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Journal ArticleDOI

Remark on the effect of varying density of states in superconducting A-15 compounds

01 Mar 1982-Solid State Communications (Pergamon)-Vol. 41, Iss: 10, pp 777-779
TL;DR: In this paper, it was pointed out that a recently claimed result regarding the removal of sharp structure in the electronic density of states N (E ) of A-15 superconducting compounds at T ∼ T c was in fact, shown earlier by one of the present authors (M.N.M.).
About: This article is published in Solid State Communications.The article was published on 1982-03-01. It has received None citations till now. The article focuses on the topics: Density of states & Fermi level.
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Journal ArticleDOI
TL;DR: The theory of the structural properties of the A-15 compounds is developed starting with a picture of linear chains of atoms of the transition elements in this paper, and the twofold-degenerate electronic term is shifted and split when interchain transfer is taken into account.
Abstract: The theory of the structural properties of the A-15 compounds is developed starting with a picture of linear chains of atoms of the transition elements. The twofold-degenerate electronic term is shifted and split when interchain transfer is taken into account. A fine structure of the electronic spectrum and the density of states are examined. The latter has two singularities at the Fermi level corresponding to an estimated variation of the composition by several percent. Among the samples showing the martensitic transformation, one of these singularities is supposed to be responsible for the peculiar properties observed, and a theory of the transformation from the cubic to the tetragonal phase is suggested. The temperature dependence of the phonon spectrum has been studied in detail. The theory explains the softening of the phonon modes at large wave vectors in some directions, and predicts features of the phonon spectrum whose observation could be crucial to the theory.

61 citations

Journal ArticleDOI
TL;DR: In this paper, the electron-phonon spectral function a/sup 2/F(w) and related physical parameters are generated by the proximity-effect inversion analysis of the tunneling density of states.
Abstract: Single-particle (Giaever) tunneling has been performed on A15 Nb/sub 3/Al thin films with good-quality junctions formed by oxidized amorphous-silicon barriers. The tunneling measurement is used as a diagnostic probe for assessing the material properties of Nb/sub 3/Al, including changes in the progressive film growth. The electron-phonon spectral function a/sup 2/F(w) and related physical parameters are generated by the proximity-effect inversion analysis of the tunneling density of states. We find that Nb/sub 3/Al is a strong-coupled superconductor with 2D/k/sub B/T/sub c/> or =4.4 only when the composition approaches the A15 phase boundary (24 at. % Al). A difference in the low-frequency behavior of a/sup 2/F(w), observed between two junctions of different coupling strength, strongly suggests the importance of a mode softening mechanism, and implies that the average 's are rather sensitive to composition, or perhaps disorder. The lattice of Nb/sub 3/Al being softer than Nb/sub 3/Sn and V/sub 3/Si contributes significantly to the large l and the high T/sub c/ of Nb/sub 3/Al.

51 citations

Journal ArticleDOI
TL;DR: In this article, the peak structure in the electronic density of states in high-dimensional materials was estimated by using band structure and electrical resistivity data, and numerical estimates were made using band structures and resistivities.
Abstract: Strong electron-phonon scattering results in a smearing of the peak structure in the electronic density of states in high-${T}_{c}$ $A15$ materials. This smearing may impose limits on the highest ${T}_{c}$ achievable for these and similar materials. Numerical estimates are made using band structure and electrical resistivity data.

41 citations

Journal ArticleDOI
TL;DR: In this paper, a simple model is applied to calculate electron lifetime effects on the density of states, Fermi velocity, and Drude plasma energy in alloys, and formulas are provided for utilizing these results to estimate a number of superconducting and normal state properties of these materials.
Abstract: A simple model is applied to calculate electron-lifetime effects on the density of states, Fermi velocity, and Drude plasma energy in ${\mathrm{Nb}}_{3}$Sn, ${\mathrm{Nb}}_{3}$Ge, and Ti-V-Cr alloys. Formulas are provided for utilizing these results to estimate a number of superconducting and normal-state properties of these materials.

33 citations

Journal ArticleDOI
TL;DR: A microscopic treatment of the consequences for superconductivity of a nonconstant electronic density of states is presented in this paper, from which the change of the effective mass with static or thermal disorder can be calculated.
Abstract: A microscopic treatment of the consequences for superconductivity of a nonconstant electronic density of states is presented. Generalized Eliashberg gap equations valid for a varying density of states are presented, from which the change of ${T}_{c}$ with static or thermal disorder can be calculated. The temperature dependence of the effective mass is shown to be altered by disorder. Use of these results provides a possible experimental approach for deducing the energy variation of the density of states of superconductors.

22 citations