Raman scattering study on Kondo semiconductors of CeRhSb and CeNiSn.

本研究的目的是通过拉曼散射来阐明CeRhSb和CeNiSn2种近藤半导体的微观机制。在室温到5K的温度范围内测量了喇曼散射光谱的详细偏振关系，从简正模计算的结果来看，在0到250 cm^-1的能量范围内观察到的峰被指定为声子。其中，CeRhSb的三个声子和CeNiSn三个声子的能量表现出反常的温度依赖性。由于这些模是Ce的振动，这种依赖关系表明在Kondo态中存在磁涨落和晶格振动之间的相互作用。在拉曼散射光谱中也观察到了较宽的背景光谱。其低能区强度降低到30K以下，能谱形状可以用赝隙的V型态密度很好地解释。得到的参数与比热和NMR的报告值相似，对LaNiSn的基态光谱没有观察到这样的抑制作用。因此，背景谱低能区的抑制源于局域4f电子与传导电子的杂化效应引起的自旋能隙状态的出现。

The purpose of this research is to clarify the microscopic mechanism of the Kondo semiconductors of CeRhSb and CeNiSn by Raman scattering. The detailed polarization dependence of Raman scattering spectra has been measured in the temperature region between room temperature and 5K.The peaks, observed in the energy region between 0 and 250cm^-^1, are assigned as the phonons, judging from the results of the normal mode calculation. Among them, three phonons of CeRhSb and one of CeNiSn show the anomalous temperature dependence of their energy. Since these modes are the vibrations of Ce, the dependence shows the existence of the interaction between magnetic fluctuation and lattice vibration in the Kondo states. The broad background spectrum has been also observed in the Raman scattering spectra. Its intensity of the low energy region decreases below 30K.The spectral shape is well explained by the V-shaped state density of the pseudo-gap. The obtained parameters are similar to the reported values by specific heat and NMR.Such suppression of the hack-ground spectra of LaNiSn has not been observed. Therefore, the suppression of the low energy region of the back-ground spectra is originated from the appearance of the spin gap state due to the hybridization effect between the localized 4f and conduction electrons.