ASCA Slew Survey

We are systematically analyzing ASCA GIS data taken during the satellite attitude maneuver operation. Our motivation is to search for serendipitous hard X-ray sources and make the ASCA Slew Survey catalog. During its operational life from 1993 February to 2000 July, ASCA carried out more than 2,500 maneuver operations, and total exposure time during the maneuver was ~415 ksec after data screening. Preliminary results are briefly reported.Comment: Proceedings for "X-ray surveys in the light of new observations", Santander (Spain), 2002 September. 1 pag

Staggered magnetism in LiV2_2O4_4 at low temperatures probed by the muon Knight shift

We report on the muon Knight shift measurement in single crystals of LiV2O4. Contrary to what is anticipated for the heavy-fermion state based on the Kondo mechanism, the presence of inhomogeneous local magnetic moments is demonstrated by the broad distribution of the Knight shift at temperatures well below the presumed "Kondo temperature" ($T^*\simeq 30$ K). Moreover, a significant fraction ($\simeq10$ %) of the specimen gives rise to a second component which is virtually non-magnetic. These observations strongly suggest that the anomalous properties of LiV2O4 originates from frustration of local magnetic moments.Comment: 11 pages, 5 figures, sbmitted to J. Phys.: Cond. Mat

Growth of ZnO nanostructures on Si by means of plasma immersion ion implantation and deposition

Crystalline zinc oxide (ZnO) nanostructures have been grown on Si substrates by means of Plasma Based Ion Implantation and Deposition (PIII&D) at temperature of about 300 0C and in the presence of an argon glow discharge. In the process a crucible filled with small pieces of metallic zinc plays the role of the anode of the discharge itself, being polarized by positive DC voltage of about 400V. Electrons produced by thermionic emission by an oxide cathode (Ba, Sr, Ca)O impact this crucible, causing its heating and vaporization of Zn. Partial ionization of Zn atoms takes place due to collisions with plasma particles. High negative voltage pulses (7 kv/40μs/250Hz) applied to the sample holder cause the implantation of metallic zinc into Si surface, while Zn deposition happens between pulses. After annealing at 700 0C, strong UV and various visible photoluminescence bands are observed at room temperature, as well as the presence of ZnO nanoparticles. The coated surface was characterized in detail using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), atomic force microscopy (AFM) and photoluminescence (PL) spectroscopy. XRD indicated the presence of only ZnO peaks after annealing. The composition analysis by EDS revealed distinct Zn/O stoichiometry relation depending on the conditions of the process. AFM images showed the formation of columns in the nanoscale range. Topography viewed by SEM showed the formation of structures similar to cactus with nanothorns. Depth analysis performed by XPS indicated an increase of concentration of metallic Zn with increasing depth and the exclusive presence of ZnO for outer regions. PIII&D allowed to growing nanostructures of ZnO on Si without the need of a buffer layer

Hyperbolic Deformation Applied to S = 1 Spin Chains - Scaling Relation in Excitation Energy -

We investigate excitation energies of hyperbolically deformed S = 1 spin chains, which are specified by the local energy scale f_j^{~} = \cosh j \lambda, where j is the lattice index and \lambda is the deformation parameter. The elementary excitation is well described by a quasiparticle hopping model, which is also expressed in the form of hyperbolic deformation. It is possible to estimate the excitation gap \Delta in the uniform limit \lambda \rightarrow 0, by means of a finite size scaling with respect to the system size N and the deformation parameter \lambda.Comment: 5 pages, 4 figure

Energy gaps and roton structure above the nu=1/2 Laughlin state of a rotating dilute Bose-Einstein condensate

Exact diagonalization study of a rotating dilute Bose-Einstein condensate reveals that as the first vortex enters the system the degeneracy of the low-energy yrast spectrum is lifted and a large energy gap emerges. As more vortices enter with faster rotation, the energy gap decreases towards zero, but eventually the spectrum exhibits a rotonlike structure above the nu=1/2 Laughlin state without having a phonon branch despite the short-range nature of the interaction.Comment: 4 pages, 4 figures, 1 tabl

Orbital and spin chains in ZnV2O4

Our powder inelastic neutron scattering data indicate that \zvo is a system of spin chains that are three dimensionally tangled in the cubic phase above 50 K due to randomly occupied $t_{2g}$ orbitals of V$^{3+}$ ($3d^2$) ions. Below 50 K in the tetragonal phase, the chains become straight due to antiferro-orbital ordering. This is evidenced by the characteristic wave vector dependence of the magnetic structure factor that changes from symmetric to asymmetric at the cubic-to-tetragonal transition

Friedel oscillations in the one-dimensional Kondo-lattice model

The paramagnetic metallic phase of the one-dimensional Kondo lattice model is studied by the density-matrix renormalization- group method. We observe charge and spin Friedel oscillations. They reflect the long range charge-charge and spin-spin correlation functions. The observed oscillations are consistent with a Tomonaga-Luttinger liquid. From the period of the oscillations it is concluded that the Fermi surface is large, including both the conduction electrons and the localized spins, $k_F=\pi (1+n_c)/2$, where $n_c$ is the density of conduction electrons.Comment: RevTeX, 4 pages, 4 Postscript figures, to be published in Physical review

Oscillons: an encounter with dynamical chaos in 1953?

We present evidences that Ben F. Laposky (1914-2000) might have been the first person who created a family of nonlinear analog circuits that allowed him to observe chaotic attractors and other trademarks of nonlinear science as early as 1953.Comment: accepted to Chao

The dynamics of condensate shells: collective modes and expansion

We explore the physics of three-dimensional shell-shaped condensates, relevant to cold atoms in "bubble traps" and to Mott insulator-superfluid systems in optical lattices. We study the ground state of the condensate wavefunction, spherically-symmetric collective modes, and expansion properties of such a shell using a combination of analytical and numerical techniques. We find two breathing-type modes with frequencies that are distinct from that of the filled spherical condensate. Upon trap release and subsequent expansion, we find that the system displays self-interference fringes. We estimate characteristic time scales, degree of mass accumulation, three-body loss, and kinetic energy release during expansion for a typical system of Rb87