Quantum dots with even number of electrons: Kondo effect in a finite magnetic field

TL;DR

This paper investigates the Kondo effect in a small quantum dot with an even number of electrons under a magnetic field, revealing a degeneracy-induced Kondo state even when the magnetic energy exceeds the Kondo temperature.

Contribution

It demonstrates that a magnetic field matching the level spacing induces a Kondo effect in an even-electron quantum dot, a novel scenario in quantum dot physics.

Findings

Kondo effect occurs at magnetic field B equal to level spacing Δ.

Degeneracy of ground state leads to Kondo resonance despite high B.

Potential experimental realization discussed.

Abstract

We study a small spin-degenerate quantum dot with even number of electrons, weakly connected by point contacts to the metallic electrodes, and subject to an external magnetic field. If the Zeeman energy B is equal to the single-particle level spacing $\Delta $ in the dot, the ground state of the dot becomes doubly degenerate, and the system exhibits Kondo effect, despite the fact that B exceeds by far the Kondo temperature $T_{K}$. A possible realization of this in tunneling experiments is discussed.