Resonance Kondo tunneling through a double quantum dot at finite bias

It is shown that the resonance Kondo tunneling through a double quantum dot (DQD) with even occupation and singlet ground state may arise at a strong bias, which compensates the energy of singlet/triplet excitation. Using the renormalization group technique we derive scaling equations and calculate the differential conductance as a function of an auxiliary dc bias for parallel DQD described by $\mathrm{SO}\mathrm{}\left(4\right)\mathrm{}$ symmetry. We analyze the decoherence effects associated with the triplet/singlet relaxation in DQD and discuss the shape of differential conductance line as a function of dc bias and temperature.