Fano resonance in electron transport through parallel double quantum dots in the Kondo regime

TL;DR

This paper investigates electron transport in parallel double quantum dots within the Kondo regime, revealing how interdot tunneling and energy level differences influence conductance and Fano resonance features.

Contribution

It introduces a finite-U slave boson approach to analyze the interplay of Kondo effect, interdot tunneling, and interference in double quantum dot systems.

Findings

Conductance reaches the unitary limit without interdot tunneling.

Interdot tunneling causes conductance suppression and plateau formation.

Fano resonance asymmetry arises from interference effects.

Abstract

Electron transport through parallel double quantum dot system with interdot tunneling and strong on-site Coulomb interaction is studied in the Kondo regime by using the finite-$U$ slave boson technique. For a system of quantum dots with degenerate energy levels, the linear conductance reaches the unitary limit ($2e^2/h$) due to the Kondo effect at low temperature when the interdot tunneling is absent. As the interdot tunneling amplitude increases, the conductance decreases in the singly occupied regime and a conductance plateau structure appears. In the crossover to the doubly occupied regime, the conductance increases to reach the maximum value of $G=2e^2/h$. For parallel double dots with different energy levels, we show that the interference effect plays an important role in the electron transport. The linear conductance is shown to have an asymmetric line shape of the Fano resonance as a function of gate voltage.