Electronic Relation Effects On Kondo Resonances In The Series-coupled Double Quantum Dots

The quantum dot system as the typical representation of exhibiting quantum effect in low dimensional mesoscopic system has become the hot topic recently. Especially, after the Kondo effect had been find in tunnelling conductance of quantum dot, it was widely studied in condensed matter physics. The Kondo phenomenon is a well-known physics phenomenon, it originally arises from the physically abnormal phenomenon under low temperature in dilute magnetic alloy. Follow the development of echnology in nanofabrication, it possible to investigate various Kondo resonances by means of Quantum Dots. One used Quantum Dots coupled to circuit by tunneling barriers under controlled circumstances experimentally, which has greatly aroused new interest in both the effects of the mesoscopic system. At the quantum dot. system, the Kondo resonance near the Fermi level localized provides a new channel for the mesoscopic current, so it leads to an increase of the conductance in a quantum dot. That is difference of the enhancement of the resistivity of the Kondo effect in a bulk metal. Recently, a great effort has been dedicated to the study of Kondo effect in the series-coupled double quantum dots coupled to ferromagnetic leads. And most of the previous studies on those systems have treated the Coulomb interaction effects on quantum dot (the intradot Coulomb repulsion) but have ignored the Coulomb interaction effects between quantum dots (the interdot Coulomb repulsion). However, the Coulomb electron-electron interaction is known to play a significant role in electronic transport through DQD. It is thus interesting to study how the Kondo effect and Coulomb interaction effects in spin-polarized transport through two coupled quantum dots coupled to two ferromagnetic (FM) leads in series. We have found that:(â…°) when the effect of the interdot Coulomb repulsion between quantum dots can't be ignored, both in P and AP configuration, the original Kondo resonance is compressed in the equilibrium case. (â…±) but in the noequilibrium case, when the effect of the interdot Coulomb repulsion between quantum dots is large enough, the width of original Kondo resonance become enhanced, both in P and AP configuration. Also the transmission probability and the Occupation number are calculated in the Kondo regime for the effect of the interdot Coulomb repulsion. The behaviors of them provide more information about the transport properties in the series-coupled double quantum dots system, as well as that the rich physical behavior can be attributed to the coexistence of both the interdot Coulomb repulsion and Kondo effect. We find that the interdot Coulomb repulsion in the DQD is one of the importance parameters to control transport phenomena via the modified Kondo resonances. The rich physical behaviour of this system can be attributed to the interdot Coulomb repulsion, we hope that this work will encourage further efforts, both theoretical and experimental, to probe the Coulomb interaction effects on quantum dots system.