Enhancement of Kondo effect in quantum dots with an even number of electrons

Mikio Eto, Yuli V. Nazarov

Published 2000-02-01, updated 2000-07-21Version 2

We investigate the Kondo effect in a quantum dot with almost degenerate spin-singlet and triplet states for an even number of electrons. We show that the Kondo temperature as a function of the energy difference between the states Delta reaches its maximum around Delta=0 and decreases with increasing Delta. The Kondo effect is thus enhanced by competition between singlet and triplet states. Our results explain recent experimental findings. We evaluate the linear conductance in the perturbative regime.