Temperature Dependent Polarized XANES Spectra for Zn-doped LSCO system

The cuprates seem to exhibit statistics, dimensionality and phase transitions in novel ways. The nature of excitations [i.e. quasiparticle or collective], spin-charge separation, stripes [static and dynamics], inhomogeneities, psuedogap, effect of impurity dopings [e.g. Zn, Ni] and any other phenomenon in these materials must be consistently understood. Zn-doped LSCO single crystal were grown by TSFZ technique. Temperature dependent Polarized XANES [near edge local structure] spectra were measured at the BL13-B1 [Photon Factory] in the Flourescence mode from 10 K to 300 K. Since both stripes and nonmagnetic Zn impurities substituted for Cu give rise to inhomogeneous charge and spin distribution it is interesting to understand the interplay of Zn impurities and stripes. To understand these points we have used Zn-doping and some of the results obtained are as follows: The spectra show a strong dependence with respect to the polarization angle, $\theta$, as is evident at any temperature by comparing the spectra where the electric field vector is parallel with ab-plane to the one where it is parallel to the c-axis. By using the XANES [temperature] difference spectra we have determined T* [experimentally we find, T* $\approx$ 160-170 K] for this sample. The XANES difference spectra shows that the changes in XANES features are larger in the ab-plane than the c-axis, this trend is expected since zinc is doped in the ab-plane at the copper site. Our study also complements the results in literature namely that zinc doping does not affect the c-axis transport.Comment: To appear in Physica C [ISS2001 Special Issue], related talk presented at ISS2001 as PC-16, 10 pages revtex and 7 pages of figures (pdf

XANES study of rare-earth valency in LRu4P12 (L = Ce and Pr)

Valency of Ce and Pr in LRu4P12 (L = Ce and Pr) was studied by L2,3-edge x-ray absorption near-edge structure (XANES) spectroscopy. The Ce-L3 XANES spectrum suggests that Ce is mainly trivalent, but the 4f state strongly hybridizes with ligand orbitals. The band gap of CeRu4P12 seems to be formed by strong hybridization of 4f electrons. Pr-L2 XANES spectra indicate that Pr exists in trivalent state over a wide range in temperature, 20 < T < 300 K. We find that the metal-insulator (MI) transition at TMI = 60 K in PrRu4P12 does not originate from Pr valence fluctuation.Comment: 4 page

Myositis associated with localized lipodystrophy: an unrecognized condition?

Lipodystrophies represent a heterogeneous group of diseases characterized by altered body fat repartition and often metabolic alterations. Here we illustrate a 20 year old male with myositis in association with localized lipodystrophy. Immunohistochemical stainings revealed a regular pattern of dystrophin, dysferlin, sarcoglycans, and theletonin. Furtermore, there was no evidence of Lamin A/C deficiency. A nearly identical clinical and histological picture has been described in three patients up to now. Although it is difficult to speculate on a causative pathophysiological mechanism at this time, it is possible that this association represents an unrecognized condition

A Parallel SSOR Preconditioner for Lattice QCD

A parallelizable SSOR preconditioning scheme for Krylov subspace iterative solvers in lattice QCD applications involving Wilson fermions is presented. In actual Hybrid Monte Carlo and quark propagator calculations it helps to reduce the number of iterations by a factor of 2 compared to conventional odd-even preconditioning. This corresponds to a gain in cpu-time of 30\% - 70\% over odd-even preconditioning.Comment: Talk presented at LATTICE96(algorithms), 3 pages, LaTeX file, 3 epsf-files include

Infrared study of spin crossover Fe-picolylamine complex

Infrared (IR) absorption spectroscopy has been used to probe the evolution of microscopic vibrational states upon the temperature- and photo-induced spin crossovers in [Fe(2-picolylamine)3]Cl2EtOH (Fe-pic). To overcome the small sizes and the strong IR absorption of the crystal samples used, an IR synchrotron radiation source and an IR microscope have been used. The obtained IR spectra of Fe-pic show large changes between high-spin and low-spin states for both the temperature- and the photo- induced spin crossovers. Although the spectra in the temperature- and photo-induced high-spin states are relatively similar to each other, they show distinct differences below 750 cm-1. This demonstrates that the photo-induced high-spin state involves microscopically different characters from those of the temperature-induced high-spin state. The results are discussed in terms of local pressure and structural deformations within the picolylamine ligands, and in terms of their possible relevance to the development of macroscopic photo-induced phase in Fe-pic.Comment: 6 pages (text) and 6 figures,submitted to J. Phys. Soc. Jp

Hadron Mass Predictions of the Valence Approximation to Lattice QCD

We evaluate the infinite volume, continuum limits of eight hadron mass ratios predicted by lattice QCD with Wilson quarks in the valence (quenched) approximation. Each predicted ratio differs from the corresponding observed value by less than 6\%.Comment: 13 pages of Latex + 2 PostScript files attached, IBM/HET 92-

New superconduting cuprates with no effective doping: T'-(La3+)2-x(RE3+)xCuO4

We report the synthesis of new superconducting cuprates T'-La2-xRExCuO4 (RE = Sm, Eu, Tb, Lu, and Y) using molecular beam epitaxy. The new superconductors have no effective dopant, at least nominally. The substitution of isovalent RE for La was essentially performed to stabilize the T' phase of La2CuO4 instead of the T phase. The maximum Tconset is ~ 25 K and Tczero is ~ 21 K. The keys to our discovery are (1) the preparation of high-crystalline-quality La-based T' films by low-temperature (~ 650C) thin film processes, and (2) more thorough removal of impurity oxygen at the apical site, which is achieved by the larger in-plane lattice constant (a0) of T'-La2-xRExCuO4 than other T'-Ln2CuO4 (Ln = Pr, Nd, Sm, Eu, Gd) with the aid of large surface-to-volume ratio of thin films.Comment: 10 pages, 5 figures (Proceedings of the 16th international symposium on superconductivity (ISS 2003), to be published in Physica C

Charge order, dielectric response and local structure of La5/3Sr1/3NiO4 system

Charge ordering, dielectric permittivity and local structure of La5/3Sr1/3NiO4 system have been explored X-ray charge scattering, complex dielectric impedance spectroscopy, and extended X-ray absorption fine structure (EXAFS) measurements, made on the same single crystal sample. The local structure measured by the temperature dependent polarized Ni K-edge EXAFS shows significant distortions in the NiO2 planes. These local distortions could be reasonable cause of high dielectric permittivity of the title system (e=100 at 5K) with the charge ordering in this system being a ferroelectric-like second order transition.Comment: 12 pages, 5 figure