Quantum Dots with Even Number of Electrons: Kondo Effect in a Finite Magnetic Field

Abstract

We show that the Kondo effect can be induced by an external magnetic field in quantum dots with an even number of electrons. If the Zeeman energy $B$ is close to the single-particle level spacing $\Delta$ in the dot, the scattering of the conduction electrons from the dot is dominated by an anisotropic exchange interaction. A Kondo resonance then occurs despite the fact that $B$ exceeds by far the Kondo temperature $T_K$. As a result, at low temperatures $T\ll T_K$ the differential conductance approaches a unitary limit $G_K\sim e^2/\pi ħ$. A possible experimental realization of this effect is discussed.