Detailed Topography of the Fermi Surface of Sr2RuO4

We apply a novel analysis of the field and angle dependence of the quantum-oscillatory amplitudes in the unconventional superconductor Sr2RuO4 to map its Fermi surface in unprecedented detail, and to obtain previously inaccessible information on the band dispersion. The three quasi-2D Fermi surface sheets not only exhibit very diverse magnitudes of warping, but also entirely different dominant warping symmetries. We use the data to reassess recent results on c-axis transport phenomena.Comment: REVTeX, 4 page

Thermal Conductivity near H_c2 for spin-triplet superconducting States with line nodes in Sr_2RuO_4

We calculate the thermal conductivity kappa in magnetic fields near H_c2 for spin-triplet superconducting states with line nodes vertical and horizontal relative to the RuO_2-planes. The method for calculating the Green's functions takes into account the spatial variation of the order parameter and superconducting flow for the Abrikosov vortex lattice. For in-plane magnetic field we obtain variations of the in-plane kappa with two-fold symmetry as a function of rotation angle where the minima and maxima occur for field directions parallel and perpendicular to the heat flow. The amplitude of the variation decreases with increasing impurity scattering and temperature. At higher temperatures the minima and maxima of the variation are interchanged. Since the results for vertical and horizontal line nodes are almost the same we cannot say which of the two pairing models is more compatible with recent measurements of kappa in Sr_2RuO_4. The observed four-fold modulation of kappa in YBa_2Cu_3O_(7-\delta) is obtained for d-wave pairing by taking into account the particular shape of the Fermi surface and the finite temperature effect. The results for kappa for the f-wave pairing state with horizontal line nodes disagree in some respects with the measurements on UPt_3.Comment: 8 pages, 6 figures. To be published in Phys. Rev.

Possible unconventional superconductivity in iron-based layered compound LaFePO: Study of heat capacity

Heat capacity measurements were performed on recently discovered iron based layered superconductors, non doped LaFePO and fluorine doped LaFePO. A relatively large electronic heat capacity coefficient and a small normalized heat capacity jump at Tc = 3.3 K were observed in LaFePO. LaFePO0.94F0.06 had a smaller electronic heat capacity coefficient and a larger normalized heat capacity jump at Tc = 5.8 K. These values indicate that these compounds have strong electron electron correlation and magnetic spin fluctuation, which are the signatures of unconventional superconductivity mediated by spin fluctuation.Comment: 15 Pages, 3 Figure

Single-crystal growth and dependences on the hole concentration and magnetic field of the magnetic ground state in the edge-sharing CuO2_2 chain system Ca2+x_{2+x}Y2−x_{2-x}Cu5_5O10_{10}

We have succeeded in growing large-size single-crystals of Ca$_{2+x}$Y$_{2-x}$Cu$_5$O$_{10}$ with $0 \le x \le 1.67$ and measured the magnetic susceptibility, specific heat and magnetization curve, in order to study the magnetic ground state in the edge-sharing CuO$_2$ chain as a function of hole concentration and magnetic field. In $0 \le x \le 1.3$, it has been found that an antiferromagnetically ordered phase with the magnetic easy axis along the b-axis is stabilized and that a spin-flop transition occurs by the application of magnetic fields parallel to the b-axis. The antiferromagnetic transition temperature decreases with increasing $x$ and disappears around $x =$ 1.4. Alternatively, a spin-glass phase appears around $x = 1.5$. At $x = 1.67$ where the hole concentration is $\sim$ 1/3 per Cu, it appears that a spin-gap state is formed owing to the formation of spin-singlet pairs. No sign of the coexistence of an antiferromagnetically ordered state and a spin-gap one suggested in Ca$_{1-x}$CuO$_2$ has been found in Ca$_{2+x}$Y$_{2-x}$Cu$_5$O$_{10}$.Comment: 13 pages, 12 figures, 1 tabl

Ultrasonic attenuation in magnetic fields for superconducting states with line nodes in Sr2RuO4

We calculate the ultrasonic attenuation in magnetic fields for superconducting states with line nodes vertical or horizontal relative to the RuO_2 planes. This theory, which is valid for fields near Hc2 and not too low temperatures, takes into account the effects of supercurrent flow and Andreev scattering by the Abrikosov vortex lattice. For rotating in-plane field H(theta) the attenuation alpha(theta)exhibits variations of fourfold symmetry in the rotation angle theta. In the case of vertical nodes, the transverse T100 sound mode yields the weakest(linear)H and T dependence of alpha, while the longitudinal L100 mode yields a stronger (quadratic) H and T dependence. This is in strong contrast to the case of horizontal line nodes where alpha is the same for the T100 and L100 modes (apart from a shift of pi/4 in field direction) and is roughly a quadratic function of H and T. Thus we conclude that measurements of alpha in in-plane magnetic fields for different in-plane sound modes may be an important tool for probing the nodal structure of the gap in Sr_2RuO_4.Comment: 5 pages, 6 figures, replaced in non-preprint form, to appear in Phys. Rev.

Gap Structure of the Spin-Triplet Superconductor Sr2RuO4 Determined from the Field-Orientation Dependence of Specific Heat

We report the field-orientation dependent specific heat of the spin-triplet superconductor Sr2RuO4 under the magnetic field aligned parallel to the RuO2 planes with high accuracy. Below about 0.3 K, striking 4-fold oscillations of the density of states reflecting the superconducting gap structure have been resolved for the first time. We also obtained strong evidence of multi-band superconductivity and concluded that the superconducting gap in the active band, responsible for the superconducting instability, is modulated with a minimum along the [100] direction.Comment: 4 pages, 4 figure

The difference in congenital cholesteatoma CT findings based on the type of mass

AbstractObjectiveA retrospective assessment of differences in congenital cholesteatoma CT findings with a focus on type of cholesteatoma mass.Materials and methodsThe medical records and CT images of 14 patients with congenital cholesteatomas in the middle ear who underwent surgery at our institution between January 2009 and July 2014 were reviewed. Cholesteatomas were classified as closed type, open type, or mixed type based on intraoperative findings. The CT findings including cholesteatoma size, location, and shape were retrospectively reviewed.ResultsEight patients had closed type cholesteatomas, four had mixed type, and two had open type. The mean size of all cholesteatomas was 5.1mm. None of the cholesteatoma types indicated a tendency towards a certain location. The round shape was observed more frequently in closed type cholesteatomas than in other types (closed: 5/8; mixed: 1/4; open: 0/2). Two large closed type cholseteatomas and two mixed type cholesteatomas exhibited a constricted shape. Both of the open type cholesteatomas displayed an irregular shape.ConclusionSmall closed type congenital cholesteatomas were typically observed as round shaped lesions, but large closed type cholesteatomas and other type cholesteatomas tended to display shapes other than round

Mechanism of spin-triplet superconductivity in Sr2RuO4

The unique Fermi surfaces and their nesting properties of Sr2RuO4 are considered. The existence of unconventional superconductivity is shown microscopically, for the first time, from the magnetic interactions (due to nesting) and the phonon-mediated interactions. The odd-parity superconductivity is favored in the $\alpha$ and $\beta$ sheets of the Fermi surface, and the various superconductivities are possible in the $\gamma$ sheet. There are a number of possible odd-parity gaps, which include the gaps with nodes, the breaking of time-reversal symmetry and $\vec{d}\parallel \hat{z}$.Comment: 4 pages, 3 figure

Tunneling current in triplet f-wave superconductors with horizontal lines of nodes

We calculate the tunneling conductance spectra of a normal-metal/insulator/triplet superconductor using the Blonder-Tinkham-Klapwijk (BTK) formulation. Possible states for the superconductor are considered with horizontal lines of nodes, breaking the time reversal symmetry. These results would be useful to discriminate between pairing states in superonductor Sr$_2$RuO$_4$ and also in UPt$_3$.Comment: 12 pages, 7 figure