bluuebunny/crossref_metadata_2025 huggingface dataset:
Competition in the Dutch Electricity Market: An Empirical Analysis over 2006-2011
Authors: Mulder Machiel
Published: March 2014

We assess the development of competition in the Dutch electricity wholesale market over 2006-2011. In this period domestic generation capacity, both centralized and decentralized, as well as the cross-border transmission capacity increased. Using hourly plant-level data of centralized units and engineering-costs estimates, we estimate the weighted average Lerner index. During super peak hours, the annual average value of this index decreased from 0.23 in 2006 to 0.03 in 2011, indicating more competition. We find indications that the increase in competition can be attributed to the extension of cross-border connections, a higher price elasticity of net demand and more Bertrand-like competition. Enhancing the role of decentralized generation as well as fostering integration of markets seem to be effective measures to promote competition.
Raman and Infrared Studies of Oxide Superconductors (La1-xMx)2CuO4
Authors: Sugai Shunji , Sato Masatoshi , Hosoya Shoichi , Uchida Shin-ichi , Takagi Hidenori , Kitazawa Koichi , Tanaka Shoji
Published: March 2014

Raman and infrared studies of lattice vibrations in new superconductors (La1-xMx)2CuO4 are presented. The 664 cm-1 mode which shows resonant enhancement in La2CuO4 is assigned to the planar breathing mode which strongly interacts with electrons at EF. This resonant scattering is produced by the electronic transition spanning the quasi-square Fermi surface to the nesting directions. In the spectra of Im(ε) a strong peak appears at 246 cm-1 on substituting Sr for La. It is suggested that this mode is related to the electronic transition.
Photoelectron Spectroscopy of High-Tc Superconductor (La1-xSrx)2CuO4-δ
Authors: Takahashi Takashi , Maeda Fumihiko , Miyahara Tsuneaki , Hosoya Shoichi , Sato Masatoshi
Published: March 2014

Electronic structure and chemical state of high-Tc superconductor (La1-xSrx)2CuO4-δ (x=0.075 and δ≦0.04) were studied by photoelectron spectroscopy. Resonant photoemission with synchrotron radiation snowed that the copper atom in the La–Sr–Cu–0 system is mostly divalent. The experimental results were compared with the band calculations performed for La2CuO4.
A.C. Susceptibility and Specific Heat in Low B.C. Fields of La2-xSrxCuO4 and YBa2Cu3O7 High Temperature Superconductors
Authors: Junod A. , Bezinge A. , Cattani D. , Cors J. , Decroux M. , Fischer Ø. , Genoud P. , Hoffmann L. , Jorda J.-L. , Muller J. , Walker E.
Published: March 2014

We report the giant effect of small d.c. fields on a.c. diamagnetic transitions in La2-xSrxCuO4, and YBa2Cu3O7. An unexpected frequency effect is observed. In order to elucidate the apparent conflict Between the high critical field slope as measured by magnetoresistance experiments and the large depression of a.c. diamagnetic transitions, we locate the bulk transition by high resolution specific heat measurements in small fields. The results, together with d.c. magnetization measurements near Tc and SEM micrographs, suggest a model where superconducting regions with a high critical field are separated by weak links.
Characterization of the High-Tc Superconductors Rare-Earth–Ba–Cu Oxides–Resistivity, Susceptibility and Structure–
Authors: Kagoshima Seiichi , Takahashi Toshihiro , Kanoda Kazushi , Hasumi Masahiko , Hirai Takashi , Nogami Yoshio , Koga Kei-ichi , Yasuoka Hiroshi , Minami Hidetoshi , Masumi Taizo , Hikami Shinobu
Published: March 2014

Polycrystalline samples of the high-transition temperature superconductors Y–Ba–Cu, Ho–Ba–Cu and Gd–Ba–Cu oxides are characterized by resistivity, susceptibility, and x-ray measurements. Measured magnetic moments are ascribed mostly to magnetic rare-earth ions, and partly to Cu2+ ions and some other crystal phases. It is found that an oxygen pressure and a sample-preparation temperature dominate the amount of the Cu2+ ions and of other phases, respectively.
Structural Study of (La1-xMx)2CuO4-δ by X-Ray Four Circle Diffraction
Authors: Onoda Masashige , Shamoto Shin-ichi , Sato Masatoshi , Hosoya Syoichi
Published: March 2014

Full structure determinations of (La1-xMx)2CuO4-δ (M=Sr and Ba), La2CuO4 and M'Ba2Cu3O7-δ (M'=Y, Ho and Dy) are carried out by X-ray four circle diffraction. The structures of (La1-xMx)2CuO4-δ crystal specimens (x≃0.075 and δ≃0) which exhibit superconductivity are K2NiF4-type ones with CuO6 ochtahedra. The Sr compound is tetragonal (I4/mmm) and the Ba compound is orthorhombic (Pccn) characterized by the rotation of CuO6. This rotation is different from that observed in La2CuO4. All the present specimens of M'Ba2Cu3O7-δ, which are found to be semiconducting, are tetragonal with P4/mmrn and the δ values are close to 1.0. Their structures are perovskite-related ones with the c axis triplicated due to the ordering of Ba and Y (Ho and Dy).
Superconductivity Studies on Pure and F-Containing Ln–M–Cu–O (Ln=La, Y; M=Sr, Ba) System
Authors: Radhakrishnan T. S. , Kalavathi S. , Sastry V. S. , Chandrasekharan K. , Rao C. R. Venkateswara , Paranthaman M. , Varadaraju U. V. , Rao G. V. Subba
Published: March 2014

Efforts to partly substitute fluorine for oxygen in the high Tc oxide superconductors La2CuO4 and YBa2Cu3O7 showed that under the preparative conditions employed (950°C, air and oxygen), F does not replace O in the lattice.
Many-Polaron Theory for Superconducting Transition Temperatures–Self-Consistent Method for Fluctuation from BCS Limit to Bipolaronic Limit–
Authors: Nasu Keiichiro , Yanase A.
Published: March 2014

Superconducting transition temperatures Tc of a N-site N-electron system with a strong site-diagonal electron-phonon (e-p) coupling are studied in the context of polaron theory, so as to clarify the mechanism of high-temperature superconductivity in Cu-O type new ceramics. The phonon clouds moving with electrons, as well as the mass enhancement, are taken into account within the variational method and by the mean field theory. The effect of the fluctuation of the pairing order is also taken into account by the CPA combined with the two-state approximation. The resultant theory covers the whole region of the three basic parameters characterizing this system: the inter-site transfer energy of electron T, the e-p coupling energy S and the energy of the site-localized phonon ω. Tc is found to become maximum at the intermediate region S∼T, as S increases from the weak (BCS) region S≪T to the strong (bipolaronic) region S≫T. It is also concluded that the breathing mode phonon of oxygen atoms can give a high Tc of about 100K.
Role of the Interlayer Ionic Vibration in High-Tc Oxide Superconductors
Authors: Oguri Akira , Kuroda Yoshihiro
Published: March 2014

A theoretical model for the newly discovered high-Tc oxide superconductors is proposed. We regard the systems to form the layered structures composed of CuO2-conducting layers sand-wiched by one or two metal-oxide insulating layers for each. Then, by assuming the conduction electrons within a conducting layer to form a two-dimensional tight-binding band, we study the strong coupling between the conduction electrons and the local vibrations of the O-ions in the insulating layers and find that the phonon-mediated electron-electron interaction is strong enough to dominate the on-site repulsion and has finite range, which stabilizes the anisotropic Cooper pairing states. We calculate the superconducting transition temperature Tc using a set of realistic values of the parameters included in the model and find Tc≃26∼80K for the (La1-xAx)2CuO4-systems depending on the average number of the conduction electrons per Cu-ion.
Pressure Study and the Critical Current of High-Tc Superconductors YBa2Cu3O7-y and GdBa2Cu3O7-y
Authors: Yomo Shusuke , Murayama Chizuko , Utsumi Wataru , Takahashi Hiroki , Yagi Takehiko , Mōri Nobuo , Tamegai Tsuyoshl , Watanabe Akiko , Iye Yasuhiro
Published: March 2014

The pressure dependences of the superconducting transitions of the title materials have been studied under hydrostatic pressure up to Gpa. The midpoints of the resistive transitions were 92.2 K and 93.2 K for YBa2Cu3O7-y and GdBa2Cu3O7-y, respectively, and increased with increasing pressure at a rate of (5–6)×10-3 GPa-1. The critical current of GdBa2Cu3O7-y was two to three times as large as that of YBa2Cu3O7-y; both were enhanced by the application of pressure.
Structural and Dielectric Modulations of BaPb1-xBixO3
Authors: Hidaka Masanori , Fujii Hironari , Horie Yuuji , Mase Shoichi
Published: March 2014

The origin of superconductor-semiconductor transition of BaPb1-xBixO3 system was studied, using a piezoelectric resonance and a D-E hysteresis loop measurement. The transition was clearly characterized by remarkable differences in structural and dielectric properties in the two types of conductors. The results suggest that the disappearance-appearance of a localized antiferroelectric state may be closely related to the superconductor-semiconductor transition in these solid solutions.
Structure and Superconductivity of La1.8Sr0.2CuO4 and YBa2Cu3O7 under High Pressure
Authors: Dietrich M. R. , Fietz W. H. , Ecke J. , Politis C.
Published: March 2014

Pressure dependences of crystal structure and transition temperature for La1.8Sr0.2CuO4 with 40 K and YBa2Cu3O7 with 95 K are reported. The inductively measured 90%-value of Tc initially increases with +0.295 K/kbar for La1.8Sr0.2CuO4 and with +0.160 K/kbar for YBa2Cu3O7. The bulk modulus for La1.8Sr0.2CuO4 is 1600 +/- 130 kbar for 300 K and 1700 +/-130 kbar for 15 K. An estimation of the bulk modulus for YBa2Cu3O7 gives 1700 kbar. No change of the crystal structure occurs up to 220 kbar for La1.8Sr0.2CuO4 and up to 150 kbar for YBa2Cu3O7.
Magnetic Field Dependence of the Specific Heat of Some High-Tc Superconductors
Authors: Phillips N. E. , Fisher R. A. , Lacy S. E. , Marcenat C. , Olsen J. A. , Ham W. K. , Stacy A. M.
Published: March 2014

The specific heats, C, of 5 samples of La1.85M0.15CuO4-y (M=Ca, Sr, Ba), one sample of La2CuO4-y, and one sample of YBa2Cu3O9-y have been measured between 0.4 and 40K, in magnetic fields, H, to 7T. For the La1.85M0.15CuO4-y samples the H dependence of C near Tc and near 1K, where C is dominated by the electronic contribution gives information about the fraction of the sample that is a bulk superconductor and the density of electronic states. The fraction of bulk superconductivity indicated by the Meissner effect does not correlate well with that indicated by C. La2CuO4-y has a linear term in C, in qualitative agreement with a theoretical prediction [1].
Specific Heat of La2-xSrxCuO4 and YBa2Cu3O7 Superconductors from 1 K to Room Temperature
Authors: Junod A. , Bezinge A. , Cattani D. , Cors J. , Decroux M. , Fischer Ø. , Genoud P. , Hoffmann L. , Jorda J.-L. , Muller J. , Walker E.
Published: March 2014

The specific heat of the superconductors La1.85Sr0.15CuO4 and YBa2Cu3O7 was measured from 1 to 350 K. A maximum in C/T3 near 22 K indicates enhanced phonon density of states at energies ω∼11 meV. A lattice specific heat still below 3R at room temperature implies the existence of high energy phonon states at ∼50 meV or beyond. The initial Debye temperature lies in the 380–400 K range. At low temperatures, abnormal electronic contributions are seen, mainly in YBa2Cu3O7. The specific heat jumps are resolved in six samples: ΔC/Tc≃14 mJ·K-2·mole–Cu-1 in La1.85Sr0.15CuO4 and ΔC/Tc≃13 mJ·K-2·mole–Cu-1 in YBa2Cu3O7.
Superconductivity of La–Sr–Cu–O Single-Crystal Thin Films
Authors: Adachi Hideaki , Setsune Kentaro , Wasa Kiyotaka
Published: March 2014

We have grown single-crystal thin films of layered tetragonal La-Sr-Cu-O on (100) plane of SrTiO3 substrates by rf-magnetron sputtering. The basal plane of tetragonal structure in the film was parallel to the substrate surface. The single-crystal films exhibited superconductive transition at an onset temperature of 34 K and the zero-ρ state was observed below 25 K. The transition width (10 % to 90 %) was 3 K, which was much sharper than the characteristics of polycrystal films grown on MgO substrates.
A Possible Mechanism of Exiton Exchanging Percolated Superconductivity for Oxide Balacuo
Authors: Tao Ruibao
Published: March 2014

The effect of oxygen vacancies in oxide (La1-xBax) CuO4-y (Balacuo) is analyzed. It is pointed out that the vacancies in Cu–O basal plane will break the bonds Cu–O–Cu to delete the hopping between those coppers so that the electrical conduction of Cu–O basal plane would become a bond percolation system where there is an infinite cluster to carry a current and a lot of finite clusters are hung about it. It is favorable to create some mechanism of exchanging exciton so that the transition temperature TC of superconductivity could be increased significently. The comparison with Y1Ba2Cu3O9-y is also discussed briefly.
Orbital Dynamics of Superfluid 3He
Authors: Reppy J. D. , Gammel P. L.
Published: March 2014

Because the gap of superfluid 3He is anisotropic, any motion of the anisotropy axis will lead to a non-equilibrium quasiparticle distribution. Equilibrium can only be restored through quasiparticle collisions which lead to dissipation. This dissipation was measured using the damping of torsional oscillations of a powder-filled torus about its axis of symmetry. In both the A and B phases, the orbital viscosity coefficient, µ, extracted from the damping was proportional to (1-T/T

c
) near T

c
. At low temperatures µ, is independent of temperature. Both observations are in contrast with theoretical predictions. The dissipation is also sensitive to the presence of a d.c. supercurrent. This was used to study persistent currents in the A-phase, where the flow decayed in discrete jumps of approximately 5 circulation quanta.
Structure and Superconducting Properties of Ba3(1-x)Y3xCu3O9-y Compound System
Authors: Kumakura Hiroaki , Togano Kazumasa , Fukutomi Masao , Uehara Mitsuru , Tachikawa Kyoji
Published: March 2014

Structure and superconductivity of the Ba3(1-x)Y3xCu3O9-y compound system prepared by a powder method has been investigated. The zero-resistance temperature of 92.5K has been obtained for x=0.4. Detailed analysis of crystal structure was carried out by X-ray diffraction using Rietveld technique. Critical current densities Jc's were estimated from the magnetizations,which were compared to those obtained by the resistive method.
Specific Heat and Thermal Conductivity of Superconducting UBe13 and UPt3 at Very Low Temperatures
Authors: Ott H. R. , Felder E. , Bernasconi A , Fisk Z. , Smith J. L. , Taillefer L. , Lonzarich G. G.
Published: March 2014

Non-exponential temperature dependences of various physical properties in the superconducting state of UBe13 and UPt3 have been put forward as evidence for unconventional superconductivity in these materials. We report new experimental results for the specific heat cp and the thermal conductivity λ of UBe13 and UPt3 down to temperatures well below 0.1 K. In none of these measurements can an exponential temperature dependence be recognized. In some aspects, our data differ from those that were previously published. This indicates that sample purity and imperfection may be of importance.
Specific Heat of (U0.97Th0.03)Be13 under Pressure
Authors: Fisher R. A. , Lacy S. E. , Marcenat C. , Olsen J. A. , Phillips N. E. , Fisk Z. , Smith J. L.
Published: March 2014

The specific heat, C, of (U0.97Th0.03)Be13 has been measured for 0.1≤T≤1K and 1.6≤P≤7.7 kbar, and for 0.1≤T≤20K with P=0. For T>8K both the pure and Th substituted samples have essentially the same C. The peaks in C/T at 0.33 and 0.54K for P=0 are suppressed and shifted to lower T by pressure. Anomalies in C/T can be correlated to corresponding rapid changes in magnetic susceptibility, χ Rapid suppression of the peaks and shift of Tc to lower values is in marked contrast to the behavior found for pure UBe13 whose single peak amplitude decreases approximately linearly with P to about 60% at 9.3 kbar. The broad “shoulder” in C/T near 2K that is found for UBe13, but not for any other heavy-fermion compound, HFC, is commpletely suppressed in the Th substituted sample.
Spin Susceptibility in Heavy Fermion Superconductor CeCu2Si2
Authors: Kitaoka Yoshio , Yamada Hiroshi , Ueda Koh-ich , Kohori Yoh , Kohara Takao , Oda Yasukage , Asayama Kunisuke
Published: March 2014

The Knight shifts of 29Si and 63Cu in CeCu2Si2 with Tc=0.7 K have been measured in the temperature range 0.06K-100K. The shifts K||
and K⊥ with the tetragonal c-axis parallel and perpendicular to the applied field have shown a drastic reduction below Tc. The spin susceptibilities χ||
and χ⊥ are estimated to decrease to 60-70% and 35 % of the normal state value down to 0.3K and 0.06 K, respectively. This result presents a clear evidence for the singlet pairing-state.
Ultrasonic Attenuation Experiments in the Heavy-Fermion-Superconductor UPt3
Authors: Müller Volker , Maurer Dietrich , Roth Christian , Scheidt Ernst-Wilhelm , Lüders Klaus , Bucher Ernst , Bömmel Hans E.
Published: March 2014

We report on ultrasonic attenuation experiments in UPt3 in both the normal and superconducting state. As a function of temperature and magnetic field strength the ultrasonic attenuation shows an anomalous behaviour which demonstrates that superconductivity in UPt3 does not belong to a trivial class of superconductivity.
Time Dependent Magnetization in the Heavy Fermion Superconductor UBe13
Authors: Ma Y. P. , Brooks J. S. , Schmiedeshoff G. M. , Maple M. B. , Fisk Z. , Smith J. , Ott H. R.
Published: March 2014

We have measrued the D.C. magnetization of the heavy fermion superconductor UBe13 in both the superconducting and normal state to high magnetic fields. We find an exponential time dependence for the relaxation of the mixed-state magnetization which supports the mechanism of flux jump. τ is both temperature and field dependent and UBe13 behaves differently from similar experiments in conventional type II superconductors in this respect. Other substantial difference between the two include observation of a paramagnetic background and evidence for anisotropy effects in the single crystal of UBe13 studied. These results will be discussed in light of recent theoretical and experimental work on heavy fermion systems.
Inherent Spin Density Wave Instability of Anisotropic Superconductivity in Heavy Fermion System (U1-xThx)Be13
Authors: Machida Kazushlge , Kato Masaru
Published: March 2014

We have demonstrated an inherent instability of unconventional anlsotropic superconductivity (SC) states toward the spin density wave (SDW) formation on the reason why these SC states are stabilized. Within a mean field approximation for a two dimensional tight binding model including the on-slte repulsion and attractive interaction, we examine the competition between the SDW and various types of the d- and p-pairing states. The second transition observed in (U1-xThx)Be13 is interpreted to be due to the SDW transition out of an unconventional SC pairing state.
Effect of Substitutions on Heavy-Fermion UPt3
Authors: Kadowaki K. , Sprang M. van , Menovsky A. A. , Franse J. J. M.
Published: March 2014

Substitution effects of either uranium or platinum site by several foreign elements (Y, Ce, Th, Rh, Pd, Os, Ir and B) on the electrical resistivity of UP3 have been investigated in order to study systematic trends in the heavy-fermion superconductor UPt3. Resistivities at high temperatures show a clear saturation behavior, while they behave rather differently at low temperatures. An anomalously large increase of the residual resistivity was found especially in Th and Pd (about 20 µΩcm/at.%) and Y (about 10 µΩcm/at.%) substitutions. A rapid increase of the coefficient of the quadratic term in temperature of the resistivity is noteworthy especially in the case of boron addition.
29Si NMR Study of the Heavy-Electron System URu2Si2
Authors: Kohara Takao , Kohori Yoh , Asayama Kunisuke , Kitaoka Yoshio , Maple M. B. , Torikachvili M. S.
Published: March 2014

NMR and relaxation studies of 29Si have been carried out on the Heavy Fermion Superconductor, URu2Si2. The Knight shift measurement shows that the spin-susceptibility does not change appreciably in superconducting state through T

c
down to 0.5 K. 1/T
1 decreases in proportional to T
3 from T

c
down to 0.65 K without an enhancement just below T

c
and then deviates slightly at lower temperatures. These results suggest that the pair-state of this superconductor is either singlet with spin-orbit scattering by impurities or triplet both with gap-zero on a line at the Fermi surface.
Ultrasonic Attenuation in URu2Si2
Authors: Fukase Tetsuo , Koike Yoji , Nakanomyo Takashi , Shiokawa Yoshinobu , Makanomyo Alois A. , Mydosh John A. , Kes Peter H.
Published: March 2014

The ultrasonic attenuation and the sound velocity were measured on a single crystal of URu2Sr2 at frequencies up to 285 MHz. The sound velocity increases with decreasing temperature and shows a kink anomaly at TN=17.55 K, while the attenuation shows a step increase and takes a peak value at TN. Although the transition temperature TN, is independent of magnetic filed perpendicular to the c-axis, it quadratically decreases with increasing magnetic field H parallel to the c-axis (the magnetic easy axis), that is, TN(H)-TN(0)=-aH2 where a = 12 mK/T2. The attenuation takes a broad peak at the superconducting transition temperature Tc=1.20 K. Instead of the exponential BCS behavior, T3 dependence of th attenuation temperature observed at T≪Tc.
Effect of Transition-Metal Substitution for Fe in Superconducting Lu2Fe3Si5
Authors: Xu Y. , Shelton R. N.
Published: March 2014

The effect of transition-metal substitution for Fe on the superconducting transition temperature, Tc, 'of compounds Lu2(Fe1-x
T
x
)3Si5, where T=Cr, Mn, Co, Ni, Ru, is reported. In every instance, Tc of the host compound Lu2Fe3Si5(Tc=6.11 K) is reduced by the addition of other transition metals. An analysis of the data within the framework of the theory due to Kaiser suggests the depression of Tc is due to the formation of a nonmagnetic resonance state.
Zero-Point Quantum Fluctuations in Ultra-Thin Superconducting Films
Authors: Jaeger H. M. , Haviland D. B. , Goldman A. M. , Orr B. G.
Published: March 2014

Investigations of the onset of superconductivity in ultra-thin films of Ga and Pb, deposited onto substrates held at low temperatures have been carried out. The measurements have revealed the existence of a threshold for superconductivity in which the normal-state sheet resistance is the only relevant parameter. It is found that only when the normal-state sheet resistance falls below h/4e2 does a film exhibit zero resistance at low temperatures. This value for the threshold is in agreement with recent theoretical models predicting a dissipation driven phase transition. At values greater than this threshold, but nevertheless close to it, a systematic and rapid variation of the low-temperature resistance with normal-state resistance is observed. We interpret this behavior as due to strong zero-point quantum fluctuations and speculate that it can be modelled as a 2-D XY transition in which dissipation rather than temperature is the control -parameter.
Superconductivity of Ion-Beam-Sputtered Amorphous Beryllium Thin Films
Authors: Okamoto Minoru , Takei Koji , Maeda Yasushi
Published: March 2014

In order to investigate the origin of the Tc enhancement in ion-beam-sputtered Be films, the electronic density of states at Fermi level N(0) was estimated from the temperature dependence of the critical magnetic field Hc2 and the Hall coefficient RH measurements. The Tc dependence on N(0) was discussed by considering BCS's relationship between Tc and N(0). This experiment showed that the Tc enhancement was caused by not only N(0) increment but also other factors.
Fluctuation-Induced Conductivity of Superconducting Films with the Lithium Fluoride Precoating
Authors: Kobayashi T. , Kojima S. , Okamoto K. , Ohtsuka M.
Published: March 2014

Effect of the lithium fluoride precoating on the fluctuation-induced conductivity (FIC) above the superconducting transition temperature was investigated for indium and vanadium films. Samples were precoated with lithium fluoride (about 3000A in thickness). The FIC is well explained by the traditional fluctuation theory with three parameters, the superconducting transition temperature T

c
, the pair-breaking parameter δ and the normal sheet resistance R
n
□. The precoating effect changes the coefficient b of the experimental relation δ=a+b
R
n
□. The morphology of these films was observed by the electron microscope. The correlation between the pair-breaking parameter and the grain size is discussed.
Superconducting Properties of Iron-Containing Ternary Silicides Lu–Fe–Si
Authors: Oota Akio , Fukunaga Tetsuya , Koyama Kuniyuku , Noguchi Seiichiro
Published: March 2014

The effect of off-stoichiometry on superconductivity is studied in the iron-containing silicide Lu2Fe3Si5. The superconducting transition temperature has a maximum (∼6.0K) on the stoichiometry and decreases with a deviation from it (especially on the Fe- or Lu-rich side). The resistivity and susceptibility studies, together with the metallographic study, suggest that an increase of second phases on the Fe- or Lu-rich side enhances magnetic interactions to conduction electrons and thus results in the degradation of superconductivity. A number of the parameters are evaluated from the experimental data on both stoichiometric Lu2Fe3Si5 and Y2Fe3Si5. The residual resistivity estimated from the slope of upper critical field agrees fairly well with the experimental value.
Superconductivity vs Charge Density Wave in One-Dimensional Bipolaron System with Random Potentials
Authors: Nagaosa Naoto
Published: March 2014

We investigate the ellects of the randomness and interactions on the competition between superconductivity and charge density wave in one dimensional bipolaron system in the half filled case at finite temperatures by carring out the numerical simulation on the S=1/2 XXZ spin chain using the transfer matrix by Suzuki-Trotter formula. We obtain the scaling form of the correlation functions as functions of temperature and strength of the random potentials. These results are discussed in connection with the Fukuyama-Lee length in the problem of the charge density wave pinning.
Paramagnons in Superconductors with Concentration Fluctuations
Authors: Crisan Mircea , Grosu Ion
Published: March 2014

The strong coupling theory of the supraconductors with strong concentration fluctuation is presented taking into consideration the interaction between electrons and concentration and the electron-paramagnon coupling. We also sonsidered the influence of the Anderson localization taking a modified Coulomb repulsion. An analytical formula has been obtained for the critical temperature in the strong coupling regime of localization.
Electronic Properties of New Organic Superconductors θ- and κ–(BEDT-TTF)2I3
Authors: Kajita K. , Nishio Y. , Moriyama S. , Kato R. , Kobayashi A. , Kobayashi H. , Sasaki W.
Published: March 2014

We have synthesized new organic superconductors θ- and κ-(BEDT-TTF)2I3, which have two dimensional electronic structure with the Fermi surface isotropic in the 2D plane.
This paper deals with the anomalous magnetoresistance effect observed in the normal state, which is summarized as follows.
1. The magnetoresistance is a linear function of the magnetic field. 2. It depends on the magnetic field direction relative to the crystal axis and does not depends on the current direction.
Superconductivity in the Mercury-Chain Compound Hg3-δAsF6
Authors: Sugiyama Tadao , Weger Meir
Published: March 2014

Studies for the zero-field diamagnetic susceptibility of the mercury-chain compound Hg3-δAsF6 is reviewed, using the anisotropic Ginzburg-Landau (GL) theory, with a model BCS Hamiltonian with only interchain coupling.
Quantum Dynamics of Small Josephson Junctions
Authors: Panyukov S. V. , Zaikin A. D.
Published: March 2014

The general microscopic theory of “secondary” quantum effects in small superconducting tunnel junctions is proposed. Both linear (due to the Ohmic shunt) and “cosine” (due to the quasiparticle tunneling) dissipation mechanisms are considered. Quantum diffusion in the quasicharge space may be caused either by Cooper-pair tunneling or by single-electron tunneling (SET) for low temperature and bias. Quantum corrections to the classical Ohmic resistance are calculated for both cases. Coherent oscillations of the voltage (both Bloch and SET oscillations and also their coexistence) and current-voltage characteristics are studied for all parameter regions of interest.
Secondary Quantum Macroscopic Effects in Distributed Josephson Junctions
Authors: Vasenko S. A.
Published: March 2014

The influence of a finite junction size on various macroscopic quantum effects is analyzed. Namely, we have calculated the contribution of the Fiske modes to : a - the width of the lowest Bloch energy band of an unbiased junction, b - the rate of the macroscopic quantum tunneling from a single energy well, and c - the energy splitting due to macroscopic coherence for the double-well potential.
Superconducting Fluctuations and Transition Temperatures of Ultrathin V Films and V–Si Multilayered Systems
Authors: Kanoda Kazushi , Mazaki Hiromasa , Mizutani Toshiyuki , Hosoito Nobuyoshi , Shinjo Teruya
Published: March 2014

The resistive measurements were made on ultrathin V films and V–Si multilayered systems. The superconducting transition of the V films remains sharp down to, at least, the thickness of 25 Å. The transition temperatures (T
c) decrease with the film thickness due to the localization and the bulk resistivity effect. Two-dimensional superconducting fluctuations were observed up to 2T in the V films. Multilayering with amorphous Si was found to reduce the fluctuations more and more as the Si layer becomes thinner. A variation in T
c of the V–Si multilayers was examined as a function of Si-layer thickness.
Superconductivity of Pb/Si Multilayered Films
Authors: Kawabata Kazushige , Mizutani Makoto , Tanaka Keiji , Kawasaki Kenji
Published: March 2014

Pb/Si multilayers are prepared by rf sputtering on substrates which are cooled down by liq.N2. Clear modulation of the composition in the multilayers is confirmed by the XPS depth profile examination. The superconducting transition temperatures of the multilayers are almost 7.2K, which is close to the value of bulk Pb. The critical magnetic fields are very large values and exhibit a large anisotropy.
Electron Transport Properties of Ag/Co Layered Metallic Films
Authors: Slaughter J. , Bass J. , Jr. W. P. Pratt, , Schroeder P. A. , Sato H.
Published: March 2014

Measurements of resistance parallel to the layers have been made for sample periodicities A between 16 and 160Å at temperatures of 4.2, 78, and 295K. A simple analysis, extending Fuch's theory to multiple layers and involving a single fitting parameter, fits the data well and indicates a transmission coefficient of an electron through an Ag/Co interface which is independent of A and which only changes slightly with temperature between 4.2 and 295K. Preliminary data on the resistivity perpendicular to the layers are given.
Andreev Reflections and Current Voltage Characteristics of SNS-Junctions
Authors: Kummel R. , Huckestein B. , Nicolsky R.
Published: March 2014

The Andreev reflected, accelerated electron-hole wave packet solutions of the time-dependent Bogoliubov-de Gennes equations for a three-dimensional, phase-coherent superconductor-normal metal-superconductor junction in a uniform electric field are used in order to calculate the total time-averaged current density of the system at any temperature below Tc. Scattering from impurities and phonons is taken into account in the relaxation time approximation. The theory yields the excess current experimentally observed in weak links at “high” voltages eV≫Δ (Δ=pair potential). At low voltages eV≪Δ the current voltage characteristic corresponds to the so-called “foot” of variable-thickness microconstrictions. In the intermediate voltage range eV≃Δ subharmonic energy gap structures are obtained.
Low-Temperature Thermal Diffusivity in Oriented Polyethylene
Authors: Kogure Yoshiaki , Hiki Yosio , Mugishima Toshio , Kawasaki Kenji , Nakamura Hiroaki
Published: March 2014

The thermal diffusivity has been measured for oriented polyethylene samples by the laser flash method in a wide range of temperature, 2 K - 300 K. The specimens were prepared by an extrusion process with the draw ratio 5.9. The orientation factor of the molecular-chain alignment of the specimen determined by an x-ray method was 0.967, and the crystallinity measured by the calorimetry was 68 %. It was found that the thermal diffusivity in the direction parallel to the chain molecules was about four times larger than that in the perpendicular direction at the lowest temperature.
Two and Three Dimensional Disorder in the Flux-Line Lattice
Authors: Berghuis P. , Wördenweber R. , Kes P. H.
Published: March 2014

The macroscopic pinning force FP in a thick film of amorphous Nb3Ge was measured as a function of temperature at constant field. A big jump in FP accompanied by hysteresis indicates a structural phase transition of the flux line lattice from a straight defect-free configuration to a highly disordered structure with topological defects both normal and parallel to the applied field direction (the “spaghettti” state). Above the transition temperature some novel features are observed in the behavior of FP versus temperature. A possible explanation is discussed.
Flux Cutting Phenomena in a Hollow Cylinder of a Type II Superconductor
Authors: Leblanc M. A. R. , Fillion G. , Golebiowsky A.
Published: March 2014

The magnetic flux permeating the wall of a hollow cylinder subjected to a magnetic field, whose helicity and strength are made to vary simultaneously along both its inner and outer surfaces, exhibits remarkable behaviour showing that flux cutting and flux consumption are taking place as the flux configuration evolves.
Specific Heat of Cold-Deformed Nb80Ti20-Foils at Low Temperatures
Authors: Mertig Michael
Published: March 2014

The heat capacity of Nb80Ti20-foils has been measured in the temperature range between 2 and 15 K by means of microcalorimetric methods. The influence of the thickness reduction up to 98.8% and the following annealing of the samples on the electronic part and the phonon contribution has been investigated.
Effect of Neutron Irradiation on Nb3Sn Superconducting Composites
Authors: Katagiri Kazumune , Saito Koji , Okada Toichi , Kodaka Hisao , Yoshida Hiroyuki
Published: March 2014

The influence of neutron irradiation at ambient temperature on critical current and its strain dependence in bronze processed (Nb,Ti)3Sn superconducting composites has been investigated up to the fluence of 3.0×1019 n/cm2 ( E > 0.1MeV ). The critical current Ic at 4 T increased with fluence up to ∼3×1018 n/cm2 and then decreased to almost zero at 3.0×1019 n/cm2. Addition of Ti reduced the fluence at which degradation of Ic took place. The characteristic strain values in Ic vs. strain relation are altered with fluence. These results are discussed through the changes in the upper critical magnetic field and the mechanical properties induced by neutron irradiation.
Anomalous Transport Across the 3He A–B Interface
Authors: Yip Sungkit
Published: March 2014

We consider transmission of excitations across the 3He A–B interface. It is shown that quasiparticles moving past the interface experience different effective superfluid flow dependent on the quasiparticle momentum direction. This gives rise to a transport of momentum perpendicular to ℓ and the interface normal when the bulk phases are not at the same temperature. We show that the heat current and the above transverse force can be considered as “generalized currents” in response to the “generalized forces” of temperature and normal velocity differences across the interface in the sense of Onsager. The Onsager relation is discussed.
NbTi Superconducting Wires for AC Use
Authors: Ohmatsu Kazuya , Takei Hiromi , Tateishi Hiroshi , Onishi Toshitada
Published: March 2014

NbTi superconducting wires with very fine filaments were developed for AC use. Critical current density shows a large value of 1×104 (A/mm2) in a low magnetic field when the filament size is 0.07 µm. Upper critical field decreases from 11 Tesla for 0.6 µm and reaches 9 Tesla for 0.03 µm. 5 KVA coils using these wires were successfully operated under alternating currents.
Low Noise Four-Photon Josephson Parametric Amplification
Authors: Olsson H. K. , Claeson T.
Published: March 2014

We report the first double-sideband noise temperature measurements of a Josephson parametric amplifier. The 9 GHz amplifier consists of an LC-resonant tunnel junction coupled to a low impedance transformer. TDSB=4.5±3K and GDSB=+13dB was measured in the externally pumped four photon mode with an instantaneous bandwidth of 290 MHz. Room temperature noise was reduced to a low level by a cryogenic circulator and a cooled 20 dB attenuator. The noise temperature measurements were made via a “hot/cold” technique with input temperatures close to the bath temperature.
Quasiclassical Boundary Conditions for Superfluid Fermi Systems
Authors: Hara Jun'ichiro , Nagai Katsuhiko
Published: March 2014

We show that the quasiclassical Green function for Fermi liquids can be constructed from the solutions of the Bogoliubov-de Gennes equation within the Andreev approximation and derive self-consistent relations to be satisfied by the quasiclassical Green function at the surfaces. The so called normalization condition for the quasiclassical Green function is obtained from this self-consistent relation. Our boundary condition for the randomly rippled wall is different from that previously derived by Buchholtz and Rainer and by Buchholtz.
A Low-Noise Seven-Channel DC SQUID Magnetometer for Brain Research
Authors: Kajola Matti , Ahlfors Seppo , Ahonen Antti , Hällström Jari , Knuutila Jukka , Lounasmaa Olli V. , Tesche Claudia , Vilkman Visa
Published: March 2014

The design, construction, and performance of a high-sensitivity DC SQUID magnetometer, covering a circular area of 93 mm diameter, is described. The device, now used routinely in our brain research, comprises seven asymmetric first-order gradiometers, located on a spherical surface of 125 mm radius and with the symmetry axis tilted 30° in respect to the vertical. The overall field sensitivity of the system, measured inside our magnetically shielded room, is 5 – 6 fT/√Hz ,mainly caused by thermal noise in the radiation shields of the dewar.
Subpicosecond Pulse Propagation on Superconducting Striplines
Authors: Whitaker John F. , Sobolewski Roman , Dykaar Douglas R. , Hsiang Thomas Y. , Mourou Gerard A.
Published: March 2014

We have studied the subpicosecond propagation characteristics of indium coplanar transmission lines. As the transients propagated along the striplines, they exhibited stretched rise time, increased pulse width, and entry of a ringing component. In addition, we observed a “pulse sharpening” for the first time at short propagation distances. It was found that these results could not be fully accounted for by invoking the Mattis-Bardeen theory of microwave conductivity alone. Rather, the predominant effect was due to modal dispersion resulting from the dielectric mismatch at the transmission line and substrate interface. Theoretical results are successfully compared with the experimental findings.
Interaction of a Fluxon with a Local Inhomogeneity in a Long Josephson Junction
Authors: Kivshar Yuri S. , Malomed Boris A.
Published: March 2014

We present results of the study of adiabatic and radiative effects accompanying collision of a fluxon with a localized defect which is a combination of a micro-short or micro-resistor with a dissipative inhomogeneity. Threshold values of a bias current which allow capture of a fluxon by the defect in a damped dc driven junction are found for various practically important cases. We also calculate the energy emitted by a fluxon in the form of Swihart waves, and we demonstrate that a Josephson microwave generator operating on an array of localized dissipative defects must be more effective than usual one employing micro-shorts.
Electron Beam Testing of Josephson Junction Voltages
Authors: Sadorf H. , Jutzi W.
Published: March 2014

Voltages in the mV range of Josephson junctions have been measured in a standard scanning electron microscope at liquid helium temperatures with a secondary electron analyser where a local cryopump has been integrated to avoid contamination and condensation at the specimen.
Study on Hysteresis in Josephson Tunnel Junction: Calculating the Minimum Current on Phase Plane
Authors: Huang Qiang , Wu P. H.
Published: March 2014

The quasi-particle IV curve of a Josephson tunnel junction is approximated using piece-wise linearization with slopes of 1/R1 over the gap voltage, 1/R2 below it and a vertical segment in between. Thus the original equation with nonlinear damping is replaced by two equations with different linear dampings. By solving these two equations in the proper regions of phase plane and joining together the phase trajectories across the boundary, we are able to find the stable periodic solution to the original equation from which much information can be deduced. As an example, a calculation of the minimum current, below which the junction will switch from non-zero voltage state to zero voltage state, is given. The calculated relationship between the minimum current and the critical pair-current density agrees well with the experimental data.
Niobium Nitride Josephson Junctions with Double-Tunnel Barriers
Authors: Shoji Akira , Aoyagi Masahiro , Kosaka Shin , Shinoki Fujitoshi
Published: March 2014

Multi-layered Josephson tunnel junctions composed of NbN base, intermediate(5-10 nm), counterelectrodes, and two MgO barriers have been fabricated. The NbN/MgO/NbN/MgO/NbN junctions have shown good tunneling characteristics with clear gap structures and small subgap leakage currents. The energy gaps for the intermediate electrodes have been estimated to be 2.3-2.4 meV. High uniformity of critical currents has been obtained for an array of 1000 NbN/MgO/NbN/MgO/NbN junctions.
Microscopic Theory of the Proximity Effect in the Superconducting Transistor
Authors: Tanaka Yukio , Tsukada Masaru
Published: March 2014

Based on exact single-particle eigen functions of a superconductor-inversion layer model system, microscopic theory of the superconducting proximity effect is developed. The general integral kernel of Gorkov equation is obtained, which connects the clean and the dirty limit. Numerical solutions of the pair potential are obtained for this kernel. Based on this, the boundary condition of the pair potential, and the behaviour of the extrapolation length are clarified. The result connects naturally the dirty limit, where the phenomenological theory by de Gennes is valid, to the clean limit where the wave character of the Cooper pair prevails.
Telegraph Noise Spectroscopy of Submicron Ta/PbBi Junctions
Authors: Track Elie K. , Prober Daniel E.
Published: March 2014

We report on the noise properties of Ta-Ta oxide-Pb0.9Bi0.1 tunnel junctions of area 0.2-1 µm2 and resistance RN∼15-300 Ω in the frequency range 1 Hz to 105 Hz. The noise power spectrum displays one or several distinct Lorentzian peaks associated with the observed switching of the junction resistance between discrete levels. The switching rates increase with temperature and bias voltage and are unaffected by an applied magnetic field of up to 50 kGauss.
RF-Induced Steps in Resonant Josephson Junctions
Authors: Costabile G. , Koshelets V. P. , Monaco R. , Pagano S.
Published: March 2014

We have studied experimentally the RF-induced steps in long Josephson junctions, varying the external microwave frequency in a range covering the junction geometrical resonance. We have observed a large variety of phenomena, going from a dependence of the step amplitudes on their parity, to a strong asymmetric behavior with respect to the junction resonance frequency, to a very high sensitivity to the external RF power. A comparison of our results with the existing theories is also reported.
Fluctuation Effects in Al/Stearate/Al Tunnel Junctions
Authors: Hatanaka Keisaku , Sawada Anju , Takanaka Kenji , Fujita Toshizo , Ohtsuka Taiichiro
Published: March 2014

Electron tunneling between two aluminum films separated by one molecular layer of stearate film has been investigated. Zero bias tunneling conductance anomaly we believe to be due to superconducting fluctuation effect has been observed over a wide temperature interval of 1.9 K to 4.2 K. The functional dependence of excess tunneling conductance with temperature, bias voltage and magnetic
field are in accordance with the theoretical predictions of the fluctuation tunneling between two normal metals.
Motion of the Two-Dimensional Mixed State in a Type-I Superconductor
Authors: Holguin Edgar , Rinderer Léo
Published: March 2014

We present an experimental and theoretical study of the two-dimensional mixed state (M) in a hollow type I superconductor. By introducing an axial current-carrying wire into the hole of the sample, it was possible to investigate its motion when it undergoes a displacement from the external surface of the sample to the interior. In this case, the M state moves between two normal regions and its velocity is controlled by electromagnetic damping. From experimental data, we obtained information about its stability and the total transition time.
Use of Europium Selenide Films for Magneto-Optical Studies at Low Temperatures
Authors: Dutoit Bertrand , Rinderer Leo
Published: March 2014

The resolution of the magneto-optical technique to observe directly the structure of the intermediate state in superconductors has been considerably improved by the replacement of EuS–EuF2 mixture by EuSe thin films with higher specific Faraday rotation. This allows a reduction of the magneto-optical film thickness, and consequently an enhancement of the optical and magnetic resolution. This greater rotation gives the possibility to work with the polarizers not completely crossed, and therefore to produce more luminous images. Theses images can directly be observed with a video camera so the rapidly changing structures can be recorded and flux tube velocities measured.
New Complex Magnetic Material for Ericsson Magnetic Refrigerator
Authors: Sahashi Masashi , Niu Hiromi , Tokai Yoichi , Inomata Koichiro , Hashimoto Takasu , Matsumoto Koichi , Tomokiyo Akira , Yayama Hideki
Published: March 2014

A complex magnetic material for use in the Ericsson magnetic refrigerator was investigated. In order to refrigerate effectively in the high temperature range above 10K, it is necessary to utilize the Ericsson cycle that includes two kinds of iso-magnetic field process, because lattice entropy for a magnetic refrigerant amounts to the same order of magnitude as that for magnetic entropy. Therefore in the Ericsson magnetic refrigerant, magnetic entropy change ΔSM is required to be constant in the refrigeration range. This property, however, cannot be satisfied by usual ferromagnetic material. In this paper, the complex RAl2 magnetic mixture (where R denotes heavy rare earth atoms) in grain size scale is prepared by shock compression method. Magnetic entropy changes are determined from the specific heat measurement. This magnetic mixture has high density, which is composed of several RAl2 compounds with different Curie temperatures, where each RAl2 is surrounded by gold. From these experimental results, it is concluded that the complex magnetic mixture with gold, such as (ErAl2)0.3 (HoAl2)0.2(Dy0.5Ho0.5Al2)0.5, shows an almost temperature independent magnetic entropy change ΔSM in some temperature range, which is suitable for the Ericsson cycle, satisfying the Carnot principle.
The 3He Second Virial Coefficient below 20.3 K
Authors: Matacotta F. C. , McConville G. T. , Steur P. P. M. , Durieux M.
Published: March 2014

Using a conventional gas thermometer and based on the temperature scale EPT-76 measurements of the 3He second virial coefficient B(T) have been performed in the temperature range 1.5 K - 20.3 K, referenced to B at 20.3 K. The results are compared with the predictions of the most recent potential calculations.