| Issue |
J. Phys. I France
Volume 1, Number 2, February 1991
|
|
|---|---|---|
| Page(s) | 159 - 166 | |
| DOI | https://doi.org/10.1051/jp1:1991122 | |
J. Phys. I France 1 (1991) 159-166
Geometrical correlations and the origin of
values at the maximum and intersects of
in La
2-x (Sr)
x CuO
Raphael Blumenfeld Cavendish Laboratory, Madingley Road, University of Cambridge, CB3 0HE, G. B.
(Received 16 November 1990, accepted in final form 3 December 1990)
Abstract
Many observations in doped La
2-x(Sr)
xCuO
4, including the
curve, are
explained by a simple model of the holes distribution in the CuO planes. The excitation cloud
surrounding a single hole is argued to spread on no more than about one plaquette. The Cooper pairs
are proposed to be in a combination of at least two possible states, whose energy difference is
smaller than the barrier between them. The experimental value of highest
doping
concentration
x0=0.15 emerges as the limit when the pairs are most densely packed. Further
doping above
x0 is proposed to destroy superconductivity by generating normal islands, leading
to a percolation-type structure. The model explains the observed disappearance of superconductivity
above
. It also accounts for observations of nonuniform
x-dependent diamagnetic
phase separation. Assuming low mobility of single hole excitations, this picture applies to
x<x0 as well, in agreement with recent heat capacity measurements, and explains the observed
onset of superconductivity at
.
© Les Editions de Physique 1991