Conductance through quantum dot dimer below the Kondo temperature

The conductance through two quantum dots connected in series is studied below the Kondo temperature, based on the slave boson formalism of the Anderson model. The transport properties are characterized by the ratio of the magnitude of the tunneling coupling between two dots to the width of the level broadening. When the ratio is less than unity, the Kondo resonant states are formed between each dot and an external lead, and the conductance is determined by the hopping between the two resonant states. When the ratio is larger than unity, these Kondo resonances are split into the bonding and antibonding peaks, which are located below and above the Fermi level in the leads, respectively, for low gate voltages. As a result, the conductance is suppressed. The conductance has a maximum of 2e²/h when the bonding peak is matched with the Fermi level by controlling the gate voltage.