bluuebunny/crossref_metadata_2025 huggingface dataset:
SURFACE POLARITY OF ALUMINA
Authors: BURSILL L.A. , LIN PENG JU , SMITH DAVID J.
Published: November 2004

Atomic-resolution electron microscopic surface profile images of sapphire are reported for the first time. Comparison of experimental images with computer simulations, leads to the realization that aluminium and oxygen atom surface terminations may be distinguished, for both neutral and charged surfaces. Hence surface polarity, as well as details of surface step structure and mobility may be determined. Positive surface polarity is preferred.
MACROSCOPIC PROPERTIES AND SCHOTTKY BARRIER FORMATION AT SILICIDE-SILICON INTERFACES
Authors: HO PAUL S.
Published: November 2004

This paper reviews the current understanding of the microscopic properties of silicide-silicon interfaces pertaining to the formation of Schottky barrier. Significant progress has been accomplished, including the preparation of single-crystal silicide interfaces and the observation of interface states. Some important issues remain unresolved, such as the disagreement on the epitaxial nickel silicide barriers and the origin of interface states.
DIRECTED REACTION PROCESS AND STRUCTURAL STUDY OF SINGLE-PHASE SUPERCONDUCTING COMPOUND YBa2Cu3O6.5+δ
Authors: JI CHUNLIN , CUI CHUANMENG , WAN KUIHAN , LIU SULAN , ZENG GUIYI , ZHANG GUOFAN , QIAN CUENFU , BIAN WEIMING , FAN ZHANGGUO , XUE QIAN
Published: November 2004

A directed reaction process based on physico-chemical principles has been designed for producing single-phase 90 K “zero-resistance” superconducting compound YBa2Cu3O6.5+δ. The reliability of the process has been well proved by the stability and reproducibility of results in resistance and AC magnetic susceptibility measurements of seven samples taken randomly from three batches of products. X-ray diffraction, SEM and TEM examinations have identified the product as single-phase polycrystalline material of orthorhombic structure with lattice parameters a=3.89 Å, b=3.82 Å and c=11.65 Å. Many micro-twinned defects were observed under TEM along [110] axes. The nonstoichiometric fraction, δ value, was determined using a physico-chemical method.
A STRUCTURAL CHEMICAL MODEL FOR HIGH Tc CERAMIC SUPERCONDUCTORS
Authors: OVSHINSKY S.R. , HUDGENS S.J. , LINTVEDT R.L. , RORABACHER D.B.
Published: November 2004

A structual chemical model for high Tc ceramic superconductors is proposed in which carriers pairs, coupled through a superexchange process, undergo Bose condensation. In the Y-Ba-Cu-O system, Cu atoms on “chain” sites and “sheet” sites are initially assigned formal oxidation states of +3 and +2, respectively, and “sheet”/“chain” interactions are then introduced to bring about the electrically conductive mixed oxidation state. This model explains the presence of labile oxygen in the “chain” structures, describes the structure of deoxygenated phases exhibiting ordered oxygen vacancies in the “chains”, and allows interpretation of the effects of oxygen removal on magnetic and electronic properties of the material.
SUPERCONDUCTIVITY AND CRYSTAL STRUCTURE OF LaBa2−xCaxCu3O7
Authors: DONG C. , LIANG J.K. , NI Y.M. , ZHAO Z.X. , WANG Y.G. , LI L.
Published: November 2004

The samples with nominal composition LaBa2−xCaxCu3O7 (x=0, 0.5, 1.0, 1.5, 2.0) have been prepared by solid state reactions and studied by x-ray diffraction method and transmission electron microscopy. The substitution of Ba by Ca results in the decrease of the cell volume, increase of the structural orthorhombic distortion and appearance of the c/3 translation domain. Of the five samples studied only those with x=0, 1.0, and 1.5 are superconductors. The x=0 sample shows onset temperature 90 K, the zero resistance temperature 45 K and a weak diamagnetic effect. The x=1.5 sample shows zero resistance at 72 K and sustantial diamagnetic effect. The relation between the crystal structure and superconductivity is discussed.
SUPERCONDUCTIVITY IN THE U-Y-Ba-Cu-O SYSTEM
Authors: QIN Q.Z. , HE A.D. , JIA W.J. , MA L.D. , HUA Z.Y.
Published: November 2004

High Tc superconductivity has been observed in a new U-Y-Ba-Cu-O system at ambient pressure. The zero-resistance temperature in the sample with nominal composition of U0.1Y1.1Ba0.8CuO4−δ is 87K with a width of 2K. X-ray diffraction analysis shows that none of the peaks could be fitted to the uranium oxides and the other raw material structure, and its pattern might be attributed to new multiple phases with structure different from the known single-phase superconducting oxides.
HIGH Tc “1 2 3” SUPERCONDUCTIVE FILMS ON SILICON SUBSTRATES
Authors: POULLAIN G. , MERCEY B. , MURRAY H. , RAVEAU B.
Published: November 2004

YBa2Cu3O7 films have been deposited by pulse laser evaporation on silicon substrates with metal nitrides (AIN, Si 3 N 4, GaN) buffer layers. The film superconductivity is restored after annealing at 900°C in pure oxygen atmosphere. X-ray diffraction patterns confirm the presence of the orthorhombic phase and resistivity measurements versus temperature shows a resistive transition with an onset at 90 K and a complete zero resistance at 70 K.
SINGLE CRYSTAL GROWTH OF SUPERCONDUCTING COMPOUND Bi-Ca-Sr-Cu-O
Authors: YAN Y.F. , LI C.Z. , WANG J.H. , CHANG Y.C. , YANG Q.S. , HOU D.S. , CHU X. , MAI Z.H. , ZHANG H.Y. , ZHENG D.N. , NI Y.M. , JIA S.L. , SHEN D.H. , ZHAO Z.X.
Published: November 2004

We have prepared two kinds of single crystals in Bi-Sr-Ca-Cu oxides by flux method;plate-like single crystals which exhibit metal to superconductor at 93 K, being the high-Tclayered compound BiSr (Ca 0.35 Sr 0.25 Bi 0.40)2 Cu 2Oy with orthorhombic structure with a=5.42 Å, b=5.44 Å and c=30.78 Å respectively, and another kind of bar-shapedbismuth-poor single crystals which is superconducting at the temperature below 82K whilebeing semiconducting above this temperature.
THE EFFECT OF Ag-DOPING ON THE CRITICAL CURRENT DENSITY OF YBa2Cu3O7−δ SUPERCONDUCTORS
Authors: LUE JUH TZENG , KUNG J.H. , YEN H.H. , CHEN Y.C. , WU P.T.
Published: November 2004

The superconducting state and the transition temperature Tc of the interstitially Ag-doped YBa 2 Cu 3 O 7−δ are not changed even when the Ag concentration is increased up to 20%, whereas the substitutionally doped YBa 2 Cu 3−x Ag x O 7−δ system ceases to be superconductive when the contents x of Ag is over 1.2. Magnetic susceptibility measurement indicates that the interstitial Ag-doping yields higher diamagnetic signal and enhances the critical current density by 15 folds. Photoelectron emission and electron spin resonance spectroscopic studies elucidate that the copper ions change from diamagnetic to paramagnetic states at some doping levels.
INVESTIGATIONS OF AFTERGLOWS FROM SURFACE-WAVE- PRODUCED PLASMA
Authors: COTRINO J. , GAMERO A. , SOLA A. , BENAVIDES M.T. , COLOMER V.
Published: November 2004

We report on the experimental investigations of the afterglows of a surface-wave-produced Argon plasma. Electron density decay, measured by resonant scattering, is used to obtain recombination and diffusion coefficients. A Pyrex cylindrical tube of internal radius a=4.5 mm was employed. The gas used in the discharge was Argon and two gas pressures were tested, 0.08 and 0.2 Torr. A gradient of neutral temperature provokes an axial variation of these magnitudes.
SUPERCONDUCTING AND NORMAL STATE PROPERTIES OF YBaCuO THIN FILMS SPUTTERED ON ZrO2 SUBSTRATES AND THEIR MORPHOLOGY
Authors: WANG H.S. , ZHANG Y.Z. , YUAN C.W. , ZHAO Y.Y. , ZHAO B.R. , LU Y. , LI L.
Published: November 2004

Superconducting and normal state properties of YBaCuO thin films sputtered on single crystal ZrO 2 substrates and their morphology have been studied by SEM, X-ray diffraction and electric measurements. Approximate linear relationships were found between Jc and α, ρo and α. The zero resistance temperature T co was dependent more on a than Tc onset. Jc varied with the function (Tc−T)3/2. Dense film structure and thin grain boundaries are beneficial for high Jc and T co .
MAGNETORESISTANCE OF HIGH TEMPERATURE SUPERCONDUCTORS
Authors: HIKAMI S. , LARKIN A.I.
Published: November 2004

Magnetoresistance for high temperature superconductors is investigated above the critical point. Near transition temperature, there is a crossover from two dimensions to three dimensions. According to superconducting fluctuation, a crossover between different contributions of magnetoresistance appears. The phase relaxation time and the theoretical formula of the crossover in the magnetoresistance are discussed.
CONDUCTIVITY NEAR ANDERSON TRANSITION: SCALING AND MESOSCOPIC FLUCTUATIONS
Authors: IOFFE L.B. , SAGDEEV I.R.
Published: November 2004

The d.c. conductivity in infinite three-dimensional system consisting of a disordered cubic sample and two half-infinite ideal bars is studied by means of numerical simulation. The distribution of conductivity acquires a universal (independent of the system size) form at the same energy at which conductance does not depend on the system size. Identification of this energy with the transition point yields the value of exponent ν=1.1±0.1 (σ~(E−Ec)ν). However, the value of Ec obtained disagrees with Ec obtained from the data on the finite systems.
PHASE SEPARATION DYNAMICS AND EXTERNAL FORCE FIELD
Authors: KITAHARA K. , OONO Y. , JASNOW DAVID
Published: November 2004

If spinodal decomposition is modeled by the Cahn-Hilliard (-Cook) equation, the effect of a uniform external force such as gravitation does not appear in the bulk phase kinetics. In contrast, in the Kawasaki exchange modeling of the local dynamics of binary alloys, this effect directly modifies the bulk phase kinetics. We resolve this paradox through the cell-dynamical-system modeling of the Kawasaki exchange dynamics. Its continuum version has turned out to be a modified Cahn-Hilliard equation already proposed by Langer et al. about ten years ago. We demonstrate some examples in which the correction to the Cahn-Hilliard equation is significant.
MAGNETIC HYSTERESIS OF HIGH-TEMPERATURE YBa2Cu3Ox-AgO SUPERCONDUCTORS: EXPLANATION OF MAGNETIC SUSPENSION
Authors: HUANG C.Y. , SHAPIRA Y. , MCNIFF E.J. , PETERS P.N. , SCHWARTZ B.B. , WU M.K. , SHULL R.D. , CHIANG C.K.
Published: November 2004

We have measured the magnetization M of superconducting YBa 2 Cu 3 O x- AgO composites with T c approximately equal to 92K as a function of an applied magnetic field H at 77 and 87K. A very pronounced M-H hysteresis loop occurs even at 87K, indicating the presence of extremely strong pinning centers. The results of these measurements, together with a simple model, explain quantitatively why these superconductors could be suspended below a magnet.
LIQUID PHASE SINTERING OF Tl-Ba-Ca-Cu-O WITH SUPERCONDUCTING TRANSITION AT 122K
Authors: DOU S.X. , LIU H.K. , BOURDILLON A.J. , TAN N.X. , ZHOU J.P. , SORRELL C.C.
Published: November 2004

The Tl-Ba-Ca-Cu-O system, when prepared by standard sintering procedure, showed mass loss by volatilization of Tl even at sintering temperature lower than the decomposition temperature of Tl 2 O 3 (875°C). The disappearance is a result of difficulty in preparation and Tl 2 O 3 emission is severely toxic. The use of a two stage sintering technique involves the preparation of Ba-Ca-Cu-O by standard ceramic processing, so that Tl 2 O 3 can be added to the sintered Ba-Ca-Cu-O enclosed in a silver tube, and sintered. This technique ensures reproducible results and safety. Bright field transmission electron microscopy demonstrates a layered structure by absorption contrast, and stacking faults.
PRESSURE DEPENDENCE OF SUPERCONDUCTIVITY OF THE Tl-Ba-Ca-Cu OXIDE
Authors: ZHANG J.L. , CUI C.G. , LI S.L. , ZHANG Y.L. , CHENG X.R. , YANG Q.S.
Published: November 2004

The pressure dependence of the superconductivity of the Tl-Ba-Ca-Cu-O sample with T c >110 K was studied. It is observed that the superconducting transition temperature increases at the rate of d T co / d P≈1.83 K/GPa up to 1.8K/GPa and the gentle steps of T c are always followed by a jump of the normal state resistance which is considered exhibiting the change of some fine structure related to the Cu-O planes.
SUPERCONDUCTIVITY AND THERMOELECTRIC POWER IN Tl2Ca2Ba2Cu3O10 AND TlCa3BaCu3O9
Authors: ALCÁCER L. , ALMEIDA M. , BRAUN U. , GONÇALVES A.P. , GREEN S.M. , LOPES E.B. , LUO H.L. , POLITIS C.
Published: November 2004

We report the synthesis and superconducting temperature of the high-T c compounds Tl 2 Ca 2 Ba 2 Cu 3 O 10 and TlCa 3 BaCu 3 O 9. The transition to the superconducting state was measured by the magnetic susceptibility changes and by the temperature dependence of the electrical a.c. and d.c. resistivity and by thermoelectric power measurements. For Tl 2 Ca 2 Ba 2 Cu 3 O 10 a superconducting transition with zero resistance at 114.5K have been observed. Higher T c with zero resistance at 122K have been found in TlCa 3 BaCu 3 O 9.
TIP INSTABILITY DURING CONFINED DIFFUSION-LIMITED GROWTH
Authors: KESSLER DAVID A. , LEVINE HERBERT
Published: November 2004

We study diffusion-limited crystal growth in a two dimensional channel geometry. We demonstrate that although there exists a linearly stable steady-state finger solution of the pattern evolution equations, the true dynamical behavior can be controlled by a tip-widening instability. Possible scenarios for the long-time behavior of the system are presented.
DYNAMICS OF AN INTERFACE COUPLED TO A DIFFUSIVE BULK MODE
Authors: ZIA R.K.P. , BAUSCH R. , JANSSEN H.K. , DOHM V.
Published: November 2004

We consider the dynamics of an interface in the two-phase region of two component systems where the order parameter is coupled to a non-ordering, diffusive bulk mode. Equations of motion for the soft modes, appropriate for low temperatures, are presented. Studying the dispersion relations in the linear regime, we find ω∝q2 or q3, depending on a certain symmetry between the phases.
THERMOELECTRIC POWER OF SOME HIGH-TcBi AND Tl COMPOUNDS
Authors: YAN SHOUSHENG , CHEN TONG , ZHANG HAIBO , PENG JINLIN , SHEN ZHAOHUI , WEI CHONGDE , WEN QINGZHE , WU KE , TONG LITAI , ZHANG HONG
Published: November 2004

Thermoelectric power(S) measurements are reported in several high-T c Bi and Tl compounds. It is positive and decreases with increasing temperature. In samples which are rich in superconducting phase, an enhancement of S just above T c was observed. For Bi compounds with two superconducting phases, S (T) measurement has some advantages.
THE SUPERCONDUCTING STUDY OF TlBaCaCu2Oy
Authors: YAN JIE , YANG XIAOMING , PEI GUANGWEN , MEN ZHENYU , SONG DEYING
Published: November 2004

The relation of the superconductivity of TlBaCaCu 2 O y to the sintering temperature, sintering time, annealing rate and sintering atmosphere was studied. It was shown that the zero-resistance temperature of the superconductors of the type was up to 118K and the stability was to some extent quite good. Through X-ray diffraction analysis, the TlBaCaCu 2 O y was found to possess two kinds of tetragonal structures. The T co =118 K sample has the unit cell parameters of a=5.446(2)Å, c=35.698(2)Å; while for T co =93.5 K , one has the parameters of a=5.469(2)Å, c=30.051(2)Å, the substitution of Tl, Ba, Ca , by many other elements show that only TlBaMgCu 2 O y and TlMg 2 Cu 2 O y are superconductors and others are insulators.
THE EFFECT OF PREMELTING STUDIED BY MOLECULAR DYNAMICS
Authors: SCHOMMERS W. , BLANCKENHAGEN P. VON , ROMAHN U.
Published: November 2004

The effect of premelting is investigated by four molecular-dynamics models. It is shown that premelting is initiated by a disorder (roughening) normal to the surface. Also the interlayer spacings strongly influence the structural and dynamical properties of the outermost surface layer.
OBSERVATIONS ON THE PROCESSING AND PROPERTIES OF THE Y-Ba-Cu-O SUPERCONDUCTOR
Authors: LEVENTOURI TH.
Published: November 2004

We report on the dependence of the properties of the YBa 2 Cu 3 O x superconductor on the process by which it is prepared. Resistance measurements indicate the quality of the samples. X-ray diffraction data show an impressive enhancement followed by a saturation of the intensities of some diffraction lines with the hours of thermal treatment of the sample and the number of times it is ground.
XPS STUDIES OF 3D CORE LEVELS OF Ba IN RBa2Cu3O7−δ (R= Y and Gd)
Authors: Padalia B.D. , Mehta P.K. , Reddy S.R. , Prakash Om , Venkataramani N.
Published: November 2004

The XPS 3d core level spectra of Ba in the oxygen annealed high T c superconducting YBa 2 Cu 3 O 7−δ (δ~0.07) sample at 295 K and ~77 K show asymmetry. An attempt has been made to see the effects on the Ba 3d spectra due to air and nitrogen annealing as well as the substitution of magnetic Gd ions for Y ions. Our XPS results show that the observed asymmetry in the Ba 3d peaks is not associated with the superconducting behavior.
INVARIANT SOLUTIONS AND THE CONSERVATION LAWS FOR THE HOT—POINT DEVELOPMENT MODEL
Authors: BADALOV V.G. , RUSTAMOV K.A.
Published: November 2004

Analytical heat point development model is investigated. With the aid of group analysis, invariant solutions are obtained for many practically important cases. Conserved currents connected with associated linear equations are constructed.
DISCOVERY OF DICKE SUPERRADIATION BY SYSTEM OF NUCLEAR MAGNETIC MOMENTS
Authors: KISELEV J.F. , PRUDKOGLYAD A.F. , SHUMOVSKY A.S. , YUKALOV V.I.
Published: November 2004

Spontaneous generation of the Dicke superradiation (SR) state has been found in the system of inversely polarised proton spins with “frozen” polarisation. SR is observed at the moment when the Larmor frequency crosses the resonance frequency of the passive oscillatory circuit. SR arises from incoherent maser generation of spins. The frequency of a SR generator can be retuned from several hundreds of kilohertz to hundreds of megahertz at very low temperatures. Dependence of incoherent and coherent radiation on the initial polarisation has been investigated. A radio frequency analogue of the optical SR laser is shown to be possible both for weak-amplifying and for strong-amplifying active media, depending on the factor of filling and polarisation of nuclei. SR-reverse of negative polarisation is observed in the latter case.
TUNNELING STUDIES OF COMPOSITIONALLY MODULATED PB/Fe FILMS
Authors: WAWRO A. , WITEK A. , NOWAK J. , MAJEWSKI J. , RAULUSZKIEWICZ J.
Published: November 2004

Preliminary results of preparation and investigation of compositionally modulated Pb/Fe films are reported. These films have been used as electrodes in Al/Al2O3/k(Pb/Fe) tunnel junctions and the tunneling characteristics I−V, dV/dI and d2V/dI2vs V have been studied in dependence on the modulation period.
THE SURFACE IMPEDANCE OF HIGH Tc SUPERCONDUCTORS
Authors: CARINI J. , DRABECK L. , GRÜNER G.
Published: November 2004

Recent experiments on the surface impedance of the high temperature superconductors are summarized. The overall temperature dependence of the penetration depth is in broad qualitative agreement with conventional pairing, but with an anomolous power law behavior observed at low temperatures. The surface resistance is orders of magnitude larger than estimates based on the Mattis-Bardeen theory. One possibility is unconventional pairing, but structural inhomogenities are the most likely explanation for the experimental results.
THE CRYSTAL STRUCTURES OF TlBa2Ca3Cu4O10.5 and Tl2Ba2CuO6
Authors: HUANG J.Q. , LIANG J.K. , ZHANG Y.L. , XIE S.S. , CHEN X.R. , ZHAO Z.X.
Published: November 2004

We reported the crystal structures of TlBa 2 Ca 3 Cu 4 O 10.5 and Tl 2 Ba 2 CuO 6. The atomic parameters were determined by means of X-ray powder diffraction method. We also discussed the relationship between the crystal structure and properties as well as the relation among the crystal structures of the high T c superconductors.
PACKING OF EQUAL DISCS ON A PARABOLIC SPIRAL LATTICE
Authors: FAN XUDONG , BURSILL L.A. , PENG JULIN
Published: November 2004

A contact disc model is investigated to determine the most closely-packed parabolic spiral lattice. The most space-efficient packings have divergence angles in agreement with the priority ranking of natural spiral structures.
NEW POSSIBLE EFFECT IN HOMOGENEOUS HIGH-Tc SUPERCONDUCTORS
Authors: GORZKOWSKI W.
Published: November 2004

The following effect should be observed in certain high-T c superconductors: for T<T c , the superconducting state, after being destroyed by an applied magnetic field greater than H c2 (at T), cannot spontaneously reappear or does so after a long delay, at the temperature T.
TETRAHEDRAL ZAMOLODCHIKOV ALGEBRA AND THE TWO-LAYER FLAT MODEL IN STATISTICAL MECHANICS
Authors: KOREPANOV I.G.
Published: November 2004

The tetrahedral Zamolodchikov algebra arises in the theory of the tetrahedron equations. From this algebra, the solutions of triangle equations corresponding to a model on the two neighboring layers of the 3-dimensional cubic lattice are obtained.
A RAMAN SPECTROSCOPIC STUDY OF BARIUM COPPER OXIDE
Authors: LOO B.H. , BURNS D.H. , ROLIN T.D.
Published: November 2004

Various physical treatments of BaCuO 2 samples result in irreversible changes in its Raman spectrum. The prominent peaks at 576 and 628 cm −1 in the spectra of sintered pellets of BaCuO 2 disappear upon further annealing in air or oxygen or upon mere regrinding of the pellets. Further annealing in air, oxygen, or vacuum does not restore these peaks. Similar but less intense peaks reappear upon exposure of pellets to laboratory environment for several weeks, but these broaden and disappear upon further exposure.

These spectral characteristics contrast with those observed in Y123 Raman spectrum. It is concluded that the peaks at 582 cm −1 and 636 cm −1 in the spectra of sintered pellets of Y123 are not due to the presence of BaCuO 2.
MEASUREMENT OF ANISOTROPIC THERMOPOWER IN SINGLE CRYSTALS Bi2Sr2CaCu2Oy
Authors: CHEN G.H. , WANG J.H. , ZHENG D.N. , YAN Y.F. , JIA S.L. , YANG Q.S. , NI Y.M. , ZHAO Z.X.
Published: November 2004

The thermopower in single crystals of the high T c superconductor Bi 2 Sr 2 CaCu 2 O y has been measured in both a-b plane (S ab ) and along c axis (Sc) respectively. The temperature dependences are distinctly anisotropic. S c increases monotonously with temperature and is positive from T c to room temperature, while S ab increases rapidly near T c and then decreases with temperature. The maximum of S ab is at 115 K and S ab changes its sign at 250 K.
THE SIMULATION OF MODULATED PENDELLÖSUNG FRINGES OF PERFECT CRYSTALS FOR SPHERICAL X-RAY WAVE
Authors: JIANG S.S. , QIU Y.
Published: November 2004

The modulation in Pendellösung fringe visibility in perfect crystal is due to the interference between σ and π polarization states of X-ray wave. It is simulated by superposition of two polarization states by computer based on spherical X-ray wave dynamical theory and compared with fringe pattern on X-ray diffraction section topograph. It is found that the agreement between experimental result and theoretical calculation is satisfactory.
STRUCTURE OF Bi-Pb-Sr-Ca-Cu-O SUPERCONDUCTOR WITH Tc OF 108 K
Authors: WANG R.K. , HE Q. , YU D.A. , DI X.X. , LI Y.H.
Published: November 2004

Five different phases have been observed in the Bi-Pb-Sr-Ca-Cu-O superconducting compound with T c of 108 K. The high-T c and low-T c superconducting phases with their compositions near ( Bi 0.82 Pb 0.18)4 Sr 4 Ca 3 Cu 6 O y and ( Bi 0.82 Pb 0.18)4 Sr 4 Ca 2 Cu 4 O y respectively have face-centered orthorhombic structure with a=0.540 nm , b=0.545 nm , c=3.669 nm and a=0.540 nm , b=0.546 nm , c=3.077 nm , respectively, and the former has the super-structure of 3.24 nm, the latter has the super-structure of 2.7 nm and is incommensurate in the b-direction. In addition, two kinds of minor phases with their compositions near ( Sr 0.6 Ca 0.4) Cu 1.75 O y and ( Bi 0.86 Pb 0.14)3 Sr 1 Ca 4 Cu 1 O y as well as CuO have also been observed.
ON CONDENSATION IN NON-IDEAL BOSE GAS
Authors: SANKOVICH D.P.
Published: November 2004

A model of the non-ideal Bose gas is considered. We prove the existence of condensate in the model at sufficiently low temperature. The method of majorizing estimates for the Duhamel Two Point Functions is used. The equation for the critical temperature and the upper bound for the one-particle excitations energy are obtained.
CHANGES IN PHYSICAL PROPERTIES OF THE HIGH-Tc SUPERCONDUCTOR Y-Ba-Cu-O DUE TO Cu DEFICIENCY
Authors: YAO Y.D. , KAO Y.H. , SIMMINS J.J. , SNYDER R.L. , TAO Z. , JONES K.W.
Published: November 2004

Stoichiometry of the well-known high-T c compound YBa 2 Cu 3 O y is modified by varying the Cu concentration in the system, and changes in the oxygen content and superconducting properties are investigated. The oxygen content shows a nonlinear dependence on the Cu concentration. For Cu deficiency up to 20%, the transition temperature T c remains at a nearly constant value of 93 K. X-ray diffraction measurements show that the compound is orthorhombic in this range of stoichiometric variation, and the Cu -deficient superconductor is single phase. The room temperature resistivity increases exponentially while the critical current density decreases exponentially with increasing Cu deficiency. These results indicate that the predominant mechanism for high-T c superconductivity is closely related to the local structure around the Cu and O atoms.
ASSOCIATIVE MEMORY IN NEURAL NETWORKS WITH THE HEBBIAN LEARNING RULE
Authors: TSODYKS M.V.
Published: November 2004

We consider the Hopfield model with the most simple form of the Hebbian learning rule, when only simultaneous activity of pre- and post-synaptic neurons leads to modification of synapse. An extra inhibition proportional to full network activity is needed. Both symmetric nondiluted and asymmetric diluted networks are considered. The model performs well at extremely low level of activity p<K−1/2, where K is the mean number of synapses per neuron.
ZERO RESISTANCE AT 113 K IN THE (Bi1.9−xPbxSb0.1)Sr2Ca2Cu3Oy SYSTEM (x=0.1, 0.2, 0.3, 0.4)
Authors: LIU H.B. , MAO Z.Q. , ZHOU L. , ZHANG W.J. , LU J. , LI B.Y. , CHEN Z.J. , CAO L.Z. , RUAN Y.Z. , PENG D.K. , ZHANG Y.H.
Published: November 2004

The 110 K superconducting transition in Bi-Pb-Sr-Ca-Cu-O system has been observed by S.M. Green et al.1 However, T c, zero was 107 K. We have achieved zero resistance at temperature 113 K in Bi-Pb-Sb-Sr-Ca-Cu-O system, higher than that of Bi-Pb-Sr-Ca-Cu-O by more than 6 K. At room temperature, this high temperature phase is steady. After several heating-cooling circle, T c, zero decreases slowly.
AN EMPIRICAL RELATIONSHIP BETWEEN Tc AND THE NUMBER OF THE AVERAGE VALENCE ELECTRON IN HIGH-Tc SUPERCONDUCTORS
Authors: YUAN S.L. , ZHU B. , WANG W.
Published: November 2004

A large number of Cu-O perovskite-type materials are analysed. An empirical relationship between Tc and the number of the average valence electron in these oxide materials is suggested. Some experimental phenomena could be interpreted by this empirical rule.
THE TEMPERATURE DEPENDENCE OF RESISTANCE AND CRITICAL CURRENT IN GRANULAR YBa2Cu3Ox SUPERCONDUCTING FILMS
Authors: ŠTRBÍK V. , BEŇAČKA Š. , GAŽI Š. , CHROMIK Š. , LEVÁRSKY J. , SITH J.
Published: November 2004

Temperature dependence of resistance R(T) and critical transport current I c (T) was measured for high-Tc YBa 2 Cu 3 O x granular thin films prepared by vacuum co-evaporation. The results are interpreted in terms of superconductor-constriction-superconductor (ScS) or superconductor-normal metal-superconductor (SNS) models, shown to be more adequate than the superconductor-insulator-superconductor (SIS) one.

The films with nearly the same superconducting phase transition can exhibit both metallic (dR/dT>0) or semiconductor (dR/dT<0) behavior at T>Tcon. This is ascribed to intragranular defects which are shunted below T con .
SUPERCONDUCTING Bi-Sr-Ca-Cu-O THIN FILMS PREPARED BY rf MAGNETRON SPUTTERING
Authors: IVANOV Z. , NURGALIEV T. , DONCHEV T. , CHERNAKOVA A. , TODOROV B.
Published: November 2004

High-Tc superconducting thin films were deposited on MgO (100) and SrTiO 3 (110) substrates by rf magnetron sputtering of Bi2Sr2Ca3Cu4O x target. Critical temperature Tc above 78 K were obtained after annealing the films for one hour at 850°C in oxygen atmosphere. The films showed good stability of Tc and resistivity within a period of 30 days.
NEUTRON SCATTERING STUDY OF HYDROGEN VIBRATIONS IN POLYCRYSTAL AND GLASSY Ti2CuHx
Authors: XIANGXIN ZENG , JINGHUI RUAN , SUQIAO LI , MINGZHONG CAO , GENSHI WANG
Published: November 2004

Hydrogen vibration spectra for both polycrystalline Ti 2 CuH 1.03 and amorphous Ti 2 CuH 1.26 have been measured in the energy range of 50–210 meV using a beryllium filter detector spectrometer. From the experimental curves it can be seen that although there is some similarity in vibrational density of states of the hydrogen atoms in these two samples, large differences between them are evident. The optical vibration peak of crystalline sample reveals a narrow frequency distribution with a FWHM of 54 meV and consists apparently of two peaks at 92 and 147 meV. In the amorphous sample, the optical peak occurs at nearly the same frequency as the main peak of the former but with strongly increased width (~104 meV FWHM). The result shows that on the average, the H-sites occupied in amorphous and crystalline structures are mainly tetrahedral type holes, but the distribution of local environment for the hydrogen atoms in the alloy glass is much broader because the polyhedra in it may be heavily distorted and there is local fluctuation in its chemical composition.
SOLID REACTION, OXYGEN ABSORPTION AND AMORPHOUS STATE IN Bi-Ca-Sr-Cu-O SYSTEM
Authors: ZHU N.P. , ZHOU L.J. , LI T.F. , Wang Y.Z. , ZHANG Y.S. , QIAO G.W. , SHI C.X.
Published: November 2004

Solid reaction, oxygen relief and absorption in Bi-Sr-Ca-Cu-O system have been investigated by TGA technique. Oxygen contents (x=5.5 and 5.64) for BiSrCaCu 2Ox samples quenched and furnace-cooled were determined, respectively. No oxygen absorption and relief happens below 800°C. Amorphous state can be obtained by heating the sample up to 1000°C and then cooling it quickly. Magnetic susceptibility measurement and oxygen content determination suggest that Cu+ and Cu3+ exist in the quenched and furnace-cooled samples.
THE COPPER VALENCE STATE AND THE STRUCTURE OF Li, Ce, Eu, V-DOPED Y-Ba-Cu-O SYSTEM
Authors: ZHANG J.B. , QU L.F. , HOU K.Y. , YANG D.L. , CHEN D.J. , LI X.D. , ZHU D.B.
Published: November 2004

High-Tc superconductors with nominal composition of YBa 2 Cu 3 O y and Y 1−x L x Ba 2 Cu 3 O y ( L=Li , Ce, Eu, V) were synthesis by the solid state reaction of appropriate amount of Y 2 O 3, BaO or BaCO 3, Cu 2 O , CuO, and LO x. The Cu 3+/ Cu 2+ ratio was determined by Iodometric titration and oxygen content in the oxides calculated from the ratio. The crystal structure was determined by electron and powder X-ray diffraction analysis. It shows that that ratio of Cu 3+/ Cu 2+ and the crystal structure could be changed as dopping appropriate amount of metal in the Y-Ba-Cu-O system.
INVESTIGATION OF OXIDE SUPERCONDUCTOR Ca2BiSrCu2Ox
Authors: DJUREK D. , MEDUNIĆ Z. , MANOJLOVIĆ V. , PRESTER M. , BABIĆ E. , ZADRO K. , RAKVIN B. , POŽEK M.
Published: November 2004

A new member of the series of oxide superconductors Ca–Sr–Bi–Cu–O has been prepared from nominal composition Ca 2 BiSrCu 2 O x. Heat treatment at 840°C results in the compound with T c ≈ 85 K (L-phase) while heat treatment at 880°C leads to the majority phase which undergoes the transition to superconducting (SC) state at T c ≈ 117 K (H-phase). One bismuth atom per unit formula suggests the onset of SC in a single Bi–O layers, in contrast to the usual Ca–Sr–Bi–Cu–O superconductors known so far.
A NEW 50 K SUPERCONDUCTOR, Tl1+xBa2−x−yLayCuO5−δ, FIRST MEMBER OF THE SERIES TlA2Cam−1CumO2m+3
Authors: MARTIN C. , BOURGAULT D. , HERVIEU M. , PROVOST J. , MICHEL C. , RAVEAU B.
Published: November 2004

New superconductors Tl 1+x Ba 2−x−y La y CuO 5−δ(x = 0, y = 0.6 and x = 0.25, y = 0.75) have been isolated, which exhibit a zero resistance below 50 K and a diamagnetic fraction volume ranging from 7% to 35%. Their tetragonal structure corresponds to the intergrowth of single perovskite layers with double rock-salt type layers. These latter slabs exhibit two original features, presence of oxygen vacancies and distribution of thallium over two sorts of sites. This particular behavior is discussed in terms of mixed valence of thallium, Tl(I)/Tl(III) taking into account the 6s2 lone pair of T1(I).
OBSERVATION OF THERMALLY RECYCLEABLE ZERO-RESISTANCE STATES IN YBaCuO ABOVE DRY ICE TEMPERATURES
Authors: CHEN J. T. , QIAN L.-X. , WANG L.-Q. , WENGER L. E. , LOGOTHETIS E. M.
Published: November 2004

Thermally recycleable zero-resistance states with transition temperatures above 200 K are observed in mixed-phase YBaCuO materials that are treated by a low-temperature (< 150° C ) oxygenation process and enclosed in an oxygen atmosphere during electrical and magnetic measurements. The zero-resistance state is verified through multiple lead and contact arrangements as well as by measurements of the current-voltage characteristics for several paths with the highest transition temperature (zero resistance) for any sample being 265 K and with a zero-voltage current exceeding 4.3 mA at 240 K. Although a full Meissner effect is not obtained, diamagnetic-like deviations and hysteretic behavior are observed to occur at the same temperatures as the resistive transitions. This indicates that the zero resistance, if related to superconductivity, is due to filamentary superconducting paths or materials of lower dimensionality.
SU(1,1) SQUEEZED STATES AS DAMPED OSCILLATORS
Authors: CELEGHINI E. , RASETTI M. , TARLINI M. , VITIELLO G.
Published: November 2004

The conventional squeezed states of quantum optics, which can be thought of as generalized coherent states for the algebra SU(1,1), are dynamically generated by single-mode hamiltonians characterized by two-photon process interactions. By the explicit construction of a (highly non-linear) faithful realization of the group [Formula: see text] of automorphisms of SU(1,1), such hamiltonians are shown to be equivalent — up just to elements of [Formula: see text] — to that describing quantum mechanically a damped oscillator.
SUPERCONDUCTIVITY DUE TO CHARGE DENSITY WAVE INSTABILITY IN Ba1−xKxBiO3 COMPOUNDS
Authors: TING C. S. , CHEN X. Y. , WENG Z. Y.
Published: November 2004

Recent experiments seem to indicate that the superconductivity in Ba 1−x K x BiO 3 type compound occurs in the metallic state before its transformation to the charge density wave (CDW) state as the doping parameter x is reduced. Assuming the local breathing modes around Bi-atoms are responsible for both the CDW and superconducting states. We show that the superconducting transition temperature T c can be substantially enhanced as x approaches the CDW instability from the metallic side. Similar calculation has been carried out for a two-dimensional system and the results are in qualitative agreement with a recent Monte Carlo simulation.
SUPERCONDUCTING TRANSITION CURVE OF HIGH TEMPERATURE OXIDE CERAMICS
Authors: SOSNOWSKI J.
Published: November 2004

The superconducting transition curve of high temperature oxide ceramics is investigated on the basis of a developed statistical approach. Two-step transition curve is interpreted according to the model, including proximity effect appearance.
NUMERICAL CHECK OF THE EXACT MASS SPECTRUM OF THE SCALING LIMIT OF T = Tc ISING MODEL WITH MAGNETIC FIELD
Authors: SAGDEEV I. R. , ZAMOLODCHIKOV A. B.
Published: November 2004

We compute numerically the mass spectrum and the specific free energy for the T = T c Ising model with nonzero magnetic field in the scaling limit. The results are in good agreement with the proposed exact S-matrix.
TWO DIMENSIONAL LARGE AMPLITUDE QUASI SOLITONS IN THIN HELIUM FILMS
Authors: SREEKUMAR J. , NANDAKUMARAN V. M.
Published: November 2004

Large amplitude local density fluctuations in a thin superfluid 4 He film is considered. It is shown that these large amplitude fluctuations travel and behave like "quasi-solitons" under collision, even when the full nonlinearity arising from the Van der Waals potential is taken into account.
TUNNELING AND RESISTIVE STUDIES OF NORMAL STATE PROPERTIES OF YBCO THIN FILMS
Authors: SVISTUNOV V. M. , KHACHATUROV A. I. , BELOGOLOVSKII M. A. , KOCHERGIN I. V. , BENAČKA Š. , PLECENIK A. , CHROMIK Š.
Published: November 2004

Tunneling and resistive measurements have been performed on high-T c YBCO thin films. Both the effects of electron-electron correlations and those of electron-phonon interactions are found and discussed.
STUDY ON ZERO RESISTANCE AT 118 K IN (Bi, Pb)–Sr–Ca–Cu–(O, F) SUPERCONDUCTOR
Authors: GAO XIAOHUI , WU XIAOLIN , YAN HUI , YIN ZHOULAN , LIN CAIDONG , FU YINGSHENG , XIE WUXI
Published: November 2004

(Bi, Pb)–Sr–Ca–Cu–(O, F) superconductors of transition with onset at 125 K and zero resistance at 118 K have been synthesized successfully with CuF 2 as one of the components. The effects of fluorine on sintering technique and superconductivity have been investigated. The best ratio of doping-F has been experimentally obtained. The contribution of fluorine to kinetic process of high-T c phase growth has been discussed. The results of X-ray powder diffraction show that only two phases exist in this superconductor, a low-T c 85 K phase and a high-T c 110 K phase. No fluoride or other impure phases are found in the system.
SCALING PROPERTIES OF ORTHORHOMBIC SUPERCONDUCTORS
Authors: BLAGOEVA E. J. , MILLEV Y. T. , UZUNOV D. I.
Published: November 2004

A Landau-Ginzburg-Wilson quasimacroscopic model of orthorhombic superconductors is studied by means of the renormalization group theory. The fixed points are enumerated and their stability properties analysed using the ε-expansion about four spatial dimensions. The existence of new fixed points is reported. The results are related to the properties of heavy-fermion systems and high temperature superconductors.
EFFECT OF COOLING RATE ON THE TRANSITION TEMPERATURE IN Bi–Pb–Sr–Ca–Cu–O SYSTEM
Authors: WANG YUGUI , WANG JINSONG , WANG NANLIN , JIAO XINPING , HAN GUCHANG , CHEN ZHAOJIA , WANG KEQIN , WU XIAOGUANG
Published: November 2004

The resistance and ac susceptibility measurements show that cooling rate of the cast-annealing samples in heat treatment process has some effect on the 110 K superconducting phase in Bi–Pb–Sr–Ca–Cu–O system. Rapid quenching of the sample in air from 845°C causes oxygen deficiency in lattice and brings about a trifling change of unit cell size along c-axis direction. The dc magnetization and specific heat anomaly ∆c measurements demonstrate that fast cooling rate can reduce the transition temperature of high T c phase and the lower critical field, and weaken the pinning forces for vertex lines. The peak value of specific heat anomaly of the sample with nominal composition of Bi 1.7 Pb 0.3 Sr 2 Ca 2 Cu 4.5 O y is still small in comparison with YBa 2 Cu 3 O 7. From the magnetization curve we can estimate that the superconducting volume fraction is about 20%.
HIGHLY STRUCTURE-CONFINED Y:Ba:Cu:O SUPERCONDUCTORS PREPARED BY COPRECIPITATION TECHNIQUES
Authors: HSIEH P. Y. , YE JAMES , SHI Z. , CHU W. K.
Published: November 2004

Results from the study of highly structure-confined YBa 2 Cu 3 O 7−x superconductors synthesized by different coprecipitation processes are presented, with the superconducting samples made from oxalic-nitrate salts demonstrating higher critical temperature and critical current in comparison with solid reaction oxides. Among the measured samples, the critical temperature, T c , is typically 90–95 K (T c (maximum)=105 K) and the critical current is 1.2 – 1.9 × 104 A/cm 2 at 4.5 K and 1200 A/cm 2 at 78 K. Peak patterns similar to those of solid-state reactions by X-ray diffraction analysis have also been found although these spectra show considerably broadness. Superconductors resulted from coprecipitation techniques with no calcining (heat-treatment) processing can be attained. Further studies on producing single-crystal with increasing critical current and temperature are discussed.
ON THE COUPLING BETWEEN ELECTRONS AND SOFT-MODE PHONONS IN La2CuO4
Authors: PETRU Z. K. , PLAKIDA N. M.
Published: November 2004

An interaction between soft bond-bending phonon modes and localized 3d – 2p electrons is considered. Its strength is estimated to be of the order of 1 eV/Å. By means of the tight-binding model, the electronic energy bands of La 2 CuO 4 are calculated. It is explicitly shown that a tetragonal to orthorhombic transition does not open a gap at the Fermi energy.
THE DIMER-CLUSTER FERMI-LINEARIZED HUBBARD MODEL: GROUND STATE AND PHASE SPACE
Authors: MONTORSI A. , RASETTI M.
Published: November 2004

The zero temperature phase space for the Hubbard model is constructed — in the frame of fermionic linearization with a two-site (dimer) cluster — resorting to its ground state, realized in the form of supercoherent state for the model dynamical superalgebra. Such phase space is characterized by the existence of regions in which the pairing order parameter is different from zero.
ELECTRICAL CONDUCTING AND THERMOELECTRIC PROPERTIES OF Ba4Na2Nb10O30−Ba3NaLaNb10O30 SYSTEM
Authors: TSUKIOKA MASAYUKI , TANOKURA YASUO , SHIMAZU MASAZI , KUROIWA SHINICHIRO , TSUTSUMI SADAO
Published: November 2004

Ceramic samples of BNN-BNLN ( Ba 4 Na 2 Nb 10 O 30− Ba 3 NaLaNb 10 O 30) system were prepared in flowing N 2 gas at about 1410°C, which has been confirmed to have continuous solid solutions over the whole range of BNN-BNLN system by X-ray diffraction measurement. Electrical resistivity and Seebeck coefficient measurements were carried out at temperatures from 77 K to 773 K and from 60 K to 200 K, respectively for the samples of different composition belonging to the BNN-BNLN system. These experiments revealed that all these materials were extrinsic semiconductors and change from p-type semiconductors to n-type during the process of rising temperature.
ON CALCULATION OF ENERGY OF PLANAR LATTICE FERMIONS IN A MAGNETIC FIELD
Authors: ABANOV A. G. , KHVESHCHENKO D. V.
Published: November 2004

We calculate the energy of lattice fermions with a small density moving in a weak magnetic field. It is shown that the ground state energy has a minimum at B = 2πν/ea2. Based on this fact we discuss some aspects of the modern theory of strongly correlated fermionic systems.
ASSOCIATIVE MEMORY IN NEURAL NETWORKS WITH BINARY SYNAPSES
Authors: TSODYKS M.V.
Published: November 2004

The simple learning algorithm in the neural network with binary synapses, which take one step for storing one pattern is considered. The resulting model turns out to be palimpsestic, and the number of patterns which can be effectively retrieved is L~N1/2.
SO4 SYMMETRY IN A HUBBARD MODEL
Authors: YANG CHEN NING , ZHANG S.C.
Published: November 2004

For a simple Hubbard model, using a particle-particle pairing operator η and a particle-hole pairing operator ζ, it is shown that one can write down two commuting sets of angular momenta operators J and J′, both of which commute with the Hamiltonian. These considerations allow the introduction of quantum numbers j and j′ and lead to the fact that the system has SO 4=( SU 2× SU 2)/Z2 symmetry, j is related to the existence of superconductivity for a state and j′ to its magnetic properties.
PREPARATION OF SUPERCONDUCTING Bi–Pb–Sr–Ca–Cu–O FILMS BY DC MAGNETRON SPUTTERING METHOD
Authors: WANG Y.H. , ZHANG Y.Z. , ZHAO Y.Y. , QIU X.G. , XU P. , LIN L.
Published: November 2004

Superconducting Bi–Pb–Sr–Ca–Cu–O thin films of zero resistivity temperature 108 K and critical current density of 1000 A/cm2 (at 77 K) were deposited on MgO(100) single-crystal substrates by DC magnetron sputtering. After depositing at 350–400°C and post annealing at 837.5°C for 1–5 hours in air, with different cooling rate we got highly c-axis oriented thin films which show zero resistivity at 103 K, 108 K. The results we got show an interesting phenomenon: the mixture of high and low Tc phase exhibit a low onset, sharp transition and high current density.
HEURISTIC PRINCIPLE FOR QUANTIZED HALL STATES
Authors: GREITER MARTIN , WILCZEK FRANK
Published: November 2004

It is argued that the incompressibility of fractional quantized Hall states, and the qualitative form of their wavefunction, can be understood by an argument based on adiabatic localization of magnetic flux. The hierarchy of allowed filling fractions is derived in a very simple way, that makes no reference to successive condensations of quasiparticles.
RELATIVISTIC QUANTUM HALL CONDUCTIVITY FOR 3D AND 2D ELECTRON PLASMA IN AN EXTERNAL MAGNETIC FIELD
Authors: FELIPE R. GONZALEZ , MARTINEZ A. PEREZ , PEREZ-ROJAS H.
Published: November 2004

The complete antisymmetric form of the conductivity tensor in the static limit, as well as the expression for the Hall conductivity, is obtained for the relativistic 3D and 2D electron gas in a magnetic field. The non-relativistic 2D limit is also discussed. The typical step form of the 2D Hall conductivity at zero temperature is obtained under the simple hypothesis of constancy of the chemical potential.
LATTICE DYNAMICS AND ANYON SUPERCONDUCTORS
Authors: GAITONDE D.M. , RAO SUMATHI
Published: November 2004

We consider a model of anyons—fermions coupled to a statistical gauge field—also coupled to phonons via the usual electron-phonon coupling. We study the phonon response when the system is in the superconducting anyon ground state and show the existence of peaks in the phonon spectral function whose frequencies shift with carrier concentration. We suggest that when the electron-phonon coupling is the dominant effect, there could arise a new type of BCS ground state with a spontaneously generated P and T violating supercurrent, that expels the statistical magnetic field.
THE BOUNCING BALL REVISITED
Authors: MEHTA ANITA , LUCK J.M.
Published: November 2004

We consider a ball under the influence of gravity on a vibrating platform where the ball-platform collisions are completely inelastic. The temporal phase space is seen to be divided into transmitting and absorbing regions, which are responsible for the abrupt termination of a period-doubling sequence and the onset of a locking regime, in which an appropriately defined winding number has intriguing scaling properties.
THEORY OF PAIRING IN THE ANYON MODEL
Authors: XIE X.C. , FERTIG H.A. , SARMA S. DAS
Published: November 2004

We study the semion pairing problem in the fermion representation by considering a semion as a fermion with a flux tube of ϕ=ϕ0/2. We solve analytically the problem of a pair of semions in a semion gas by treating the rest of the semions in the mean field approximation. We find that a bound pair forms that consists of two fermions from the two lowest Landau levels and a flux tube with ϕ=ϕ0.
100 K SUPERCONDUCTING PHASE IN THE Tl-Pb-Sr-R-Cu-O SYSTEM WITH R=RARE EARTHS
Authors: SHENG Z.Z. , XIN Y. , MEASON J.M.
Published: November 2004

Superconductivity around 100 K was observed in the Tl-Pb-Sr-R-Cu-O system (R=rare earths) by resistance and ac susceptibility measurements. Powder X-ray diffraction analyses showed that the phase responsible for the superconductivity is of a tetragonal structure with a general formula ( Tl 1−x Pb x)( Sr 3−y R y) Cu 2 O z (132 phase).
QUANTUM TUNNELING TIME OF CARRIERS THROUGH SUPERLATTICES IN A TRANSVERSE MAGNETIC FIELD
Authors: CRUZ H. , CABRERA A. HERNÁNDEZ , ACEITUNO P.
Published: November 2004

Multiple Finite Quantum Well structure under transverse magnetic field action has been analyzed theoretically by means of the behavior of the carriers wavefunctions. Confluent hypergeometric functions as analytical solutions of the carriers effective-mass equation appear to us to be a powerful tool for the study of several physical properties of superlattices. In particular, the electrons and holes magnetotunneling times through the barrier separating two close wells have been calculated. It is found that the escaping time can be lower than the radiative recombination time, depending on the barrier widths and magnetic field intensity and, therefore, allowing the tunneling of the carriers.