Published for the Division of Materials Sciences, Office of Basic Energy Sciences, USDOE, under Contract W-7405-eng-82 with the Ames Laboratory, Iowa State University. Funded by DMS/BES/USDOE, ARPA, and other agencies, organizations, and individuals.
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NOTA BENE:
Na0.05WO3
A recent preprint by S. Reich and Y. Tsabba (Weizmann Institute) reported experimental evidence suggesting the possibility of superconductivity with Tc ~~ 91 K in WO3 crystals with a surface composition of Na0.05WO3. (For further details, see Nota Bene and the preprint listing in the May 1 issue of High-Tc Update.) A. Shengelaya and K. A. Mueller (Zurich) now have joined with Reich and Tsabba to carry out electron-spin-resonance (ESR) measurements on samples of WO3 doped with Na. According to a new preprint, the authors detected an ESR signal with unresolved fine and/or hyperfine structure, and they used the saturation method to determine the spin-lattice relaxation rate 1/T_1 of these paramagnetic centers. Upon cooling below about 100 K, 1/T_1 decreased markedly with decreasing temperature. Except for the absence of a Hebel-Slichter peak, the results resemble NMR 1/T_1 measurements when a gap opens in the superconducting state. Below about T = 0.6 Tc, where Tc is assumed to be 91 K, the authors found that 1/T_1 proportional to exp(-Delta/k_BTc) with a gap parameter Delta = 160 K or 2Delta/k_BTc = 3.5, in good agreement with the weak-coupling BCS theory. The authors emphasize that for YBa2Cu3O7-d compounds, no ESR such as that reported here is known, thus excluding possible contamination of the WO3:Na samples by YBCO as the origin of the superconducting signatures with a Tc of 91 K.
The authors also report temperature-dependent field-cooled (FC) and zero-field-cooled (ZFC) dc susceptibility data obtained with a SQUID magnetometer. The two curves differ strongly below Tc, with the FC magnetization lying above the ZFC magnetization. In contrast to the cuprate superconductors, the parent compound WO3 is nonmagnetic, indicating that when WO3 is doped with Na, antiferromagnetism could not be responsible for either the magnetization hysteresis or the high Tc. The authors interpret all their results as suggesting a 91 K transition from a semiconducting to a nonpercolating 2D superconducting state on the surface of an insulator (a bulk WO3 crystal) when the surface is doped with sodium.
RBa2Cu3O7-d
According to a preprint by D. Mihailovic et al. (Ljubljana), a systematic quantitative comparison of pseudogap values obtained from an analysis of charge- and spin-excitation spectroscopies in underdoped YBa2Cu3O7-d using a temperature-independent gap shows two distinct excitations, one (Delta_s) visible in spin-flip spectroscopies such as NMR and spin-polarized neutron scattering, and the other (Delta_p) revealed in charge-excitation spectroscopies such as single-particle tunneling and time-resolved quasiparticle relaxation. Both Delta_s and Delta_p appear to decrease with doping x approximately as 1/x and are T- independent, existing both above and below Tc. The authors suggest that the spin excitation can be explained by an intragap local triplet state, while the charge excitation can be attributed to a pair-breaking local gap.
The Pr concentration dependence of the superconducting transition temperature Tc in the Ho1-xPrxBa2Cu3O7-d system has been determined by Z. Tomkowicz (Krakow) via measurements of the dc electrical resistance. Both this system and Y1-xPrxBa2Cu3O7-d have the same value of the critical concentration x_c = 0.58, in accordance with the nearly equal ionic radii of Ho^[3+] and Y^[3+]. The author finds that the Tc(x) curve can be described with a single mechanism based on a decreasing number of sheet holes trapped by Pr^[IV] ions, provided one takes into account that the number of these ions changes with x.
>From magneto-optical imaging performed on heavy-ion-irradiated YBa2Cu3O7-d single crystals, M. V. Indenbom (Chernogolovka and Ecole Polytechnique) et al. have found that at fields and temperatures where strong single vortex pinning by individual irradiation-induced amorphous columnar defects is to be expected, vortex motion is limited by the nucleation of vortex kinks at the specimen surface rather than by half- loop nucleation in the bulk. Deep in the material, vortex motion occurs through easy kink sliding, irrespective of the relative alignment between vortex lines and ion tracks.
The effects of adding insulating 211 particles [(NdxEuxGd1-2x)2BaCuO5 or NEG-211] into melt-textured 123 superconductors of the type (Nd0.33Eu0.33Gd0.33)Ba2Cu3O7-d (NEG-123) have been studied by M. Muralidhar et al. (SRL-ISTEC). The authors found that the position of the secondary peak in Jc vs B can be shifted to higher values of B by increasing the Gd content within the 211 particles, but the largest Jc at the peak was achieved with x = 0.33.
Bi Cuprates
The interlayer phase coherence in Bi2Sr2CaCu2O8+d (Bi-2212) has been quantitatively determined over a wide field range by T. Shibauchi et al. (Tokyo) using the Josephson plasma resonance. At the first-order- transition (FOT) line, the authors found a frequency-independent Josephson plasma resonance with a narrow width, indicating that the interlayer phase coherence abruptly changes at the FOT. Above the FOT line, sample-moving magnetization measurements showed an anomaly similar to the new phase boundary reported by D. T. Fuchs et al. [Phys. Rev. Lett. 80, 4974 (1998)], but the interlayer phase coherence showed no anomaly. These results indicate the decoupling nature of the FOT and rule out a vortex line-liquid state over the fields investigated.
By sweeping the microwave frequency continuously, M. B. Gaifullin (Tokyo) et al. have measured the Josephson plasma resonance for underdoped Bi2Sr2CaCu2O8+d (Bi-2212) and Bi2Sr2CuO6 (Bi-2201). The authors determined the superfluid density and the quasiparticle conductivity sigma_c^[qp] along the c axis from measurements of the resonance frequency and line width. In slightly underdoped crystals, the superfluid density shows very little change at low temperatures, a result consistent with a d-wave coherent-tunneling model. In the strongly underdoped crystals, sigma_c^[qp] falls to low values below Tc but then decreases only gradually with decreasing T, a behavior very different from that in the ab plane.
Measurements of the in-plane and out-of-plane resistivities rho_[ab] and rho_cvs temperature in the fluctuation-conductivity range above Tc have been carried out by C. Boulesteix (Marseille) et al. on different kinds of as-grown Bi-2212 crystals. For weakly oxidized (underdoped) crystals, 2D fluctuations occur over a large temperature range, while for highly oxidized crystals (with a metallic out-of-plane conductivity), 3D fluctuations occur over a large temperature range.
The position of Dy dopant atoms in the unit cell of Bi-2212 has been determined by P. Shang (Birmingham) et al. using direct-space chemical crystallography (EDX). The authors stress that such methods of determining sublattice occupancy are favored over classical x-ray diffraction methods as the number of components rises.
Results related to the use of the PAIR process (pre-annealing and intermediate rolling) for the fabrication of Bi-2212/Ag tapes are presented in three preprints listed in this issue. H. Miao (NRIM and CREST, Tsukuba) et al. report the optimal melt-processing temperature schedule to achieve high Jc values of 4.0 x 10^5 A/cm^2 at 4.2 K in a 10 T field parallel to the tape surface. H. Kitaguchi (NRIM) et al. report studies of the dependence of Jc upon the Bi-2212 thickness. The authors attribute the success of the PAIR process to improvements in the macroscopic homogeneity of the Bi-2212 layer. A second paper by H. Kitaguchi (NRIM) et al. reports on the Jc performance of PAIR-processed tapes in the temperature range 10-50 K.
Other Cuprates
An NMR-pulse double-irradiation method that allows the separation of magnetic and quadrupolar contributions to the spin-lattice relaxation has been developed by A. Suter et al. (Zurich). The pulse sequence fully saturates one transition while another is observed. The method is especially useful when only one NMR-sensitive isotope is available. A second preprint by A. Suter et al. (Zurich) describes the application of this method to carry out an [17]^O NMR study in the stoichiometric superconductor YBa2Cu4O8. The authors find that below 180 K, the spin- lattice relaxation rate of plane oxygens is driven not only by magnetic fluctuations but also by quadrupolar fluctuations, i.e., low-frequency charge fluctuations. In the superconducting state, as the temperature is lowered, the quadrupolar relaxation diminishes faster than the magnetic relaxation. These results show that, with the opening of the pseudo spin gap, a charge degree of freedom of mainly oxygen character is present in the electronic low-energy excitation spectrum.
Inelastic neutron scattering has been used by B. Lake (Toronto, Oak Ridge, and Riso) et al. [Nature 400, 43 (1999)] to determine the wavevector dependence of spin pairing in superconducting La2-xSrxCuO4. The authors found that the spin pairing energy (spin gap) is wavevector independent, even though superconductivity significantly alters the wavevector dependence of the spin fluctuations at higher energies. These measurements, which are sensitive only to the spin sector, taken together with the evidence for d-wave superconductivity in the charge sector, suggest that the high-Tc superconductors are Luther-Emery liquids: materials with gapped (triplet) spin excitations and gapless spin-zero charge excitations.
Local structural evidence supporting the presence of charge inhomogeneities in the CuO2 planes of underdoped La2-xSrxCuO4 are presented in a paper by E. S. Bozin (Michigan State) et al. High- resolution atomic pair distribution functions (PDFs) were obtained from neutron powder diffraction data over the range of doping 0 <= x <= 0.30 at 10 K. As x increases, although the average structure becomes less orthorhombic, the authors find a broadening of the in-plane Cu-O bond distribution up to optimal doping, but thereafter the peak abruptly sharpens. Complementary evidence also comes from the observation of octahedral tilt disorder in the PDF at higher atomic separation. This suggests a crossover from a charge-inhomogeneous state below optimal doping to a homogeneous charge state above optimal doping.
A preprint by I. M. Abu-Shiekah (Leiden) et al. reports a study of stripe fluctuations in La2NiO4.17 by [139]^La NMR using the field and temperature dependence of the linewidth and relaxation rates. The authors find strong similarities in slow stripe fluctuations between Sr- doped cuprates (La2-xSrxCuO4) and oxygen-doped nickelates. In the formation process of the stripes in La2NiO4.17, the NMR line intensity is maximal below 230 K, starts to diminish around 140 K, disappears around 50 K, and recovers at 4 K, below which the stripes become static. The authors show that these results are consistent with but completely complementary to neutron measurements, and that they are generic for oxygen-doped nickelates and underdoped cuprates.
Tunneling spectra and the superconducting gap in Bi-2212 and Tl2Ba2CuO6+d (Tl-2201) are reported by L. Ozyuzer (Argonne and IIT) et al. Using superconductor/insulator/superconductor (SIS) break junctions, the authors investigated the tunneling spectra in Bi-2212 over a wide doping range and found that the energy gap displays a monotonic dependence on doping, increasing to large values in the underdoped region even as Tc decreases. This leads to unphysically large values of the ratio 2Delta/k_BTc ~ 20. Each spectrum exhibits dip and hump features at high bias with characteristic energies that scale with the superconducting gap. The tunneling spectra of near optimally doped Tl-2201 also display a weak dip feature in superconductor/insulator/normal-metal (SIN) junctions. The authors conclude that dip and hump features in SIS junctions are generic to high-temperature superconductors.
After examining recent tunneling data on hole-doped cuprates, A. Mourachkine (Brussels) concludes that there are two superconducting order parameters: one (Delta_c) for Cooper pairing and the other (Delta_p) for phase coherence.
Films
The use of quasiparticle planar tunneling spectroscopy to investigate the density of states in YBa2Cu3O7-d is described by L. H. Greene (UIUC) et al. The dependencies upon temperature, crystallographic orientation, doping, damage, and magnetic field confirm that the observed zero-bias conductance peak (ZBCP) is an Andreev bound state, an intrinsic property of a d-wave superconducting order parameter at an interface. In zero applied field, the splitting of the ZBCP below ~8 K confirms a near- surface phase transition into a superconducting state with spontaneously broken time-reversal symmetry. Tunneling into the Andreev bound state provides a phase-sensitive spectroscopy that can be used to measure a variety of properties of the density of states in an unconventional superconductor.
A systematic study of texturing mechanisms in pure Ag is presented in a preprint by H. Suo (Geneva and Beijing Polytechnic) et al., the goal being to obtain a cube-textured {100}<001> tape that can be used as a substrate for superconducting coated conductors. The authors report details of how a sharp cube texture can be produced after preheated deformation and recrystallization. The stability of the cube texture at high temperatures up to 900^oC indicates that the tapes are suitable for epitaxial growth of superconducting oxides.
As reported by A. Wang et al. (Northwestern), smooth, epitaxial cerium dioxide (CeO2) thin films have been grown in-situ in the 450-650^oC temperature range on (001) yttria-stabilized zirconia (YSZ) substrates by metal-organic chemical vapor deposition (MOCVD) using a fluorine-free liquid Ce precursor. As assessed by x-ray diffraction, transmission electron microscopy (TEM), and high-resolution electron microscopy (HREM), the epitaxial films exhibited a columnar microstructure with atomically abrupt film-substrate interfaces and with only minor bending of the crystal plane parallel to the substrate near the interface and at the column boundaries. With fixed precursor temperature and gas flow rate, the CeO2 growth rate decreased from ~10 Angstroms/min at 450^oC to ~6.5 Angstroms/min at 540^oC. The root-mean-square roughness of the films also decreased from 15.5 Angstroms at 450^oC to 4.3 Angstroms at 540^oC. High-quality, epitaxial YBa2Cu3O7-d films were deposited on these CeO2 films via pulsed organometallic beam epitaxy (POMBE); they exhibited Tc = 86.5 K and self-field Jc = 1.08 x 10^6 A/cm^2 at 77.4 K.
A preprint by E. V. Pechen (Lebedev Institute) reports that a special shaping of the YAG:Nd^[3+] laser beam profile can improve homogeneity and Tc of pulsed-laser-deposited (PLD) YBa2Cu3O7-d films. Targets of nonstoichiometric composition and substrates with slanting cuts were found to be necessary for high-quality film growth. The author found that multiple droplets and solid particles ejected from the target surface by infrared radiation could be removed from the laser-induced plasma by use of a velocity filter (disk-chopper).
The resistive transition of (YBCO)24/(PBCO)2 multilayer thin films has been measured by X. W. Cao (Hefei) et al. as a function of temperature and the angle theta between the CuO2 planes and the 4 T applied magnetic field. The angular dependence of the characteristic temperature T* was found to exhibit either 2D or 3D behavior. The data also revealed a lock-in transition at a critical angle theta_c of about 13 degrees.
Applications
High-Tc current leads for electrical connection to low-Tc superconducting magnet coils are attractive because the high-Tc oxides have a low thermal conductivity at temperatures below their Tc, thus allowing the length of the current leads to be reduced. A preprint by X. K. Fu et al. (Wollongong) reports that a new method using a combination of cold isostatic pressing (CIP) and hot pressing (HP) has been applied to fabricate Bi-2223 bar current leads. The critical current density achieved by this method reached as high as 10^3 A/cm^2 at 77 K in self-field.
Vortices
The vortex-lattice melting transition in magnetic fields parallel to the ab planes has been studied by Yu. Eltsev (KTH-Stockholm and SRL-ISTEC) and OE. Rapp (KTH-Stockholm) in twinned YBa2Cu3O7-d single crystals using transport measurements along the c axis. In contrast to a previously studied geometry with both field and current parallel to the planes [W. K. Kwok et al., Phys. Rev. Lett. 72, 1088 (1994)], the present authors found a step-like c-axis resistive transition for exact field alignment along the ab planes. The authors also studied the angular dependence of rho_c with rotation of the crystal around the c axis. The results show that below the resistive step, the pinning force is anomalously increased when the field is aligned along ac or bc crystal facets, indicating strong surface-pinning effects.
Vortex-lattice melting and depinning have been studied theoretically by J. P. Rodriguez (California State, Los Angeles) using the uniformly frustrated layered XY model in its Villain form. The author identified a decoupled pancake vortex liquid phase, which is bounded by both first- order and second-order decoupling lines in the magnetic field vs temperature (H vs T) plane. These transitions, respectively, account for the vortex-lattice melting and vortex-lattice depinning behavior observed in the mixed state of clean high-temperature superconductors.
Using realistic London Langevin computer simulations with parameters corresponding roughly to YBCO, C. J. Olson et al. (UC-Davis) have found an enhancement of the critical current when artificial columnar defects are introduced in a splayed configuration. When vortex entanglement is not present, the improvement in transport properties appears only for regimes of vortex creep when the splay angle is sufficiently small, and the improvement then results from the suppression of kink propagation. At higher applied currents, the resistivity in the splayed sample becomes as large as that in a sample with parallel columnar pins. The authors find that the best angle for splay is related to the accommodation angle of the columnar pins; the highest Jc was found for transverse bimodal splay angles theta ~~ +-10 degrees.
A preprint by A. W. Smith (Chicago) et al. reports measurements of the onsets of a resistive response and transverse flux penetration in the Bose-glass phase in an untwinned YBa2Cu3O7-d single crystal containing columnar defects along the c axis. The resistive onset was measured using an ac technique with a pickup coil placed near the sample, while the onset of a local magnetic field component perpendicular to the columnar defects was probed using a micron-sized InAs Hall-probe array. Even for tilt angles as small as one degree, the two measurements yielded strikingly different demarcations for the Bose-glass phase. The authors suggest that a new intermediate regime exists between the glass and the liquid state which exhibits no vortex flow even in the absence of a fully developed transverse Meissner effect, and they stress that these results evidently are in conflict with the current theoretical framework for two-dimensional bosonic states, which allows for only a single transition.
A preprint by A. P. Hope (SUNY-Buffalo) et al. reports observations in superconducting single-crystal YBa2Cu3O7-d of a series of avalanche-like flux jumps, seen as a saw-tooth pattern in the torque vs sample orientation in a magnetic field. While reminiscent of the classical flux jump instability, the present discontinuous jumps are proposed to be associated with the layered nature of the material and twin-boundary pinning, the combination of which promotes a crossover from a tilted to a kinked vortex structure.
Simulations of vortex avalanches in the critical state of a type-II superconductor with periodic pinning have been carried out by R. Cruz et al. (Havana). The authors found that the results could be scaled, and they extracted numerical values of the resulting critical exponents. The authors report that they have found a new universality class for strong and dense periodic distributions of pinning centers.
Investigations of quasi-Josephson effects due to coherent vortex motion in artificial reversible periodic pinning potential structures in YBa2Cu3O7-d thin films have been carried out by Y. Yuzhelevski (Ben Gurion University of the Negev) et al. To produce periodic pinning conditions, a magnetic tape containing a prerecorded harmonic signal was placed on the surface of the superconducting thin film. The authors found that current-driven motion of Abrikosov vortices in wide and short macrobridges of this film led to the appearance of Josephson-like effects, manifested as a series of self-induced current steps on the current-voltage characteristics.
Abrikosov and Josephson vortices trapped in bicrystalline YBa2Cu3O7-d washer-type dc SQUIDs containing regular arrays of micrometer holes (antidots) have been directly imaged by S. Keil (Tuebingen) et al. using a standard electron microscope equipped with a liquid-nitrogen- temperature cryostage. Signal generation is based on the electron-beam- induced local vortex displacement, which is detected as a flux change in the SQUID loop. This technique allows vortices to be imaged with a spatial resolution of about 1 micrometer at variable temperature and magnetic field. The magnitude of the vortex signal is a direct measure of the amount of flux a vortex couples into the SQUID hole. In addition to the static local distribution of vortices, this technique can provide information on the dynamic behavior of vortices trapped in the SQUID loop if the beam is used as a local perturbation and the low-frequency noise induced by vortex motion is measured.
The sine-Gordon equation governing magnetic flux penetration into Josephson junctions with arbitrarily misaligned anisotropic superconducting banks has been derived by R. G. Mints (Tel Aviv) and V. G. Kogan (Ames Lab, Iowa State). The authors apply the theory to compute the mechanical torque on vortices in Josephson junctions at twin planes of YBCO-like material. This torque and its predicted angular dependence should be measurable in small fields, since flux penetration into twinned crystals evidently begins with the penetration of Josephson vortices along twin planes.
Flux Penetration
The magnetization of ideal type-II superconductors without bulk vortex pinning has been derived from first principles by E. H. Brandt (MPI- Stuttgart) for superconductors with constant thickness. The magnetization is irreversible because of a macroscopic geometric barrier for flux penetration at the edges, which yields a sharply defined entry field H_[en]. Above the irreversibility field H_[rev] > H_[en], the magnetization becomes reversible and coincides with that of an ideal, appropriately defined ellipsoid. The author illustrates the results with numerical calculations of the field-increasing and field-decreasing magnetization of pin-free slabs, strips, disks, and cylinders with a variety of aspect ratios.
The dependence of the magnetic susceptibility components chi_1', chi_1", chi_3', and chi_3" upon the amplitude of the applied ac magnetic field have been calculated by G. M. Maksimova et al. (Nizhny Novgorod) for thin superconducting films (d < lambda) in the form of narrow strips (W << lambda_[perp.], where d = film thickness, lambda = London penetration depth, W = width, and lambda_[perp.] = 2lambda^2/d = 2D screening length). The authors considered the behavior in two limits, one being when the edge barrier dominates the magnetization hysteresis and the other when bulk pinning dominates. The authors found that the signs of chi_3' and chi_3" depend strongly upon which mechanism dominates the hysteresis.
The critical state in a thin superconducting circular disk (d << R) with an arbitrary magnetic-field dependence of the critical current density Jc(B) has been analyzed by D. V. Shantsev (Oslo and St. Petersburg) et al. The authors assume either that d >= lambda or, if d < lambda, that lambda_[perp.] << R, where d = film thickness, lambda = London penetration depth, R = disk radius, and lambda_[perp.] = 2lambda^2/d = 2D screening length. The authors derive and solve a set of coupled integral equations for the magnetic-flux and current-density distributions when a magnetic field B_a is applied perpendicular to the disk. The method accounts self-consistently for the suppression of Jc at places in the disk where, because of demagnetizing effects and self- fields, the local value of B is largest.
Theory
The thermodynamic properties of the SO(5) theory unifying antiferromagnetism (AF) and d-wave superconductivity (SC) have been explored extensively by X. Hu (NRIM) using Monte Carlo simulations with a classical model Hamiltonian. The author took into account thermal fluctuations both in the rotation of the SO(5) superspins between the AF and SC subspaces and in the phase variables of the SC order parameters. The author also investigated the consequences of an external magnetic field and found, for example, that short-range AF fluctuations are larger in the cores of vortex lines than elsewhere and that these fluctuations decrease continuously to zero with increasing symmetry- breaking (g) field. At intermediate g fields, the author finds a region of coexistence of the vortex-line lattice with long-range SC order and long-range AF order. Appearing in the corresponding simulated structure factor, surrounding the strong AF Bragg peaks at Q = (+-pi,+-pi), are superlattice spots identified with modulation by the triangular SC vortex lattice. The author suggests neutron-scattering measurements to search for these superlattice spots.
The fermionic states of the antiferromagnetically ordered vortex cores predicted to exist in the superconducting phase of the SO(5) model of strongly correlated electrons have been studied by B. M. Andersen et al. (Copenhagen). The authors stress that their model calculation gives a natural explanation of recent STM vortex-core studies by Ch. Renner et al. [Phys. Rev. Lett. 80, 149 (1998); 80, 3606 (1998)], which showed striking differences between Bi-2212 and YBCO.
The interplay between lattice-symmetry breaking and superconducting order in a two-dimensional model of doped antiferromagnets with long- range Coulomb interactions and Sp(2N) spin symmetry has been investigated by M. Vojta and S. Sachdev (Yale) at zero temperature in the large-N limit. The authors propose a global phase diagram for the cuprate superconductors, and they also describe the quantum transitions between the phases, the evolution of their fermion excitation spectrum, and the experimental implications.
The development of a non-crossing approximation (NCA) for the effective cluster problem of the recently developed dynamical cluster approximation (DCA) is described in a preprint by Th. Maier (Cincinnati and Regensburg) et al. The authors discuss the method in detail and present results for the one-particle properties of the Hubbard model. Near half filling, the spectra display pronounced features including a pseudogap and non-Fermi-liquid behavior due to short-ranged antiferromagnetic correlations.
Low-energy magnetic excitations of doped spin ladders have been studied by Y. Bai (POSTECH), using an effective Hamiltonian describing interactions of mobile spins and background spins. The author calculated the helicity modulus against fluctuations, both in the ladder plane and out of the plane, as functions of the doping concentration, leg number, and interaction strengths in the ladder. The system has the lowest energy in spiral phases with out-of-plane modes in addition to in-plane spirals. The author's results for the doping range for a gapped mode in odd-legged ladders are in agreement with existing numerical studies.
Two-leg spin-ladder systems have been studied analytically by Y. Bai and S.-I. Lee (POSTECH) using a t-J model including interchain spin exchange and interchain hopping terms. The authors map the spin part to a quantum sine-Gordon model via a bosonization method that accounts for phase fluctuations. The spin gap in the Luther-Emery phase evolves to gapless Luttinger-liquid phases in even ladders at certain doping levels. The authors estimate the transition temperature at which the conventional electron phase is deconfined to spinons and holons.
The low-energy charge excitations of a doped antiferromagnetic ladder have been modeled by J. P. Rodriguez (Madrid and California State, Los Angeles) using a system of interacting spinless fermions that live on the same ladder. A relatively large spin gap is assumed to freeze out all spin fluctuations. The author finds that the formation of rung hole pairs coincides with the opening of a single-particle gap for charge excitations along chains and with the absence of coherent tunneling between chains. The author also finds that such hole pairs condense into either a crystalline or superconducting state as a function of the binding energy.
The electronic structure of the high-Tc cuprates has been studied by J. Ashkenazi (Miami) on the basis of both large-U and small-U orbitals. The author finds a striped structure and three types of carriers: polaron-like stripons carrying charge, quasielectrons carrying charge and spin, and svivons carrying spin and lattice distortion. Anomalous properties of the cuprates and their transport properties are derived. The author finds that pairing results from transitions between pair states of quasielectrons and stripons through the exchange of svivons. The pairing results in superconductivity when the stripons conduction is coherent, and in a pseudogap phase when it is not.
As noted by B. K. Chakraverty (Grenoble), if phase coherence determines the superconducting transition temperature in the cuprates, it is of great interest to understand the role that phase-fluctuation dynamics plays in bringing about depletion of the superconducting condensate. The author presents a theory for how this occurs and shows that, in two dimensions, dynamic phase fluctuation or pair fluctuation gives rise to condensate depletion linear with temperature as T --> 0 in superconductors with nodes at the Fermi surface.
The effects of dilute Zn impurities on the uniform magnetic susceptibility have been calculated by N. Bulut (Koc) in the normal metallic state for a model of spin fluctuations in the layered cuprates. The author finds that scattering from extended impurity potentials can lead to a coupling of the q ~ (pi,pi) and q ~ 0 components of the magnetic susceptibility chi(q). In the presence of antiferromagnetic correlations, this coupling can enhance the uniform susceptibility. The author discusses the implications of this result for experimental data on Zn-substituted YBa2Cu3O7-d.
As reported by C. Grimaldi (EPFL), the effects of impurity and spin- orbit scattering potentials can strongly affect the Zeeman response of a d-wave superconductor. The author calculates both the phase diagram and the quasiparticle density of states within the Born approximation and finds that the spin-orbit interaction influences the Zeeman responses of d-wave and s-wave superconductors in a qualitatively different way.
The BCS-BEC (Bose-Einstein-condensation) crossover scenario within the superconducting state has been investigated by I. Kosztin (Chicago) et al., using a T-matrix approach that yields the ground state proposed by Leggett. Here the authors extend this ground-state analysis to finite temperatures and interpret the resulting physics. The authors find and examine the properties of two types of bosonic-like excitations of the system: long-lived, incoherent pair excitations and collective modes of the superconducting order parameter, which have different dynamics. The authors emphasize how, at finite T, BCS-BES approaches introduce an important parameter Delta_[pg]^2 = Delta^2 - Delta_[sc]^2 into the description of superconductivity, where Delta is the excitation gap and Delta_[sc] is the superconducting order parameter.
Using a diagrammatic BCS-BEC crossover theory, J. Maly et al. (Chicago) have investigated the pseudogap onset temperature T*, the superconducting transition temperature Tc, and the general nature of the pseudogap phase. The theory is based on the pairing approximation of Kadanoff and Martin, which was further extended by Patton (KMP). This approach was driven by the objective to obtain BCS-like behavior in the weak-coupling limit. As the coupling constant g increases, the system crosses over to Bose-Einstein behavior. The authors' Tc equations, which turn out to be rather simple as a result of the KMP scheme, reveal a rich structure as a function of g in which the pseudogap is found to compete with superconductivity.
The effects of critical superconducting fluctuations upon the scaling of the linear ac conductivity sigma(omega) of a bulk superconductor slightly above Tc in zero applied magnetic field have been considered by R. A. Wickham and A. T. Dorsey (Florida). The authors derive a universal scaling function S(y) and find that it deviates only slightly from its Gaussian form, calculated earlier. The authors also compare their results with experimental measurements of the ac conductivity of YBa2Cu3O7-d near Tc, and they discuss the implications of their theory for such experiments.
A theory of mesoscopic fluctuations in disordered thin superconducting films in a parallel magnetic field has been developed by F. Zhou (Princeton). At zero temperature and in a sufficiently strong magnetic field, the superconducting state is predicted to undergo a phase transition into a state characterized by superfluid densities of random signs instead of a spin-polarized disordered Fermi-liquid phase.
A preprint by A. Kallio et al. (Oulu) shows that the upper critical field H_[c2](T) of an unconventional superconductor can be expressed in a simple way in terms of a single universal function f(t). Here t = T/T*, where T* is connected with the temperature-independent gap 2Delta = 2k_[B]T*, and 2Delta is the binding energy of a pair in analogy with dissociation of molecules. The function f(t) determines the fraction of bosons (B^[++]) and fermions (h^[+]) at temperature T; it is obtained from a mathematical treatment of chemical equilibrium with respect to the reaction B^[++] <--> 2h^[+]. The authors show that this theory accounts for all the shapes of H_[c2](T) observed in several unconventional superconductors, including Tl2Ba2CuO6+d (Tl-2201) with Tc = 15 K.
The origin of superconductivity in electron-doped cuprates of composition Ln2-xCexCuO4-z (Ln = Nd, Pr, and Sm) is considered in a preprint by L. Jansen (ETH-Zurich) and R. Block (Amsterdam). The authors propose that the origin of superconductivity in these materials is due to indirect-exchange coupling between conduction electrons (quasiparticles) via diamagnetic oxygen anions, the mechanism the authors previously applied to the hole-doped cuprates. The authors argue that the electron-doped cuprates are, in fact, hole-doped because of overcompensation of doped excess positive charge by oxygen anions.
As noted in a preprint by D. F. Agterberg (Florida State), there now exists a wealth of experimental evidence that Sr2RuO4 is an odd-parity superconductor. Experiments further indicate that among the bands stemming from the Ru {xy,xz,yz} orbitals, the portion of the Fermi surface arising from the xy orbitals exhibits a much larger gap than the portions of the Fermi surface arising from the {xz,yz} orbitals. In this preprint, the author examines the role of impurities on such an orbital-dependent superconducting state within the Born approximation. In contrast to expected results for a nodeless p-wave superconductor, the unique nature of the superconducting state in Sr2RuO4 implies that a low concentration of impurities strongly influences the low-temperature behavior.
Andreev bound states in superconductor/ferromagnet (S/F) superlattices have been studied theoretically by V. Prokic and L. Dobrosavljevic- Grujic (Belgrade), assuming tunneling between S and F layers in the perpendicular direction. Andreev reflection at the S/F interfaces is found to be strongly affected by the exchange interaction h in F layers. In the ground state, zero-energy states (ZES) form on S and F layers when h not equal to 0. For h = 0, corresponding to superconductor/normal (S/N) superlattices, ZES may appear in the nonequilibrium phase, phi = pi. This behavior is found for both s-wave and d-wave symmetry of the order parameter in S. The authors obtain the conditions for ZES as a function of h, the transfer integral t for movement of quasiparticles between S and F layers, and the ground-state phase difference phi_[eq] between two neighboring S layers.
Recent theoretical developments that relate to high-temperature superconducting Josephson junctions are discussed by G. Wendin (Chalmers): (a) isolated (S/I) and resonantly coupled (S/I/S) Andreev interface states, (b) d-wave models with resonantly coupled midgap states for ab-plane junctions, and (c) resonant-tunneling models for c- axis junctions.
Three preprints by M. W. Coffey (Colorado) provide underlying theory for the examination of spheres of superconducting or linear magnetic materials by magnetic force microscopy (MFM). One of these calculates the levitation force between a point magnetic dipole and a superconducting sphere (of uniform penetration depth lambda) in the Meissner state. A second preprint shows how a penetration depth lambda(r) depending only upon the radial coordinate r could be determined from measurements of the levitation force at various distances from a superconducting sphere. The third shows how a permeability mu(r) depending only upon the radial coordinate r could be determined from measurements of the levitation force at various distances from a sphere made of a linear magnetic material.
Contributed by John R. Clem
Contents: Technology News begins on page 6; Preprints begin on page 7; and Coming Events are on page 15.
High-Tc Update is available without charge to interested persons. Recipients are expected to participate in this information exchange by sending us preprints, reprints, meeting news, research news, etc. Contributions to defray the cost of newsletter printing and mailing are welcome.
TECHNOLOGY NEWS (Also see Applications section of Nota Bene.)
This section describes progress in manufacturing, product development, and technology transfer in the high-Tc superconductivity field. Please send your contributions (product development information, news regarding technology transfer efforts, or any information you would like to share about your corporation or laboratory) to the editor.
Recently, American Superconductor Corporation (ASC) announced a contract with the Office of Naval Research (ONR) to design a 25,000-hp HTS ship propulsion motor for naval ship propulsion systems. The basic motor design is a variant on the one being employed for industrial HTS motors, which have been under development for the last decade. The company will also develop and demonstrate key motor components under the program. The application of HTS technology to ship propulsion is expected to yield inherently quieter motors that have much higher power density; that is, they are expected to be approximately one-fifth the size and weight of conventional motors of the same horsepower rating. (A conventional 25,000-hp ship propulsion motor is about the size of a city bus -- the HTS model is expected to be about the size of a sport utility vehicle.) The company believes that the market for HTS ship propulsion motors for both commercial and defense applications will add significantly to the addressable market for HTS motors, which is already over $1 billion per year based on industrial motor applications. This first contract for HTS ship propulsion motors has a value of $2 million, of which the company expects to recognize approximately $1.5 million over the next 12 months. The remainder will be directed to parallel development efforts at the ONR, the Naval Research Laboratory, and the National High Magnetic Field Laboratory. For further information, contact American Superconductor Corporation, Two Technology Drive, Westborough, MA 01581; telephone (508) 836-4200; telefax (508) 836-4248. Media contact is Kevin Coates, telephone (202) 434-8308, e-mail kcoates@washington.com.
The two corporations, OMICRON Vakuumphysik GmbH and Oxford Instruments Research Instruments, have recently announced their cooperation in the development of low-temperature scanning-probe microscopy systems. OMICRON has, over the past years, invested heavily in the development of low temperature microscopes, and has rapidly extended its range of products for low-temperature SPM applications. Oxford Instruments has, for many years, been involved in the field of cryogenic applications. The cooperation will combine the core skills and expertise of both partners in the creation of a new class of research instruments and intends to open up new development perspectives to cater better to the increasing demand from the research community and to meet the stringent requirements of complex applications. For further information, contact Michael Sander, Marketing Manager, OMICRON Vakuumphysik GmbH, Idsteiner Str. 78, D-65232 Taunusstein, Germany; telephone +49 61 28 9870; telefax +49 61 28 987185; Web site http://www.omicron-instruments.com/ or http://www.omicron.de/. Or contact Steve Vale, Director of Marketing and Systems, Oxford Instruments Research Instruments, Tubney Woods, Abingdon, Oxfordshire, United Kingdom OX13 5QX; telephone +44 1865 393200; telefax +44 1865 393333; Web site http://www.oxford- instruments.com/.
Contributed by Sreeparna Mitra
PREPRINTS To obtain a particular preprint, contact the first author at the address given at the end of the citation. Help us expand this list by sending us your complete preprint. Please specify where and when your paper was submitted. An * next to an entry indicates it is a correction or revision of a previous entry. PACS codes and/or key words are given at the end of the citation.
For help on using or submitting your preprint to the cond-mat e-print archive at Los Alamos (Subject class: Superconductivity), go to http://xxx.lanl.gov/help/.
I. M. Abu-Shiekah, O. O. Bernal, A. A. Menovsky, H. B. Brom, and J. Zaanen, "Similarity of Slow Stripe Fluctuations Between Sr-Doped Cuprates and Oxygen-Doped Nickelates." Kamerlingh Onnes Laboratory, Leiden University, P.O. Box 9506, 2300 RA Leiden, THE NETHERLANDS; H. B. Brom's telephone +31 71 5275-425 or -475; telefax +31 71 5275-404; e- mail brom@phys.leidenuniv.nl. 76.60.-k; 74.72.Dn; 75.30.Ds; 75.40.Gb.
D. F. Agterberg, "Impurities and Orbital Dependent Superconductivity in Sr2RuO4." To be published in Phys. Rev. B. National High Magnetic Field Laboratory, Florida State University, 1800 East Paul Dirac Drive, Tallahassee, FL 32306; e-mail agterber@fangio.magnet.fsu.edu; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9902174. 74.20.Mn; 74.25.Bt; 74.25.Jb.
Brian Moller Andersen, Henrik Bruus, and Per Hedegard, "SO(5) Theory of Insulating Vortex Cores in High-Tc Materials." Orsted Laboratory, Niels Bohr Institute for APG, Universitetsparken 5, DK-2100 Copenhagen O, DENMARK; e-mail bma@fys.ku.dk; Per Hedegard's e-mail hedegard@fys.ku.dk; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9906233. 74.20.De; 74.25.Ha; 74.60.-w.
M. Aprili, M. Covington, E. Paraoanu, and L. H. Greene, "Doppler Shift of the Surface Bound States in YBCO." To be published in Physica B: Proc. of the 22nd Int. Conf. on Low Temp. Phys. (LT22), Helsinki, Finland, Aug. 5-11, 1999. CSNSM-CNRS, Universite Paris-Sud, Batiment 108, F-91405 Orsay Cedex, FRANCE; e-mail aprili@csnsm.in2p3.fr. Key words: tunneling spectroscopy, HTSC, Andreev bound states, superconducting screening.
Josef Ashkenazi, "Stripes, Carriers, Pseudogap, and Superconductivity in the Cuprates." To be published in Int. J. Mod. Phys. B. Department of Physics, University of Miami, P.O. Box 248046, Coral Gables, FL 33124; e-mail ashkenazi@phyvax.ir.miami.edu; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9906256.
Yujoung Bai, "Topological Excitations in Doped Spin Ladders." National Creative Research Initiative Center for Superconductivity, Department of Physics, Pohang University of Science and Technology, Pohang, Kyungbuk 790-784, SOUTH KOREA; telephone +82 562 279-5848 or -9929; telefax +82 562 279-5299; e-mail ybai@postech.ac.kr; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9906365. 75.10.-b; 74.20.Mn; 71.27.+a; 71.45.-d.
Yujoung Bai and Sung-Ik Lee, "Phases from Lightly Doped Two-Legged Spin Ladders." National Creative Research Initiative Center for Superconductivity and Department of Physics, Pohang University of Science and Technology, Pohang, Kyungbuk 790-784, SOUTH KOREA; telephone +82 562 279-5848 or -9929; telefax +82 562 279-5299; e-mail ybai@postech.ac.kr; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9906302.
Yunkyu Bang, "New Gap Equation for Strongly Correlated Metals." To be published in Physica C (in press). Department of Physics, Chonnam National University, Kwangju 500-757, KOREA; telephone +82 62 530 3363; telefax +82 62 530 3369; e-mail ykbang@chonnam.chonnam.ac.kr. Key words: superconductivity, gap equation, marginal Fermi liquid, strongly correlated electron systems. 74.20.Fg; 74.20.Mn.
C. Boulesteix, Y. Marietti, T. Badeche, H. Tatarenko-Zapolsky, V. Grachev, O. Monnereau, H. Faqir, and G. Vacquier, "Use of Out-of-Plane Resistivity for Determination of the 2D or 3D Character of Superconductive Fluctuations for Bi-2212 Crystals in the Mixed State and Origin of Anomalous High Out-of-Plane Resistivity for Weakly Oxidized Crystals." To be published in J. Phys. Chem. Solids. Laboratoire Materiaux Organisation et Proprietes (MATOP), CNRS URA 1530, Case 151, Faculte des Sciences et Techniques St. Jerome, Universite d'Aix- Marseille III, F-13397 Marseille Cedex 20, FRANCE; telephone +33 4 91 28 8390; telefax +33 4 91 28 8775; e-mail cboulest@matop.u-3mrs.fr.
E. S. Bozin, G. H. Kwei, H. Takagi, and S.J.L. Billinge, "Neutron Diffraction Evidence of Microscopic Charge Inhomogeneities in the CuO2 Plane of Superconducting La2-xSrxCuO4 (0 <= x <= 0.30)." Submitted to Phys. Rev. Lett. Department of Physics and Astronomy and Center for Fundamental Materials Research, Michigan State University, East Lansing, MI 48824-1116; e-mail bozin@kepler.pa.msu.edu; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9907017. 61.12-q; 71.38.+i; 74.20.Mn; 74.72.Dn; 74.72.-h.
Ernst Helmut Brandt, "Irreversible Magnetization of Pin-Free Type-II Superconductors." Max Planck Institut fuer Metallforschung, D-70506 Stuttgart, GERMANY. 74.60.Ec; 74.60.Ge; 74.55.+h.
David W. Brown, Aldo H. Romero, and Katja Lindenberg, "Franck-Condon Factors as Spectral Probes of Polaron Structure." Institute for Nonlinear Science, University of California at San Diego, La Jolla, CA 92093-0402; Katja Lindenberg's e-mail kl@hypatia.ucsd.edu; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9906259. 71.38.+i; 71.15.-m; 71.35.Aa; 72.90.+y.
Georg M. Bruun and Charles W. Clark, "Detection of the BCS Transition of a Trapped Fermi Gas." Electron and Optical Physics Division, National Institute of Standards and Technology, US Department of Commerce, Gaithersburg, MD 20899-8410; e-mail in Oxford, United Kingdom g.bruun1@physics.oxford.ac.uk; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9906392.
N. Bulut, "Effects of Dilute Zn Impurities on the Uniform Magnetic Susceptibility of YBa2Cu3O7-d." Department of Mathematics, Koc University, Istinye 80860 Istanbul, TURKEY; e-mail nbulut@ku.edu.tr; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9906185. 76.60.-k; 74.62.Dh; 75.40.Cx; 74.72.Bk.
X. W. Cao, Z. H. Wang, and K. B. Li, "Angle Dependence of Thermally Activated Dissipation in (YBCO)24/(PrBCO)2 Multilayer Thin Films." To be published in Physica C. High Magnetic Field Laboratory, Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031, PEOPLE'S REPUBLIC OF CHINA.
B. K. Chakraverty, "Quantum Phase Fluctuation in High-Tc Superconductors." Submitted to Phys. Rev. Lett. Laboratoire d'Etudes des Proprietes Electroniques des Solides, Centre National de la Recherche Scientifique (CNRS), 25 Avenue des Martyrs, BP 166, F-38042 Grenoble Cedex 9, FRANCE; telephone +33 476 88 1185; telefax +33 476 88 7988; e-mail chakrav@lepes1.polycnrs-gre.fr; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9907035.
Mark W. Coffey, "Determining the Permeability of a Sphere of Linear Magnetic Material by Magnetic Force Microscopy." To be published in Phys. Rev. B. Department of Physics, University of Colorado, Boulder, CO 80309; e-mail mcoffey@newton.colorado.edu. 75.30.-m; 02.30.-f.
Mark W. Coffey, "An Inverse Problem for the Magnetic Force Microscopy of a Superconducting Sphere." To be published in Inverse Problems. Department of Physics, University of Colorado, Boulder, CO 80309; e-mail mcoffey@newton.colorado.edu.
Mark W. Coffey, "Levitation Force Between a Point Magnetic Dipole and Superconducting Sphere." To be published in J. Supercond. Department of Physics, University of Colorado, Boulder, CO 80309; e-mail mcoffey@newton.colorado.edu. Key words: magnetic force microscopy, Meissner state, inverse problem, penetration depth, London theory, point dipole, levitation force, scalar potential, vector potential, method of images. 74.20.De; 02.30.-f; 74.25.Nf; 74.25.Ha.
R. Cruz, R. Mulet, and E. Altshuler, "Universality of Vortex Avalanches in a Type II Superconductor with Periodic Pinning." To be published in Physica A. Natural Science Faculty, ISPH Holguin, Cuba Superconductivity Laboratory, IMRE-Physics Faculty, University of Havana, 10400 Havana, CUBA.
A. Dertinger, A. Kreyssig, M. Loewenhaupt, C. Ritter, and H. F. Braun, "Superconductivity, Magnetic Ordering, and Its Interplay in HoNi2^[11]B2C." To be published in the Proc. of the 22nd Int. Conf. on Low Temp. Phys. (LT22), Helsinki, Finland, Aug. 5-11, 1999. Physikalisches Institut, Experimentalphysik V, Universitaet Bayreuth, D- 95440 Bayreuth, GERMANY; telephone +49 921 55 3259; telefax +49 921 55 3647; e-mail armin.dertinger@uni-bayreuth.de; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9906328. Key words: superconductivity, magnetic order, borocarbides.
J. Dukelsky and G. Sierra, "A Density Matrix Renormalization Group Study of Ultrasmall Superconducting Grains." To be published in Phys. Rev. Lett. Instituto de Estructura de la Materia, Consejo Superior de Investigaciones Cientificas, 28006 Madrid, SPAIN; G. Sierra's e-mail sierra@sisifo.imaff.csic.es; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9903332. 74.20.Fg; 74.25.Ha; 74.80.Fp.
Yuri Eltsev and OEsten Rapp, "First-Order-Like Out-of-Plane Resistive Transition in YBa2Cu3O7-d for B Exactly Parallel to ab Planes." Submitted to the Int. Conf. on Phys. and Chem. of Molecular and Oxide Supercond. (MOS'99), Stockholm, Sweden, July 28-Aug. 2, 1999. Superconductivity Research Laboratory, International Superconductivity Technology Center (ISTEC), 10-13 Shinonome 1-chome, Koto-ku, Tokyo 135- 0062, JAPAN. 74.60.Ge; 74.72.Bk.
J. K. Freericks, V. Zlatic, and M. Jarrell, "Approximate Scaling Relation for the Anharmonic Electron-Phonon Problem." Department of Physics, Georgetown University, Washington, DC 20057-0995; e-mail jkf@taz.physics.georgetown.edu; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9906143.
X. K. Fu, V. Rouessac, Y. C. Guo, P. N. Mikheenko, H. K. Liu, and S. X. Dou, "Bi-2223 Bar Current Leads Fabricated by the Combination of Cold Isostatic Pressing and Hot Pressing." To be published in Physica C (in press). Institute for Superconducting and Electronic Materials, University of Wollongong, NSW 2522, AUSTRALIA. Key words: Bi-2223, cold isostatic pressing, hot pressing.
M. B. Gaifullin, Yuji Matsuda, N. Chikumoto, J. Shimoyama, K. Kishio, and R. Yoshizaki, "c-Axis Superfluid Response and Quasiparticle Damping of Underdoped Bi:2212 and Bi:2201." Contact Yuji Matsuda, Institute for Solid State Physics, University of Tokyo, Roppongi 7-22-1, Minato-ku, Tokyo 106, JAPAN; e-mail ym@issp.u-tokyo.ac.jp. 74.25.Nf; 74.50.+r; 74.72.Hs.
L. H. Greene, M. Covington, M. Aprili, E. Paraoanu, and D. E. Pugel, "Observation of Broken Time-Reversal Symmetry with Andreev Bound State Tunneling Spectroscopy." To be published in Physica B: Proc. of the 22nd Int. Conf. on Low Temp. Phys. (LT22), Helsinki, Finland, Aug. 5-11, 1999. Department of Physics, University of Illinois at Urbana- Champaign, Urbana, IL 61801-3080; e-mail lhg@uiuc.edu. Key words: high-temperature superconductivity, unconventional superconductivity, tunneling spectroscopy, order-parameter symmetry, broken time-reversal symmetry, Andreev bound states, thin films.
C. Grimaldi, "Zeeman Response of d-Wave Superconductors: Born Approximation for Impurity and Spin-Orbit Scattering Potentials." Submitted to Physica C. Departement de Microtechnique IPM, Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne, SWITZERLAND; telephone +41 21 693 5825; telefax +41 21 693 3866; e-mail claudio.grimaldi@epfl.ch; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9907004. Key words: d-wave superconductivity, spin-orbit coupling, Zeeman splitting. 74.20.Fg; 71.70.Ej; 74.62.Dh.
Valery P. Gusynin, Vadim M. Loktev, Rachel M. Quick, and Sergei G. Sharapov, "Phase Fluctuations and Non-Fermi-Liquid Properties of 2D Fermi System with Attraction." Presented at the Second Int. Conf. on New Theories, Discoveries and Applications of Superconductors and Related Materials (New3SC-2), Las Vegas, Nev., May 31-June 4, 1999; to be published in Int. J. Mod. Phys. B. Bogolyubov Institute for Theoretical Physics, 252143 Kiev, UKRAINE; Sergei G. Sharapov's e-mail in South Africa sharapov@nsnper1.up.ac.za; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9906407.
A. P. Hope, M. J. Naughton, D. A. Gajewski, and M. B. Maple, "Flux Jump Avalanches in Torque Studies of Single Crystal YBa2Cu3O7-d." To be published in Physica C (in press). Contact M. J. Naughton, Department of Physics, Boston College, Chestnut Hill, MA 02467; telephone (617) 552-3598; telefax (617) 552-8478; e-mail naughton@bc.edu. Key words: single crystal YBa2Cu3O7-d, flux jump, torque. 74.60.Ge; 74.25.Ld; 74.60.Ec.
Xiao Hu, "Thermodynamic Properties of the SO(5) Theory for the Antiferromagnetism and d-Wave Superconductivity: A Monte Carlo Study." National Research Institute for Metals, 1-2-1 Sengen, Tsukuba, Ibaraki 305 0047, JAPAN; telephone +81 298 59 2627; telefax +81 298 59 2601; e- mail xhu@nrim.go.jp; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9906237. 74.25.Dw; 05.50.+q; 74.20.-z; 74.25.Ha.
M. V. Indenbom, C. J. van der Beek, M. Konczykowski, and F. Holtzberg, "Do Columnar Defects Produce Bulk Pinning?" Submitted to Phys. Rev. Lett. Laboratoire des Solides Irradies, Ecole Polytechnique, F-91128 Palaiseau, FRANCE; C. J. van der Beek's e-mail beek@hp1sesi.polytechnique.fr; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9906362.
L. Jansen and R. Block, "Common Origin of Superconductivity in Hole- and Electron-Doped Cuprates Based on Indirect-Exchange Coupling: Doping Dependence of Chemical Potentials." To be published in Physica A. Institut fuer Theoretische Physik, ETH-Hoenggerberg, CH-8093 Zurich, SWITZERLAND; telefax +41 1 633 1115; e-mail jansen@itp.phys.ethz.ch.
M. Jimenez-Melendo, A. Dominguez-Rodriguez, and J. L. Routbort, "Transient Creep of YBa2Cu3O7-x Superconductor." To be published in Physica C (in press). Departamento de Fisica de la Materia Condensada, Universidad de Sevilla, Aptdo. 1065, E-41080 Sevilla, SPAIN; e-mail melendo@cica.es. Key words: transient creep, YBa2Cu3O7-x, diffusion.
Masato Kakihana, Shingo Kato, Valery Petrykin, Joakim Baeckstroem, Lars Boerjesson, and Minoru Osada, "A Simple and Reproducible Way to Synthesize PrBa2Cu4O8 Under 1 atm of Oxygen by Amorphous Citrate Method." To be published in Physica C (in press). Materials & Structures Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, JAPAN; e-mail kakihana@rlem.titech.ac.jp. Key words: PrBa2Cu4O8, amorphous citrate method, ambient pressure synthesis. 81.20.Fw; 74.72.Jt.
A. Kallio, J. Hissa, T. Haeyrynen, and V. Braeysy, "Upper Critical Field of Unconventional Superconductors from Chemical Equilibrium." To be published in Int. J. Mod. Phys. B. Theoretical Physics Division, Department of Physical Sciences, University of Oulu, P.O. Box 3000, FIN- 90401 Oulu, FINLAND.
S. Keil, R. Straub, R. Gerber, R. P. Huebener, D. Koelle, R. Gross, and K. Barthel, "Imaging of Vortices and 1/f Noise Sources in YBCO dc SQUIDs Using Low-Temperature Scanning Electron Microscopy." To be published in IEEE Trans. Appl. Supercond.: Proc. of the 1998 Appl. Supercond. Conf. (ASC), Palm Desert, Calif., Sept. 13-18, 1998. Contact D. Koelle, II. Physikalisches Institut, Lehrstuhl fuer Angewandte Physik, Universitaet zu Koeln, Zuelpicher Str. 77, D-50937 Koeln, GERMANY; telephone +49 221 470 3583; telefax +49 221 470 5178; e-mail koelle@ph2.uni-koeln.de; S. Keil's e-mail at Universitaet Tuebingen keil@uni-tuebingen.de.
M. I. Khabipov, W. Kessel, F.-Im. Buchholz, R. Dolata, and J. Niemeyer, "Bit Error Rate Experiments in Ring-Shaped RSFQ Circuits." To be published in Appl. Supercond. (in press). Physikalisch-Technische Bundesanstalt, Bundesallee 100, D-38116 Braunschweig, GERMANY; telephone +49 3641 206 121; telefax +49 3641 206 399; e-mail khabipov@ipht- jena.de.
H. Kitaguchi, K. Itoh, T. Takeuchi, H. Kumakura, H. Miao, H. Wada, K. Togano, T. Hasegawa, and T. Koizumi, "Performance at 10-50 K of Bi- 2212/Ag Multilayer Tape Fabricated by Using Pre-Annealing and Intermediate Rolling Process." To be published in Physica C (in press). National Research Institute for Metals, 1-2-1 Sengen, Tsukuba 305-0047, JAPAN; telephone +81 298 59 2329; telefax +81 298 59 2301; e-mail hk@nrim.go.jp. Key words: superconductor, Bi2Sr2CaCu2Ox, critical current, cryocooler. 74.72.Hs; 85.25.Kx.
H. Kitaguchi, H. Miao, H. Kumakura, and K. Togano, "Relationship Between Bi2Sr2CaCu2Ox Layer Thickness and Jc Enhancement by Pre-Annealing and Intermediate Rolling Process." To be published in Physica C (in press). National Research Institute for Metals, 1-2-1 Sengen, Tsukuba 305-0047, JAPAN; telephone +81 298 59 2329; telefax +81 298 59 2301; e-mail hk@nrim.go.jp. Key words: Bi-2212, tape, PAIR process, critical current density, thickness. 74.72.Hs; 85.25.Kx.
Ioan Kosztin, Qijin Chen, Ying-Jer Kao, and K. Levin, "Pair Excitations, Collective Modes and Gauge Invariance in the BCS--Bose-Einstein Crossover Scenario." James Franck Institute, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637; e-mail kosztin@rainbow.uchicago.edu; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9906180. 74.20.-z; 74.20.Fg; 74.25.Nf.
B. Lake, G. Aeppli, T. E. Mason, A. Schroeder, D. F. McMorrow, K. Lefmann, M. Isshiki, M. Nohara, H. Takagi, and S. M. Hayden, "Spin Gap and Magnetic Coherence in a Clean High-Temperature Superconductor." To be published in Nature. Oak Ridge National Laboratory, Oak Ridge, TN 37831; T. E. Mason's e-mail masont@ornl.gov; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9906456.
Francois Lefloch, David Quirion, and Marc Sanquer, "Proximity Effect in Planar Superconductor/Semiconductor Junction." Submitted to Physica B: Proc. of the 22nd Int. Conf. on Low Temp. Phys. (LT22), Helsinki, Finland, Aug. 5-11, 1999. Departement de Recherche Fondamentale sur la Matiere Condensee, Service de Physique Statistique, Magnetisme et Supraconductivite (SPSMS), CEA/Grenoble, 17 Avenue des Martyrs, F-38054 Grenoble Cedex 9, FRANCE; telephone +33 4 76 88 4822; telefax +33 4 76 88 5096; e-mail flefloch@cea.fr; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9906330. Key words: proximity effect, superconductor/semiconductor junction, coherent Andreev reflection.
Th. Maier, M. Jarrell, Th. Pruschke, and J. Keller, "A Non-Crossing Approximation for the Study of Intersite Correlations." Submitted to Eur. Phys. J. B. Department of Physics, University of Cincinnati, Cincinnati, OH 45221; e-mail tmaier@physics.uc.edu; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9906253. 71.10.Fd; 71.27.+a; 75.20.Hr; 75.30.Kz; 75.30.Mb.
G. M. Maksimova, D. Yu. Vodolazov, M. V. Balakina, and I. L. Maksimov, "Effect of an Edge Barrier on Magnetization and Higher Harmonics of ac Susceptibility of Narrow Superconducting Film." To be published in Solid State Commun. Nizhny Novgorod University, Nizhny Novgorod 603600, RUSSIA; I. L. Maksimov's e-mail ilmaks@phys.unn.runnet.ru. Key words: edge barrier, bulk pinning, ac susceptibility.
Jiri Maly, Boldizsar Janko, and K. Levin, "Numerical Studies of the s- Wave Pseudogap State and Related Tc: The 'Pairing Approximation' Theory." To be published in Physica C (in press). Contact K. Levin, James Franck Institute, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637; telephone (773) 702-7186; telefax (773) 834-0471; e- mail levin@control.uchicago.edu. Key words: pseudogap, BCS/Bose- Einstein crossover theory, Fermi liquid state. 74.20.Mn; 74.20.Fg; 74.25.Jb; 74.62.-c.
C. Marin, T. Charvolin, D. Braithwaite, and R. Calemczuk, "Properties of a Large La1.92Sr0.08CuO4+d Single Crystal Grown by Traveling-Solvent Floating-Zone Method." To be published in Physica C (in press). Departement de Recherche Fondamentale sur la Matiere Condensee, Service de Physique Statistique, Magnetisme et Supraconductivite, CEA-Grenoble, 17 rue des Martyrs, F-38054 Grenoble Cedex 9, FRANCE; telephone +33 4 76 88 4837; telefax +33 4 76 88 5098; e-mail cmarin@cea.fr. Key words: crystal growth, lanthanum-based high-Tc superconductors, magnetic properties, neutron diffraction, resistance measurement. 74.72.Dn; 74.25.Ha; 61.12.-q; 84.37.+q.
H. Miao, H. Kitaguchi, H. Kumakura, K. Togano, T. Hasegawa, and T. Koizumi, "Optimization of Melt-Processing Temperature and Period to Improve Critical Current Density of Bi2Sr2CaCu2Ox/Ag Multilayer Tapes." To be published in Physica C (in press). Contact H. Kitaguchi, National Research Institute for Metals, 1-2-1 Sengen, Tsukuba 305-0047, JAPAN; telephone +81 298 59 2329; telefax +81 298 59 2301; e-mail hk@nrim.go.jp. Key words: superconductor, Bi2Sr2CaCu2Ox, critical current density, melt process. 74.72.Hs; 85.25.Kx.
D. Mihailovic, V. V. Kabanov, K. Zagar, and J. Demsar, "Distinct Charge and Spin Gaps in Underdoped YBa2Cu3O7-d from Analysis of NMR, Neutron Scattering, Tunneling and Quasiparticle Relaxation Experiments." To be published in Phys. Rev. B. Solid State Physics Department, Jozef Stefan Institute, Jamova 39, 1001 Ljubljana, SLOVENIA; telephone +386 61 177 3729; telefax +386 61 125 1077; e-mail dragan.mihailovic@ijs.si; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9907005.
Roman G. Mints and Vladimir G. Kogan, "Josephson Junction Between Anisotropic Superconductors." To be published in Phys. Rev. B. School of Physics and Astronomy, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 69978, ISRAEL; e-mail mints@ccsg.tau.ac.il; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9906327.
R. Mittal, S. L. Chaplot, H. G. Salunke, G. P. Das, P. Raj, A. Sathyamoorthy, K. Shashikala, and S. K. Dhar, "Electrons, Phonons and Superconductivity in C16 Structured Zr2Fe." To be published in Physica C (in press). Condensed Matter Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, INDIA; telefax +91 22 550 5151; e-mail chaplot@magnum.barc.ernet.in. Key words: phonons, neutron inelastic scattering, electronic structure. 74.25.Kc; 78.70.Nx; 74.25.Jb; 63.20.Dj.
A. Mourachkine, "The Order Parameters for Pairing and Phase Coherence in Cuprates." Service de Physique des Solides, Universite Libre de Bruxelles, CP233, Boulevard du Triomphe, B-1050 Brussels, BELGIUM; telephone +32 2 650 5751; telefax +32 2 650 5916; e-mail anmourac@ulb.ac.be; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9906358. 74.25.Dw; 74.72.-h; 74.20.Mn.
M. Muralidhar, M. R. Koblischka, and M. Murakami, "Embedding of 211 Particles in NEG-123 Superconductors." To be published in Supercond. Sci. & Technol. Division 3, Superconductivity Research Laboratory, International Superconductivity Technology Center (ISTEC), 3-35-2 Iioka- Shinden, Morioka, Iwate 020, JAPAN; telephone +81 19 635-9015 or -9016; telefax +81 19 635-9017; e-mail miryala1@istec.or.jp. Key words: (Nd,Eu,Gd)Ba2Cu3Oy, melt processing, critical current density, flux pinning.
C. J. Olson, R. T. Scalettar, and G. T. Zimanyi, "Splayed Pins Reduce Creep and Enhance Critical Current." Department of Physics, University of California at Davis, Davis, CA 95616.
L. Ozyuzer, J. F. Zasadzinski, and N. Miyakawa, "Tunneling Spectra and Superconducting Gap in Bi2Sr2CaCu2O8+d and Tl2Ba2CuO6+d." Presented at the Second Int. Conf. on New Theories, Discoveries and Applications of Superconductors and Related Materials (New3SC-2), Las Vegas, Nev., May 31-June 4, 1999; to be published in Int. J. Mod. Phys. B. Contact Janice Coble, Materials Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439; telephone (630) 252-5497; telefax (630) 252-9595; e-mail coble@anl.gov; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9906205.
T. K. Park, B. J. Mean, K. H. Lee, S. W. Seo, K. S. Han, D. H. Kim, Moohee Lee, H. S. Lee, H. B. Kim, W. C. Lee, and Joung-Sook Cho, "Suppression of Antiferromagnetic Spin Fluctuation in Zn-Substituted YBa2Cu3O7." To be published in Physica C (in press). Contact Moohee Lee, Department of Physics, Konkuk University, 93-1 Mo-Jin-Dong, Kwang- Jin-Ku, Seoul 143-701, KOREA; telephone +82 2 450 4084; telefax +82 2 3436 5361; e-mail mhlee@kkucc.konkuk.ac.kr. Key words: substitution effects, NQR, spin-lattice relaxation time T_1. 74.72.Bk; 74.25.Ha; 74.62.Dh; 76.60.Gv.
Evgeny V. Pechen, "Pulsed-Laser Beam Profiling for Deposition of High-Tc YBCO Films." Submitted to Physica B. P. N. Lebedev Physical Institute, Russian Academy of Sciences, Leninsky Prospect 53, 117924 Moscow, RUSSIA; e-mail pechen@sci.lpi.msk.su or pechen@sci.lebedev.ru; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9906040. Key words: films, laser deposition, high-Tc superconductor.
V. Prokic and L. Dobrosavljevic-Grujic, "Zero-Energy Bound States in Superconductor/Ferromagnet Superlattices." To be published in Physica C (in press). Faculty of Physics, University of Belgrade, Studentski trg 12-16, P.O. Box 368, 11000 Belgrade, YUGOSLAVIA; telephone +381 11 630 152; telefax +381 11 3282 619; e-mail prokic@phy.bg.ac.yu. Key words: zero-energy bound states, superconductor/ferromagnet superlattices, Josephson supercurrent. 74.50.+r; 74.80.Dm.
J. P. Rodriguez, "Nature of Decoupling in the Mixed Phase of Extremely Type-II Layered Superconductors." Department of Physics and Astronomy, California State University, Los Angeles, CA 90032; telephone (323) 343- 2133; telefax (323) 343-2497; e-mail jrodrig@calstatela.edu; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9906199. 74.60.-w; 74.25.Dw; 74.25.Ha; 74.60.Ge.
J. P. Rodriguez, "Superconductivity Versus Tunneling in a Doped Antiferromagnetic Ladder." To be published in Phys. Rev. B. Department of Physics and Astronomy, California State University, Los Angeles, CA 90032; telephone (323) 343-2133; telefax (323) 343-2497; e-mail jrodrig@calstatela.edu; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9903251. 74.20.Mn; 75.10.Jm; 74.72.Jt; 74.25.Fy.
P. Shang, G. Yang, I. P. Jones, C. E. Gough, J. S. Abell, K. Nadarzinski, and M. Kawazaki, "Locating Dysprosium Dopant Atoms in the Bi2Sr2CaCu2Oy Unit Cell: Direct Space Chemical Crystallography." To be published in Phil. Mag. Lett. School of Metallurgy and Materials, University of Birmingham, Edgbaston, Birmingham B15 2TT, UNITED KINGDOM; G. Yang's telephone +44 121 414-5220 or -5221; telefax +44 121 414-5232; e-mail yanggz@novell2.bham.ac.uk.
D. V. Shantsev, Y. M. Galperin, and T. H. Johansen, "Thin Superconducting Disk with B-Dependent Jc: Flux and Current Distributions." Submitted to Phys. Rev. B. Department of Physics, University of Oslo, P.O. Box 1048, Blindern, N-0316 Oslo, NORWAY; e-mail daniel.shantsev@fys.uio.no; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9906297. 74.25.Ha; 74.76.Bz; 74.80.Bj.
A. Shengelaya, K. A. Mueller, S. Reich, and Y. Tsabba, "Electron Spin Resonance and Magnetic Susceptibility Suggest Superconductivity of WO3 Doped with Sodium." To be published in Eur. Phys. J. B. Physik- Institut der Universitaet Zurich, CH-8057 Zurich, SWITZERLAND. 71.38.+i; 74.72.-h; 76.30.-v.
T. Shibauchi, T. Nakano, M. Sato, T. Kisu, N. Kameda, N. Okuda, S. Ooi, and T. Tamegai, "Interlayer Phase Coherence in the Vortex Matter Phases of Bi2Sr2CaCu2O8+y." To be published in Phys. Rev. Lett. Department of Applied Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113- 8656, JAPAN. 74.25.Dw; 74.25.Nf; 74.60.-w; 74.72.Hs.
A. W. Smith, H. M. Jaeger, T. F. Rosenbaum, A. M. Petrean, W. K. Kwok, and G. W. Crabtree, "Vortex Flow and Transverse Flux Screening at the Bose Glass Transition." James Franck Institute and Department of Physics, University of Chicago, Chicago, IL 60637.
Hongli Suo, Jean-Yves Genoud, Gilles Triscone, Eric Walker, Michael Schindl, Reynald Passerini, Francois Cleton, Meiling Zhou, and Rene Flukiger, "Preparation and Characterization of {100}<001> Cube Textured Ag Substrates for In-Plane Oriented HTS Tapes." To be published in Supercond. Sci. & Technol. Departement de Physique de la Matiere Condensee, Universite de Geneve, 24 quai Ernest-Ansermet, CH-1211 Geneva 4, SWITZERLAND; telefax +41 22 702 68 69; e-mail suo.hongli@physics.unige.ch. Key words: texture, epitaxy, silver, thick films, superconducting tapes.
A. Suter, M. Mali, J. Roos, and D. Brinkmann, "Charge Degree of Freedom and Single-Spin Fluid Model in YBa2Cu4O8." MST-10, Condensed Matter and Thermal Physics, MS K764, Los Alamos National Laboratory, Los Alamos, NM 87545; telephone (505) 665-0759; telefax (505) 665-7652; e-mail suter@lanl.gov; preprint also available at http://xxx.lanl.gov/abs/cond- mat/9907043. 71.45.-d; 74.25.Nf; 74.72.Bk; 76.60.-k.
A. Suter, M. Mali, J. Roos, and D. Brinkmann, "Separation of Quadrupolar and Magnetic Contributions to Spin-Lattice Relaxation in the Case of a Single Isotope." Submitted to J. Magn. Res. MST-10, Condensed Matter and Thermal Physics, MS K764, Los Alamos National Laboratory, Los Alamos, NM 87545; telephone (505) 665-0759; telefax (505) 665-7652; e- mail suter@lanl.gov; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9906229. Key words: NMR, NQR, double- irradiation method, spin-lattice relaxation, quadrupolar relaxation.
T. Tatsuki, S. Adachi, T. Tamura, and K. Tanabe, "Thermoelectric Power and Irreversibility Field of (Hg,Tl)2Ba2Can-1CunOy (n=2-5) Superconductors." To be published in Physica C (in press). Contact S. Adachi, Superconductivity Research Laboratory, International Superconductivity Technology Center (ISTEC), 10-13 Shinonome 1-chome, Koto-ku, Tokyo 135-0062, JAPAN; e-mail adachi@istec.or.jp. Key words: Hg-Tl-Ba-Ca-Cu-O, thermoelectric power, irreversibility field, homologous superconducting series. 74.72.Gr; 74.72.Fq; 74.25.Fy; 74.25.Ha.
Z. Tomkowicz, "Trapping Mechanism of Superconductivity Suppression Induced by Pr Substitution in the Ho1-xPrxBa2Cu3O7-d System." To be published in Physica C (in press). Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Krakow, POLAND; telephone +48 12 632 4888 5554; telefax +48 12 633 7086; e-mail uftomkow@if.uj.edu.pl. Key words: superconductivity suppression, Pr substitution, electrical resistivity, metal-insulator transition. 74.62.Dh; 74.72.Bk; 74.25.Fy.
J.-C. Villegier, B. Delaet, V. Larrey, M. Salez, Y. Delorme, and J.-M. Murtier, "Fabrication of NbN/AlN/NbN Junctions with Al Embedding Circuits on Si Membrane for 1.5 THz SIS Mixers." To be published in Appl. Supercond. (in press). Departement de Recherche Fondamentale sur la Matiere Condensee, Service de Physique Statistique, Magnetisme et Supraconductivite, CEA-Grenoble, 17 rue des Martyrs, F-38054 Grenoble Cedex 9, FRANCE.
Matthias Vojta and Subir Sachdev, "Charge Order, Superconductivity, and a Global Phase Diagram of Doped Antiferromagnets." Department of Physics, Yale University, P.O. Box 208120, New Haven, CT 06520-8120; e- mail matthias.vojta@yale.edu; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9906104.
T. A. Wagner, A. Dertinger, W. Ettig, A. Krause, H. Schmidt, and H. F. Braun, "The Effect of Thermal Treatment on Superconductivity in HoNi2B2C." To be published in Physica C. Contact A. Dertinger, Physikalisches Institut, Experimentalphysik V, Universitaet Bayreuth, D- 95440 Bayreuth, GERMANY; telephone +49 921 55 3259; telefax +49 921 55 3647; e-mail armin.dertinger@uni-bayreuth.de. Key words: superconductivity, re-entrant behaviour, borocarbides, thermal treatment, long-range crystallographic order (LRO). 74.72.Ny; 74.62.-c; 74.62.Bf.
Anchuan Wang, John A. Belot, Tobin J. Marks, Paul R. Markworth, Robert P.H. Chang, Michael P. Chudzik, and Carl R. Kannewurf, "Buffers for High Temperature Superconductor Coatings: Low Temperature Growth of CeO2 Films by Metal-Organic Chemical Vapor Deposition and Their Implementation as Buffers." To be published in Physica C (in press). Contact Tobin J. Marks, Department of Chemistry and the Science and Technology Center for Superconductivity, Northwestern University, Evanston, IL 60208; telephone (847) 491-5658; telefax (847) 491-2990; e- mail tjmarks@casbah.acns.nwu.edu. Key words: CeO2 films, metal-organic chemical vapor deposition, buffer.
Z. H. Wang and H. Zhang, "Effective Activation Energy U_e(T,J,H) in Textured Bi1.84Pb0.4Sr2Ca2Cu3Oy Silver-Clamped Thick Films." To be published in Physica C (in press). Shanghai Institute of Metallurgy, Chinese Academy of Sciences, 865 Changning Road, Shanghai 200050, PEOPLE'S REPUBLIC OF CHINA; telephone +86 21 6251 1070, ext. 8924; telefax +86 21 6251 3510; e-mail zhwang@itsvr.sim.ac.cn. Key words: activation energy, temperature, current density, applied magnetic field. 74.60.Ge; 74.72.Bk; 74.76.-w.
Roy Weinstein, Alberto Gandini, Yanru Ren, Ravi Sawh, Drew Parks, Yuanchang Guo, Bernhard Zeimetz, Shi X. Dou, Susanne Toenies, Christof Klein, and Harald W. Weber, "Increase in Jc and Irreversibility Field, Decrease in Anisotropy and Lowered Radioactivity in BiSCCO 2223 Irradiated by U Fission Fragments." Presented at the 9th Int. Workshop on Critical Currents (IWCC9-99), Madison, Wis., July 7-10, 1999. Department of Physics and Texas Center for Superconductivity, University of Houston, Houston, TX 77204-5506; telephone (713) 743-8200; telefax (713) 743-8201; e-mail preprints@www.tcs.uh.edu.
G. Wendin, "Modeling of HTS Josephson Junctions." To be published in Appl. Supercond. (in press). Department of Microelectronics and Nanoscience, Chalmers University of Technology and Goeteborg University, S-41296 Goeteborg, SWEDEN.
Robert A. Wickham and Alan T. Dorsey, "Critical Scaling of the ac Conductivity for a Superconductor Above Tc." Submitted to Phys. Rev. B. Department of Physics, University of Florida, P.O. Box 118440, Gainesville, FL 32611-8440; telephone (352) 392-8755; telefax (352) 392- 0524; e-mail wickham@phys.ufl.edu; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9906124. 74.25.Fy; 74.40.+k; 64.60.Ht.
X. S. Wu, F. Z. Wang, J. S. Liu, S. S. Jiang, and J. Gao, "Effects on Structure and Superconductivity for La and Ca Codoping in YBa2Cu3Oy Cuprates." To be published in Physica C (in press). National Laboratory of Solid State Microstructures, Department of Physics, Institute of Solid State Physics and Center for Advanced Studies in Science and Technology of Microstructures, Nanjing University, Nanjing 210093, PEOPLE'S REPUBLIC OF CHINA; telefax +86 25 3300 535; e-mail xswu@netra.nju.edu.cn. Key words: Y0.8Ca0.2Ba2Cu3Oy with La doping, zero resistance temperature, structural effects.
Victor M. Yakovenko, Hsi-Sheng Goan, Jonghwa Eom, and Woowon Kang, "Temperature Evolution of the Quantum Hall Effect in the FISDW State: Theory vs Experiment." Submitted to the Proc. of the Int. Workshop on Electronic Crystals (ECRYS-99). Department of Physics, University of Maryland, College Park, MD 20742-4111; e-mail yakovenk@physics.umd.edu; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9906276.
H. Yamaguchi, K. Oka, and T. Ito, "Anisotropic Magnetic Susceptibility of Single Crystal Ca2Y2Cu5O10 with Edge-Sharing CuO2 Chain." To be published in Physica C (in press). Electrotechnical Laboratory, 1-1-4 Umezono, Tsukuba, Ibaraki 305-8568, JAPAN; telephone +81 298 54 5398; telefax +81 298 54 5085; e-mail hirotaka@etl.go.jp. Key words: Ca2Y2Cu5O10, edge-sharing linear chain, crystal growth, single crystal, antiferromagnetism. 74.72.Jt; 75.50.Ee; 81.10.Fq.
K. Yoshida, H. Sasakura, S. Tsukui, and Y. Mizokawa, "Superconductivity in Bi-2212 Thin Films of Bi2LaxCa3-xCu2Oz Prepared by Laser Ablation Method." To be published in Physica C (in press). Department of Physics, Hamamatsu University School of Medicine, Handa-cho, Hamamatsu, Shizuoka 431-3192, JAPAN; telephone +81 53 435 2345; telefax +81 53 435 2315; e-mail kyoshida@hama-med.ac.jp. Key words: superconductivity, Bi-2212, Bi2LaxCa3-xCu2Oz, thin film, laser ablation. 74.72.Hs; 74.76.- w.
Y. Yuzhelevski, G. Jung, C. Camerlingo, M. Russo, M. Ghinovker, and B. Ya. Shapiro, "Current Driven Vortex Dynamics in a Periodic Potential." To be published in Phys. Rev. B. Department of Physics, Ben-Gurion University of the Negev, P.O. Box 653, 84105 Beer-Sheva, ISRAEL; G. Jung's telephone +972 7 646 1166; telefax +972 7 647 2903; e-mail jung@bgumail.bgu.ac.il.
Xiaoru Zhao, Wenbin Wu, Xuefeng Sun, and Xiao-Guang Li, "New Experimental Evidence of the Structural Modification in Single Crystal Bi2Sr2CaCu2Oy by x-Ray Diffraction Observation." To be published in Physica C (in press). Kitazawa Laboratory, Department of Superconductivity, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-8656, JAPAN. Key words: x-ray diffraction, ac susceptibility, full width at half maximum, Bi-O.
Fei Zhou, "A Novel Superconducting Glass State in Disordered Thin Films in Clogston Limit." To be published in Int. J. Mod. Phys. B. Department of Physics, Princeton University, Princeton, NJ 08544; e-mail zhou@research.nj.nec.com; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9906257. 05.20.-y; 82.20.-w.
COMING EVENTS (An * indicates a previously listed event. Also see complete listing of upcoming conferences and workshops at our Web site http://www.iitap.iastate.edu/htcu/comevents.html.)
Oct. 11 - 22, 1999: Fourth Training Course in the Physics of Correlated Electron Systems and High-Tc Superconductors, Vietri sul Mare, Salerno, Italy. Aimed at postdoc-level researchers, the school will offer the opportunity to meet various experts from different physics contexts, all relevant to the investigation of strongly correlated electron systems. The proposed project of practical training courses intends to promote theoretical research in the field by putting together senior researchers with outstanding experience and skill and young researchers. Courses will be offered to 25 young (under 35) European researchers. The registration fee is $250. A limited number of grants for European researchers, covering part of the costs, will be available. Topics are theory of the spin-polaron for 2D antiferromagnets, magnetic and orbital ordering in cuprates and manganites, and Bose-Einstein condensation in traps. Application forms and grant request forms are available from Prof. F. Mancini, Dipartimento di Scienze Fisiche "E. R. Caianiello," Universita di Salerno, Via S. Allende, I-84081 Baronissi (SA), Italy; telephone +39 089 965 322; telefax +39 089 965 275; e-mail mancini@physics.unisa.it.
High-Tc Update is the high-Tc superconductivity information exchange newsletter. Please send 1) preprints, reprints, and other research reports; 2) descriptions of on-going work; 3) meeting announcements and summaries.
The information contained herein is intended for limited distribution. Readers are expected to respect the rights of the authors.
Please address all contributions and inquiries to:
Dr. Sreeparna Mitra, A219 Physics Ames Laboratory/Iowa State University Ames, Iowa 50011-3020 Telephone: (515) 294-3877 Telefax: (515) 294-1134 E-mail: MITRA@AMESLAB.GOV or MITRA@IASTATE.EDU
Project Director/Editor: Sreeparna Mitra Science Editor: John R. Clem High-Tc Update, Vol. 13, #15, August 1, 1999.