Suppression of Kondo screening by the Dicke effect in multiple quantum dots

Abstract

The interplay between the coupling of an interacting quantum dot to a conduction band and its connection to localized levels has been studied in a triple quantum dot arrangement. The electronic Dicke effect, resulting from quasi-resonant states of two side-coupled non-interacting quantum dots, is found to produce important effects on the Kondo resonance of the interacting dot. We study in detail the Kondo regime of the system by applying a numerical renormalization group analysis to a finite-U multi-impurity Anderson Hamiltonian model. We find an extreme narrowing of the Kondo resonance, as the single-particle levels of the side dots are tuned towards the Fermi level and "squeeze" the Kondo resonance, accompanied by a strong drop in the Kondo temperature, due to the presence of a supertunneling state. Further, we show that the Kondo temperature vanishes in the limit of the Dicke effect of the structure. By analyzing the magnetic moment and entropy of the three-dot cluster versus temperature, we identify a different local singlet that competes with the Kondo state, resulting in the eventual suppression of the Kondo temperature and strongly affecting the spin correlations of the structure. We further show that system asymmetries in couplings, level structure or due to Coulomb interactions, result in interesting changes in the spectral function near the Fermi level. These strongly affect the Kondo temperature and the linear conductance of the system.

11 pages, 15 figures. To appear in Physical Review B

References in corpus (11)

• The numerical renormalization group method for quantum impurity systems
• Strongly correlated regimes in a double quantum-dot device
• Two path transport measurements on a triple quantum dot
• Fano-Kondo effect in side-coupled double quantum dots at finite temperatures and the importance of the two-stage Kondo screening
• Zero-field Kondo splitting and quantum-critical transition in double quantum dots
• Kondo-Dicke resonances in electronic transport through triple quantum dots
• Conductance through an array of quantum dots
• Kondo and Dicke effect in quantum-dots side coupled to a quantum wire
• Tunable pseudogap Kondo effect and quantum phase transitions in Aharonov-Bohm interferometers
• Kondo screening suppression by spin-orbit interaction in quantum dots
• Two-channel Kondo tunneling in triple quantum dot