Kondo effect in coupled quantum dots under magnetic fields

Abstract

The Kondo effect in coupled quantum dots is investigated theoretically under\nmagnetic fields. We show that the magnetoconductance (MC) illustrates peak\nstructures of the Kondo resonant spectra. When the dot-dot tunneling coupling\n$V_C$ is smaller than the dot-lead coupling $\\Delta$ (level broadening), the\nKondo resonant levels appear at the Fermi level ($E_F$). The Zeeman splitting\nof the levels weakens the Kondo effect, which results in a negative MC. When\n$V_{C}$ is larger than $\\Delta$, the Kondo resonances form bonding and\nanti-bonding levels, located below and above $E_F$, respectively. We observe a\npositive MC since the Zeeman splitting increases the overlap between the levels\nat $E_F$. In the presence of the antiferromagnetic spin coupling between the\ndots, the sign of MC can change as a function of the gate voltage.\n