and polaritons: review and extension

Fabrice P. Laussy, Thomas Taylor, Ivan A. Shelykh, and Alexey V. Kavokin
A system where a Bose-Einstein condensate of exciton-polaritons coexists with a Fermi gas of electrons has been recently proposed as promising for realization of room-temperature superconductivity. In order to find the optimum conditions for exciton and exciton-polariton mediated superconductivity, ... [J. Nanophoton. 6, 064502 (2012)] published Fri May 4, 2012.