Fano-Kondo and the Kondo-box regimes crossover in a quantum dot coupled to a quantum box

TL;DR

This paper investigates the crossover between Fano-Kondo and Kondo-box regimes in a quantum dot system coupled to a quantum ring, analyzing conductance and fluctuations using SBMFT to understand the interplay of discrete and continuum states.

Contribution

It introduces a detailed analysis of the crossover between Fano-Kondo and Kondo-box regimes in a quantum dot coupled to a quantum ring, highlighting the role of magnetic flux and coupling strength.

Findings

Differential conductance shows Fano-Kondo antiresonances in weak coupling.

Sharp resonances appear in conductance in strong coupling when Kondo sub-levels are tuned.

Physical properties of the regimes are characterized by conductance, current fluctuations, and Fano coefficient.

Abstract

In this work,we study the Kondo effect of a quantum dot (QD) connected to leads and to a discrete set of one particle states provided by a quantum box represented by a quantum ring (QR) pierced by a magnetic flux side attached to the QD. The interplay between the bulk Kondo effect and the so called Kondo box regime is studied. In this system the QR energies can be continuously modified by the application of the magnetic field. The crossover between these two regimes is analyzed by changing the connection of the QD to the QR from the weak to the strong coupling regime. In the weak coupling regime, the differential conductance develops a sequence of Fano-Kondo antiresonances due to destructive interferences between the discrete quantum ring levels and the conducting Kondo channel provided by the leads. In the strong coupling regime the differential conductance has very sharp resonances when one of the Kondo discrete sub-level characterizing the Kondo box is tunned by the applied potential. The conductance, the current fluctuations and the Fano coefficient result to be the relevant physical magnitudes to be analyzed to reveal the physical properties of these two Kondo regimes and the crossover region between them. The results were obtained by using the Slave Boson Mean Field Theory (SBMFT).