Berlin 2015 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 108: Spin-Dependent Transport Phenomena II (organized by MA)

TT 108.9: Vortrag

Donnerstag, 19. März 2015, 17:15–17:30, H 0112

Spin-dependent Fano effect and two-stage Kondo effect in T-shaped double quantum dots with ferromagnetic leads — •Krzysztof P. Wójcik and Ireneusz Weymann — Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań, Poland

We analyze the influence of ferromagnetism of the leads on the transport properties of T-shaped double quantum dots. The calculations are performed by using the numerical renormalization group method. We focus on two particularly interesting phenomena occurring in such systems: the Fano-like interference causing a strong antiresonance in the dependence of the linear conductance on the gate voltage, and the two-stage Kondo effect. The latter effect is related with a nonmonotonic dependence of the linear conductance on temperature T: with lowering T below the Kondo temperature the conductance is first enhanced, but then at the second stage it becomes suppressed due to the formation of spin singlet state between two singly occupied quantum dots. We find that spin-resolved tunneling can suppress the second stage of the Kondo effect for appropriately chosen dots’ energy levels. Moreover, we show that the presence of ferromagnets results in spin-dependent conditions for the Fano destructive interference, which gives the possibility of tuning the spin polarization of the linear conductance in the range [−1,+1].