Spin-resolved bunching and noise characteristics in double quantum dots coupled to ferromagnetic electrodes

We study spin-resolved noise in Coulomb blockaded double quantum dots coupled to ferromagnetic electrodes. The modulation of the interdot coupling and spin polarization in the electrodes gives rise to an intriguing dynamical spin $uparrow$-$uparrow$ ($downarrow$-$downarrow$) blockade mechanism: Bunching of up (down) spins due to dynamical blockade of an up (down) spin. In contrast to the conventional dynamical spin $uparrow$-$downarrow$ bunching (bunching of up spins entailed by dynamical blockade of a down spin), this new bunching behavior is found to be intimately associated with the spin mutual-correlation, i.e., the noise fluctuation between opposite spin currents. We further demonstrate that the dynamical spin $uparrow$-$uparrow$ and $uparrow$-$downarrow$ bunching of tunneling events may be coexistent in the regime of weak interdot coupling and low spin polarization.