Magnetotransport through a quantum wire side coupled to a quantum dot

We study the spin-dependent zero-bias conductance through a quantum wire with a single ballistic channel side coupled to a quantum dot as a function of gate voltage $V_g$, magnetic field $B$, and temperature $T$. The system is modeled with the Anderson model, solved using an interpolative approximation for moderate values of the Coulomb repulsion $U$, and within the slave-boson mean field for infinite $U$ and $T=0$. Tuning $V_g$, for large enough $B$ and small enough $T$, the system is a very efficient spin filter.

Figure 1

Spectral density for majority spin at the quantum dot as a function of energy for $T=0$, $\Delta =1$, and different values of $U$ and $B$. The result for minority spin is obtained inverting the sign of $\omega -{\epsilon }_F$.

Figure 2

(a) Total conductance and (b) conductance for majority spin, in units of $G_0=2e^2∕h$ as a function of gate voltage for $T=0$, $\Delta =1$, $U=5$, and different values of $B$. Open circles correspond to the result using a simple resonant level density of states [from Eq. (7)] with ${\epsilon }_{\mathrm{eff}}^{\uparrow }=E_d-B$, ${\epsilon }_{\mathrm{eff}}^{\downarrow }=E_d+U+B$, and $B=0.9$.

Figure 3

Same as Fig. 2 for $U\to \infty$.

Figure 4

Conductance for majority spin in units of $G_0=2e^2∕h$ as a function of gate voltage for, $\Delta =1$, $U=5$, two values of $B$ and different temperatures.