Scaling Theory of Antiferromagnetic Heisenberg Ladder Models

The $S=1/2$ antiferromagnetic Heisenberg model on multi-leg ladders is investigated. Criticality of the ground-state transition is explored by means of finite-size scaling. The ladders with an even number of legs and those with an odd number of legs are distinguished clearly. In the former, the energy gap opens up as $\Delta E\sim{J_\perp}$, where ${J_\perp}$ is the strength of the antiferromagnetic inter-chain coupling. In the latter, the critical phase with the central charge $c=1$ extends over the whole region of ${J_\perp}>0$.Comment: 12 pages with 9 Postscript figures. To appear in J. Phys. A: Math. Ge

A Cross-Whiskers Junction as a Novel Fabrication Process for Intrinsic Josephson Junction

A Bi2Sr2CaCu2O8+d cross-whiskers junction has been successfully discovered as a novel intrinsic Josephson junction without using any technique for micro-fabrication. Two Bi2Sr2CaCu2O8+d whisker crystals were placed crosswise on a MgO substrate and heated at 850C for 30 min. They were electrically connected at their c-planes. The measurement terminals were made at the four ends of the whiskers. The I-V characteristics of the cross-whiskers junction at 5K were found to show a clear multiple-branch structure with a spacing of approximately 15 mV that is a feature of the intrinsic Josephson junction. The critical current density Jc was estimated to be 1170 A/cm2. The branch-structure was strongly suppressed by the magnetic field above 1kOe.Comment: 4 pages, PDF fil

Preliminary Study of H₂O Adsorption on Cr₂O₃ and Al₂O₃ Surfaces by Ab Initio Cluster Calculations

Adsorption and desorption of water over Cr-oxide and alumina are of great concern with the contamination of stainless steel and gas chromatographic isotope separation. However,the mechanisms of those phenomena have not been fully clarified. A preliminary ab inito study on the behavior of water molecules on the (001) surfaces of α-Cr₂O₃ and α-Al₂O₃ was carried out for small clusters of Me4O4 (Me=Cr or Al) by use of the Gaussian 03 package. It was found that water molecules can be adsorbed molecularly and dissociatively on these surfaces. Molecular adsorption of a H₂O molecule takes place on a metal atom of the cluster as Me-OH₂, with the bond length of about 2.0 Å. Dissociative adsorption occurs by forming Me-OH (on-top site) or Me2-OH (bridge site) and O-H bonds. There appeared a feature that the bond length of Me2-OH is greater than that of Me-OH. Calculated adsorption energies were examined by comparing with the values estimated from the thermal desorption spectra of water for α-Cr₂O₃ and γ-alumina. The ab initio calculations coincided quite well with the observed thermal desorption spectrum for α-Cr₂O₃, whereas they did not for γ-alumina. Further studies are required to clarify the structures of adsorbed species, adsorptiron energies and kinetic processes

Core structure of EAS in 10(15) to 10(17) eV

With the use of Akeno calorimeter, the attenuation of particles in concrete is analyzed as the function of the shower size of 10 to the 5th power to 10 to the 7th power. The attenuation length does not depend much on the shower size but depends a little on the shower age. The average value is approx. 150 g/sq cm for s = 0.5 to 0.85 and approx. 40 g/sq cm for s = 0.85 to 1.15. These values and their fluctuations are consistent with the equi-intensity curves of extensive air showers (EAS)