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NOTA BENE:
Vortices
Two preprints by Y. Fasano (Bariloche) et al. report on a new type of vortex pinning, which the authors call Bitter pinning. The authors decorated the vortex lattice in NbSe2 with ferromagnetic particles, which form clumps on the sample surface where the vortices exit. The authors present data showing that the resulting array of magnetic dots act as pinning sites for vortices in subsequent experiments. The authors note that this method allows one to produce periodic, quasiperiodic, or disordered pinning structures for static and dynamic vortex experiments.
Using an ac susceptibility technique and an ultrapure YBa2Cu3O6.993 crystal, made possible by the recent breakthrough in crystal growth of high-Tc oxide superconductors using BaZrO3 crucibles, J. Shi (Brown) et al. have observed a giant peak in the critical current density Jc(T). At H = 2.0 T (H||c), the authors found that Jc(T) exhibited a 35-fold increase with a temperature rise of 0.5 K. The authors find that the peak coincides with the vortex-lattice melting transition.
A preprint by Z. L. Xiao (Rutgers) et al. reports on flow-induced organization and memory of a vortex lattice in an Fe-doped single crystal of 2H-NbSe2. As is typical of weak-pinning superconductors, the samples exhibited a strong peak effect in the critical current density Jc. By using fast transport measurements to follow the vortex organization, the authors also found that the current enables the vortex system to explore its energy landscape and to access new configurations, ending up, after a characteristic response time, in a state whose pinning depends on the driving current. The authors present a dynamic phase diagram that contains a regime where the critical current can be increased or decreased by applying an appropriate driving current.
Vortex pinning in textured Ag-clad Bi2Sr2CaCu2O8+d (Bi-2212) superconducting tapes containing randomly oriented columnar defects produced by Bi fission after irradiation with 0.8 GeV protons has been studied by J. R. Thompson (Oak Ridge and Tennessee) et al. The authors found that the thermally activated decay of the current density J was much less than in unirradiated tapes. The authors conclude, however, that temperature-independent quantum tunneling of vortices considerably limits J and its temporal stability over a significant fraction of the finite-Tc region.
The influence of thermally created vortices on the low-field vortex phase diagram of slightly underdoped Bi2Sr2CaCu2O8+d (Bi-2212) single crystals has been investigated by L. Miu (NIMR, Bucharest-Magurele) et al. using resistive and dc magnetic measurements. The authors found that the resistive tail observed in these samples could be used to determine the layer decoupling temperature.
The nature of quasiparticles in the vortex lattice of unconventional superconductors in low and intermediate fields has been explored theoretically by M. Franz and Z. Tesanovic (Johns Hopkins). For a periodic vortex lattice, the authors find that the natural quasiparticle states are Bloch waves and not Landau levels.
The effective mass of a single quantized vortex in a BCS superconductor at finite temperature has been calculated by J. H. Han (APCTP-Seoul) et al. The authors argue that the mass and viscous drag are closely related because they arise from the same mechanism: interaction with the surrounding fermionic degrees of freedom.
A preprint by M. Ozaki (Kochi) et al. presents a theoretical study of local symmetric order parameters (s-wave, p-wave, and d-wave) of the vortex-lattice states in singlet superconductors with s-wave, p-wave, and d-wave symmetry.
A Giaever dc-dc transformer, which involves flux-flow vortex motion in two superimposed thin films separated by a thin insulating layer, has been fabricated by S. Berger et al. (Thomson-CSF) using a ramp-based multilayer technology and an YBa2Cu3O7-d-based SIS structure grown by pulsed laser deposition. Transport measurements exhibiting coupling and decoupling of the vortex arrays in the two superconducting films were carried out.
The superconducting behavior of a 100 nm TiN thin film (Tc = 4.6 K) in a perpendicular magnetic field has been studied by F. Lefloch et al. (Grenoble). The authors observed an electronic instability at high vortex velocities, and from its dependence upon the applied magnetic field, the authors extracted the inelastic scattering time and the diffusion length of the quasiparticles.
Vortices in Layer-Parallel Fields
The hysteresis in the magnetization M of a melt-textured YBa2Cu3O7-d (Y- 123) superconducting plate in the critical state has been studied experimentally and theoretically by L. M. Fisher (Moscow) et al. The hysteresis was found to be suppressed by a sweeping magnetic field h(t) applied perpendicular to a dc magnetic field H, both fields being parallel to the plate. For every quarter period of the sweeping field with amplitude h_0, a noticeable decrease in the magnitude of M was observed for both paramagnetic and diamagnetic initial states, even for h_0 << H. Both the double critical state model and a two-velocity hydrodynamic model were used to analyze the experiments, but the latter was found to give better agreement.
As reported by K. Deligiannis (Southampton) et al., an oscillating magnetization appears in high-purity YBa2Cu3O7-d (Y-123) single crystals when the applied field is applied parallel to the layers. The authors show that these oscillations are the fingerprints of interlayer Josephson vortices and that they directly yield the anisotropy factors gamma_[cb] = (m_c/m_b)^[1/2] and gamma_[ca] = (m_c/m_a)^[1/2] when the applied field is parallel to the a or b axis, respectively. The temperature dependence of this lock-in magnetization, however, is not in agreement with theory.
Oscillations of the magnetization induced by commensurability between vortex-plane and CuO2-plane distances in YBa2Cu3O7-d (Y-123) single crystals have been studied by A. A. Zhukov (Imperial, Karlsruhe, and Moscow State) et al. The authors found a sharp peak in the temperature dependence of the amplitude of oscillations at T_f ~ 60 K, which they suggest reflects the vortex freezing transition from a smectic to a solid phase. The authors also construct the phase diagram as a function of the angle of the field relative to the CuO2 layers.
The mixed-state c-axis resistivity of YBa2Cu4O8 (Y-124) has been measured by N. E. Hussey (Tokyo and CREST) et al. with the magnetic field applied parallel to the a, b, and c axes. For all orientations of the magnetic field, a kink is observed in the resistive transition, associated with the first-order melting of an anisotropic three- dimensional vortex lattice. While the melting lines for H||b and H||c obey the relation H_m = H_0(1-T/Tc)^n with n = 1.5, H_m(T) for H||a follows a different T dependence with a lower exponent. The authors attribute this to a reduction in the dimensionality of Y-124 in this field geometry, as observed in normal-state magnetoresistance measurements.
RBa2Cu3O7-d
Local magnetic measurements vs temperature by D. Giller (Bar-Ilan) et al. in an untwinned YBa2Cu3O7-d crystal reveal a number of features along the same line B_k(T) in the field-temperature plane well below the melting line: (a) an abrupt increase in the local magnetization vs temperature, (b) a pronounced kink in curves of the magnetization vs field, (c) a marked change in the behavior of the magnetic relaxation rate with field, and (d) a time-independent B_k unlike the peak field, which drifts with time to lower fields. The authors fit B_k(T) to a model describing a disorder-induced vortex solid-to-solid phase transition that explains similar behavior in YBa2Cu3O7-d (YBCO), Nd1.85Ce0.15CuO4-d (NCCO), and Bi2Sr2CaCu2O8+d (Bi-2212), and they infer that the microscopic origin of pinning in YBCO is fluctuations in the charge-carrier mean free path near lattice defects.
As reported by Z. A. Zhu et al. (Princeton), in underdoped YBa2Cu3O7-d (YBCO) with x = 6.63, the opening of the pseudogap at T_s ~~ 160 K has a strong effect on the Hall angle tan-theta. While the Hall response is significantly reduced, the diagonal current is relatively unaffected. The authors present evidence that the Hall suppression continues below Tc down to 40 K. In the flux-flow state, the Hall conductivity is also qualitatively different from that in optimally doped YBCO.
Superconducting transitions in field-cooled-cooling (FCC) and field- cooled-warming (FCW) modes in external magnetic fields ranging between 1 mT and 7 T in various Nd-based 123 superconductors (NdBa2Cu3O7-d single crystals and melt-processed samples, and melt-textured ternary compounds) have been measured by M. R. Koblischka (SRL-ISTEC) et al. Most of the Nd-based superconductors exhibited a two-step transition when cooled or warmed in fields larger than 4 T. The authors ascribe this effect to the presence of a Nd-rich phase producing spatial variation of the transition temperature Tc throughout the sample. A single crystal with an extremely high Tc of 95.7 K, indicating that the Nd/Ba solid solution is nearly completely suppressed, does not show the second step.
The superconducting and magnetic properties of oxygen-controlled-melt- grown (OCMG) (Nd,Eu,Gd)Ba2Cu3O7-d (NEG-123) superconductors containing Pr in the concentration range x = 0 to 0.15 are reported by M. Muralidhar et al. (SRL-ISTEC). The Pr doping suppresses the superconducting transition temperature Tc somewhat, but reduces the critical current density Jc at the fishtail peak by about five orders of magnitude. The authors attribute these effects to partial substitution of Pr on the rare-earth site and hole localization due to trivalent ions on the Ba site.
Two preprints by V.P.S. Awana (UNICAMP) et al. report results on structure, superconducting Tc, and antiferromagnetic ordering temperature T_N in various Pr-substituted cuprates, including Y1- xPrxBaSrCu3O7, La1-xPrxBaCaCu3O7, and Nd1-xPrxBaCaCu3O7. The authors find that the suppression of superconductivity due to Pr in all these systems is less than that in the R-123 counterparts, Y1-xPrxBa2Cu3O7, La1-xPrxBa2Cu3O7, and Nd1-xPrxBa2Cu3O7. The authors also report a correlation between the Tc suppression due to Pr and the value of T_N of the fully substituted Pr moments in these systems; a less deleterious effect on superconductivity is associated with a lower T_N.
Bi Cuprates
The c-axis transport of Bi2Sr2CaCu2O8+d (Bi-2212) stacked intrinsic junctions fabricated from single crystal whiskers by a double-sided ion- beam-processing technique has been studied by Yu. I. Latyshev (Tohoku) et al. The authors measured the I-V characteristics and obtained the superconducting gap, the Josephson critical current, and the temperature and voltage dependence of the quasiparticle c-axis conductivity. The authors show that the BCS clean-limit d-wave model for resonant intralayer impurity scattering with a significant contribution from coherent interlayer tunneling satisfactorily describes the low- temperature and low-energy c-axis transport of both quasiparticles and Cooper pairs.
The far-infrared sphere resonance in Bi2Sr2CaCu2O8+d (Bi-2212) samples with various oxygen concentrations has been measured in zero applied magnetic field by H. Shibata and A. Matsuda (NTT) down to 5 cm^[-1]. Although no peaks were observed in this frequency range for the optimally doped sample, the Josephson plasma peak was observed at 5 cm^[-1] for a 1 atm O2-annealed sample. The peak was found to shift to higher frequencies as the doping increased, and was observed at 11 cm^[- 1] for a 150 atm O2-annealed sample. The c-axis penetration depth lambda_c obtained from the peak frequencies was determined to be 77 to 35 micrometers. The doping dependence is qualitatively explained by the Josephson-coupled-layer model.
The magnetic-field dependence of the magneto-thermopower DeltaS(T,H) in textured Bi2Sr2CaCu2O8+d (Bi-2212) is theoretically explained by S. Sergeenkov and M. Ausloos (Liege) by introducing a field-dependent chemical potential of holes mu(H) into the Ginzburg-Landau theory.
Two related papers, one by J. Jiang (Birmingham) et al. and the other by D. C. Larbalestier (Wisconsin) et al., report experiments elucidating the current-limiting mechanisms in Ag-sheathed Bi2Sr2Ca2Cu3O10+d [(Bi,Pb)-2223] tapes. The authors find that cracks, actual or incipient, exist on the submicron to several hundred micron scale, and that even composites with the highest values of Jc exhibit strong signs of unhealed rolling damage. The authors of both papers assert that today's best 2223 tapes are still far from being fully optimized, and they suggest that the performance could be further improved by controlling the liquid phase to better heal the cracks.
Experiments by K.-H. Mueller et al. (CSIRO) et al. show that the remanent magnetic moments of YBCO thin-film networks and of Bi-2223/Ag monofilamentary tapes show remarkable similarities, as their magnetic moments are composed of intersquare (intergrain) and intrasquare (intragrain) magnetic moments. Starting from the geometrical definition of connectivity in a thin-film network, the authors show that connectivity in a Bi-2223/Ag monofilamentary tape is defined solely by the ratio of the average grain size to the width of the superconducting core and by the ratio of the intergrain to intragrain remanent magnetic moments at saturation. The measured upper limit for the connectivities ranged from 4.2 x 10^[-3] in a tape with low critical current density Jc to 2.9 x 10^[-2] in a tape with Jc(77K,0T) ~~ 2 x 10^4 A/cm^2. The authors conclude that even good Bi-2223/Ag tapes suffer from very low grain connectivity, and they estimate that in the case of perfect connectivity a Jc(77K,0T) between 8 x 10^5 A/cm^2 and 6 x 10^6 A/cm^2 would be achievable.
A method for incorporating nanosize MgO particles into the Bi-2223 grains of Ag/Bi-2223 multilayer composite tapes has been developed by H. Wu et al. (TCSUH). The authors found, however, that the MgO particles do not have a significant effect on the field performance of the critical current density at 77 K.
Other Cuprates
A preprint by A. W. Hunt et al. (MIT) demonstrates that one can measure the charge-stripe order parameter in the hole-doped planes of La1.875Ba0.125CuO4, La1.48Nd0.4Sr0.12CuO4, and La1.68Eu0.2Sr0.12CuO4 utilizing the wipeout effects of [63]^Cu NQR. Application of the same approach to La2-xSrxCuO4 reveals the presence of similar stripe order for the entire underdoped superconducting regime 1/16 <= x <= 1/8.
A [63]^Cu and [139]^La NMR/NQR study of a superconducting (Tc = 7 K) La1.94Sr0.06CuO4 single crystal is reported by M.-H. Julien (Pavia and Iowa State/Ames Lab) et al. [139]^La NMR relaxation revealed the coexistence of spin-glass and superconducting phases below ~5 K. [63]^Cu and [139]^La NMR spectra show that, upon cooling, CuO2 planes progressively separate into two magnetic phases, one of them having enhanced antiferromagnetic correlations. The results establish the antiferromagnetic-cluster nature of the spin glass. The authors also discuss how this phase can be related to the microsegregation of mobile holes and to the possible pinning of charge stripes.
The effect of zinc doping on the anomalous temperature dependence of the magnetoresistance and the Hall effect in the normal state has been studied by A. Malinowski (Rutgers and Warsaw) et al. in a series of La2- xSrxCu1-yZnyO4 films with values of y between zero and 0.12. The orbital magnetoresistance at high temperatures was found to be proportional to the square of the tangent of the Hall angle, as predicted by the model of two relaxation rates, for all Zn-doped specimens, including nonsuperconducting films.
Data on the suppression of Tc in Bi-2212 and Tl-2212 by substitution of Co impurities at Cu sites are analyzed in a preprint by B. Chattopadhyay et al. (SINR-Calcutta). Using the Abrikosov-Gor'kov formalism and a tight-binding model accounting for suppression of the Fermi-level density of states, the authors extract the pseudogap.
Two preprints by L. Zhang (Cal State-Stanislaus) et al. report measurements of the magnetic properties in single crystals of the four- CuO2-layer compound TlBa2Ca3Cu4O11+d (Tl-1234, Tc = 128 K). In one of the papers, the authors obtained a Ginzburg-Landau parameter kappa = 109 and an extrapolated H_[c2](0) = 160 T for magnetic fields along the c axis. In the other, the authors report measurements of the flux-creep rate dlnM/dlnt as a function of temperature and magnetic field, which yielded a temperature-independent energy barrier in the range 2-30 K.
Microwave (2-18 GHz) measurements of the complex susceptibility chi(omega,T) = chi' + ichi" of Sr14-xCaxCu24O41 are reported by Z. Zhai (Northeastern) et al. The authors observed a frequency- and temperature-dependent loss peak, which they associate with a rapid decrease of spin disorder and corresponding spin relaxation rate with decreasing temperature, representing a spin-freezing transition accompanying charge ordering, which occurs at temperatures ~250 K for the x = 0 compound.
Films
The competition between a-axis and c-axis growth in RBa2Cu3O7-d (R = rare earth or Y) superconducting thin films has been analyzed by F. Miletto (Napoli) et al. The relative a/c-axis content was estimated by x-ray diffraction and plotted as a function of deposition temperature. The authors found that the a/c-axis content, plotted vs a normalized deposition temperature, has a universal behavior, valid for all RBa2Cu3O7-d oxides. The authors present a theoretical model that agrees with the observations.
YBa2Cu3O7-d films grown on both SrTiO3 single crystals and rolling- assisted biaxially textured Ni substrates (RABiTS) carry high critical current densities. As pointed out by H. R. Kerchner (Oak Ridge) et al., a geometrical barrier to vortex motion at the edge of the film increases the apparent Jc but also raises the ac transport-current power losses at high ac current amplitudes above the losses expected for bulk pinning only. The authors present evidence that the ferromagnetic Ni substrate makes no significant contribution to the tape self-field loss.
A preprint by C.-J. Kim (SRL-KAERI) et al. reports on the control of YBCO growth at the compact/substrate interface by bottom seeding and Yb2O3 coating in seeded melt-growth-processed YBCO oxides using an MgO substrate.
The magnetic-field and angular dependencies of the critical current density and resistive broadening of a textured Bi1.84Pb0.4Sr2Ca2Cu3O10+d thick film in applied magnetic fields up to 0.3 T are reported by Z. H. Wang (Shanghai). The author reports angular scaling laws for Jc(H) and the characteristic temperature at which the magnetoresistance R(H) drops to a fraction (e.g., 1%) of the normal-state resistance R_n.
The effects of the oxygen-annealing temperature upon the superconductivity of epitaxial HgBa2Ca2Cu3O8+d (Hg-1223) thin films fabricated by pulsed laser deposition are reported by W. H. Kang (POSTECH) et al. The highest transition temperature of 133 K for the films grown on (100) SrTiO3 were obtained after oxygen annealing at 340^oC for 12 hours. The observed critical current density of 2.6 x 10^5 A/cm^2 at 120 K in zero field is high enough for applications in SQUIDs operated at 120 K.
A phenomenological model proposed by A. V. Velichko (Birmingham and IRE- NAS, Ukraine) accounts for the effects of both dc and rf magnetic fields on the surface impedance Z_s = R_s + jX_s of a superconducting weak link. Under certain conditions, the predicted values of Z_s(H) fall below the zero-field values.
Nonlinear microwave (8 GHz) surface-impedance measurements on three YBCO thin films in dc magnetic fields H_[dc](parallel to the c axis) up to 2 mT have been carried out by A. P. Kharel (Birmingham) et al. using a coplanar resonator technique. In zero dc field, the three films, deposited by the same method, show a spread of low-power residual surface resistance R_[res] and penetration depth lambda(T = 15 K) within a factor of 1.9. However, while X_s vs microwave field H_[rf]is nearly the same for all three films, the surface resistance R_s vs H_[rf] is dramatically different for the three films. Application of a dc field was found to affect both the absolute values of R_s and X_s and the functional dependencies R_s(H_[rf]) and X_s(H_[rf]). For some of the samples, the dc field was found to decrease R_s below its zero-field low-power value.
Junctions
According to a preprint by A. M. Zagoskin (UBC), the unique properties of a ballistic D/N/D (d-wave superconductor / normal metal / d-wave superconductor) or a grain-boundary D/D junction, possessing a doubly degenerate ground state with a tunable potential barrier between the up and down states and nonquantized spontaneous magnetic flux, make it a good candidate for a solid-state qubit (SSQ) in a quantum computer. (Other SSQ candidates are quantum dots, mesoscopic Josephson junctions, and superconducting single-electron transistors or parity switches.) The author asserts that the role of the quantum spin variable is played by the sign of the equilibrium superconducting phase difference on the junction, which is revealed in the direction of spontaneous supercurrent flow in equilibrium. The author discusses possibilities of design- specific simultaneous operations with several integrated qubits.
Anisotropic microwave emission properties of ErBa2Cu3O7/insulator/Au (S/I/N) tunnel junctions resulting from direction-oriented quasiparticle injection are reported by K. Lee et al. (Tokyo Tech and CREST). Two types of samples with different S/I/N tunnel junction geometries were prepared, one allowing quasiparticle injection mainly along the c axis and the other only into the ab plane. Microwave emission was observed, and a strongly nonequilibrium state was established, only for quasiparticle injection along the c axis.
Strong suppression of supercurrent through a YBa2Cu3O7-d (YBCO) superconductor upon injection of spin-polarized quasiparticles from a ferromagnetic Co injector is reported by K. Lee (Tokyo Tech and CREST) et al. The authors report that the injection of spin-polarized quasiparticles generates a much larger nonequilibrium population than does an unpolarized injection current. The differential conductance of a YBCO/Au/Co junction exhibited a zero-bias conductance peak when the thickness of the Au interlayer (d_[Au]) was about 15 nm, but when d_[Au] was increased, the conductance peak was converted to a zero-bias resistance peak. The authors suggest that these results may be due to spin-scattering processes at a ferromagnet / d-wave superconductor junction.
Tunneling spectroscopy on near optimally doped single crystals of Tl2Ba2CuO6+d (Tl-2201) is reported by L. Ozyuzer (Argonne and Izmir) et al. S/I/N tunneling conductances, obtained via the point-contact technique with a Au tip, reproducibly show a sharp cusplike subgap, prominent quasiparticle peaks with a consistent asymmetry, and weakly decreasing backgrounds. The authors note that the tunneling density of states of Tl-2201 is reproducibly consistent with d_[x^2-y^2]-wave gap symmetry.
Experimental results on c-axis tunneling in Nb/Au/YBa2Cu3O7-d structures are reported by P. V. Komissinski (IREE-Moscow) et al. The authors observed no Josephson critical current and no YBCO gap feature.
Numerical calculations of the conductance of an interface between a phase-coherent two-dimensional electron gas and a superconductor with a quantum point contact in the normal region are presented by N. A. Mortensen (TU Denmark, Lyngby) et al. The normalized conductance is found to depend strongly on the position of the Fermi level, and to be enhanced by a factor of two when the Fermi level corresponds to a conductance plateau.
Nonequilibrium proximity effects in wide mesoscopic superconducting/normal/superconducting (S/N/S) junctions are studied theoretically in a preprint by N. Argaman (ITP-Santa Barbara). The author examines the behavior at temperatures for which the equilibrium Josephson effect is exponentially small and the second harmonic of the Josephson frequency dominates the supercurrents.
A strong mutual influence between superconductors (S) and ferromagnetic (F) conductors in hybrid F/S (i.e., Ni/Al) nanostructures has been observed by V. T. Petrashov (London and Chernogolovka) et al. The magnitude of the proximity-induced conductance on the F side is more than two orders of magnitude larger than that predicted by theory.
A scattering treatment of transport in S/F/S junctions, i.e., between superconductors with a small ferromagnetic metal region inside the junction, is presented in a preprint by R. Melin and O. Bourgeois (Grenoble). The authors find reasonable agreement between their theory and experiments in Al/Gd/Al junctions.
A preprint by T. K. Kopec (Northeastern and Wroclaw) and J. V. Jose (Northeastern) reports a study of a quantum Hamiltonian that models an array of ultrasmall Josephson junctions with short-range Josephson couplings E_J and charging energies E_C due to the small capacitance of the junctions. In the self-capacitive limit and in the presence of an external uniform background of charges q_x, the authors obtain the zero- temperature superconductor-insulator phase diagram E_J^[crit](E_C,q_x). The authors also obtain a closed-form expression for the conductivity of a square array and derive a universal scaling relation valid about the zero-temperature quantum critical point.
Applications
As noted by K. Barthel (Juelich) et al., dc SQUIDs made from high-Tc superconductors typically exhibit a still unexplained higher white noise and a smaller transfer function than numerical simulations based on the coupled Langevin equations predict. The authors present a systematic study that compares experimental results with both numerical simulations and a recently developed analytical approach based on a Fokker-Planck equation. To cover a wide range of SQUID parameters, two samples of different inductances were measured at variable temperature. While several predictions of the analytical theory could be verified and good qualitative agreement with both theories was found, only one sample showed good quantitative agreement. The simulations performed in the limit of large thermal fluctuations showed excellent agreement with the analytic theory.
A closely related paper by B. Chesca (Juelich) presents an analytical analysis of dc SQUIDs with small inductances operating in the presence of thermal fluctuations. The author uses the Fokker-Planck equation to derive expressions for the output voltage across the Josephson junctions and the circulating current in the SQUID loop. The author notes that it then is straightforward to obtain and optimize all the important SQUID characteristics (current-voltage curves, dynamic resistance, transfer function, and energy sensitivity).
Theory
A preprint by E. Demler (UC-Santa Barbara) and S.-C. Zhang (Stanford) reviews their explanation for resonant neutron-scattering experiments in YBa2Cu3O7-d and Bi2Sr2CaCu2O8+d from the point of view of a triplet excitation in the particle-particle channel, the pi excitation. The authors discuss the relation of such resonances to the superconducting condensation energy and their role in stabilizing the superconducting state. The authors note that because of superconducting fluctuations, the pi resonance may appear as a broad peak above Tc.
An SU(4) model of high-Tc superconductivity is presented in a preprint by M. Guidry (Tennessee) et al. One dynamical symmetry of this model corresponds to the SO(5) unification of superconductivity and antiferromagnetism [S.-C. Zhang, Science 275, 1089 (1997)], but there are two additional dynamical symmetries: SO(4), associated with antiferromagnetic order, and SU(2), associated with a d-wave pairing condensate. These provide a three-phase microscopic model of high-Tc superconductivity and permit an understanding of the role played by the SO(5) symmetry.
A theoretical example of a quantum spin liquid with a superconducting phase in a 2D electron system close to an electronic topological transition is presented by F. Onufrieva and P. Pfeuty (Saclay). The authors apply the theory to the high-Tc cuprates to shed light on the 40 meV resonance peak, incommensurability at lower omega, and the spin gap.
A model study for the coexistence of spin-density waves and superconductivity is presented by H. Ghosh (Arizona) et al. The authors assume the presence of nested energy bands. The single-band Hubbard model, when treated within the Hartree-Fock mean-field theory, leads to a spin-density-wave (SDW) ground state. The authors find that the phase diagram, describing the amplitudes of the superconducting and spin- density-wave gaps vs band filling, resembles that of the high-Tc cuprates only when the superconducting order parameter has d-wave symmetry.
Pseudogap phenomena of high-Tc cuprates have been examined by S. Onoda and M. Imada (ISSP-Tokyo). Using self-consistent renormalization, the authors calculate the NMR relaxation rate T_1^[-1], the spin correlation length xi_[sigma], and the pairing correlation length xi_d. From this calculation, a mechanism of pseudogap formation emerges as the region where d-wave short-range order dominates over antiferromagnetic short- range order.
Two-leg t-J ladders have been investigated by Y. L. Lee (National Tsing Hua) et al. in the framework of a combination of the phase-string formulation and the bond-operator representation. The authors develop a mean-field theory in the strong rung interaction regime, i.e., J_[perp.] >> (J, t), which provides a unified description of the undoped insulating phase and the low-doping phase. Both are characterized by a resonating-valence-bond (RVB) order parameter, with a gap opened up in all spin excitations. The ground state of the doped phase in intrinsically a superconductor with d-wave symmetry, driven by RVB correlations, and the ground-state energy is in good agreement with numerical results.
The spin-gap effect on dc resistivity in the t-J model of high-Tc cuprates has been calculated by M. Onoda (Tokyo) et al. using Ginzburg- Landau theory coupled with a gauge field as its effective field theory. The authors obtain rho(T) proportional to T[1 - c(T*-T)^d], where T* is the spin-gap onset temperature and d is a nonuniversal exponent.
To investigate non-Fermi-liquid behavior, O. Sushkov (New South Wales) has considered the extended 2D t-J model including additional hopping t". The author solved the model analytically in the regime (t, J) << t" and found a rich phase diagram including the antiferromagnetic (AF) insulator and AF strange metal with different kinds of pseudospin- singlet superconducting pairings (p-, d-, and g-wave). The author also found a collective triplet excitation with energy below the superconducting gap.
A preprint by A. S. Alexandrov (Loughborough) and V. V. Kabanov (JINR- Dubna and Ljubljana) presents an adjustable-parameter-free expression for the superconducting critical temperature of layered cuprates, which allows Tc to be expressed in terms of experimentally measured parameters (e.g., lambda_[ab], lambda_c, and R_H). The resulting theoretical values of Tc are in fair agreement with the experimental Tc values of about 30 La-, Y-, and Hg-based cuprates for different levels of doping. The authors conclude that many cuprates are close to the Bose-Einstein condensation regime.
A model for the superconducting cuprates with multiple components of the pairing amplitude in different oxygen p-orbitals has been studied by I. Chaudhuri (IIT-Kharagpur) et al. The authors show that the model captures certain unusual features observed in the tunneling spectra of Bi-2212 single crystals.
As shown by M. Houzet et al. (Bordeaux), in 3D superconductors the transition between the normal phase and a nonuniform superconducting phase, such as the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state, is always of first order. The authors also determine the transition temperature and the structure of the modulated state using a generalized Ginzburg-Landau functional near the tricritical temperature and the exact Gor'kov equations over the entire temperature range.
A preprint by R. Weht et al. (UC-Davis) suggests that the most likely explanation for the coexistence of superconductivity and ferromagnetism in RuSr2GdCu2O8-d (Ru-1212) (superconducting Tc ~~ 35 K, Curie temperature 132 K) is an FFLO-like inhomogeneous superconducting order parameter in the cuprate layers. The authors note that although magnetism in the Ru layer is strong, the exchange coupling to the Cu layers is quite small.
Local-density-functional results are presented by R. Weht et al. (UC- Davis) for the electron-doped quasi-2D metallochlorides AxZrNCl and AxHfNCl (A = Li or Na), which superconduct up to 25 K. The authors predict a change in behavior at a doping level of x = 0.3.
Other Activities
Both x-ray absorption spectroscopy (XAS) and x-ray photoemission spectroscopy (XPS) studies of single-crystal Ba1-xKxBiO3 (BKBO) covering the whole composition range 0 <= x <= 0.60 are reported by K. Kobayashi (Tokyo) et al. Comparison with XAS results in BaPb1-xBixO3 reveal quite different doping dependencies between BKBO and BPBO.
Various electronic and transport anomalies observed in superconducting perovskites are discussed in a preprint by D. Pavuna (EPFL). The author considers (a) the complex electronic phase diagram, (b) the symmetry of the gap, and (c) non-Fermi-liquid resistivity in superconducting Sr2RuO4-d, which exhibits a linear resistivity up to 1050 K.
As noted by M. J. Graf (Boston) et al., the rate of suppression of Tc of UPt3 is much larger for Pd substitution than for other impurity substitutions or by increased defect density. The authors note that this effect is correlated with an increase in the inelastic scattering coefficient and may be related to Pd-induced changes in the magnetic fluctuation spectrum.
A paper by V. N. Bogomolov (St. Petersburg) examines earlier experimental data on the absorption of light by xenon under high pressures up to 200 GPa and notes some discrepancies with theory that assumes metallization of Xe as a result of a band-gap closure. As an alternative explanation of the optical results, the author suggests a superconducting transition with a Tc of about 5000 K.
Overviews
The development of numerous scanning probe microscopes and their application to studies of high-temperature superconductors are discussed in a review by A. de Lozanne (Texas-Austin). The author emphasizes scanning microscopes based on tunneling (STM), atomic force (AFM), magnetic force (MFM), the Hall effect (SHPM), a SQUID sensor, microwaves, near-field optics, and magneto-optic techniques (107 refs.).
Experimental data and theoretical aspects of the thermal conductivity kappa and magneto-thermal conductivity kappa(B) of high-Tc superconductors and heavy fermions are treated in a review by M. Ausloos and M. Houssa (Liege). The authors show how the experiments reveal the order-parameter symmetry. For the high-Tc cuprates, the experimental results in YBa2Cu3O7-d (Y-123) and Bi2Sr2CaCu2O8+d (Bi-2212) are inconsistent with an isotropic s-wave energy gap but are well described by an anisotropic d_[x^2-y^2] gap with nodes (100 refs.).
The Faraday effect in ferrimagnetic garnet films and its application to magneto-optical imaging of magnetic flux in magnetic materials and high- temperature superconductors are reviewed by A. A. Polyanskii et al. (Wisconsin). Using composite multilayer indicator films, this technique operates in fields up to 0.2 T and over a temperature range 2-400 K with micrometer to mm spatial resolution (88 refs.).
Contributed by John R. Clem
Contents: Preprints begin on page 8; Coming Events begin on page 14; Resources are on page 15; and FYI is on page 15.
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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.
A. S. Alexandrov and V. V. Kabanov, "Parameter-Free Expression for Superconducting Tc in Cuprates." To be published in Phys. Rev. B. Department of Physics, Loughborough University, Loughborough LE11 3TU, UNITED KINGDOM; e-mail vvk20@cus.cam.ac.uk; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9903071.
Nathan Argaman, "Nonequilibrium Josephson-Like Effects in Wide Mesoscopic S-N-S Junctions." To be published in Superlatt. and Microstruc. Department of Physics, Nuclear Research Centre-Negev, P.O. Box 9001, 84190 Beer-Sheva, ISRAEL; e-mail argamann@bgumail.bgu.ac.il; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9903069. 74.50.+r; 74.40.+k; 74.80.Fp; 73.23.Ps.
M. Ausloos and M. Houssa, "Thermal Conductivity of Unconventional Superconductors: A Probe of the Order Parameter Symmetry." To be published in Supercond. Sci. & Technol. SUPRAS, Institute of Physics B5, University of Liege, B-4000 Liege, BELGIUM; e-mail ausloos@gw.unipc.ulg.ac.be. 74.25.Fy; 74.60.Ec; 74.72.-h; 74.70.Tx.
V.P.S. Awana, Claudio A. Cardoso, O. F. de Lima, Rajvir Singh, A. V. Narlikar, W. B. Yelon, and S. K. Malik, "Suppression of Superconductivity with Pr Substitution in Nd1-xPrxBaCaCu3O7 System." To be published in Physica C. Instituto de Fisica 'Gleb Wataghin,' Universidade Estadual de Campinas (UNICAMP), 13083-970 Campinas, SP, BRAZIL; telefax +55 19 289 3137; e-mail awana@ifi.unicamp.br. Key words: NdBaCaCu3O7, Pr substitution, ac susceptibility, antiferromagnetic ordering, Pr-4f hybridization.
V.P.S. Awana, O. F. de Lima, S. K. Malik, W. B. Yelon, and A. V. Narlikar, "Decreasing Superconductivity Suppression of Pr in RE:123 Compounds by Isolating the Same from Cu-O Conduction Band." To be published in the Proc. of the University of Miami Conf. on High Temp. Supercond. (HTS99), Miami, Fla., Jan. 7-13, 1999. Instituto de Fisica 'Gleb Wataghin,' Universidade Estadual de Campinas (UNICAMP), 13083-970 Campinas, SP, BRAZIL; telefax +55 19 289 3137; e-mail awana@ifi.unicamp.br.
K. Barthel, D. Koelle, B. Chesca, A. I. Braginski, A. Marx, R. Gross, and R. Kleiner, "Transfer Function and Thermal Noise of YBa2Cu3O7-d Direct Current Superconducting Quantum Interference Devices Operated Under Large Thermal Fluctuations." To be published in Appl. Phys. Lett. Institut fuer Schicht- und lonentechnik (ISI), Forschungszentrum Juelich, D-52425 Juelich, GERMANY; D. Koelle's telephone at Universitaet zu Koeln +49 221 470 3583; telefax +49 221 470 5178; e-mail koelle@ph2.uni-koeln.de. 74.40.+k; 74.72.Bk; 85.25.Am; 85.25.Dq.
Sebastien Berger, Karim Bouzehouane, Denis Crete, Jean-Pierre Contour, "Realization of a Flux-Flow dc-Transformer Using High-Temperature Superconductors." Unite Mixte de Physique, CNRS/Thomson-CSF, Domaine de Corbeville, F-91404 Orsay Cedex, FRANCE; telephone +33 1 69 33 0905; telefax +33 1 69 33 0740; e-mail sebastien.berger@lcr.thomson-csf.com. 85.25.Am; 74.60.Ge; 74.80.Dm.
V. N. Bogomolov, "Metallic Xenon: Conductivity or Superconductivity?" Preprint #1734 RAS. A.F. Ioffe Physical-Technical Institute, Russian Academy of Sciences, 26 Polyteknicheskaya, St. Petersburg 194021, RUSSIA; e-mail v.bogomolov@shuvpop.ioffe.rssi.ru; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9902353.
Biplab Chattopadhyay, B. Bandyopadhyay, Asok Poddar, P. Mandal, A. N. Das, and B. Ghosh, "Suppression of Tc by Impurities in Bi2212 and Tl2212: Studies on Pseudogap and Its Effects." Condensed Matter Physics Group, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Calcutta 700 064, INDIA; e-mail biplab@cmp.saha.ernet.in. 74.72.-h; 74.72.Hs; 74.72.Fq; 74.25.Fy.
Indira Chaudhuri, S. K. Ghatak, and A. Taraphder, "Density of States in a Multi-Component Model for Superconductivity in Cuprates." Department of Physics and Meteorology, Indian Institute of Technology, Kharagpur 721302, INDIA; e-mail indira@phy.iitkgp.ernet.in; A. Taraphder's telephone +91 3222-55221, ext. 4928; telefax +91 3222-55303 or -55239; e-mail arghya@phy.iitkgp.ernet.in; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9902291. 74.25.Dw; 74.25.Fy; 74.90.+n.
Boris Chesca, "The Effect of Thermal Noise on the Operation of dc SQUIDS at 77 K: A Fundamental Analytical Approach." To be published in IEEE Trans. Appl. Supercond.: Proc. of the 1998 Appl. Supercond. Conf. (ASC), Palm Desert, Calif., Sept. 13-18, 1998. Institut fuer Schicht- und lonentechnik (ISI), Forschungszentrum Juelich, D-52425 Juelich, GERMANY.
K. Deligiannis, S. Kokkaliaris, M. Oussena, P.A.J. de Groot, L. Fruechter, R. Gagnon, and L. Taillefer, "Evidence of 2D Josephson Strings in High Purity YBa2Cu3O7-d Single Crystals." To be published in Phys. Rev. B. Centre de Recherches sur les Tres Basses Temperatures (CRTBT), Centre National de la Recherche Scientifique (CNRS), 25 Avenue des Martyrs, F-38000 Grenoble, FRANCE; e-mail kostas@labs.polycnrs- gre.fr. 74.72.Bk; 74.25.Ha; 74.60.Ge.
Alex de Lozanne, "Scanning Probe Microscopy of High-Temperature Superconductors." To be published in Supercond. Sci. & Technol. Department of Physics, University of Texas, Austin, TX 78712-1081; telephone (512) 471-6108 or -5544; telefax (512) 471-9637 or -6518; e- mail lozanne@physics.utexas.edu.
Eugene Demler and Shou-Cheng Zhang, "Resonant Neutron Scattering on the High Tc Cuprates and pi and eta Excitation of the t-J and Hubbard Models." To be published in the Proc. of the University of Miami Conf. on High Temp. Supercond. (HTS99), Miami, Fla., Jan. 7-13, 1999. Institute for Theoretical Physics, University of California, Santa Barbara, CA 93106-4030; e-mail demler@itp.ucsb.edu; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9903195.
Yanina Fasano, Juan Herbsommer, and Francisco de la Cruz, "Superficial Periodic Pinning Induced by Bitter Decoration Applied to the Study of Vortex Structure Nucleation and Growth." To be presented at the Intl. Conf. on Solid State Spectroscopy (ICSSS), Schwaebisch Gmuend, Germany, Sept. 5-7, 1999; to be published in Phys. Status Solidi (b). Centro Atomico Bariloche and Instituto Balseiro, Comision Nacional de Energia Atomica, 8400 S.C. de Bariloche, ARGENTINA; e-mail fasanoy@cabbat1.cnea.gov.ar. 74.60.Ge; 74.72.Hs.
Y. Fasano, J. A. Herbsommer, F. de la Cruz, F. Pardo, P. L. Gammel, E. Bucher, and D. J. Bishop, "Observation of Periodic Vortex Pinning Induced by Bitter Decoration." Submitted to Phys. Rev. Lett. Centro Atomico Bariloche and Instituto Balseiro, Comision Nacional de Energia Atomica, 8400 S.C. de Bariloche, ARGENTINA; e-mail fasanoy@cabbat1.cnea.gov.ar.
L. M. Fisher, K. V. Il'enko, A. V. Kalinov, M.A.R. LeBlanc, F. Perez- Rodriguez, S. E. Savel'ev, I. F. Voloshin, and V. A. Yampol'skii, "The Suppression of the Magnetic Moment Under the Action of a Transverse Magnetic Field in Hard Superconductors." All-Russian Electrical Engineering Institute, 12 Krasnokazarmennaya Str., 111250 Moscow, RUSSIA. 74.25.Ha; 74.60.Ec; 74.60.Ge.
M. Franz and Z. Tesanovic, "Quasiparticles in the Vortex Lattice of Unconventional Superconductors: Bloch Waves or Landau Levels?" Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218; e-mail franz@benz.pha.jhu.edu; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9903152.
Haranath Ghosh, S. Sil, and S. N. Behera, "Interplay of Spin Density Wave and Superconductivity with Different Pairing Symmetry." To be published in Physica C. Department of Physics, University of Arizona, Tucson, AZ 85721; e-mail hng@physics.arizona.edu; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9903234. 75.30.Fv; 75.10.Jm; 74.20.Fg.
D. Giller, A. Shaulov, Y. Yeshurun, and J. Giapintzakis, "Vortex Solid- Solid Phase Transition in Untwinned YBa2Cu3O7-d Crystal." To be published in Phys. Rev. B. Department of Physics, Institute for Superconductivity, Bar-Ilan University, Ramat-Gan 52900, ISRAEL; e-mail giller@physnet.ph.biu.ac.il. 74.60.Ge; 74.72.Bk; 74.25.Ha.
M. J. Graf, R. J. Keizer, A. de Visser, A. A. Menovsky, and J.J.M. Franse, "Suppression of Superconductivity in Single Crystals of UPt3 by Pd Substitution." Submitted to Phys. Rev. B. Department of Physics, Boston College, Chestnut Hill, MA 02467; e-mail grafm@bc.edu; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9903075. 71.27.+a; 74.70.Tx.
Mike Guidry, Lian-Ao Wu, Cheng-Li Wu, and Yang Sun, "An SU(4) Theory of High-Temperature Superconductivity and Antiferromagnetism." Submitted to Phys. Rev. Lett. Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996; Yang Sun's e-mail yangsun@utknp3.phys.utk.edu; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9903150.
J. H. Han, P. Ao, and X.-M. Zhu, "Effective Mass of a Vortex in a Clean Superconductor." Asia Pacific Center for Theoretical Physics, 207-43 Cheongryangri-dong Dongdaemun-gu, Seoul 130-012, KOREA; e-mail hanjh@apctp.kaist.ac.kr; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9903125.
M. Houzet, Y. Meurdesoif, O. Coste, and A. Buzdin, "Structure of the Non-Uniform Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) State in 3D Superconductors." To be published in Physica C. Contact A. Buzdin, Centre de Physique Theorique et de Modelisation, Universite Bordeaux I, CNRS-URA 1537, F-33405 Talence Cedex, FRANCE; telephone +33 5 5796 2502; telefax +33 5 5796 2501; e-mail buzdin@pth.u-bordeaux.fr. Key words: nonuniform superconducting state, paramagnetic limit, generalized Ginzburg-Landau functional. 74.60.Ec.
A. W. Hunt, P. M. Singer, K. R. Thurber, and T. Imai, "[63]^Cu NQR Measurement of Stripe Order Parameter in La2-xSrxCuO4." Department of Physics and Center for Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139; e-mail awhunt@mit.edu; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9902348. 74.25.Nf; 74.72.Dn.
N. E. Hussey, H. Takagi, N. Takeshita, N. Mori, Y. Iye, S. Adachi, and K. Tanabe, "Melting of the Vortex Lattice in YBa2Cu4O8 in Parallel Fields." To be published in Phys. Rev. B. Institute for Solid State Physics, University of Tokyo, 7-22-1 Roppongi, Minato-ku, Tokyo 106, JAPAN; telephone +81 3 3478 6811, ext. 5663; telefax +81 3 3478 7698; e- mail nehussey@troy.issp.u-tokyo.ac.jp.
J. Jiang, T. C. Shields, J. S. Abell, A. Polyanskii, M. Feldmann, and D. C. Larbalestier, "Microstructural and Magneto-Optical Characterization of High Jc BSCCO-2223/Ag Tapes." Presented at the 1998 Appl. Supercond. Conf. (ASC), Palm Desert, Calif., Sept. 13-18, 1998. Applied Superconductivity Center, University of Wisconsin-Madison, 1500 Engineering Drive, Madison, WI 53706-1687; A. Polyanskii's e-mail polyansk@coefac.engr.wisc.edu.
M.-H. Julien, F. Borsa, P. Carretta, M. Horvatic, C. Berthier, and C. T. Lin, "Charge Segregation, Cluster Spin-Glass and Superconductivity in La1.94Sr0.06CuO4." Dipartimento di Fisica "A. Volta," Unita INFM di Pavia, Via Bassi 6, I-27100 Pavia, ITALY; telephone +39 0382 507483, ext. 465; telefax +39 0382 507563; e-mail julien@pv.infn.it or marc.henri.julien@pv.infn.it; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9903005. 76.60.-k; 74.25.Ha; 74.72.Dn.
W. N. Kang, S. I. Lee, and C. W. Chu, "Oxygen Annealing and Superconductivity of HgBa2Ca2Cu3O8+y Thin Films." Preprint #99:009; to be published in Physica C. National Creative Research Initiative Center for Superconductivity, Department of Physics, Pohang University of Science and Technology, Kyungbuk, 790-784, SOUTH KOREA; e-mail wnkang@anyon.postech.ac.kr; preprint also available from Texas Center for Superconductivity, University of Houston, Houston, TX 77204-5932; telephone (713) 743-8200; telefax (713) 743-8201; e-mail preprints@www.tcs.uh.edu. Key words: HgBa2Ca2Cu3O8 thin films, high-Tc superconductors, critical current density, dimensional crossover.
H. R. Kerchner, D. P. Norton, A. Goyal, J. D. Budai, D. K. Christen, D. M. Kroeger, M. Paranthaman, D. F. Lee, F. A. List, R. Feenstra, and E. H. Brandt, "Alternating Transport-Current Flow in Superconductive Films: The Important Role of a Geometrical Barrier to Vortex Motion." Submitted to Phys. Rev. Solid State Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831. 74.60.Jg; 74.76.Bz; 84.70.+p.
A. P. Kharel, K. H. Soon, J. R. Powell, A. Porch, M. J. Lancaster, A. V. Velichko, and R. G. Humphreys, "Non-Linear Microwave Surface Impedance of Epitaxial HTS Thin Films in Low dc Magnetic Fields." To be published in IEEE Trans. Appl. Supercond.: Proc. of the 1998 Appl. Supercond. Conf. (ASC), Palm Desert, Calif., Sept. 13-18, 1998. Contact A. V. Velichko, School of Electronic and Electrical Engineering, University of Birmingham, Edgbaston, Birmingham B15 2TT, UNITED KINGDOM; telephone +44 121 414 4348; telefax +44 121 414 4291; e-mail velichko@ee-wp.bham.ac.uk or a.v.velichko@bham.ac.uk; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9903309.
Chan-Joong Kim, Young A. Jee, Tae-Hyun Sung, and Gye-Won Hong, "Control of YBCO Growth at the Compact/Substrate Interface by Bottom Seeding and Yb2O3 Coating in Seeded Melt-Growth Processed YBCO Oxides Using a MgO Substrate." To be published in Physica C. Superconductivity Research Laboratory, Korea Atomic Energy Research Institute, P.O. Box 105, Yusung, Taejon 305-600, SOUTH KOREA; telephone +82 42 868 8908; telefax +82 42 862 5496; e-mail cjkim2@nanum.kaeri.re.kr.
K. Kobayashi, T. Mizokawa, A. Ino, J. Matsuno, A. Fujimori, H. Samata, A. Mishiro, Y. Nagata, and F.M.F. de Groot, "Doping Dependence of the Electronic Structure of Ba1-xKxBiO3 Studied by X-ray Absorption Spectroscopy." To be published in Phys. Rev. B. Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, JAPAN; telephone +81 3 5800 3325; telefax +81 3 5800 3325; e-mail kobayasi@wyvern.phys.s.u-tokyo.ac.jp; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9903273. 79.60.-i; 71.30.+h; 74.25.Jb; 74.70.Ad.
M. R. Koblischka, M. Muralidhar, T. Higuchi, K. Waki, N. Chikumoto, and M. Murakami, "Superconducting Transitions of Nd-Based 123 Superconductors in Fields up to 7 T." To be published in Supercond. Sci. & Technol. Superconductivity Research Laboratory, International Superconductivity Technology Center (ISTEC), 1-16-25 Shibaura, Minato- ku, Tokyo 105, JAPAN; e-mail koblischka@istec.or.jp. 74.60.Ec; 74.25.Ha; 74.72.Jt.
P. V. Komissinski, G. A. Ovsyannikov, N. A. Tulina, and V. V. Ryazanov, "c-Axis Tunneling in Nb/Au/YBaCuO Structures." Institute of Radio Engineering and Electronics, Russian Academy of Sciences, Moscow, RUSSIA; P. V. Komissinski's e-mail at Chalmers University of Technology filippe@fy.chalmers.se; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9903065. 74.50.+r; 74.72.Bk.
T. K. Kopec and J. V. Jose, "Quantum Critical Point and Scaling in a Layered Array of Ultrasmall Josephson Junctions." Submitted to Phys. Rev. B. Department of Physics and Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston, MA 02115; J. V. Jose's e-mail jose@citlalli7.physics.neu.edu; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9903222. 74.50.+r; 67.40.Db.
D. C. Larbalestier, J. Wa. Anderson, S. E. Babcock, X. Y. Cai, S. E. Dorris, M. Feldmann, J. Jiang, Q. Li, J. A. Parrell, R. Parrella, M. Polak, A. Polyanskii, G. N. Riley, Jr., M. Rupich, and Y. Wu, "New Experiments Elucidating the Current Limiting Mechanisms of Ag-Sheathed (Bi,Pb)2Sr2Ca2Cu3Ox Tapes." To be published in Advances in Supercond. XI: Proc. of the 11th Int. Symp. on Superconductivity (ISS'98), Fukuoka, Japan, Nov. 16-19, 1998; edited by N. Koshizuka and S. Tajima (Springer-Verlag, Tokyo). Applied Superconductivity Center, University of Wisconsin-Madison, 1500 Engineering Drive, Madison, WI 53706-1687; A. Polyanskii's e-mail polyansk@coefac.engr.wisc.edu. Key words: BSCCO- 2223, critical current density, irreversibility fields, cracks, ultrasonic fractures.
Yu. I. Latyshev, T. Yamashita, L. N. Bulaevskii, M. J. Graf, A. V. Balatsky, and M. P. Maley, "Interlayer Transport of Quasiparticles and Cooper Pairs in Bi2Sr2CaCu2O8+d Superconductors." Preprint #LA-UR-99- 1180. Research Institute of Electrical Communications, Tohoku University, 2-1-1, Katahira, Aoba-ku, Sendai 980-8577, JAPAN; M. J. Graf's e-mail at Los Alamos National Laboratory graf@lanl.gov; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9903256. 74.25.Fy; 74.50.+r; 74.72.Hs.
Kiejin Lee, Wan Wang, Ienari Iguchi, Barry Friedman, Takayuki Ishibashi, and Katsuaki Sato, "Spin-Polarized Quasiparticle Tunnel Injection in a YBa2Cu3Oy/Au/Co Junction." Submitted to Appl. Phys. Lett. Department of Applied Physics, Tokyo Institute of Technology, Oh-Okayama, Meguro- ku, Tokyo 152, JAPAN; telephone +81 3 5734 2454; telefax +81 3 5734 2751; e-mail klee@htsc.ap.titech.ac.jp. 74.80.Dm; 74.60.Jg; 74.80.Fp.
Kiejin Lee, Hitoshi Yamaguchi, Wan Wang, Eiji Kume, and Ienari Iguchi, "Directon-Oriented Quasiparticle Injection and Microwave Emission in an ErBa2Cu3Oy Superconductor." To be published in Phys. Rev. Lett. Department of Applied Physics, Tokyo Institute of Technology, Oh- Okayama, Meguro-gu, Tokyo 152, JAPAN; telephone +81 3 5734 2454; telefax +81 3 5734 2751; e-mail klee@htsc.ap.titech.ac.jp.
Y. L. Lee, Y. W. Lee, C.-Y. Mou, and Z. Y. Weng, "The Two-Leg t-J Ladder: A Mean-Field Description." NCTS and Department of Physics, National Tsing Hua University, Hsinchu, Taiwan 300, REPUBLIC OF CHINA; Z. Y. Weng's e-mail at University of Houston weng@mira.tcs.uh.edu; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9903059.
F. Lefloch, C. Hoffmann, and O. Demolliens, "Nonlinear Flux Flow in TiN Superconducting Thin Film." Submitted to Physica C. 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 4290; telefax +33 4 76 88 5096; e-mail flefloch@cea.fr; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9903060. Key words: flux flow, thin films, electrical resistivity, granular superconductivity.
A. Malinowski, A. Krickser, Marta Z. Cieplak, S. Guha, K. Karpinska, M. Berkowski, and P. Lindenfeld, "Two Lifetimes and the Pseudogap in the Orbital Magnetoresistance of Zn-Substituted La1.85Sr0.15CuO4." Department of Physics and Astronomy, 136 Frelinghuysen Road, Rutgers University, Piscataway, NJ 08855-0849; P. Lindenfeld's telephone (732) 445-2536; telefax (732) 445-4343; e-mail lindenf@physics.rutgers.edu; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9903080. 74.20.Mn; 74.25.-q; 74.72.Dn; 74.25.Fy; 74.76.Bz.
R. Melin and O. Bourgeois, "Interplay Between Spin Polarization and Out- of-Equilibrium Transport in S-F-S Junctions." Centre de Recherches sur les Tres Basses Temperatures (CRTBT), Laboratoire Associe a l'Universite Joseph Fourier, CNRS, B.P. 166, F-38042 Grenoble Cedex, FRANCE; e-mail merlin@labs.polycnrs-gre.fr; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9903209.
F. Miletto, M. Salluzzo, U. Scotti di Uccio, I. Maggio-Aprile, and O. Fischer, "Competition Between a-Axis and c-Axis Growth in Superconducting REBCO Thin Films: A New Model." Submitted to Phys. Rev. B. INFM-Dipartimento di Scienze Fisiche, Universita di Napoli "Federico II," Piazzale Tecchio 80, I-80125 Napoli, ITALY; telephone +39 081 768 2423; telefax +39 081 239 1821; e-mail miletto@na.infn.it. 74.50.+r; 74.72.Bk; 74.76.Bz; 74.80.Fp.
L. Miu, E. Cimpoiasu, T. Stein, C. C. Almasan, G. Jakob, and H. Adrian, "Influence of Thermally Created Vortices on the Low-Field Vortex-Phase Diagram of Bi2Sr2CaCu208+d Single Crystals." Submitted to Phys. Rev. B. National Institute for Materials Physics, P.O. Box MG-7, Bucharest, ROMANIA; e-mail elmiu@alpha1.infim.ro. 74.72.Hs; 74.25.Fy; 74.25.Ha.
Niels Asger Mortensen, Antti-Pekka Jauho, Karsten Flensberg, and Henning Schomerus, "Conductance Enhancement in Quantum Point Contact- Semiconductor-Superconductor Devices." Submitted to Phys. Rev. B. Mikroelektronik Centret, Bldg. 345 East, Technical University of Denmark, DK-2800 Lyngby, DENMARK; telephone +45 4525 5782; e-mail nam@mic.dtu.dk; preprint also available at http://xxx.lanl.gov/abs/cond- mat/9903205. 72.10.-d; 74.50.+r; 74.80.Fp.
K.-H. Mueller, C. Andrikidis, J. Du, K. E. Leslie, and C. P. Foley, "Connectivity and Limitation of Critical Current in Bi-2223/Ag Tapes." To be published in Phys. Rev. B. Telecommunications and Industrial Physics, CSIRO, Bradfield Road, West Lindfield, Lindfield NSW 2070, AUSTRALIA; telephone +61 2 9413 7052; telefax +61 2 9413 7202; e-mail karl@tip.csiro.au. 74.60.Jg; 85.25.Kx; 74.80.Bj; 74.72.Hs; 74.80.-g; 74.76.-w.
M. Muralidhar, S. Koishikawa, M. R. Koblischka, and M. Murakami, "Study of Superconducting Properties of OCMG Processed (Nd,Eu,Gd)-Ba-Cu-O with Pr Doping." To be published in Physica C (in press). Superconductivity Research Laboratory, International Superconductivity Technology Center (ISTEC), 3-35-2 Iioka-Shinden, Morioka, Iwate 020-0852, 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 superconductors, Pr doping, melt-processing, flux pinning, peak effect, critical current densities.
Masaru Onoda, Ikuo Ichinose, and Tetsuo Matsui, "Spin-Gap Effect on Resistivity in the t-J Model." Submitted to Phys. Rev. Lett. Department of Physics, University of Tokyo, Hongo, Tokyo 113-0033, JAPAN; e-mail onoda@cms.phys.s.u-tokyo.ac.jp; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9903243. 74.25.Fy; 71.27.+a; 71.10.Pm; 11.15.-q.
Shigeki Onoda and Masatoshi Imada, "d_[x^2-y^2] Wave Pairing Fluctuations and Pseudo Spin Gap in Two-Dimensional Electron Systems." Submitted to J. Phys. Soc. Jpn. Institute for Solid State Physics, University of Tokyo, 7-22-1 Roppongi, Minato-ku, Tokyo 106-8666, JAPAN; e-mail onoda@ginnan.issp.u-tokyo.ac.jp; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9903030. Key words: antiferromagnetism, d_[x^2-y^2]-wave superconductivity, self-consistent renormalization, van Hove singularity, high-Tc superconductivity, pseudogap.
F. Onufrieva and P. Pfeuty, "SC State in the Underdoped High-Tc Cuprates as a Quantum Spin Liquid: A Microscopic Theory." Laboratoire Leon Brillouin, CE-Saclay, F-91191 Gif-sur-Yvette, FRANCE; e-mail onufri@llb.saclay.cea.fr; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9903097.
Masa-aki Ozaki, Yoshiki Hori, and Akira Goto, "On Local Symmetric Order Parameters of Vortex Lattice States." To be published in Prog. Theor. Phys. 101, No. 3 (1999). Department of Physics, Kochi University, Kochi 780-8072, JAPAN; Yoshiki Hori's e-mail at Kochi National College of Technology hori@ge.kochi-ct.ac.jp; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9902255.
Lutfi Ozyuzer, Zikri Yusof, John F. Zasadzinski, Ting-Wei Li, Dave G. Hinks, and Kenneth E. Gray, "Tunneling Spectroscopy of Tl2Ba2CuO6." Materials Science Division and the Science and Technology Center for Superconductivity, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439; telephone (630) 252-8457; telefax (630) 252-7777; e- mail ozyuzer@anl.gov. Key words: high-temperature superconductivity, tunneling, superconducting gap. 74.50.+r; 74.80.Fp; 74.72.Fq.
Davor Pavuna, "On Electronic and Transport 'Anomalies' in Layered Oxides." Submitted to the Proc. of the Euroconf. on Polarons: Condensation, Pairing, Magnetism, Erice, Italy, June 9-17, 1998; to be published in J. Supercond. Institut de Physique Appliquee, Ecole Polytechnique Federale de Lausanne, IPA-EPFL, CH-1015 Lausanne, SWITZERLAND; telephone +41 21 693 1111; e-mail pavuna@epfl.ch.
V. T. Petrashov, I. A. Sosnin, I. Cox, A. Parsons, and C. Troadec, "Giant Mutual Proximity Effects in Ferromagnetic/Superconducting Nanostructures." Submitted to Phys. Rev. Lett. Department of Physics, Royal Holloway, University of London, Egham, Surrey TW20 0EX, UNITED KINGDOM; I. A. Sosnin's e-mail i.sosnin@rhbnc.ac.uk; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9903237. 74.50.+r; 74.80.Fp; 85.30.St.
A. A. Polyanskii, X. Y. Cai, D. M. Feldmann, and D. C. Larbalestier, "Visualization of Magnetic Flux in Magnetic Materials and High Temperature Superconductors Using the Faraday Effect in Ferrimagnetic Garnet Films." Presented at the NATO Adv. Res. Workshop, Sozopol, Bulgaria, Sept. 27-Oct. 3, 1998; to be published in NATO ASI Series: Ferrimagnetic Nanocrystalline and Thin-Film Magneto-optical and Microwave Materials, edited by M. Ausloos and I. Nedkov (Kluwer). Applied Superconductivity Center, University of Wisconsin-Madison, 1500 Engineering Drive, Room 934 ERB, Madison, WI 53706-1687; e-mail polyansk@coefac.engr.wisc.edu; Web site http://magneto- optical.engr.wisc.edu.
Sergei Sergeenkov and Marcel Ausloos, "Probing the Field-Induced Variation of the Chemical Potential in Bi2Sr2CaCu2Oy via the Magneto- Thermopower Measurements." To be published in JETP Lett. SUPRAS, Institute of Physics, University of Liege, B-4000 Liege, BELGIUM; e-mail serge@gw.unipc.ulg.ac.be; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9903206.
Jing Shi, X. S. Ling, Ruixing Liang, D. A. Bonn, and W. N. Hardy, "Giant Peak Effect Observed in an Ultra-Pure YBa2Cu3O6.993 Crystal." Submitted to Phys. Rev. Lett. Contact X. S. Ling, Department of Physics, Brown University, Providence, RI 02912; e-mail xsling@brown.edu. 74.60.Ge; 64.60.Cn.
H. Shibata and A. Matsuda, "Josephson Plasma Frequencies in Overdoped Bi2Sr2CaCu2O8+d." To be published in Phys. Rev. B. NTT Basic Research Laboratories, 3-1 Morinosato Wakamiya, Atsugi-shi, Kanagawa 243-0198, JAPAN; telephone +81 462 40 3356; telefax +81 462 40 4717; e-mail shibata@will.brl.ntt.co.jp. 74.25.Gz; 74.72.Hs.
Oleg Sushkov, "Superconducting Pairing, and the Collective Magnetic Excitation in the Extended Two-Dimensional t-J Model." To be published in Studies of High Temp. Supercond., edited by A. V. Narlikar. School of Physics, University of New South Wales, Sydney 2052, AUSTRALIA; e- mail sushkov@phys.unsw.edu.au; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9903028.
J. R. Thompson, J. G. Ossandon, L. Krusin-Elbaum, K. J. Song, D. K. Christen, and J. L. Ullmann, "Quantum Constraints on Technological Superconductors." Submitted to Appl. Phys. Lett. Bldg. 3115, MS 6061, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6061; telephone (423) 574-0412; telefax (423) 574-6263; e-mail jrt@utk.edu. 74.60.Ge; 74.60.Jg; 74.72.Hs.
Anton V. Velichko, "Phenomenological Model of the Nonlinear Microwave Response of a Superconducting Weak Link." School of Electronic and Electrical Engineering, University of Birmingham, Edgbaston, Birmingham B15 2TT, UNITED KINGDOM; telephone +44 121 414 4348; telefax +44 121 414 4291; e-mail velichko@ee-wp.bham.ac.uk or a.v.velichko@bham.ac.uk; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9903304.
Z. H. Wang, "Transport Current Characteristics in Textured Bi1.84Pb0.4Sr2Ca2Cu3Oy Silver Clamped Thick Films." To be published in Physica C. Shanghai Institute of Metallurgy, Chinese Academy of Sciences, 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.
R. Weht, A. Filippetti, and W. E. Pickett, "Electronic Characteristics of Quasi-2D Metallochloronitrides: NaxHfNCl (Tc = 25 K)." To be published in the Proc. of the University of Miami Conf. on High Temp. Supercond. (HTS99), Miami, Fla., Jan. 7-13, 1999. Department of Physics, University of California at Davis, Davis, CA 95616; W. E. Pickett's e-mail pickett@solid.ucdavis.edu; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9903214.
R. Weht, A. B. Shick, and W. E. Pickett, "On the Coexistence in RuSr2GdCu2O8 of Superconductivity and Ferromagnetism." To be published in the Proc. of the University of Miami Conf. on High Temp. Supercond. (HTS99), Miami, Fla., Jan. 7-13, 1999. Department of Physics, University of California at Davis, Davis, CA 95616; W. E. Pickett's e- mail pickett@solid.ucdavis.edu; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9903210.
H. Wu, J. Tang, A. Miyase, and S. S. Wang, "Ag-Bi2223 Multilayer Composite with Nanosize MgO Inclusions." Preprint #99:008; submitted to Physica C. Department of Mechanical Engineering and Texas Center for Superconductivity, University of Houston, Houston, TX 77204-5932; telephone (713) 743-8200; telefax (713) 743-8201; e-mail preprints@www.tcs.uh.edu.
Z. L. Xiao, E. Y. Andrei, and M. J. Higgins, "Flow Induced Organization and Memory of a Vortex Lattice." Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08855.
Z. A. Xu, Y. Zhang, and N. P. Ong, "Effect of the Pseudogap on the Hall Conductivity in Underdoped YBa2Cu3O6+x." Joseph Henry Laboratories of Physics, Jadwin Hall, Princeton University, P.O. Box 708, Princeton, NJ 08544-0708; telephone (609) 258-4400; telefax (609) 258-1124; e-mail zhuan@princeton.edu; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9903123. 72.15.Gd; 74.72.Bk; 74.25.Fy; 74.40.+k.
Alexandre M. Zagoskin, "A Scalable, Tunable Qubit, Based on a Clean DND or Grain Boundary D-D Junction." Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, BC, CANADA V6T 1Z1; e-mail zagoskin@physics.ubc.ca; preprint also available at http://xxx.lanl.gov/abs/cond-mat/9903170.
Z. Zhai, P. V. Patanjali, N. Hakim, J. B. Sokoloff, S. Sridhar, U. Ammerahl, A. Vietkine, and A. Revcolevschi, "Observation of Spin Freezing and Relaxation at Microwave Frequencies in the Spin Ladder Compound Sr14-xCaxCu24O41." Department of Physics, Northeastern University, 360 Huntington Avenue, Boston, MA 02115; S. Sridhar's e-mail srinivas@neu.edu.
Lu Zhang, J. Z. Liu, and R. N. Shelton, "Magnetic Relaxation of Four- CuO2-Layer TlBa2Ca3Cu4O11+d Single Crystals." To be published in Physica C. Department of Physics, California State University, Stanislaus, 801 West Monte Vista Avenue, Turlock, CA 95382; telephone (209) 667-3774; telefax (209) 667-3099; e-mail zhang@toto.csustan.edu.
Lu Zhang, J. Z. Liu, and R. N. Shelton, "Upper Critical Field of Four- CuO2-Layer TlBa2Ca3Cu4O11+d Single Crystals." To be published in Solid State Commun. Department of Physics, California State University, Stanislaus, 801 West Monte Vista Avenue, Turlock, CA 95382; telephone (209) 667-3774; telefax (209) 667-3099; e-mail zhang@toto.csustan.edu. Key words: high-Tc superconductor, TlBa2Ca3Cu4O11+d, magnetization.
A. A. Zhukov, H. Kuepfer, G. K. Perkins, A. D. Caplin, T. Wolf, K. I. Kugel, A. L. Rakhmanov, M. G. Mikheev, V. I. Voronkova, M. Klaeser, and H. Wuehl, "Commensurability Oscillations and Smectic Vortex Phase Transition in YBa2Cu3Oy Single Crystals." Submitted to Phys. Rev. B. Department of Physics, University of Southampton, Southampton SO16 1BJ, UNITED KINGDOM; telephone +44 1703 592077; telefax +44 1703 593910; e- mail aaz@phys.soton.ac.uk. 74.60.Ge; 74.60.Jg; 74.72.Bk.
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.)
June 16 - 17, 1999: Workshop on Applications of SQUID Magnetometry, INSA de Lyon, Lyon, France. Current and emerging applications of both HTS and LTS SQUIDs will be covered by the following lecturers: A. Braginski, Juelich (Geophysics); J. Clarke, Berkeley (rf Amplifiers and Biophysics); G. Donaldson, Strathclyde (Nondestructive Evaluation); R. Fagaly, Tristan Technologies (Commercial SQUIDs & Gastrointestinal Applications); G.-L. Romani, Chieti (Magnetoencephalography, Basic Research & Clinical Applications); A. Schirdewan, Berlin (New Clinical Application of Magnetocardiography); H. Weinstock, AFOSR (Introduction & Overview of SQUID Magnetometry & Its Applications). Limited to 50 participants. Workshop will conclude with D.H.C. award to H. Weinstock. For further information, contact Pierre-Louis Vuillermoz, INSA de Lyon; telephone +33 4 7243 8067; telefax +33 4 7243 6082; e-mail plv@insa.insa-lyon.fr.
*Aug. 4 - 11, 1999: 22nd International Conference on Low Temperature Physics (LT22), Helsinki University of Technology (HUT), Otaniemi, Espoo and Helsinki, Finland. Topics will include: quantum gases, fluids, and solids; superconductivity; magnetism and lattice properties; quantum electron transport; applications; materials; and techniques. LT22 will have limited funds to assist graduate students, junior faculty, as well as participants from institutions and countries where support is difficult to obtain. Preregistration and abstract deadline, April 15, 1999. Proceedings will appear as a special issue of Physica B -- Cond. Mat., in April 2000. For information, contact Conference Service Bureau, TSG-Congress Ltd., Kaisaniemenkatu 3 B 31, FIN-00100 Helsinki, Finland; telephone +358 9 628044; telefax +358 9 667675; e-mail info@tsgcongress.fi. For technical information, contact the LT22 Office, Low Temperature Laboratory, Helsinki University of Technology, P.O. Box 2200, FIN-02015 HUT, Finland; telephone +358 9 451 2962; telefax +358 9 451 2969; e-mail info@LT22.hut.fi; Web site http://lt22.hut.fi/lt22/lt22.html.
*Aug. 17 - 20, 1999: 1999 Taiwan International Conference on Superconductivity (TICS'99) & 6th Workshop on Low Temperature Physics (WLTP6), Kenting, Taiwan, ROC. Continuation of the five previous TICS conferences. Topics are: superconducting materials (new, bulk, single crystal, and thin film); material characterization and physical properties; theories and applications of superconductivity; strongly correlated electron systems; and other low-temperature-physics-related topics. All papers will be refereed and published in the Chinese Journal of Physics (Taipei) as a special issue. Conference language is English. Abstract deadline, May 1, 1999. For information, contact Hsiung Chou, Department of Physics, National Sun Yat-Sen University, Kaohsiung, Taiwan 804, Republic of China; telephone +886 7 5253700; telefax +886 7 5253709; e-mail chou@mail.phys.nsysu.edu.tw or tics99@mail.phys.nsysu.edu.tw; Web site http://www2.nsysu.edu.tw/Physics/tics99.
Sept. 8 - 12, 1999: 9th International Workshop on Weak Superconductivity (WWS'99), Papiernicka, Slovak Republic. Organized by the Institute of Electrical Engineering SAS, Bratislava, in collaboration with University of Erlangen and Friedrich-Schiller University, Jena. Co-chairs: Stefan Benacka, Paul Mueller, and Paul Seidel. Aim of WWS'99 is the international exchange of latest results in the study of Josephson effects in low-and high-critical-temperature superconductors and their applications. Workshop will concentrate on the following areas: physics of Josephson effects and tunneling; Josephson effects in arrays, stacks, and mesoscopic systems; intrinsic Josephson effects; properties and role of interface in multilayer thin films with Josephson coupling; materials for thin film Josephson junctions and devices; rf properties and applications in low- and high- frequency range. Invited talks, oral and poster presentations. Abstract deadline, May 15, 1999. Papers to be published as a special issue of Physica C. Attendance limited to about 100 persons. For further information, contact Organizing Committee, WWS'99, Institute of Electrical Engineering SAS, Dubravska cesta 9, 842 39 Bratislava, Slovak Republic; telephone +421 7 54775820, ext. 2139 or 2059; telefax +421 7 54775816; e-mail elekws99@savba.sk; Web site http://cryo.savba.sk/conf.htm. Or contact Stefan Benacka, Conference Chair, at e-mail benacka@savba.sk.
*Sept. 19 - 23, 1999: Superconducting Materials Aspects: Research & Technology (SMART 99), Giens Peninsula, Hyeres, France. Second SMART Conference; satellite to the EUCAS'99 Conference in Sitges, Barcelona, Spain (Sept. 14-17, 1999). Will provide an opportunity to present new results and exchange ideas on the following research and technology topics: phase chemistry and processing of bulk and thick-film materials, crystal-growth processes, relationships between materials structure and relevant properties, electromagnetic interactions, and applications. Materials of interest are mainly superconducting ceramics, superionic conductors, giant-magnetoresistive materials, nanocrystals, ferroelectrics, organic electronics and photonics materials, nanotubes, thermoelectric materials, and ceramic matrix composites. Organizers plan for four working days without parallel sessions. Program will consist of keynote and contributed papers (oral or posters). Industrial participants are encouraged to present technological state-of-the-art and to raise practical questions. Level of the meeting is that of an advanced research workshop with ample time for discussions. Attendance limited to about 80 persons. Abstract deadline, May 15, 1999. For information, contact Gilbert Vacquier, Co- Chair and Conference Secretary, LPCM (Case 26), Centre Saint-Charles, 3 Place V. Hugo, F-13331 Marseille Cedex 03, France; telephone +33 491 10- 6271; telefax +33 491 10-6448 or -6237; e-mail smart@newsup.univ-mrs.fr; Web site http://www.supras.phys.ulg.ac.be/smart-99.html. * Note extended abstract deadline.
*Nov. 2 - 4, 1999: The Third International Workshop on Material Science (IWOMS'99), Hanoi, Vietnam. Workshop covers various aspects of materials science, from bulk to nanoscale materials, including fundamentals and technical applications. Main objective is to provide a forum where most relevant and recent results are discussed. Topics include: intermetallics -- phase diagram, microstructure, and physical properties; magnetic materials and applications; thin films -- materials and applications; high-Tc superconductors and superconductivity-related phenomena; advanced ceramic materials; physics of nanostructures; and others. Invited and contributed papers. Workshop language is English. Abstract deadline, April 15, 1999. For information, contact Secretary IWOMS'99, International Training Institute for Materials Science (ITIMS), ITIMS Building, Dai hoc Bach Khoa Hanoi, 1 DAI CO VIET Road, Hanoi, Vietnam; telephone +84 4-869-2518 or -868-0787; telefax +84 4- 869-2963; e-mail iwoms@itims.edu.vn.
*Feb. 20 - Feb. 25, 2000: 6th International Conference on Materials and Mechanisms of Superconductivity and High Temperature Superconductors (M2S-HTSC-VI), George R. Brown Convention Center, Houston, Texas. Hosted by the Texas Center for Superconductivity at the University of Houston and sponsored by federal agencies and industry. Co-Chairs: C. W. Chu, W. K. Chu, and K. Salama. This series of meetings, established in 1988 two years after the discovery of high-temperature superconductors, is dedicated to superconductivity and related phenomena, and the host materials of these phenomena. The conference will bring together members of the international low- and high- temperature superconductivity community to focus on recent insights into LTS and HTS physics, materials, and devices. Emerging areas and future trends will also be highlighted. General conference topics include, but are not limited to: Experimental and Theoretical Studies of Superconducting Materials -- low temperature, high temperature, fullerite, heavy fermion, organic, new; Physical Properties -- mechanisms, magnetic, electrical, optical, thermal, mechanical, acoustic; Synthesis and Processing -- thin films, superlattices, thick films, bulk; and Applications -- small current (SQUIDs, junctions, microwave devices) and large current (cables, transformers, motors, generators, magnetic-levitation devices). Abstract deadline, September 15, 1999. For information, contact M2S-HTSC-VI Conference Secretariat, Texas Center for Superconductivity, University of Houston, 3201 Cullen Boulevard, Houston, TX 77204-5932; telefax (713) 7743-8216; Web site http://m2s-conf.uh.edu.
RESOURCES
Products and Services
A new MagLabExa Multi-Measurement System was launched recently by Oxford Instruments -- Research Instruments. Using specially designed easily interchangeable probes, the system enables the complete range of materials-characterization measurements to be performed in a single high-field, low-temperature environment. Probes include -- Magnetic Properties Probe for ac susceptibility and dc extraction for magnetic characterization of superconductors, recording media, and a host of other materials; Cantilever Magnetometer Probe for highly sensitive torque and force measurements of microscopic samples and small single crystals; Heat Capacity (Relaxation) Probe for microcalorimetry for thermal and structural characterization of microscopic samples and small single crystals; Electrical Properties Probe for resistivity, critical current, and Hall effect measurements; Custom Experiment Probe for specialized applications requiring a custom-designed measurement cell. System features are 30 mm diameter probe access, 1.5 K to 400 K temperature range, millikelvin resolution below 20 K, automatic cryogen control for fast cool down, low helium consumption giving up to 21 day standby time, 7 T, 9 T, and 12 T magnetic-field options, high field stability (10 ppm/^oC), soft quench facility on 7 T and 9 T options, and smooth sweep through zero field. For further information contact Emma Comer, Marketing Communications Manager, Oxford Instruments, Research Instruments, Tubney Woods, Abingdon, Oxon OX13 5QX, United Kingdom; telephone +44 1865 393200; e-mail info.ri@oxinst.co.uk.
FYI (High-Tc Update takes no responsibility for want ads listed in this section.)
Position open: A two-year postdoctoral position, with possible extension, is available at the Department of Electric Power Engineering, Technical University of Denmark (near Copenhagen). The R&D work is focused on the development of large-scale electric transmission superconducting power cables using liquid-nitrogen-cooled BSCCO-2223 tapes. The R&D work will mainly deal with the design, construction, and test of superconducting cable models with lengths up to 30 m and nominal current and voltage of approx. 3 kA, 72 kV. It is preferred that the applicant has good measurement expertise with high-temperature superconductors and experience with large-scale liquid-N2 cooling systems. Candidates should send a curriculum vitae and the names of three references to Professor Ole Toennesen, Department of Electric Power Engineering, Building 325, The Technical University of Denmark, DK-2800 Lyngby, Denmark; telephone +45 4525 3511; telefax +45 4588 6111; e-mail ot@eltek.dtu.dk.
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, #8, April 15, 1999.