Non-Crossing Approximation Study of Multi-Orbital Kondo Effect in Quantum Dot Systems

TL;DR

This study uses the non-crossing approximation to analyze the three-orbital Kondo effect in quantum dots, revealing how Hund-coupling and orbital splitting influence transport properties and Kondo temperature.

Contribution

It provides new insights into the three-orbital Kondo effect, highlighting the role of Hund-coupling and the suppression of Kondo temperature enhancement due to the third orbital.

Findings

Hund-coupling is more significant in three-orbital systems.

Orbital splitting affects tunneling conductance and transport behavior.

Kondo temperature enhancement is suppressed by the third orbital.

Abstract

We study the three-orbital Kondo effect in quantum dot (QD) systems by applying the non-crossing approximation to the three-orbital Anderson impurity model. By investigating the tunneling conductance through a QD, we show that the competition between the Hund-coupling and the orbital level-splitting gives rise to characteristic behavior in transport properties. It is found that the Hund-coupling becomes more important in the three-orbital case than in the two-orbital case. We also show that the enhancement of Kondo temperature due to the singlet-triplet mechanism suggested for the two-orbital model tends to be suppressed by the existence of the third orbital.