EFFECTIVE PAIR INTERACTIONS BETWEEN LOCALISED DEFECTS INSIDE A CUO2 PLANE IN THE SUPERCONDUCTING COPPER OXIDES

摘要

The effective pair interaction potentials between localised defects inside a CuO2 plane are deduced from our calculated susceptibility of the electron gas. The very peculiar shape of the Fermi line, which is perfectly square for a half-filled band, leads to a strongly anisotropic interaction, changing from the expected two-dimensional behaviour along the [1, 0] or [0, 1] direction to a purely one-dimensional one along the [1, 1] or [1, (1) over bar] direction. Thus, the impurities in the CuO2 planes of the new superconductors are not independent since the range of their interactions can be much larger than in a usual two-dimensional system. This could lead to superstructure effects. These results, applied to magnetic impurities, highly complicate the discussion of the frustration in a possible spin-glass phase, since the interaction between two localised spins strongly depends on the considered direction. [References: 18]