Kondo effect in a two-level quantum dot coupled to an external fermionic reservoir

TL;DR

This paper theoretically analyzes the conductance behavior of a two-level quantum dot coupled to an external reservoir, revealing new regimes and temperature dependencies of the Kondo effect across different coupling strengths.

Contribution

It introduces a comprehensive study of the Kondo effect in a two-level quantum dot, identifying a novel mixed-valence regime with unique energy level structures and temperature dependence.

Findings

Identification of a strong coupling mixed-valence regime

Discovery of sub- and super-tunneling effects in energy levels

Observation of a novel temperature dependence of the Kondo effect

Abstract

We investigate theoretically the linear conductance of a two-level quantum dot as a function of the gate voltage and different strength of coupling to the external electronic system (the reservoir). Apart from the weak coupling regime, characterized by the Kondo-enhancement of the conductance in the spinful ground state, a strong coupling regime, which can be called mixed-valence (MV), is found. This regime is characterized by a qualitative change of the energy level structure in the dot, resulting in sub- and super-tunneling coupling of the levels, which in turn yield a novel temperature dependence of the Kondo effect in the quantum dot.