Resonant impurity scattering in the ±\pms-gap state of the Fe-based superconductors

We study the impurity scattering on the $\pm$s-wave superconductor, with realistic parameters for the Fe-pnictide superconductors. Using $\mathcal{T}$-matrix method, generalized for the two bands, we found that impurity scattering of the unitary limit forms off-centered bound states inside of the superconducting gap, which modifies, surprisingly, the density of states (DOS) of a fully opened gap to a V-shaped one as in the case of a d-wave superconductor. This behavior provides coherent explanations to the several conflicting experimental issues of the Fe-pnictide superconductors: the V-shaped DOS but with an isotropic gap observed in the photoemission and tunneling experiments; the power law behavior of the nuclear spin-lattice relaxation rate ($1/T_1 \approx T^{\alpha}$ ; $\alpha \approx 3$), down to very low temperatures.Comment: 5 pages, 3 figures, Revisions of Figures and their captions; references update

Quasiparticle spectrum of the hybrid s+g-wave superconductors YNi_2B_2C and LuNi_2B_2C

Recent experiments on single crystals of YNi$_2$B$_2$C have revealed the presence of point nodes in the superconducting energy gap Delta(k} at k = (1,0,0), (0,1,0), (-1,0,0), and (0,-1,0). In this paper we investigate the effects of impurity scattering on the quasiparticle spectrum in the vortex state of s+g-wave superconductors, which is found to be strongly modified in the presence of disorder. In particular, a gap in the quasiparticle energy spectrum is found to open even for infinitesimal impurity scattering, giving rise to exponentially activated thermodynamic response functions, such as the specific heat, the spin susceptibility, the superfluid density, and the nuclear spin lattice relaxation. Predictions derived from this study can be verified by measurements of the angular dependent magnetospecific heat and the magnetothermal conductivity.Comment: 8 pages, RevTex, 4 figure

Quasiparticle Spectrum of d-wave Superconductors in the Mixed State

The quasiparticle spectrum of a two-dimensional d-wave superconductor in the mixed state, H_{c1} << H << H_{c2}, is studied both analytically and numerically using the linearized Bogoliubov-de Gennes equation. We consider various values of the "anisotropy ratio" v_F/v_Delta for the quasiparticle velocities at the Dirac points, and we examine the implications of symmetry. For a Bravais lattice of vortices, we find there is always an isolated energy-zero (Dirac point) at the center of the Brillouin zone, but for a non-Bravais lattice with two vortices per unit cell there is generally an energy gap. In both of these cases, the density of states should vanish at zero energy, in contrast with the semiclassical prediction of a constant density of states, though the latter may hold down to very low energies for large anisotropy ratios. This result is closely related to the particle-hole symmetry of the band structures in lattices with two vortices per unit cell. More complicated non-Bravais vortex lattice configurations with at least four vortices per unit cell can break the particle-hole symmetry of the linearized energy spectrum and lead to a finite density of states at zero energy.Comment: 16 pages, 14 figures, RevTe

Measuring anisotropic scattering in the cuprates

A simple model of anisotropic scattering in a quasi two-dimensional metal is studied. Its simplicity allows an analytic calculation of transport properties using the Boltzmann equation and relaxation time approximation. We argue that the c-axis magnetoresistance provides the key test of this model of transport. We compare this model with experiments on overdoped Tl-2201 and find reasonable agreement using only weak scattering anisotropy. We argue that optimally doped Tl-2201 should show strong angular-dependent magnetoresistance within this model and would provide a robust way of determining the in-plane scattering anisotropy in the cuprates.Comment: 12 pages, 8 figures, typset in REVTeX 4. Version 2; added references and corrected typo

Why d-wave superconductivity?

In recent years we have seen remarkable success of d-wave superconductivity in describing a variety of features of high $T_{\rm c}$ superconducting cuprates. After brief introduction on d-wave superconductivity we shall describe some fascinating properties of the vortex state in high $T_{\rm c}$ cuprates

<i>Trichosanthes kirilowii</i> ameliorates cisplatin-induced nephrotoxicity in both <i>in vitro</i> and <i>in vivo</i>

<div><p>The aim of this study was to explore the protective effects of <i>Trichosanthes kirilowii</i> ethanol extract (TKE) against cisplatin-induced acute renal failure (ARF). In the <i>in vitro</i> study, TKE-pretreated porcine kidney cells (PK15) exhibited enhanced cell viability after cisplatin (15 μg mL^− 1) treatment in both MTT and crystal violet assays. PK15 cells pretreated with TKE (50 μg mL^− 1) exhibited increased glutathione content, decreased reactive oxygen species production and ameliorated p53 expression. <i>In vivo</i> study, rats were administered with TKE for 4 weeks before cisplatin (5 mg kg^− 1) injection. TKE (100 mg kg^− 1) decreased blood urea nitrogen and creatinine levels by 24% and 47%, respectively, in comparison with cisplatin-alone group. In addition, TKE pretreatment ameliorated cisplatin-induced oxidative stress, as evidenced by increased antioxidative enzyme levels and decreased lipid peroxidation levels. Moreover, TKE pretreatment reduced histopathological alterations in the kidney with decreased apoptotic cells. Taken together, TKE might be beneficial in treating cisplatin-induced ARF.</p></div