bluuebunny/crossref_metadata_2025 huggingface dataset:
A technique for local area transfer and simultaneous crystallization of amorphous silicon layer with midair cavity by irradiation with near-infrared semiconductor diode laser
Authors: Sakaike Kohei , Kobayashi Yoshitaka , Nakamura Shogo , Akazawa Muneki , Higashi Seiichiro
Published: March 2014

A technique for local layer transfer and simultaneous crystallization of amorphous silicon (a-Si) films with midair cavity induced by near-infrared semiconductor diode laser (SDL) irradiation is demonstrated. After SDL irradiation, the silicon (Si) films were completely transferred and crystallized simultaneously on counter substrates. Electron backscatter diffraction pattern maps confirmed that the maximum grain size of the transferred Si films is 20 µm. High-performance polycrystalline Si thin-film transistors (TFTs) were successfully fabricated on the locally transferred Si films. These TFTs showed a high on/off ratio of more than 106 and a field-effect mobility as high as 492 cm2 V−1 s−1.
Extraction of semiconducting single-walled carbon nanotubes encapsulating fullerenes by poly(9,9-dioctylfluorene-alt-benzothiadiazole)
Authors: Tange Masayoshi , Kwon Jin Kyoung , Okazaki Toshiya , Iijima Sumio
Published: March 2014

Single-walled carbon nanotubes (SWCNTs) encapsulating fullerenes, the so-called “nanopeapods (NPDs)”, are expected as building blocks in future nanoelectronics because the mechanical and electronic properties of SWCNTs frequently undergo considerable modification with the encapsulation of molecules at a nanometer scale. The separation of semiconducting species from metallic counterparts is the next step in the application of NPDs in electronics and photonics. Here, semiconducting NPDs are successfully extracted in toluene using a fluorene-based polymer, poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT). Although F8BT shows a high extraction selectivity for (15, 4) SWCNTs, such a high selectivity disappears in the obtained photoluminescence excitation (PLE) map of NPDs. The change in electronic energy level by the encapsulation of C60 may induce the loss of the selectivity.
An implantable CMOS device for blood-flow imaging during experiments on freely moving rats
Authors: Haruta Makito , Kitsumoto Chikara , Sunaga Yoshinori , Takehara Hironari , Noda Toshihiko , Sasagawa Kiyotaka , Tokuda Takashi , Ohta Jun
Published: March 2014

An observation technique for animal brain activity under freely moving conditions is important to understand brain functions because brain activity under an anesthetized condition is different from that under a nonanesthetized condition. We have developed an ultrasmall CMOS imaging device for brain activity observation under freely moving conditions. This device is composed of a CMOS image sensor chip and nine LEDs for illumination. It weighs only 0.02 g and its small size enables experiments to be performed without restricting animal movement. This feature is advantageous for brain imaging, particularly in freely moving situations. In this study, we have demonstrated blood-flow imaging using the device for the stable observation of brain activity over a long period. The blood flow can be observed without staining the brain during optical imaging. We have successfully estimated the blood-flow velocity under freely moving conditions.
Superconductivity in Ba2LnCu3Oy (Ln=Y, Lanthanides)
Authors: Takagi H. , Uchida S. , Sato H. , Kishio K. , Kitazawa K. , Fueki K. , Tanaka S.
Published: March 2014

Superconducting and magnetic properties are investigated for Ba2LnCu3Oy (Ln=y, Eu, Dy, Ho, Er, Tm and Yb). All these compounds exhibit a bulk superconductivity of 90 K range in spite of the fact that these compounds contain lanthanide atoms. From the magnetic susceptibility measurements, it is found that lanthanide atoms exist as almost free Ln3+ ions and that the interaction between Ln3+ ions is weak. These facts can be interpreted in terms of recently established crystal strycture.
Superconductivity Transition of High-Tc Y–Ba–Cu–O Systems with Multi- and Single-Phase; Tc and Hc2
Authors: Takita Kôki , Ippōshi Takashi , Uchino Takashi , Akinaga Hiroyuki , Katoh Hideo , Masuda Kohzoh
Published: March 2014

Superconducting transition in the magnetic field up to 9T and the upper critical field Hc2 near Tc were investigated for Y1Ba2Cu3O7-δ with orthorhombic single phase, comparing with the Y–Ba–Cu–O samples with multi-phase. The upper critical field Hc2 is very large for single phase sample; the offset field Hc2
off defined at 1% point is about 10T even at 76K and the slope (-dHc2/dT) for mid-point is 3.8T/K.
Electron Diffraction and Microscopy of the Structures of La–Ba(Sr)–Cu–O and Ba–Y–Cu–O at Room and Liquid Helium Temperatures
Authors: Hirotsu Yoshihiko , Nagakura Sigemaro , Murata Yuzo , Nishihara Takaharu , Takata Masasuke , Yamashita Tsutomu , Iwatsuki Masashi , Harada Yoshiyasu
Published: March 2014

Structural study of the superconducting oxides in the La–Ba (Sr)–Cu–O and Ba–Y–Cu–O systems has been made at room and liquid helium temperatures by electron diffraction and high resolution electron microscopy. La1.9Ba0.1CuO4, which is not superconductive down to 4.2 K, is orthorhombic and belongs to the space group pccm. La1.8Ba0.2CuO4 with Tc=28 K and La1.8Sr0.2CuO4 with Tc=36 K are tetragonal and belong to the space group 14/mnm. At liquid helium temperature, these oxides did not show any structural change. Oxides in the Ba–Y–Cu–O system with Tc=68 and 85 K are orthorhombic and belong to the space group Pmmm. (110) twins are formed in the structure. High resolution electron microscopy revealed the metal atom arrangement in these superconductive oxides.
Electron-Phonon Coupling and Superconductivity in Strongly Polar Semimetals
Authors: Yin Daole , Han Rushan , Dai Yuandong , Zhang Jinlong
Published: March 2014

The popular idea of Tc
max\doteq30–40K for electron-phonon (E-P) mechanism is based on an estimation of E-P coupling strength in usual cation metallic solids. However, we have made a model study of the interaction of itinerant electrons with anion cores, Y–Ba–Cu–O is believed to be the case, in LMTO formulation. It turns out that anion repulsive core favours the high angular momentum hybridization of the itinerant wave-function around it. Thus, we will have a strong E-P coupling of λ\doteq1.3 with optical ω\doteq77mev so a Tc of the order of 90K.
Superconducting Properties of High-Tc Ceramics
Authors: Koyama Kuniyuki , Tsunemi Takeo , Miki Takeshi , Oota Akio , Ueno Akifumi , Noguchi Seiichiro
Published: March 2014

Superconducting properties are studied through electrical resistivity, magnetic susceptibility and X-ray diffraction on the high temperature superconductor Y0.4Ba0.6CuO3-x. The X-ray powder diffraction pattern of the sample indicates almost an orthorhombic phase. The onset superconducting transition temperature Tc(onset) and the transition width ΔTc are sensitive to the sintering temperature. The best superconducting properties are obtained when the sample is sintered at about 1000°C in oxygen flow; Tc(onset)=91.2K, ΔTc=1.4K and the critical current density at 77K Jc≧60A/cm2.
Superconducting Properties in Y1-xBaxCuO3-y and Y(Ba1-xSrx)2Cu3O7-y
Authors: Saito Yoshitami , Noji Takashi , Endo Akihiko , Higuchi Naoaki , Fujimoto Kenji , Oikawa Tokuju , Hattori Atsuhlko , Furuse Kazuyuki
Published: March 2014

The concentration dependence of the transition temperature Tc has been studied in high-Tc Y1-xBaxCuO3-y and Y(Ba1-xSrx)2Cu3O7-y systems. In Y1-xBaxCuO3-y, Tc exhibits a maximum at x=0.67 compound with a stoichiometry YBa2Cu3O7-y. In Y(Ba1-xSrx)2Cu3O7-y, Tc decrease monotonically with an increase of Sr content.
Metastability and Glass State in Superconducting La2CuO4-y: Ba
Authors: Takashige Masaaki , Muller K. Alex , Bednorz J. Georg
Published: March 2014

Susceptibility measurements for 1.9 to 35K in magnetic field from 0.015 to 1.5 Tesla in superconducting La2CuO4-y: Ba are reported. The diamagnetism created by the zero-field cooling and switching on a field shows non-exponential time-decays indicating an existence of superconducting glass state. Measuring with different fields, a quasi de Almeida-Thouless line separating ergodic from nonergodic areas in H–T plane has also been obtained.
Carrier Density of Superconducting (La1-xSrx)2CuO4 Single Crystal Thin Films
Authors: Suzuki Minoru , Moriwaki Kazuyuki , Murakami Toshiaki
Published: March 2014

Superconducting single crystal thin films of (La1-xSrx)2CuO4 have been prepared by rf magnetron sputtering. Resistivity and Hall coefficient were measured on these thin films over the temperature range from 30 K to 300 K. The carrier density obtained from the Hall coefficients ranged from 6.8 to 8.5×1021 cm-3 at 300 K. Its temperature dependence exhibited notable decrease with falling temperature, indicating some kind of carrier localization.
High Tc Superconductivity of Sr–La–Cu–O and Ba–Y–Cu–O Thin Films
Authors: Zhao Zhao , Bairu Bairu , Wang Wang , Huisheng Huisheng , Lu Lu , Yong Yong , Shi Shi , Yinhuan Yinhuan , Zhao Zhao , Yuying Yuying , Li Li , Lin Lin
Published: March 2014

High Tc Sr–La–Cu–O and Ba–Y–Cu–O thin films have been successfully prepared by the magnetron sputtering method. The Tc onsets for Sr–La–Cu–O are 25–30K and Δ Tc are 7.5–8.5K. The slope near Tc is 3.05T/K. The Tc onsets of Ba–Y–Cu–O thin films are 87–89.5K and the zero resistance is at 20K. The samples are diamagnetic and the Meissner effect appeared around 10K.
All-Electron Local Density Theory of Electronic Structure and Superconductivity in YBa2Cu3O7 and YBa2Cu3O6
Authors: Freeman A. J. , Massidda S. , Yu Jaejun , Koelling D. D.
Published: March 2014

Results of highly precise all-electron local density calculations are presented for the quasi-2D superconductor YBa2Cu3O7 and for the non-superconducting YBa2Cu3O6. The two dimensionality is important for understanding various properties. As in the case of the La2-xMxCuO4 (M = Ba, Sr,...) systems, these materials consist of metallic Cu–O planes separated by ionic (insulating) Y–O and Ba–O planes of atoms. Stoner magnetic instabilities and the role of chains vs planes for superconductivity are briefly discussed.
Magnetic Properties of the High-Tc Superconductors La1.85Sr0.15CuO4 and YBa2Cu3O7
Authors: Renker B. , Apfelstedt I. , Küpfer H. , Politis C. , Rietschel H. , Schauer W. , Wühl H. , Gottwick U. , Kneissel H. , Rauchschwalbe U. , Spille H. , Steglich F.
Published: March 2014

For the high-Tc superconductors La1.85Sr0.15CuO4 and YBa2Cu3O7 we present results for the low-field magnetization and the lower and upper critical fields Bc1(T) and Bc2(T). Losses in the Meissner state observed in magnetization and susceptibility measurements disappeared after powdering the sample. This is taken as strong evidence for intergrain Josephson coupling in the bulk sample. The Bc2(T) obtained by inductive measurements indicates a large anisotropy due to the layered structure of these compounds.
Critical Current Density Characteristics in Superconducting YxBa1-xCu-Oxides
Authors: Noto Koshichi , Morita Hiroaki , Watanabe Kazuo , Murakami Yoshitake , Obi Yoshihisa , Fujimori Hiroyasu , Kobayashi Norio , Muto Yoshio
Published: March 2014

The transition temperature, Tc, and the critical current density, Jc(B), at 4.2 K have been studied in high-Tc YxBa1-xCu-Oxide system. Previously observed two maxima in Tc were reexamined. A very large anisotropy, very fast degradations at low fields, and a large hysteresis in Jc(B) have been observed in this system. The cause of the large anisotropy might be the strong c-axis orientation perpendicular to the pressed surface and the low dimensionality of the crystal structure of this material. Although Jc value is very small, the decrease in Jc from 2 to 27 T is only about 20 %, which shows a high potential for practical use at high fields when Jc is raised by the introduction of strong pinning centers in this material.
High Tc Superconductivity and S-I Transition in Ba–Y–Cu–O
Authors: Zhang Zhang , Qirui Qirui , Qian Qian , Yitai Yitai , Chen Chen , Zuyao Zuyao , Guan Guan , Weiyan Weiyan , Zhao Zhao , Yong Yong , Cao Cao , Liezhao Liezhao , Chen Chen , Zhaojia Zhaojia , Ji Ji , Mingrong Mingrong , Xia Xia , Jiansheng Jiansheng , Pan Pan , Guoqiang Guoqiang , Zhang Zhang , Han Han , Zhang Zhang , Minjian Minjian , Yu Yu , Daoqi Daoqi , He He , Zhenghui Zhenghui , Sun Sun , Shifang Shifang , Zhang Zhang , Tao Tao , Fang Fang , Minghu Minghu
Published: March 2014

Superconductor-Insulator transition and superconductivity have been studied by the measurements of resistivity, specific heat, XPS, a.c.magnetic susceptibility and X-ray diffraction in Ba–Y–Cu–O system. The experimental results show that the S-I (superconductor-insulator) transition which might be driven by the electrons occurs near x=0 and the high electronic density of states at Fermi level usually associated with the high Tc in this system. A λ-type phase transition which is probably related to the antiferromagnetism was also observed near 12K.
Bulk and Wire Type Y–Ba–Cu Oxide Superconductor
Authors: Yamada Yutaka , Fukushima Noburu , Nakayama Sigeo , Niu Hiromi , Takemura Momoko , Hayashi Masaru , Yoshino Hisashi , Murase Satoru
Published: March 2014

We have fabricated the bulk Y–Ba–Cu oxide, various types of wire conductors and coils, and especially studied the critical current density Jc. Large Jc's were obtained at 77K and OT: 725A/cm2 for the non sheath wire, 560A/cm2 for the Ag sheathed wire. However, the Jc(77K) drastically decreased by a factor of hundred in a magnetic field lower than 1T while Jc(4.2K) little changed up to 12T. Based on the magnetic field dependence of Jc, for example, 2T of upper critical field Bc2(77K) and 47 to 80T of Bc2(4.2K) were obtained for the wire conductor.
Anomalous Temperature Dependence of Hc2 on Tm(Rh0.9Ru0.1)4B4
Authors: Iwasaki Hideo , Hayashi Hideaki , Muto Yoshio
Published: March 2014

Hc2 was measured on a single crystal Tm(Rh0.9Ru0.1)4B4 With bct structure. Hc2 shows the antsotropy not only in the a plane but also in the c plane. The easy magnetization axis is in the c plane and Hc2 for the [110] direction is the smallest. Hc2 in the c plane has negative curvature for 5 K<T<Tc and takes upturn curvature below 5 K. The Hc2 anomaly comes from the fact that the magnetization curves almost saturate at Hc2 at low temperatures, where superconductivity coexists with field induced ferromagnetism.
Electronic Structure and Superconducting and Magnetic Properties of bct Ho(Rh1-xTMx)4B4 with TM=Os or Ru
Authors: Möhle W. , Roas B. , Adrian H. , Johnson R. L.
Published: March 2014

The influence of chemical composition and lattice disorder on the electronic structure and superconductivity of pseudoternary borides is reported. Photoelectron spectra of bulk Ho(Rh1-xOsx)4B4 reveal a shift of EF as well as a broadening of the d-band structure quantitatively explaining the Tc(x) behavior. Alternatively a d-band broadening in thin films of Ho(Rh1-xRux)4B4 was observed by heavy ion irradiation. The defect induced x-dependent depressions as well as enhancements of Tc can be explained soley on the basis of this broadening.
Superconductivity of LuRhxSny Thin Films
Authors: Cendlewska Barbara , Rojek Andrzej
Published: March 2014

Thin films of RE-Rh-Sn compounds were obtained by cathode sputtering method. As a target composition LuRh1.2 Sn4.0 was used. The X-ray analysis and the resistivity measurements were carried out. The observed superconducting critical temperature (Tc=2.25 K) of thin film was lower than for LuRh1.2Sn4.0 single crystal (Tc=4.08 K).
Dependence of Upper Critical Field and Magnetoresistivity of Superconducting Amorphous (Mo0.6Ru0.4)100-xBx Films on Structural Inhomogeneities
Authors: Adrian H. , Toyota N. , Hensel B. , Söldner K.
Published: March 2014

The influence of structural inhomogeneities on the superconducting critical temperature Tc, upper critical field BC2(T) and magnetoresistivity Δρ(B,T) of amorphous (Mo0.6Ru0.4)100-xBx films is reported. We find that the inclusion of pores with dimensions up to about 10 nm leads to an enhancement of the initial slope -BC2' by nearly one order of magnitude accompanied by a depression of Tc. From the ρ- and Bc2-data we conclude a further reduction of the electronic diffusivity due to these inhomogeneities, in spite of the already short mean free path in amorphous metals, which may be also responsible for the observed Tc-behavior. Additionally we find systematic differences of the magnetoresistivities measured up to 23 Tesla between homogeneous and inhomogeneous films.
Sharp Transition in Superconducting Al Small Particles
Authors: Komori Fumio , Goto Takayuki , Kobayashi Shun-ichi
Published: March 2014

The critical magnetic field for superconductivity is studied in Al small particles at 30 mK. The shift and shape of 27A1 NMR is measured in the ensemble of the small particles with distributed size. The amount of the superconducting particles is estimated as a function of magnetic field from the analysis of the line shape. The dependence of the critical field on the size and the width of the transition are discussed.
A New Type of Multivalued Ic–H Characteristic
Authors: Guan Guan , Weiyan Weiyan , Zhang Zhang , Qirui Qirui , Zhou Zhou , Xianyi Xianyi , Jia Jia , Yunfa Yunfa , Zhang Zhang , Minjian Minjian , Zhao Zhao , Zhongxian Zhongxian , Chen Chen , Jun Jun , Liu Liu , Zhiguo Zhiguo
Published: March 2014

The IC(H) characteristic of the as quenched metallic glass Zr78Co22 nas been measured under transverse fields. At T\leqslantTC, a new type of multivalued IC(H) characteristic has been observed for the first time. Based on the analysis of microstructure and crystalline phases of samples, a model of superconducting phase separation has been proposed and the observed experimental phenomena have been explained qualitatively.
Superconducting Transition Temperature of Sb/Sn Thin Films
Authors: Kojima S. , Kobayashi T. , Okamoto K. , Ohtsuka M.
Published: March 2014

The variation in the superconducting transition temperature of Sb/Sn thin films with a fixed thickness ratio was measured as a function of the total layer number. Samples were prepared by alternate deposition of Sb and Sn. The thickness ratios of Sb layer to Sn layer were 2/8, 4/8, 8/8(Å/Å). The total layer number with a fixed thickness ratio were 11, 21, 31, 41. As the observed transition temperature was independent of the total layer number, the Cooper limit approximation is employed for a proximity-effect analysis of the samples. The observed transition temperature was always higher than that calculated by the Cooper theory. This is explained by the existence of the interfaces, which suppress the decrease of the transition temperature, and by the change in the BCS coupling constants of the compositions due to the alternate deposition.
Fluctuation and Percolation Effect of Superconductivity in Nb3Ge Films
Authors: Akinaga Masahiro
Published: March 2014

Electrical resistivity ρ (T) of R.F. sputter-deposited Nb3Ge films has been investigated in detail in the neighborhood of the transition temperature. Upon cooling from room temperature, many samples exhibited a logarithmic type of increase in ρ(T) before undergoing the transition to superconductivity. These films have very large resistivity in the normal state and show fairly high onset temperature Tc-on>25 K. The films with rather small resistivity exhibited a metalic behaivior in the normal state. But it has been found that the fluctuation effect on the electrical conductivity starts from fairly higher temperature than usual onset temperature. These experimental results have been qualitatively compared with the theory of superconductivity fluctuation.
Andreev Scattering at a Rough Surface of 3He–B
Authors: Zhang Weiyi , Kurkijärvi Juhani , Rainer Dierk , Thuneberg Erkki V.
Published: March 2014

We present a theoretical framework for calculating Andreev scattering rates in superconductors and superfluid 3He. The theory is applied to Andreev scattering at diffusely scattering surfaces of 3He, and representative results are given for the energy-dependent scattering rates.
Observation of the Correlated Discrete Single-Electron Tunneling
Authors: Kuzmin L. S. , Likharev K. K.
Published: March 2014

We have observed large oscillations in the dc I–V curves of special tunnel junctions containing submicron indium grains embedded between two continuous thin-film electrodes. The effect is identified as a result of the correlated discrete transfer of electrons through a pair of tunnel junctions formed between a single grain and the electrodes. The experiments have also proved feasibility of ultrasensitive (sub-electron) electrometry based on the discrete correlated tunneling.
Possibility of Dual Macroscopic Quantum Phenomena in 2D Superconductor Granular System
Authors: Sugahara Masanori , Yoshikawa Nobuyuki
Published: March 2014

A theoretical study on the microjunctions in highly resistive granular superconductor films reveals that there can appear two dual granular 2D systems depending on the structures and parameters of microjunctions.
Resonant Tunneling of Macroscopic Variables in Ultrasmall Josephson Junctions and SQUID Rings
Authors: Hatakenaka Noriyuki , Kurihara Susumu
Published: March 2014

A resonant tunneling phenomenon in a current-biased ultrasmall Josephson junction is predicted. It is shown that the tunneling is possible only at discrete values of bias current due to the quantization of Josephson plasma oscillation. We also predict an emission of a microwave photon accompanying the resonant tunneling, and suggest that observation of this photon may provide a possible proof for the existence of Macroscopic Quantum Coherence (MQC).
Stability of Coherent Oscillations in Josephson Junction Arrays
Authors: Hadley P. , Beasley M. R.
Published: March 2014

When series arrays of Josephson junctions are included in circuits there exists the possibility that the junctions will phaselock and oscillate coherently. We present a method to study the stability of the phase coherent state based on a determination of the eigenvalues of the return map associated with the dynamics. The eigenvalues indicate how close the coherent state is to an instability. Therefore knowledge of the eigenvalues allows us to find the operating point which maximizes the stability of the coherent state. The power of our method is that arbitrarily large arrays are handled as easily as small arrays. For series arrays of N junctions with small shunt capacitances we show that the coherent state always loses stability in the same way, via a codimension N-1 bifurcation. We apply this method to Josephson junction arrays proposed as rf generators.
Superconducting Properties of Ge–Nb–Ge Sandwich Films
Authors: Idei A. , Kuwasawa Y. , Nakano S.
Published: March 2014

The sandwich Ge-Nb-Ge films and Nb-Ge multilayer films were fabricated on the sapphire substrate in ultra high vacuum. The superconducting properties and the magnetoresitance of these films were studied in the framework of the two dimensional disorder. The spin-orbit scattering time of Nb was estimated, and found to be larger than expected. For the thinner films, spin-orbit scattering time become abruptly small.
Superconductivity in Randomly Stacked Superconducting and Normal Layers
Authors: Ota S. B.
Published: March 2014

The proximity effect in a randomly stacked superconducting and normal layers, has been investigated theoretically. The superconducting transition in such a multilayer has been shown to acquire width δTc, because of the presence of varying length segments of the superconducting regions sandwiched by normal regions. The superconducting transition temperature is found to decrease monotonically, while δTc goes through a maximum as the fraction of the normal layers is increased from 0 to 1.
Observations on the Flow Properties of 3He Films below 1 mK
Authors: Davis J. C. , Amar Ajay , Pekola J. P. , Packard R. E.
Published: March 2014

We have performed an experiment designed to observe superfluid film flow in 3He. Our apparatus measures flow rates as small as 4×10-5 mm3/s onto a horizontal surface located a distance h above a reservoir. Results indicate that when h is several millimeters no flow is detected. However when h is less than 2.5 mm from the horizontal surface, film flow is observed at temperatures well below Tc.
Pinning Behavior of Laser Irradiated Nb3Al (Ge)
Authors: Yamada Yutaka , Murase Satoru , Sasaki Mituo , Nakamura Eí , Kumakura Hiroaki , Togano Kazumasa , Tachikawa Kyoji
Published: March 2014

We have developed laser irradiated Nb3Al and NB3(Al, Ge) superconductors: A high power CO2 laser beam was irradiated onto moving powder metallurgy Nb-Al and Nb-Al-Ge composite tapes. A15 phase was synthesized on the irradiated area through the melting and quenching process. The resultant specimen shows a large critical current density Jc, over 104 A/cm2 at 20T. These specimens include different pinning centers; the interface, the σ phase precipitates, grain boundary in A15 phase and Nb dendrites in A15 phase matrix. This complicated structure brings forth a peak effect in a pinning curve.
Flux-Line Pinning in a Superconducting Vibrating Reed
Authors: Esquinazi Pablo , Brandt Ernst Helmut
Published: March 2014

A thin ribbon of a superconducting material clamped at one end and excited to flexural vibrations may be used to study flux pinning. The resonance frequency, strongly enhanced in a longitudinal magnetic field, slightly decreases and the damping drastically increases when the flux lines are allowed to move relative to the pins. The reed may be further used as a sensitive magnetometer and to measure Bc1 (≦7mT) of ceramic high-Tc superconductors from which we made reeds.
Elementary Pinning Force of Grain Boundaries
Authors: Pruymboom A. , Kes P. M.
Published: March 2014

Perturbation of the electronic mean free path at a grain boundary, results in an elementary pinning interaction with a magnetic flux line, proportional to |∂Ψ(r)|2. The expression of the interaction energy for an isolated flux line is elaborated in the Ginzburg-Landau limit, yielding an approximate closed form expression for the pinning force.
Electron Tunneling Study of Superconducting Proximity Effect in Silicon Backed with Pb Alloy
Authors: Nishino Toshikazu , Hatano Mutsuko , Kawabe Ushio
Published: March 2014

The superconducting state in p-type Si single crystal backed with a Pb-In alloy has been studied by electron tunneling spectroscopy. The superconducting pair potential in the Pb alloy can be reduced either by an increase in the boron impurity concentration in the Si or by the accumulation of carrier concentration in the Si due to the electric field effect. The presence of the superconducting pair potential is also observed in the Si, and its pair potential is enhanced by an increase in the boron impurity concentration. These facts provide evidence for the superconductivity induced in the Si by the proximity effect, which is dependent on carrier concentration.
Direct Observation System of Fluxon-Antifluxon Collision
Authors: Nakajima Koji , Fujimaki Akira , Sawada Yasuji
Published: March 2014

We have constructed a direct observation system of fluxon-antifluxon collision. The system which is a modification of the Josephson sampling system comprises a mechanical delay, an electrical delay, a feedback circuit, and a superconducting circuit on a chip. We have observed the wave forms of the fluxon-antifluxon collision and annihilation in time and space coordinates which is the first direct observation of the quantum soliton interaction in the solid.
Tunneling at High Magnetic Fields and 3He Temperatures Using a Squeezable Tunnel Junction Apparatus
Authors: Tkaczyk J. E. , Tedrow P. M.
Published: March 2014

An apparatus similar to that described by Moreland and Hansma has been constructed; However, the junction gap is mechanically adjusted without use of an electromagnet, allowing for a compact design. High quality Pb-Pb junctions with conductances showing phonon structure have been-obtained. A crossover from ohmic to tunneling conduction across the junction gap is observed as the squeezing force on an Al-normal metal junction is decreased. The tunneling conductance of an Al-ferromagnet junction measured in an applied magnetic field and 0.4K shows the asymmetry due to spin-polarized tunneling. This is the first observation of spin-polarized tunneling in a junction with a mechanically adjustable gap. Application to bulk samples will be discussed.
Characterization of Brain Noise with a 7-Channel SQUID Magnetometer
Authors: Hämäläinen Matti S. , Knuutila Jukka
Published: March 2014

The characteristics of neuromagnetic fields produced by spontaneous brain activity have been studied using of a large-area 7-channel DC SQUID magnetometer. By means of correlation analysis, it is shown that the signals from the brain are highly correlated on the area covered by the magnetometer. These findings illustrate the possibility of taking into account this correlated noise to provide more accurate description for the neural sources associated with specific sensory stimuli in the evoked response measurements.
Transducer Characteristics of a Josephson Line as an Analog Amplifier
Authors: Yoshida K. , Hashimoto T. , Enpuku K. , Yamafuji K.
Published: March 2014

Experimental studies are made of the transducer characteristics of Flux-Flow Amplifier(FFA), which is an analog amplifier utilizing the flux-flow phenomenon in a long Josephson tunnel junction. Transresistances ranging from 0.1 Ω to 0.4 Ω and linear output voltages as large as 1mV are obtained for different geometries and junction critical-current densities of FFA's.
Microscopic Simulation of Shapiro Steps near the Gap Voltage of Very High Current Density Josephson Junctions
Authors: Jutzi W. , Crocoll E. , Marz J.
Published: March 2014

First order Shapiro steps near the gap voltage of a Josephson point junction have been simulated with a microscopic model closely approximating Werthamer's theory as a function of generator impedance. The simulated results are in reasonable agreement with reported measurements of coupled tunnel junctions and in disagreement with an adiabatic approximation assuming only a sinusoidal voltage at at the junction. No basic inconsistency between the frequency dependence of the pair current real part according to Werthamer and present measurements can be deduced.
Propagating Normal Zones and Transient Heat Transfer Effects in Superconducting Wires
Authors: Casas Juan , Rinderer Leo
Published: March 2014

Theoretical and experimental data of normal zone propagating velocities along superconducting wires immersed in a normal helium bath are presented. Longitudinal destruction of the superconductivity arises from thermal instabilities along the superconducting wire. Propagating normal zone velocities are thus strongly dependent on the thermal transfer mechanism between the helium bath and the superconducting wire. Transient heat transfer effects are necessary to obtain good agreement between experiment and theory. The used transient heat transfer coefficient depends on the bath temperature and on the sample resistivity as it can be seen from our results.
Imaging of the Spatial Structure of Inhomogeneous Energy-Gap States in Nonequilibrium Superconductors
Authors: Gross R. , Schmid D. B.
Published: March 2014

Using Low Temperature Scanning Electron Microscopy (LTSEM) the spatial structure of inhomogeneous energy gap states in nonequilibrium PbIn-alloy films has been studied under injection of quasiparticles both at and well above the gap sum voltage. By LTSEM for the first time the spatial homogeneity of the quasiparticle injection and the spatial distribution of the energy gap of the perturbed film have been imaged directly with a spatial resolution of a few µm. In this way the nucleation and the spatial development of the inhomogeneous energy gap state with increasing quasiparticle injection and the characteristic length scales of the inhomogeneous state can be observed directly.
Magnetic Hysteresis of Thin Film DC SQUIDs
Authors: Mizuno Kazuo , Aomine Takafumi
Published: March 2014

The thin film DC SQUID has been used to monitor the phase difference of the order parameter between neighboring corners of a square film, which is also one of bank films of a Dayem bridge and has an area, 100×100 µ m2. The voltage of the SQUID has been measured at a constant bias current. Both the voltage vs. an external perpendicular field and the voltage vs. an external current through the Dayem bridge show hysteresis with discontinuous changes. The discontinuity is considered to indicate the penetration of vortex into the square film.
Three Terminal Josephson Junction with a Semiconductor Accumulation Layer
Authors: Ivanov Z. , Claeson T. , Andersson T.
Published: March 2014

Experimental results are presented for a three terminal, voltage regulated Josephson device. Superconducting (Sn) source and drain electrodes were weakly connected via thinned ohmic contacts and an accumulation layer induced at an Al.5Ga.5As/n-GaAs insulator/semiconductor interface. A maximum product of Josephson current times normal state resistance, IoRo, of 10 µV was registered at a gate voltage of 2.6 V and a temperature of 1.6 K.
Quantized Current-Step Structure Observed in RF-Irradiated Microbridge Made of NbN Granular Thin Film
Authors: Yoshikawa N. , Akeyoshi T. , Kojima M. , Sugahara M.
Published: March 2014

Qunatized current-step structure are observed in rf-irradiated Dayem type microbridges with narrow width made of very high resistance NbN granular thin film. The step width is found to be proportional to the irradiation frequency. Some discussion is made on the assumption that the structure is caused by a new macroscopic quantum effect dual to Shapiro step.
Decay of the Zero Voltage State of a Josephson Junction Shunted by an Adjustable Impedance
Authors: Turlot E. , Linkwitz S. , Martinis J. M. , Esteve D. , Urbina C. , Devoret M. H. , Grabert H.
Published: March 2014

The decay of the zero voltage state of a Josephson junction shunted by an adjustable transmission line has been calculated. The junction obeys a generalized RSJ model with a time delayed damping term. In the low damping region of energy diffusion limited decay, the decay rate depends on the
delay time in an oscillatory manner. In contrast, in the moderate-to-high damping region, the decay rate depends monotonically on the delay time. We propose an experimental set-up in which the delay time can be varied in situ by changing the length of the transmission line leaving all the other junction parameters unchanged. The experiment should provide a test of the theoretical predictions of the influence of damping on the pre-exponential factor of the rate.
A Novel Point Contact Geometry for Thin Film- and Bulk-Materials
Authors: Koch Hans
Published: March 2014

When cleaving thin film coated silicon wafers or when breaking bulk samples, it is often possible to obtain very sharp edges. If the edges of two such samples are brought into contact to form a crossed wedge geometry, a point contact results. Experimental data will be presented for such point contacts made of Nb thin film, Nb single crystal and Y-Ba-Cu-O samples.
Performance of Large-β SQUID with a Damping Resistance
Authors: Enpuku K. , Kohjiro S. , Yoshida K.
Published: March 2014

Performance of a large-β dc SQUID is studied when a damping resistance in shunt with a SQUID inductance is introduced. In the presence of the damping resistance, the large-β SQUID can be used with little degradation of performance. The large-β SQUID relaxes the previous constraint in the design of the SQUID, and brings several merits when magnetometers are constructed with the SQUID.
Detection of Vortices by Quasiparticle Tunneling
Authors: Dittrich R. , Heiden C.
Published: March 2014

An SIS-tunnel junction was made using a niobium tip and a niobium sheet as electrodes. Stable normal resistances of the order of 0.1 to 100 kOhms could be obtained. Operating such junctions in the constant current mode a clearly visible modulation of the sum gap voltage Vsg could be detected caused by the passage of vortices across the contact area. In this experiment, with the tip position at rest, the variation of Vsg was induced by the motion of vortices that were driven either by a change of applied magnetic field or by an electric transport current of suitable magnitude in the niobium sheet. The results indicate on the other hand the feasibility of scanning tunneling microscopy of vortices at rest, using a suitable scanner for the tip electrode.
Spin-Dependent Interactions at a Superconductor-Magnetic Material Interface
Authors: Tkaczyk J. E. , Tedrow P. M.
Published: March 2014

The tunneling conductance of junctions on thin Al films with submonolayer surface layers of rare-earths has been measured for the purpose of studying the interaction of superconducting quasiparticles with rare-earth moments. The pairbreaking effect on the density of states is analyzed with the Abrikosov-Gor'kov theory. In a small applied field theory the rare-earth moments align whereupon the conductance shows a Zeeman splitting due to an exchange field of the order of 2 tesla. The observation of spin-splitting indicates a low spin-orbit scattering rate.
Phonon-Mediated Detection of Alpha Particles with Aluminum Transition Edge Sensors
Authors: Neuhauser Barbara , Cabrera Blas , Martoff C. Jeff , Young Betty A.
Published: March 2014

We report on particle detection experiments using aluminum superconducting transition edge sensors deposited on silicon wafers. The detectors consist of a 40 nm thick aluminum film patterned as a labyrinth with 299 lines. These films have Tc∼1.35 K and Ic∼8 µA at 1.30 K. New data have been obtained using a thin encapsulation 241Am alpha source (∼1% FWHM source linewidth for 5.5 MeV) which allows a detailed study of these sensors. With a bias current of 1.2 µA at 1.33 K, 0.4 mV pulses 1.5 µs long are obtained for alpha particles incident directly on the aluminum film. The pulse height distributions are strongly peaked (∼7% FWHM) and temperature dependent. In a second series of experiments, we have used the same alpha source to bombard the back of the silicon wafer (275 µm thick). With an alpha range of 25 µm, only the phonons generated by the alpha can produce the observed pulses in the aluminum film, demonstrating phonon mediated particle detection.
Relaxation of Brinkman-Smith Mode in Superfluid 3He–B between Parallel Plates
Authors: Ohmi Tetsuo , Tsubota Makoto , Tsuneto Toshihiko
Published: March 2014

The relaxation of the Brlnkman-Smlth (B–S) mode in superfluld 3He–B placed between parallel plates is considered. It Is known that the Leggett-Takagi mechanism does not lead to relaxation of the B–S mode In bulk 3He–B. In the presence of the boundaries, however, the B–S mode relaxes due to the surface torque, since this torque generates time dependent spatial variation of the texture which makes the Leggett-Takagi mechanism operative. Assuming that the perturbation due to the surface is small, we have calculated the recovery of the magnetization as a function of time. The result is compared with the data obtained by the pulsed N.M.R. experiment of Ishikawa et al., presented in this Conference.
Quasiperiodic and Chaotic States Observed in Taconis Oscillations
Authors: Yazaki T. , Okada A. , Mizutani F. , Tominaga A. , Narahara Y.
Published: March 2014

Highly nonlinear phenomena are observed in Taconis oscillations, which are spontaneous oscillations of gas columns induced by steep temperature gradients. Two different modes with incommensurate frequencies can be generated simultaneously and competition between them leads to quasiperiodic and chaotic states.
Phase Transitions of 2D Josephson Tunnel Junction Arrays
Authors: Zant H. S. J. van der , Wees B. J. van , Muller C. J. , Rijken H. A. , Mooij J. E.
Published: March 2014

We have studied square 2D arrays of Josephson tunnel junctions at different values of the normalized magnetic flux per cell f. At f=0 Kosterlitz-Thouless behaviour is observed in the linear as well as in the non-linear resistance. For low nonzero values of f the linear resistance shows thermally activated behaviour at low temperatures with f-dependent activation energy. At f=l/2 the phase transition is different from that at arbitrary or zero field
Superconduction Phase Coherence in Very Weak Aluminium Strips
Authors: Run A. J. van , Romijn J. , Mooij J. E.
Published: March 2014

In one-dimensional superconductors phase coherence is broken by phase-slip events. In the usual strips studied before, the resulting resistance was too small to be measured except in an extremely narrow temperature range near the critical temperature. We study strips with small cross-section and very small mean free path where quantitative comparison with theory is possible over a wide temperature range. Current is passed through the strips and the probability distribution for switching into the dissipative state determined. Results partly agree with predictions for localized occurrence of thermally activated phase-slip. Measurements are extended to lower temperatures to investigate the possibility of phase-slip by quantum tunneling.
High Field Studies of Superfluid 3He
Authors: Gould C. M. , Israelsson U. E. , Crooker B. C. , Bozler H. M.
Published: March 2014

We have measured the properties of zero sound propagating through superfluid 3He-A and -A1 in magnetic fields from 0 to 3 T. The phase diagram of the A1 phase has been measured and used to extract values of the Landau-Ginzburg β parameters which reflect microscopic quasiparticle scattering amplitudes. We also derive the ratio of the specific heat jumps at the A1 transition (in a magnetic field) to that at the A transition (in zero field) as a function of pressure. The excess susceptibility of the A phase over the normal liquid is similarly extracted. Finally, we present evidence for f-wave interactions in super fluid 3He.
Ballistic Quasiparticle Generation and Propagation in Superfluid 3He–B
Authors: Carney J. P. , Coates K. F. , Guénault A. M. , Pickett G. R. , Spencer G. F.
Published: March 2014

Ballistic quasiparticles are produced by means of a supercritically driven wire resonator in 3He-B at temperatures below 0.25 T

C
. At 0 bar pressure the observed critical velocity of the wire is about 9 mm/s relative to the container (or about 18 mm/s relative to the maximum superfluid back flow). This velocity scales with (Δ/p

F
) as a function of pressure, confirming that pair-breaking of the superfluid is the dissipation mechanism. At higher temperatures, the scattering of existing quasiparticles leads to dissipation at much lower velocities. The ballistic propagation of a pulse of quasiparticles through the superfluid is demonstrated by the mechanical force it applies to a second wire resonator at a distance of up to 6 mm. The detector is incorporated into a SQUID circuit to yield an ultra-sensitive force detector. We observe strong signals at the detector at the same frequency as the power dissipation in the generating wire, and of a magnitude proportional to the power dissipation. The order of magnitude of these signals agrees with a simple theoretical model of ballistic quasiparticle propagation. Comparison of the received forces from a number of different driving wires suggests that the quasiparticles are emitted with almost cylindrical symmetry, with a low flux emitted parallel to the wire axis. The phase of the received signals at 0 bar indicates that the propagation is rapid. The small reduction in signal as the temperature is raised shows that the attenuation of the quasiparticle beam is low. Future experiments are proposed on the influence of Andreev scattering of quasiparticles from a super flow field.
Nucleation and Growth of 3He-B in 3He-A
Authors: Swift G. W. , Buchanan D. S.
Published: March 2014

The 3He A → B transition is remarkable for a number of reasons. Because of the small bulk free energy difference between the two phases, the probability of homogeneous thermal nucleation of the B phase is vanishingly small. Thus the experimental fact that the B phase nucleates readily from the A phase is not understood. The A → B transition is also remarkable in that when it occurs after cooling from above the critical temperature, it occurs in an extreme state of supercooling known as hypercooling. In this situation, the velocity of propagation of the A-B phase interface is controlled by microscopic phenomena rather than by thermal diffusion. We briefly review our recent work on both these topics, including the velocity of propagation of the A-B interface through hypercooled 3He-A, a search for cosmic-ray-induced B-phase nucleation, and preliminary observations of B-phase nucleation locations and temperatures.
The Polarization of Liquid 3He by Fast Melting of Polarized Solid: Present State of the Art
Authors: Frossati G.
Published: March 2014

3He is a fermion, with a very small (nuclear) magnetic moment of 0.8 mK/Tesla. Because of its Pauli-spin susceptibility at T ≪ TF, large polarizations by brute-force would require magnetic fields of several hundred Tesla, which is impossible at present. In the last years two methods have been developed which allow large liquid polarization. The first used by the group of the Ecole Normale of Paris uses a laser to polarize the gas phase at room temperature followed by condensation. With this method liquid polarizations larger than 40% at 400 mK have been obtained and the results will be discussed by M. Leduc and co-workers. The second method which will be the subject of this paper is presently being used in 7 or 8 laboratories and was pioneered in Grenoble and Kopenhagen. It consists in quickly melting the highly polarized solid phase which, being Curie-like can be magnetized to more than 80% at a few mK in presently attainable fields. In this way liquid has been produced with polarization up to 60%, while the final temperatures range from 300 mK to 25 mK depending on the polarization. Relaxation times of 20 minutes have been obtained and several experiments are being carried out concerning viscosity, sound velocity, lowering of the melting curve, relaxation time etc. which will give important information on the nature of liquid 3He and the 3He-3He interaction.
Collective Modes of Super fluid 3He in High Fields: Group Velocity of High Frequency Sound in Super fluid 3He–B
Authors: Movshovich R. , Ziercher E. L. , Lee D. M.
Published: March 2014

Measurements of attenuation and group velocity of pulsed high frequency sound have been performed up to 137.6 MHz in superfluid 3He-B near the squashing mode of the order parameter. Passage through the collective mode was accomplished by sweeping pressure. The group velocity has been observed to decrease by more than a factor of 15 from the zero-sound velocity. The width of the squashing mode was seen to increase with magnetic field, as inferred from the group velocity data, making it the first observation of an effect of splitting of this mode in magnetic field.
Localization and Magnetic Interactions in Semimagnetic Semiconductors at Low Temperatures
Authors: Dietl Tomasz
Published: March 2014

Selected properties of I
I–V
I semiconducting compounds containing substitutional Mn or Fe are reviewed. The former (e.g.,Cd
1-x

Mn

x

Te) can be classified as dilute Heisenberg antiferromagnets while some of the latter (e.g.,Hg
1-x

Fe

x

Se) are mixed-valence systems. The origin of the sp–d and d–d exchange interactions in the Mn-based compounds and the influence of these interactions on low-temperature properties are discussed. Special attention is paid to experimental results and theoretical models which help to understand the striking behavior of doped magnetic semiconductors in the neighborhood of the Anderson-Mott transition. Low-temperature properties of Hg
1-x

Fe

x

Se are presented emphasizing the experimental findings and theoretical ideas which point to a substantial reduction of the electron scattering rate in the mixed-valence region. An experimental result suggesting the existence of superconductivity in this material is discussed.
Quantum Transport and Fluctuations in Small Systems
Authors: Lee Patrick A.
Published: March 2014

A review of the theory of conductance fluctuations in metals at low temperatures is given, with emphasis on the intuitive understanding of the basic physics, and the rich variety of physical phenomena that have been uncovered upon entering the quantum regime.