Spin-Phonon Coupled Modes in the Incommensurate Phase of CuGeO₃

抄録

The folded phonon mode at 98 cm^-1 on CuGeO₃, which was found in our previous study, was determined to be strongly coupled to the spin system. The splitting of the folded phonon mode was formulated to be caused by the interaction between the spin-phonon coupled modes at k=±(q_SP - Δq) through the modulation of the spin polarization with periodicity of 2Δq in the incommensurate (IC) phase. This mode can successfully explain the behavior of the 98 cm^-1 folded phonon mode in the IC phase. We have also formulated the reason why the intensity of the folded modes in general decreases in the IC phase.