Interactions aspherical Coulomb

If instead of the isotropic exchange interaction (A, S) = (0,1) we consider the aspherical Coulomb interaction (A, 2 ) = (2,0) we obtain fig. 17.15 instead. The negative sign for y indicates pair-enhancement instead of pair-breaking. Since this is a dynamical effect it vanishes for 5 = 0. The maximum effect occurs for 8 = lOTc. It resembles the one of additional Einstein oscillators put into the matrix. The quantity t, in the definition of y has to be replaced by to which is defined in a similar way as Ts (see eq. (17.66)) but now with Hac instead of He. ... 

In order to study the influence of conduction electrons we restrict ourselves to the aspherical Coulomb charge scattering A, S) = (2,0) which is described by the hamiltonian H c as given by eq. (17.44). Furthermore we consider again the simple case of cubic symmetry and specialize our considerations to a shear wave polarized in x-direction and propagating in z-direction. The interaction of the RE-ions via the conduction electrons is taken into account by extending the diagrammatic equations for the mode under consideration so that they are of the form shown in fig. 17.39. 

---