paper

Spin-Orbital Wave Excitations in Orbitally Degenerate Exchange Model with Multipolar Interactions

arXiv:cond-mat/0104274 · doi:10.1143/JPSJ.70.3076

Abstract

Elementary excitations in the multipole ordered state, which models the phase III in CeB6, are investigated by means of a generalized Holstein-Primakoff formalism. When different kinds of nearest-neighbor exchange interactions between multipoles are comparable to each other, orbital-flip excitations exhibit almost one-dimensional dispersion along the z axis. With high symmetry of the interactions, zero modes appear due to the macroscopic degeneracy of the ground state. The next-nearest-neighbor dipole-dipole interaction, which stabilizes the magnetic order of the phase III in CeB6, lifts the degeneracy and leads to gapfull excitation spectrum. When the octupole-octupole next-nearest-neighbor interaction exists simultaneously, the spectrum shows softening at Γand Z points. These excitations may be probed by neutron scattering and ultrasonic measurements.

8 pages, 5 figures, 1 table, submitted to J. Phys. Soc. Jpn

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