Abstract
Model of hole-pairs in electrical transport along ab plane in cuprate superconductors has already been proposed. It has been found to be in the shape of 3dx2–y2 orbital of an electron in an atom. This time, model of hole-pairs in transport along c-axis in cuprate superconductors is proposed. In ab-plane, hole-pairs are formed along CuO2 plane; one hole-pair covering 9 - 10 two dimensional CuO2 unit cells in 3dx2–y2 configuration. In the investigation of c-axis hole-pairs, cuprate superconductors have been sub-divided into three categories depending on the number of CuO2 planes/formula unit. There is a little different treatment for finding out the order parameter in each category. Coherence lengths along ab-planes are of the order of a few tens of Angstroms, whereas along c-axis, they are less than even their a-, b-lattice constants. In cuprates with 2 or 3 CuO2 planes, the order parameter is of 3dz2–x2 type in zx-plane with lobes along both the axes much constrained. For cuprates with a single CuO2 layer, the order parameter is of 3dx2–y2 type, but its dimensions are less than a-, b-lattice constants.
Highlights
Holes are Fermionic particles and are charge carriers in cuprate superconductors in the normal state
In the investigation of c-axis hole-pairs, cuprate superconductors have been sub-divided into three categories depending on the number of CuO2 planes/formula unit
There are two more points worth considering: 1) Why Tc of a superconductor increases when number of CuO2 layers per unit cell increases from one to three. It is because more the number of CuO2 layers, greater will be the number of hole-pairs formed and transition temperature will be reached at higher temperature
Summary
Holes are Fermionic particles and are charge carriers in cuprate superconductors in the normal state. It can be said that the following equation will hold good: An isolated (CuO) plaquette = a (CuO) unit cell in the continuous CuO2 sheet + a hole inside it. A peak at 41 meV (with a little difference in energy from one to other superconductor) is observed in neutron diffraction and nuclear magnetic resonance spectra of high temperature superconductors This peak is associated with spin angular momentum. 41 meV when equated to hν, ν comes to be equal to 1013 hertz or time-period T = 10–13 sec We associate this frequency with oscillations of spins of 4 Cu2+ holes, which means that they oscillate with this frequency from vertically upward direction to the vertically downward direction. They come back to the CuO2 plane producing zero magnetic field and so on
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