High tc of aA5 compounds: Linear chains or cubic symmetry?

M. Weger*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

Intermetallic compounds with the A15 crystal structure are frequently excellent superconductors, with Tc considerably exceeding the value expected for the electron/atom ratio. This high value of Tc has been attributed to the linear chain structure of the transition metal atoms. However, uniaxial stress experiments point to the importance of the cubic symmetry, rather than of the chain structure per se. The high Tc may be due to sharp peaks in the electronic density of states or to the softening of some phonons due to nesting of the Fermi surface or probably to both of these effects. Band structure calculations indicate that the large cubic unit cell, with its high symmetry, is essential for the large Van Hove peaks in the electronic density of states. Disorder thus reduces Tc drastically, as is found experimentally. The positron annihilation method has been employed to determine the shape of the Fermi surface and several planar sections have been observed. The high Tc is attributed to the reduction in the group velocity over large regions in k space by the destructive interference due to multiple scattering by the various equivalent transition metal atoms in the unit cell. Thus Matthias' claim that cubic symmetry is essential for high Tc is indeed accounted for.

Original languageEnglish
Pages (from-to)39-48
Number of pages10
JournalJournal of the Less-Common Metals
Volume62
Issue numberC
DOIs
StatePublished - 1978

Fingerprint

Dive into the research topics of 'High tc of aA5 compounds: Linear chains or cubic symmetry?'. Together they form a unique fingerprint.

Cite this