Interplay of Kondo and superconducting correlations in the nonequilibrium Andreev transport through a quantum dot

Using the modified perturbation theory, we theoretically study the nonequilibrium Andreev transport through a quantum dot coupled to normal and superconducting leads (N-QD-S), which is strongly influenced by the Kondo and superconducting correlations. From the numerical calculation, we find that the renormalized couplings between the leads and the dot in the equilibrium states characterize the peak formation in the nonequilibrium differential conductance. In particular, in the Kondo regime, the enhancement of the Andreev transport via a Kondo resonance occurs in the differential conductance at a finite bias voltage, leading to an anomalous peak whose position is given by the renormalized parameters. In addition to the peak, we show that the energy levels of the Andreev bound states give rise to other peaks in the differential conductance in the strongly correlated N-QD-S system. All these features of the nonequilibrium transport are consistent with those in the recent experimental results [R. S. Deacon {\it et al.}, Phys. Rev. Lett. {\bf 104}, 076805 (2010); Phys. Rev. B {\bf 81}, 12308 (2010)]. We also find that the interplay of the Kondo and superconducting correlations induces an intriguing pinning effect of the Andreev resonances to the Fermi level and its counter position.Comment: 22 pages, 23 figure

A Search for H-alpha Absorption in the Exosphere of the Transiting Extrasolar Planet HD 209458b

There is evidence that the transiting planet HD 209458b has a large exosphere of neutral hydrogen, based on a 15% decrement in Lyman-alpha flux that was observed by Vidal-Madjar et al. during transits. Here we report upper limits on H-alpha absorption by the exosphere. The results are based on optical spectra of the parent star obtained with the Subaru High Dispersion Spectrograph. Comparison of the spectra taken inside and outside of transit reveals no exospheric H-alpha signal greater than 0.1% within a 5.1A band (chosen to have the same Delta_lambda/lambda as the 15% Ly-alpha absorption). The corresponding limit on the column density of n=2 neutral hydrogen is N_2 <~ 10^9 cm^{-2}. This limit constrains proposed models involving a hot (~10^4 K) and hydrodynamically escaping exosphere.Comment: To appear in PASJ [9 pages, 5 figures]. Minor corrections to match published versio

Subaru HDS Transmission Spectroscopy of the Transiting Extrasolar Planet HD 209458b

We have searched for absorption in several common atomic species due to the atmosphere or exosphere of the transiting extrasolar planet HD 209458b, using high precision optical spectra obtained with the Subaru High Dispersion Spectrograph (HDS). Previously we reported an upper limit on H alpha absorption of 0.1% (3 sigma) within a 5.1\AA band. Using the same procedure, we now report upper limits on absorption due to the optical transitions of Na D, Li, H alpha, H beta, H gamma, Fe, and Ca. The 3 sigma upper limit for each transition is approximately 1% within a 0.3\AA band (the core of the line), and a few tenths of a per cent within a 2\AA band (the full line width). The wide-band results are close to the expected limit due to photon-counting (Poisson) statistics, although in the narrow-band case we have encountered unexplained systematic errors at a few times the Poisson level. These results are consistent with all previously reported detections and upper limits, but are significantly more sensitive.Comment: 10 pages, 9 figure

Fabrication of Chitin Nanofiber-Reinforced PLA Nanocomposites by an Environmentally Friendly Process

Polylactic acid (PLA) reinforced with chitin nanofibers was produced from a mixture of a colloidal suspension of PLA particles with chitin nanofiber suspension. The dispersion medium was solely water, which was removed by filtration and drying. Nanocomposites were obtained by compression molding of the filtrates. Static tensile test and dynamic mechanical analysis were performed to evaluate the reinforcement as a function of nanofiber content. Chitin nanofibers delivered reinforcement similar to cellulose nanofibers, being especially effective at up to 70 wt% fiber load. The ultimate tensile modulus and strength reached 7.7 GPa and 110 MPa, respectively, at a nanofiber content of 70 wt%

3-D eddy current analysis in moving conductors of permanent magnet type retarders using moving coordinate system

A 3-D DC steady state eddy current analysis of a permanent magnet type retarder which rotates at high speed is carried out using a moving coordinate system. The method of DC steady state analysis using a moving coordinate system is described. The calculated results, braking torque etc., are compared with measured ones</p