14 research outputs found
Resonant impurity scattering in the s-gap state of the Fe-based superconductors
We study the impurity scattering on the s-wave superconductor, with
realistic parameters for the Fe-pnictide superconductors. Using
-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 ( ; ), 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 YNiBC 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 superconducting cuprates. After brief introduction on d-wave superconductivity we shall describe some fascinating properties of the vortex state in high 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<sup>− 1</sup>) treatment in both MTT and crystal violet assays. PK15 cells pretreated with TKE (50 μg mL<sup>− 1</sup>) 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<sup>− 1</sup>) injection. TKE (100 mg kg<sup>− 1</sup>) 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