Kondo effect in coupled quantum dots under magnetic fields

The Kondo effect in coupled quantum dots is investigated theoretically under magnetic fields. We show that the magnetoconductance (MC) illustrates the peak structures of Kondo resonant spectra. When the dot-dot tunneling coupling V-C is smaller than the dot-lead coupling Delta (level broadening), Kondo resonant levels appear at the Fermi level (E-F). The Zeeman splitting of the levels weakens the Kondo effect, which results in a negative MC. When V-C is larger than Delta, the Kondo resonances form bonding and antibonding levels, located below and above E-F, respectively. We observe a positive MC since the Zeeman splitting increases the overlap between the levels at E-F. In the presence of anti ferromagnetic spin coupling between the dots, the sign of the MC can change as a function of the gate voltage.