RKKY interactions of CeB₆ based on effective Wannier model

We examine the RKKY interactions of CeB₆ between multipole moments based on the effective Wannier model obtained from the band structure calculation including 14 Ce-f orbitals and 60 conduction orbitals of Ce-d, s and B-p, s. By using the f-c mixing matrix elements of the Wannier model together with the conduction band dispersion, the multipole couplings with the RKKY oscillation are obtained for the active moments in Γ₈ subspace. Both of the Γ_5g quadrupole O_xy and the Γ_2u octupole T_xyz couplings are largely enhanced with q = (π, π, π) which naturally explains the antiferro-quadrupolar phase of the phase II, and are also enhanced with q = (0, 0, 0) corresponding to the elastic softening of C₄₄. Also the couplings of the Γ_5u octupole T_z^β is quite large for q = (0, 0, π) which is related to the antiferro-octupolar ordering of a possible candidate for the phase IV of Ce_xLa_1-xB₆. (author)