Pauli spin blockade in the presence of strong spin-orbit coupling

We study electron transport in a double quantum dot in the Pauli spin blockade regime in the presence of strong spin-orbit coupling. The effect of spin-orbit coupling is incorporated into a modified interdot tunnel coupling. We elucidate the role of the external magnetic field, the nuclear fields in the dots, and the spin relaxation. We find qualitative agreement with experimental observations, and we propose a way to extend the range of magnetic fields in which blockade can be observed.

Figure 1

(Color online) Double quantum dot in the Pauli spin blockade regime. (a) The double dot is coupled to two leads. Due to a voltage bias, electrons can only run from the left to the right lead. (b) Energy diagram assuming spin-conserving interdot coupling. The only accessible (0,2) state is a spin singlet: all (1,1) triplet states are not coupled to the (0,2) state and the current is blocked. (c) Energy levels and transition rates assuming nonspin-conserving interdot coupling. We consider the “high”-field limit and neglect the effects of the nuclear fields. Then three of the four (1,1) states can decay, leaving only one spin blockaded state $|\alpha ⟩$. Isotropic spin relaxation $\sim {\Gamma }_{\text{rel}}$ causes transitions between all (1,1) states.

Figure 2

(Color online) Current as a function of $B_0$, at $\Delta =0$, and neglecting the nuclear fields. Around zero field a dip is observed; its width depends on the magnitude and orientation of $\vec{\eta }$.

Figure 3

(Color online) The current $I=e{\rho }_{22}\Gamma$ for (a) and (b) large, (c) and (d) intermediate, and (e) and (f) small tunnel coupling. The dip observed around zero field (a) disappears when $t_0^2/\Gamma \sim K$ (c) and evolves into a peak for even smaller tunnel coupling (e).