Numéro |
J. Phys. I France
Volume 2, Numéro 6, June 1992
|
|
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Page(s) | 887 - 898 | |
DOI | https://doi.org/10.1051/jp1:1992186 |
J. Phys. I France 2 (1992) 887-898
Incommensurability and transfer mechanism in bismuth high
superconductors
G. Pan1, S. Megtert1 and G. Collin2
1 Laboratoire de Physique des Solides, Bt. 510, Université Paris-Sud, 91405 Orsay Cedex, France
2 Groupe C.P.C.M., L.L.B., CEN Saclay, 91191 Gif sur Yvette Cedex, France
(Received 2 March 1992, revised and accepted 2 April 1992)
Abstract
The structure of bismuth high
superconductors is investigated. A correlation is found between incommensurate modulations and transport properties : Bi
2Sr
2CuO
6 is not a good metal because the transfer of electrons from the Cu-O
2 layers into the Bi-O bi-layers induces an incommensurate and monoclinic distortion, responsible for the localization of carriers.
Substitution of Sr
2+ by La
3+ reduces the transfer degree and the distortion : a superconductive transition is therefore observed with the remaining carriers
after a monoclinic-orthorhombic phase transition. Futher substitution tending to a complete compensation of transfer leads
to a compensated insulator. It is suggested that the
component of the modulation is linked to the lattice distortion and the
component to the charge transfer degree. Similar changes are observed in Bi
2Sr
2(Ca
1-zY
z)Cu
2O
8 except that the monoclinic distorsion is never present.
© Les Editions de Physique 1992