Semiconducting Ground State in the Kondo-Lattice Compounds

通过体测量和显微测量，我们研究了近藤半导体CeNiSn和CeRhSb的能隙形成机制.分别用提拉法和布里奇曼法生长了CeNin和CeRhSb单晶。采用固相电迁移技术对CeNiSn进行了纯化.对于这两个系统，在低温电阻率的半导体行为被抑制的杂质的量减少。这一事实和载流子迁移率的大幅度提高支持了重准粒子态密度的各向异性能隙.两个系统的电阻率和磁化率的共同各向异性表明，差距的形成源于4f电子态与导电态的类似类型的杂化.由中子散射得到的自旋激发谱在4和2 meV处有明显的峰，前者是沿b轴沿着的准一维谱。通过隧穿测量确定的能隙对于CeNiSn为8-10 meV，对于CeNiSn为20-27 meV，该值与近藤温度相当。

We have studied the mechanism of gap formation in the Kondo semiconductors CeNiSn and CeRhSb by means of bulk and microscopic measurements.1. Single crystals of CeNin and CeRhSb were grown by the Czochralski and Bridgman methods, respectively. Purification of CeNiSn was performed by the solid-state electrotransport technique.2. For both the systems, the semiconducting behavior in the low-temperature resistivity is suppressed as the amount of impurities is decreased. This fact and the large enhancement of the carrier mobility support the anisotropic gap in the state density of heavy quasi particles.3. The common anisotropy in both the resistivity and magnetic susceptibility for the two systems indicates that the gap formation originates from a similar type of hybridization of 4f electronic states with conduction states.4. The spin excitation spectra obtained from neutron scattering show pronounced peaks at 4 and 2 meV,the former of which is quasi-one-dimensional along the b-axis.5. The energy gap determined by the tunneling measurements is 8-10 meV for CeNiSn and 20-27 meV for CeNiSn, which value is comparable to the Kondo temperature.