Abrupt enhancement of non-centrosymmetry and appearance of the spin-triplet superconducting state in Li_2(Pd_{1-x}Pt_{x})_3B beyond x=0.8

We report synthesis, ^{195}Pt, ^{11}B and ^{7}Li NMR measurements, and first-principle band calculation for non-centrosymmetric superconductors Li_{2}(Pd_{1-x}Pt_{x})_{3}B (x=0, 0.2, 0.5, 0.8, 0.84, 0.9 and 1). For 0 \leq x \leq 0.8, the spin-lattice relaxation rate 1/T_1 shows a clear coherence peak just below T_c, decreasing exponentially at low temperature, and the Knight shift ^{195}K decreases below T_c. For x=0.9 and 1.0, in contrast, 1/T_1 shows no coherence peak but a T^3 variation and ^{195}K remains unchanged across T_c. These results indicate that the superconducting state changes drastically from a spin-singlet dominant to a spin-triplet dominant state at x=0.8. We find that the distortion of B(Pt,Pd)_6 increases abruptly above x=0.8, which leads to an abrupt enhancement of the asymmetric spin-orbit coupling as confirmed by band calculation. Such local structure distortion that enhances the extent of inversion-symmetry breaking is primarily responsible for the pairing symmetry evolution. The insight obtained here provides a new guideline for searching new NCS superconductors with large spin-triplet component.Comment: to appear in Phys. Rev. B (Rapid Commun.); contact the authors for high-resolution figure

Strange magnification pattern in the large separation lens SDSS J1004+4112 from optical to X-rays

We present simultaneous XMM-Newton UV and X-ray observations of the quadruply lensed quasar SDSS J1004+4112 (RBS 825). Simultaneously with the XMM-Newton observations we also performed integral field spectroscopy on the two closest lens images A and B using the Calar Alto PMAS spectrograph. In X-rays the widely spaced components C and D are clearly resolved, while the closer pair of images A and B is marginally resolved in the XMM-EPIC images. The integrated X-ray flux of the system has decreased by a factor of 6 since it was observed in the ROSAT All Sky Survey in 1990, while the X-ray spectrum became much harder with the power law index evolving from Gamma=-2.3 to -1.86. By deblending the X-ray images of the lensed QSO we find that the X-ray flux ratios between the lens images A and B are significantly different from the simultaneously obtained UV ratios and previously measured optical flux ratios. Our optical spectrum of lens image A shows an enhancement in the blue emission line wings, which has been observed in previous epochs as a transient feature. We propose a scenario where intrinsic UV and X-ray variability gives rise to line variations which are selectively magnified in image A by microlensing. The extended emission of the lensing cluster of galaxies is clearly detected in the EPIC images, we measure a 0.5-2.0 keV luminosity of 1.4 E44 erg/s. Based on the cluster X-ray properties, we estimate a mass of 2-6 E14 solar masses.Comment: 11 pages, 10 figures, accepted for publication in Astronomy & Astrophysic

Probing the extended non-Fermi liquid regimes of MnSi and Fe

Recent studies show that the non-Fermi liquid (NFL) behavior of MnSi and Fe spans over an unexpectedly broad pressure range, between the critical pressure p_c and around 2p_c. In order to determine the extension of their NFL regions, we analyze the evolution of the resistivity rho(T) A(p)T^n at higher pressures. We find that in MnSi the n=3/2 exponent holds below 4.8 GPa=3 p_c, but it increases above that pressure. At 7.2 GPa we observe the low temperature Fermi liquid exponent n=2 whereas for T>1.5 K, n=5/3. Our measurements in Fe show that the NFL behavior rho T^{5/3} extends at least up to 30.5 GPa, above the entire superconducting (SC) region. In the studied pressure range, the onset of the SC transition reduces by a factor 10 down to T_c^onset(30.5 GPa)=0.23 K, while the A-coefficient diminishes monotonically by around 50%.Comment: 2 pages, 2 figures, Proceedings SCES 200

The Sloan Digital Sky Survey Quasar Lens Search. V. Final Catalog from the Seventh Data Release

We present the final statistical sample of lensed quasars from the Sloan Digital Sky Survey (SDSS) Quasar Lens Search (SQLS). The well-defined statistical lens sample consists of 26 lensed quasars brighter than i=19.1 and in the redshift range of 0.6<z<2.2 selected from 50,836 spectroscopically confirmed quasars in the SDSS Data Release 7 (DR7), where we restrict the image separation range to 1"<\theta<20" and the i-band magnitude differences in two image lenses to be smaller than 1.25 mag. The SDSS DR7 quasar catalog also contains 36 additional lenses identified with various techniques. In addition to these lensed quasars, we have identified 81 pairs of quasars from follow-up spectroscopy, 26 of which are physically associated binary quasars. The statistical lens sample covers a wide range of image separations, redshifts, and magnitudes, and therefore is suitable for systematic studies of cosmological parameters and surveys of the structure and evolution of galaxies and quasars.Comment: 42 pages, 2 figures, 6 tables, accepted for publication in AJ; see http://www-utap.phys.s.u-tokyo.ac.jp/~sdss/sqls/ for supplemental informatio

Phonon anomaly and anisotropic superconducting gap in non-centrosymmetric Li2(Pd1-xPtx)3B

We report the systematic investigation of the specific heat of the noncentrosymmetric supercon- ductor Li2(Pd1-xPtx)3B as a function of x. There is a large deviation of the phononic specific heat from the conventional Debye specific heat for Pt-rich samples. In contrast with the fully-gapped con- ventional behavior for small x, a power-law temperature dependence of the electronic specific heat is observed even at x = 0.5. This results manifest a strongly-anisotropic or nodal superconducting gap even at x = 0.5 and a nodal superconducting gap for x >~ 0.9.Comment: 4 pages, 4 figure

The Sloan Digital Sky Survey Quasar Lens Search. IV. Statistical Lens Sample from the Fifth Data Release

We present the second report of our systematic search for strongly lensed quasars from the data of the Sloan Digital Sky Survey (SDSS). From extensive follow-up observations of 136 candidate objects, we find 36 lenses in the full sample of 77,429 spectroscopically confirmed quasars in the SDSS Data Release 5. We then define a complete sample of 19 lenses, including 11 from our previous search in the SDSS Data Release 3, from the sample of 36,287 quasars with i<19.1 in the redshift range 0.6<z<2.2, where we require the lenses to have image separations of 1"<\theta<20" and i-band magnitude differences between the two images smaller than 1.25 mag. Among the 19 lensed quasars, 3 have quadruple-image configurations, while the remaining 16 show double images. This lens sample constrains the cosmological constant to be \Omega_\Lambda=0.84^{+0.06}_{-0.08}(stat.)^{+0.09}_{-0.07}(syst.) assuming a flat universe, which is in good agreement with other cosmological observations. We also report the discoveries of 7 binary quasars with separations ranging from 1.1" to 16.6", which are identified in the course of our lens survey. This study concludes the construction of our statistical lens sample in the full SDSS-I data set.Comment: 37 pages, 2 figures and 5 tables, accepted to A

The Sloan Digital Sky Survey Quasar Lens Search. VI. Constraints on Dark Energy and the Evolution of Massive Galaxies

We present a statistical analysis of the final lens sample from the Sloan Digital Sky Survey Quasar Lens Search (SQLS). The number distribution of a complete subsample of 19 lensed quasars selected from 50,836 source quasars is compared with theoretical expectations, with particular attention to the selection function. Assuming that the velocity function of galaxies does not evolve with redshift, the SQLS sample constrains the cosmological constant to \Omega_\Lambda=0.79^{+0.06}_{-0.07}(stat.)^{+0.06}_{-0.06}(syst.) for a flat universe. The dark energy equation of state is found to be consistent with w=-1 when the SQLS is combined with constraints from baryon acoustic oscillation (BAO) measurements or results from the Wilkinson Microwave Anisotropy Probe (WMAP). We also obtain simultaneous constraints on cosmological parameters and redshift evolution of the galaxy velocity function, finding no evidence for redshift evolution at z<1 in any combinations of constraints. For instance, number density evolution quantified as \nu_n=d\ln\phi_*/d\ln(1+z) and the velocity dispersion evolution \nu_\sigma=d\ln\sigma_*/d\ln(1+z) are constrained to \nu_n=1.06^{+1.36}_{-1.39}(stat.)^{+0.33}_{-0.64}(syst.) and \nu_\sigma=-0.05^{+0.19}_{-0.16}(stat.)^{+0.03}_{-0.03}(syst.) respectively when the SQLS result is combined with BAO and WMAP for flat models with a cosmological constant. We find that a significant amount of dark energy is preferred even after fully marginalizing over the galaxy evolution parameters. Thus the statistics of lensed quasars robustly confirm the accelerated cosmic expansion.Comment: 44 pages, 12 figures, 4 tables, accepted for publication in A

Superconducting gap and pair breaking in CeRu2 studied by point contacts

The superconducting gap in a CeRu$_{2}$ single crystal is investigated by point contacts. BCS-like behavior of the gap $\Delta$ in the temperature range below T$_{c}^{*}<$T$_{c}$, where T$_{c}$ is the critical temperature, is established, indicating the presence of a gapless superconductivity region (between T$_{c}^{*}$ and T$_{c}$). The pair-breaking effect of paramagnetic impurities, supposedly Ce ions, is taken into consideration using the Scalski-Betbeder-Matibet-Weiss approach based on Abrikosov-Gorkov theory. It allows us to recalculate the superconducting order parameter $\Delta ^{\alpha}$ (in the presence of paramagnetic impurities) and the gap $\Delta ^{P}$ (in the pure case) for the single crystal and for the previously studied polycrystalline CeRu$_{2}$. The value 2$\Delta^{P}$(0)$\approx$2 meV, with 2$\Delta ^{P}$(0)$/$k$_{B}$T$_{c} \approx$3.75, is found in both cases, indicating that CeRu$_{2}$ is a ``moderate'' strong-coupling superconductor.Comment: 4 pages incl. 3 figs., publ. in Fiz. Nizk. Temp. (http://fnte.ilt.kharkov.ua/list.html

Two New Gravitationally Lensed Double Quasars from the Sloan Digital Sky Survey

We report the discoveries of the two-image gravitationally lensed quasars, SDSS J0746+4403 and SDSS J1406+6126, selected from the Sloan Digital Sky Survey (SDSS). SDSS J0746+4403, which will be included in our lens sample for statistics and cosmology, has a source redshift of z_s=2.00, an estimated lens redshift of z_l~0.3, and an image separation of 1.08". SDSS J1406+6126 has a source redshift of z_s=2.13, a spectroscopically measured lens redshift of z_l=0.27, and an image separation of 1.98". We find that the two quasar images of SDSS J1406+6126 have different intervening MgII absorption strengths, which are suggestive of large variations of absorbers on kpc scales. The positions and fluxes of both the lensed quasar systems are easily reproduced by simple mass models with reasonable parameter values. These objects bring to 18 the number of lensed quasars that have been discovered from the SDSS data.Comment: 25 pages, 6 figures, The Astronomical Journal accepte