https://doi.org/10.1140/epjb/e2002-00399-x
On the nature of antiferromagnetism in the CuO2 planes of oxide superconductors
1
Laboratoire de Physique des Solides (associé au CNRS) , and Université Paris-Sud, bâtiment 510, 91405 Orsay, France
2
Institute for Solid State Physics, University of Tokyo,
5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
Received:
22
March
2002
Revised:
20
August
2002
Published online:
31
December
2002
Recent results regarding electron- and hole-doped CuO2 planes can be rather easily explained
by the marked covalency of CuO bonding, suggesting a band picture of long and short range
antiferromagnetism. The maxima of superconductive Tc
versus doping can be related to the
crossing by the Fermi level of the edges of the pseudogap due to antiferromagnetic short range
order (bonding edge for hole-doping, antibonding for electron-doping). The symmetry of the
superconductive gap can be related to the Bragg scattering of electronic Bloch states near the
edges of the antiferromagnetism (AF) pseudogap. Assuming a standard phonon coupling, one
then predicts for commensurate AF a pure symmetry for the superconductive gap for
underdoped samples and
symmetry plus an imaginary contribution of s or dxy symmetry
contribution increasing linearly with overdoping. This seems in agreement with recent
measurements of gap symmetry for YBCO, but should be more fully tested, especially for
electron-doped samples. Incommensurate AF, as in LSCO, is not considered here. The simple
Hartree-Fock band approximation used could no doubt be made more realistic by specific
inclusion of electron correlations and by a better description of the AF short range order.
This weak atomic repulsion U model, standard in transitional metals, is complementary to the
strong U models usually assumed in oxides. It considers specifically the possible effects, in doped
samples, of a short range AF which could be slowly dynamical or static, possibly including in that
case recent evidences of nanostructures of two different phases.
PACS: 74.72.-h – High-Tc compounds
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2002