Destruction of Kondo correlations in a four electron quantum dot withspin–orbit interactions

The zero bias anomaly in the conductance due to Kondo correlations in a quantum dot at Coulomb blockade with an even number of electrons has been only clearly experimentally seen at the singlet–triplet crossing. However, S=1 Kondo correlations should also be present in a dot in the absence of magnetic field if Hundʹs rule enforces a triplet ground state. We propose that the elusive appearance of the S=1 Kondo anomaly in semiconductor quantum dots is due to spin–orbit interactions, which we find to be a relevant perturbation of the Kondo fixed point in the NRG flow.