J. Phys. Soc. Jpn. 67, pp. 2363-2371 (1998) [9 Pages]

Theory of Multipolar Excitations in CeB 6

+ Affiliations
1Max-Planck-Institut für Chemische Physik Fester Stoffe, 01187 Dresden, Germany 2Department of Physics, Tokyo Institute of Technology, Oh-okayama, Tokyo 158 3Department of Physics, Tohoku University, Sendai 980-77

A theory for the multipolar excitations in the antiferro-quadrupolar (AFQ) phase of CeB 6 is developed. It is based on a pseudo-spin model for the Γ 8 ground state of Ce used previously to explain the B - T phase diagram. An equation of motion method for the multipolar operators is employed and the solutions for the O 2 0 and O x y phases are given. It is shown that the excitation branches are classified as being of mixed quadrupolar-dipolar, quadrupolar-octupolar and octupolar-dipolar character. The former two have strong and the latter only weak dispersion respectively. The transition from the O 2 0 to the O x y phase in the symmetric model is accompanied by the reappearance of a quadrupolar Goldstone mode. In the O x y phase of the asymmetric model some modes are gapped already at zero field and for finite field no Goldstone mode remains. In addition we give a derivation for the dynamical structure function based on the mixing scheme of multipolar excitations and discuss the result for the zero-field case.

©1998 The Physical Society of Japan


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