We examine the structure of the low-temperature fixed point of a generalized two-level-system (TLS) Hamiltonian using the perturbative renormalization-group transformation. In our model the conduction electrons scattered by the TLS are labeled by an additional flavor quantum number =1,...,Nf, the physically relevant case being Nf=2 corresponding to the two spin directions. Using the second-order scaling equations it is shown that the only stable fixed point is the one where the conduction electrons have an Se=1/2 orbital pseudospin. Thus, the relevant subspace of the electrons is essentially reduced. Our results, which are exact in the limit Nf, are in a reasonable agreement with the recent experiments made on metallic nanostrictions. We also investigate numerically the effect of orbital electron channels with higher angular momenta on the Kondo temperature and check the results of the analytical calculations.
ASJC Scopus subject areas
- Condensed Matter Physics