58 research outputs found
Weak inter-band coupling in MgB: a specific heat analysis
The superconducting state of MgB is investigated by specific
heat measurements in detail. The specific heat in the normal state is analyzed
using a recently developed computer code. This allows for an extraction of the
electronic specific heat in the superconducting state with high accuracy and a
fair determination of the main lattice features. One of the two investigated
samples shows a hump in the specific heat at low temperatures within the
superconducting state, accompanied by an unusual low value of the small gap,
, pointing to a very weak inter-band coupling. This
sample allows for a detailed analysis of the contribution from the -band
to the electronic specific heat in the superconducting state. Therefore the
usual analysis method is modified, to include the individual conservation of
entropy of both bands. From analyzing the deviation function of
MgB, the theoretically predicted weak inter-band coupling scenario is
confirmed.Comment: major revision
Comment on ``Reduction of static field equation of Faddeev model to first order PDE'', arXiv:0707.2207
The authors of the article Phys. Lett. B 652 (2007) 384, (arXiv:0707.2207),
propose an interesting method to solve the Faddeev model by reducing it to a
set of first order PDEs. They first construct a vectorial quantity , depending on the original field and its first derivatives, in terms of which
the field equations reduce to a linear first order equation. Then they find
vectors and which identically obey this linear
first order equation. The last step consists in the identification of the with the original as a function of the original field.
Unfortunately, the derivation of this last step in the paper cited above
contains an error which invalidates most of its results
Surprises in the doping dependence of the Fermi surface in Bi(Pb)-2212
A detailed and systematic ARPES investigation of the doping-dependence of the
normal state Fermi surface (FS) of modulation-free (Pb,Bi)-2212 is presented.
The FS does not change in topology away from hole-like at any stage. The data
reveal, in addition, a number of surprises. Firstly the FS area does not follow
the usual curve describing Tc vs x for the hole doped cuprates, but is
down-shifted in doping by ca. 0.05 holes per Cu site, indicating either the
break-down of Luttinger's theorem or the consequences of a significant bi-layer
splitting of the FS. Secondly, the strong k-dependence of the FS width is shown
to be doping independent. Finally, the relative strength of the shadow FS has a
doping dependence mirroring that of Tc.Comment: 5 pages, 4 figures (revtex
Point-contact spectroscopy of the antiferromagnetic superconductor HoNi2B2C in the normal and superconducting state
Point-contact (PC) spectroscopy measurements on antiferromagnetic (AF)
(T_N=5.2K) HoNi2B2C single crystals in the normal and two different
superconducting (SC) states (T_c=8.5K and T_c^*=5.6K<T_c, with 2\Delta/kT_c^*=3.9. The strong coupling
Eliashberg analysis of the low-temperature SC phase with T_c^*=5.6K =T_N,
coexisting with the commensurate AF structure, suggests a sizable value of the
EPI constant \lambda_s=0.93. We also provide strong support for the recently
proposed by us ''Fermi surface (FS) separation'' scenario for the coexistence
of magnetism and superconductivity in magnetic borocarbides, namely, that the
superconductivity in the commensurate AF phase survives at a special (nearly
isotropic) FS sheet without an admixture of Ho 5d states. Above T_c^* the SC
features in the PC characteristics are strongly suppressed pointing to a
specific weakened SC state between T_c* and T_c.Comment: 11 pages, 8 figs, to be published in PRB, Vol.75, Iss.2
Evidence for strong electron-phonon coupling in MgCNi_3
The title compound is investigated by specific heat measurements in the
normal and superconducting state supplemented by upper critical field
transport, susceptibility and magnetization measurements. From a detailed
analysis including also full potential electronic structure calculations for
the Fermi surface sheets, Fermi velocities and partial densities of states the
presence of both strong electron-phonon interactions and considerable
pair-breaking has been revealed. The specific heat and the upper critical field
data can be described to first approximation by an effective single band model
close to the clean limit derived from a strongly coupled predominant hole
subsystem with small Fermi velocities. However, in order to account also for
Hall-conductivity and thermopower data in the literature, an effective general
two-band model is proposed. This two-band model provides a flexible enough
frame to describe consistently all available data within a scenario of phonon
mediated s-wave superconductivity somewhat suppressed by sizeable
electron-paramagnon or electron-electron Coulomb interaction. For quantitative
details the relevance of soft phonons and of a van Hove type singularity in the
electronic density of states near the Fermi energy is suggested.Comment: 21 pages, 26 figures (high quality version of figures 2,11 available
at http://www.ifw-dresden.de/imw/21/coworker/waelte.priv/
Texture induced anisotropy of critical current of MgB<sub>2</sub>/Fe rolled superconducting tapes studied by synchrotron x-ray diffraction
Fear of Online Consumer Identity Theft: Cross-country Application and Short Scale Development
Rib cartilage autograft in Augmentation rhinoseptoplasty
Rhinoseptoplasty may require the addition of material to augment the nose. Augmentation is necessary for both aesthetic and functional indications. Functional reasons for augmentation include providing structural support for areas deficient of material, such as the upper or lower lateral cartilages. Typically, augmentation rhinoplasty is performed to increase the projection of the nasal dorsum on the profile view. The nasal tip may also be augmented. In addition, grafts may be placed to camouflage irregularities of the bony dorsum and of the upper or lower lateral cartilages. Augmentation may also be required for aesthetic reasons.----------------------------------------Риносептопластиката в много случаи изисква допълнителни материали (импланти) за уголемяване на външния нос. Често увеличаването на носа е необходимо както от естетично, така също и от функционално естество. Функционалните основания за уголемяваща риносептопластика са свързани с осигуряването на структурна поддръжка вследствие недостатъчен или липсващ септум и триангуларни хрущяли. Обикновено уголемяващата риносептопластика се прилага за увеличение проекцията и профила на носния дорзум и\ или носния връх. В същото време би могла да се използва и за корекция на неравности по костните и хрущялни структури. Увеличаващата ринопластика би могла да се използва и по чисто естетични причини
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