TITLE:
Model of Preformed Hole-Pairs in Cuprate Superconductors
AUTHORS:
R. J. Singh
KEYWORDS:
High Temperature Superconductor, Electron Paramagnetic Resonance, Preformed Hole-Pairs
JOURNAL NAME:
Journal of Modern Physics,
Vol.2 No.8,
August
31,
2011
ABSTRACT: A model of preformed hole-pairs in cuprate superconductors has been proposed based on some experimental results i.e., 1) electron paramagnetic resonance spectra of quenched superconductors which show very frequently the fragment (CuO)4 broken off from the CuO2 layer in the structure, 2) 41 meV peak observed in neutron diffraction and nuclear magnetic resonance spectra of superconductors, 3) Heisenberg exchange interaction leading to ferromagnetism observed in CuO which is an essential ingredient of all superconductors and some generally accepted conclusions i.e., a) that the order parameter in superconductors has dx2–y2 symmetr and b) coherence length is of the order of 15 - 20 Angstrom. Heisenberg exchange interaction between two (CuO4) plaquettes each containing a lattice hole binds the two holes which are the charge carriers in the cuprate superconductors. It is not very clear whether the hole-pair is in the triplet or singlet state, but the triplet state is supported by the experimental observation of ferromagnetism in the parent material CuO. The proposed hole-pair singlet is different from Zhang-Rice singlet.