| speaker: | C. Bolech Rice University, USA |
| time: | Tu., 14.08, 11:00-12:00 |
We will focus on the two-channel Anderson model and, in the broader context of the Kondo and Anderson single- and multi-channel impurity models, give a discussion of the different non-perturbative analytic approaches used to study its non-trivial infrared physics. We will briefly outline the history of the model and its relevance for the modern theory of certain heavy fermion compounds as well as possible quantum-dot setups. The discussion will close with an outline presentation of the bosonization approach to this type of models. We will show that the two-channel Anderson model constitutes a unique example of a bosonization-solvable mixed-valence impurity model. Using Abelian bosonization, we have established the correspondence between an anisotropic version of the two-channel Anderson model (the anisotropy being RG-irrelevant) and a particular type of bi-resonant level model. For certain values of the parameters the new model becomes quadratic. We are thus able to calculate in closed analytic form the impurity free energy and use thermodynamic magnitudes, such as the entropy and the impurity occupation, to identify the different physical energy scales of the problem. We have shown how, as the temperature goes to zero and in the absence of external fields, the model approaches an RG-stable line of non-Fermi-liquid fixed points parameterized by the impurity state of valence.