Tunneling through triple quantum dots with mirror symmetry

Indirect exchange interactions between itinerant electrons and nanostructures with nontrivial geometrical configurations manifest a plethora of unexpected results. These configurations can be realized either in quantum dots with several potential valleys or in real complex molecules with strong correlations. Here we demonstrate that the Kondo effect may be suppressed under certain conditions in triple quantum dots with mirror symmetry at odd electron occupation. First, we show that the indirect exchange has a ferromagnetic sign in the ground state of triple quantum dots in a two-terminal cross geometry for electron occupation N=3. Second, we show that for electron occupation N=1 in three-terminal fork geometry the zero-bias anomaly in the tunnel conductance is absent (despite the presence of Kondo screening) due to the special symmetry of the dot wave function.