Transport through quantum dots with magnetic impurities

TL;DR

This paper investigates electronic transport through a quantum dot with a magnetic impurity, revealing how exchange interactions and many-body effects influence conductance peak heights and Kondo phenomena.

Contribution

It provides a detailed analysis of conductance peak ratios and the emergence of Kondo peaks in quantum dots with magnetic impurities, considering both non-interacting and correlated electron regimes.

Findings

Triplet conductance peaks are three times higher than singlet peaks in non-interacting dots.

Coulomb interactions cause complex variations in singlet/triplet peak ratios.

Three Kondo peaks form in the system's spectral function.

Abstract

We analyze the electronic transport through a quantum dot that contains a magnetic impurity. The coherent transport of electrons is governed by the quantum confinement inside the dot, but is also influenced by the exchange interaction with the impurity. The interplay between the two gives raise to the singlet-triplet splitting of the energy levels available for the tunneling electron. In this paper, we focus on the charge fluctuations and, more precisely, the height of the conductance peaks. We show that the conductance peaks corresponding to the triplet levels are three times higher than those corresponding to singlet levels, if electronic correlations are neglected (for non-interacting dots, when an exact solution can be obtained). Next, we consider the Coulomb repulsion and the many-body correlations. In this case, the singlet/triplet peak height ratio has a complex behavior. Usually the highest peak corresponds to the state that is lowest in energy (ground state), regardless if it is singlet or triplet. In the end, we get an insight on the Kondo regime for such a system, and show the formation of three Kondo peaks. We use the equation of motion method with appropriate decoupling.