The Kondo Temperature of SU(4) Symmetric Quantum Dots
  A path integral approach is used to derive a closed analytical expression for the Kondo temperature of the SU(4) symmetrical Anderson model. In contrast to the SU(2) case, the prefactor of the Kondo temperature is found to display a peculiar orbital energy (gate voltage) dependence, reflecting the presence of various SU(4) mixed valence fixed points. Our analytical expressions are tested against and confirmed by numerical renormalization group computations. 
Michele Filippone and Catalin Pascu Moca and Gergely Zarand and   Christophe Mora
cond-mat.mes-hall