Spin-Dependent Transport through an Interacting Quantum Dot

We study the nonequilibrium spin transport through a quantum dot coupled to the magnetic electrodes. A formula for the spin-dependent current is obtained and is applied to discuss the linear conductance and magnetoresistance in the interacting regime. We show that the Kondo resonance and the correlation-induced spin splitting of the dot levels may be systematically controlled by internal magnetization in the electrodes. As a result, when the electrodes are in parallel magnetic configuration, the linear conductance is characterized by two spin-resolved peaks. Furthermore, the presence of the spin-flip process in the dot splits the Kondo resonance into three peaks.

Figure 1

Schematic plot of the $F\mathrm{\text{−}}\mathrm{Q}\mathrm{D}\mathrm{\text{−}}F$ system considered in this work.

Figure 2

${\rho }_{\uparrow }\left(\epsilon \right)$ (solid line) and ${\rho }_{\downarrow }\left(\epsilon \right)$ (dotted line) in the (a) parallel and (b) antiparallel magnetic configurations for $p=0.5$, $k_{B}T=0.02{\Gamma }_0$, ${\varepsilon }_d=-4{\Gamma }_0$, and $R=0$. Inset of (a) indicates spin splitting of the dot levels as a function of $p$.

Figure 3

Total spectral density ($\rho ={\rho }_{\uparrow }+{\rho }_{\downarrow }$) in the (a) parallel and (b) antiparallel magnetic configurations with $R=0.2{\Gamma }_0$. Other parameters are the same as in Fig. 2.

Figure 4

Linear conductance $G$ as a function of ${\varepsilon }_d$ in the (a) antiparallel and (b) parallel magnetic configurations in the absence of spin-flip process with $p=0.5$. Inset indicates spin-resolved conductance $G_{\uparrow }$ and $G_{\downarrow }$. The effect of intradot spin flipping on the parallel conductance is shown in (c). Linear magnetoresistance is shown in (d) for several values of temperature.