Decoherence and Dephasing in Kondo Tunneling through Double Quantum Dots

We describe the mechanism of charge-spin transformation in a double quantum dot (DQD) with even occupation, where a time dependent gate voltage v(t) is applied to one of its two valleys, whereas the other one is coupled to the source and drain electrodes. The Kondo tunneling regime under strong Coulomb blockade may be realized when the spin spectrum of the DQD is formed by the ground state spin triplet and two singlet excitations. Charge fluctuations induced by v(t) result in transitions within the spin multiplet characterized by the SO(5) dynamical symmetry group. In a weakly non-adiabatic regime the decoherence, dephasing and relaxation processes affect Kondo tunneling. Each of these processes is caused by a special type of dynamical gauge fluctuations, so that one may discriminate between the decoherence in the ground state of a DQD and dephasing at finite temperatures.