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SU(3) Kondo effect in spinless triple quantum dots

López, Rosa; Rejec, Tomaz; Martinek, Jan; Zitko, Rok
Physical Review B 87, 035135 (2013)

We discuss a device—a purely capacitively coupled interacting triple quantum dot system in an external magnetic field—for the observation of the SU(3) Kondo effect, identified by the conductance being pinned to a characteristic value of 3/4 of the unitary limit. The Kondo effect occurs in two plateaus where the dot occupancy is pinned to an integer value, either 1 or 2. We discuss the thermodynamic and spectral properties of the corresponding triple-impurity model and establish how the presence of SU(3) Kondo screening can be identified in the temperature dependence of the conductance through one of the dots. We report results about the robustness of the SU(3) Kondo effect against various perturbations present in real experimental setups, namely unequal reservoir-dot tunneling couplings, gating effects, and nonvanishing interdot tunneling rates. Finally, we describe possible mechanisms to restore the SU(3) Kondo physics by properly tuning the on-site dot potentials. We briefly comment on the spinful case (i.e., the same system in the absence of the magnetic field), which has very different behavior and shows Kondo plateaus in conductance for all integer values of the occupancy, including at the particle-hole symmetric point.