| speaker: | Veljko Zlatic Institute of Physics, Zagreb, Croatia |
| time: | Tu., 14.08, 9:00-10:00 |
We describe various facets of the Kondo effect in the case of intermetallic compounds with Ce, Eu, and Yb ions. The low-temperature behavior is explained by the N-fold degenerate periodic Anderson model which is solved by dynamical mean field theory (DMFT). This provides the Kondo temperature, TK, and leads to Fermi liquid (FL) behavior at temperatures below TK. Above the coherent FL regime (T > TK), we approximate the periodic Anderson model by an effective single impurity Anderson model in which the conduction electrons scatter incoherently off 4f states with internal structure. The influence of the degeneracy and the crystalline electrical field (CF) on the crossover from the high-temperature local-moment phase to the low-temperature Fermi liquid phase is explained. The overall description of the problem is obtained by interpolating between the FL solution, valid for T < TK, and the "poor man's" solution to the impurity problem, valid for T > TK.
The results obtained are compared with experimental observations on thermal transport. Thermoelectrics with strongly correlated electrons are interesting, because they often exhibit huge thermoelectric power S(T), which varies rapidly with temperature, pressure and doping. It is hoped that strongly correlated thermoelectrics might be useful for low temperature cooling devices.