Multiple Superconducting Phases in New Heavy Fermion Superconductor PrOs4Sb12

The superconducting gap structure of recently discovered heavy fermion superconductor PrOs4Sb12 was investigated by using thermal transport measurements in magnetic field rotated relative to the crystal axes. We demonstrate that a novel change in the symmetry of the superconducting gap function occurs deep inside the superconducting state, giving a clear indication of the presence of two distinct superconducting phases with twofold and fourfold symmetries. We infer that the gap functions in both phases have a point node singularity, in contrast to the familiar line node singularity observed in almost all unconventional superconductors.Comment: 4 Pages, 4 Figure

In situ SR-XPS observation of Ni-assisted low-temperature formation of epitaxial graphene on 3C-SiC/Si

Low-temperature (~1073 K) formation of graphene was performed on Si substrates by using an ultrathin (2 nm) N

Exciton Mediated Superconductivity in PrOs4Sb12

The most important character of the exotic superconductor PrOs4Sb12 is the existence of low-lying excitations (excitons) with a finite energy gap and it appears as the magnetic field-induced order above 4.5 T. We focus on the a_u conduction band, which hybridizes with a Pr 4f^2 state strongly, coupled to the excitons. It results in an attractive interaction between the conduction electrons. The symmetry of the superconducting order parameter is determined by dispersion relation of the exciton. For the bcc system PrOs4Sb12, a d-wave state [kx ky + omega ky kz + omega^2 kz kx, omega=exp(pm i 2 pi/3)] is stabilized with broken time reversal symmetry.Comment: 4 page

スパイラル CT オ モチイタ ガクカンセツ ノ サンジゲン ヒョウカホウ

Three-dimensional (3-D) image reconstructed from Computed Tomography (CT) data is an ef>cient method to evaluate temporomandibular joint (TMJ) morphologically. Even the 3-D image reconstructed from spiral CT data has some distortion, typically along to the table feed direction, very few studies were reported about accuracy of reconstructed 3-D image size. The purpose of this research was to evaluate the distortion on 3-D image reconstructed with spiral CT (Somatom Plas4, Siemens Co, Germany) quantitatively. We used three imaging targets, eight ceramic balls placed at corners of cubic frame, a calibration cube that has the CT value nearly equal to cortex bone of human dried mandibular head. We evaluated relation between a threshold level of CT image processing and reconstructed 3-D image size with a custom-made computer program. CT data of ceramic balls clari>ed changes of the reconstructed image, -0.215mm for table feed direction and less than ±0.006mm for the other directions. The calibration cube was used for the arrangement of optimal scanning condition (reconstruction mode, collimation, reconstitution interval) and evaluation of reconstructed image size. The distortion of the image was +0.207mm for table feed direction and less than +0.029mm for the other directions. Changes of dried skull TMJ image reconstructed with the optimal scanning condition were -1.463mm for lateral direction of the condylar head, -0.956mm for back and forth direction and -0.580mm for table feed direction. Results of this research suggested that the level of the 3-D image distortion was mostly affected with the scanning condition. And the size of 3-D image was susceptible to the threshold level of CT image processing. Consequently, we think that the standardization of scanning condition should be concerned for the quantitative evaluation of 3-D TMJ image using CT data

Multiphase Superconductivity in Skutterudite PrOs_4Sb_12

We propose a model of nodal order parameters for the superconducting A and B - phase of skutterudite PrOs_4Sb_{12} and discuss the associated angular dependent magnetothermal conductivity at low temperatures. The model for the hybrid gap functions \De(k) containing an s- and g- wave parts is consistent with recent thermal conductivity experiments in PrOs_4Sb_12. In particular the model accounts for the data on polar an azimuthal field angle dependence of \kappa_zz(\theta,\phi). The low temperature behaviour of thermodynamic properties in zero field is also presented. We show that the effect of impurity scattering on a nodal hybrid gap function immediately leads the opening of a gap and related exponential behaviour of low temperature specific heat and thermal conductivity which is very different from d- wave superconductors.Comment: 7 pages, 3 figure

Quantum Oscillation Studies of the Fermi Surface of LaFePO

We review recent experimental measurements of the Fermi surface of the iron-pnictide superconductor LaFePO using quantum oscillation techniques. These studies show that the Fermi surface topology is close to that predicted by first principles density functional theory calculations, consisting of quasi-two-dimensional electron-like and hole-like sheets. The total volume of the two hole sheets is almost equal to that of the two electron sheets, and the hole and electron Fermi surface sheets are close to a nesting condition. No evidence for the predicted three dimensional pocket arising from the Fe $d_{z^2}$ band is found. Measurements of the effective mass suggest a renormalisation of around two, close to the value for the overall band renormalisation found in recent angle resolved photoemission measurements.Comment: Submitted to Physica C special issue on iron-pnictide superconductor

The ASTRO-H X-ray Observatory

The joint JAXA/NASA ASTRO-H mission is the sixth in a series of highly successful X-ray missions initiated by the Institute of Space and Astronautical Science (ISAS). ASTRO-H will investigate the physics of the high-energy universe via a suite of four instruments, covering a very wide energy range, from 0.3 keV to 600 keV. These instruments include a high-resolution, high-throughput spectrometer sensitive over 0.3-2 keV with high spectral resolution of Delta E < 7 eV, enabled by a micro-calorimeter array located in the focal plane of thin-foil X-ray optics; hard X-ray imaging spectrometers covering 5-80 keV, located in the focal plane of multilayer-coated, focusing hard X-ray mirrors; a wide-field imaging spectrometer sensitive over 0.4-12 keV, with an X-ray CCD camera in the focal plane of a soft X-ray telescope; and a non-focusing Compton-camera type soft gamma-ray detector, sensitive in the 40-600 keV band. The simultaneous broad bandpass, coupled with high spectral resolution, will enable the pursuit of a wide variety of important science themes.Comment: 22 pages, 17 figures, Proceedings of the SPIE Astronomical Instrumentation "Space Telescopes and Instrumentation 2012: Ultraviolet to Gamma Ray

In Situ SR-XPS Observation of Ni-Assisted Low-Temperature Formation of Epitaxial Graphene on 3C-SiC/Si

Low-temperature (~1073 K) formation of graphene was performed on Si substrates by using an ultrathin (2 nm) Ni layer deposited on a 3C-SiC thin film heteroepitaxially grown on a Si substrate. Angle-resolved, synchrotron-radiation X-ray photoemission spectroscopy (SR-XPS) results show that the stacking order is, from the surface to the bulk, Ni carbides(Ni(3)C/NiC(x))/graphene/Ni/Ni silicides (Ni(2)Si/NiSi)/3C-SiC/Si. In situ SR-XPS during the graphitization annealing clarified that graphene is formed during the cooling stage. We conclude that Ni silicide and Ni carbide formation play an essential role in the formation of graphene