Kondo effect in coupled quantum dots under magnetic fields

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