Study on the Kondo effect of ions with multi-electron occupancy

我们学习了以下科目。(1)杂质安德森模型（TAM）是研究金属中磁性离子的基本模型，在大杂化极限下，TAM模型具有一定的局域费米液体（LFL）性质。LAM中是否出现了非费米液体（NFL）态？如果是这样，LFL和NFL之间会发生什么样的过渡。(2)系统1U_xTh_<1-x>Ru_2Si_2表现出类似于近藤双通道模型（TCKM）的NFL态的反常低温行为。但其电阻率随温度的降低而降低。通常认为TCKM中电阻率会增加，这种电阻率可以用IAM来解释吗？(3)已知TCKM在T=0处具有剩余熵1/ In。这将在晶体对称性降低的情况下释放，并且比热将在特征温度处显示峰值。在特征温度附近，磁化率随- In T的增加有何表现？得出以下结论。(1)IAM具有各种类型的基态，包括LFL和NFL性质，这取决于当杂化改变时的晶体场。(2)我们可以预期，当f^2和f^3原子间的原子价涨落占主导地位时，电阻率会下降。(3)特征温度约为晶场分裂的1/10。在该温度下，磁化率的增加达到饱和。即使参数非常接近LFL态的转变点，NFL态的剩余熵仍然是1/2。最近，测量了U_xTh_ Ru_2Si_2在强磁场下的比热<1-x>，没有观察到剩余熵。根据本研究的结果，我们可以得出结论，TCKM类型的场景似乎不适用于这个系统。动力学Jahn-Teller效应的作用现在正在考虑中。

We have studied following subjects.(1) It is known that the impurity Anderson model (TAM), which is a fundamental model for the magnetic ion in metal, has certainly the local Fermi liquid (LFL) properties in large hybridization limit. Does the non-Fermi liquid (NFL) state appear in the LAM? If it does, what kind of transition occurs between the LFL and the NFL states.(2) The system1 U_xTh_<1-x>Ru2Si_2 shows anomalous low temperature behaviors similar to those of the NFL state of the two channel Kondo model (TCKM) type. But its resistivity decreases with decreasing temperature. Usually it is expected to increase in the TCKM.Can this resistivity be explained based on the IAM?(3) It is known that the TCKM has a residual entropy 1/ In at T=0. This will be released under the lowering of the crystal symmetry, and the specific heat will show a peak at a characteristic temperature. How the increase of the magnetic susceptibility with - In T behave near the characteristic temperature?Following conclusions are derived. (1) The IAM has various types of ground states including both LFL and NFL natures depending on the crystalline field when the hybridization is changed. (2) We can expect the decreasing resistivity when the valence fluctuation between f^2 and f^3ates dominates. (3) The characteristic temperature is about 1/10 of the crystalline field splitting. At that temperature the increase of the susceptibility saturates. The residual entropy in the NFL state is still 1/ in 2 even when the parameters are situated very near the transition point to the LFL state.Recently, the specific heat under strong magnetic field is measured for U_xTh_<1-x>Ru_2Si_2, and the residual entropy is not observed. Based on the results of the present study, we may conclude that the scenario of the TCKM type seems not applicable simply to this system. Roles of the dynamical Jahn-Teller effect are now under consideration.