Electronic waiting-time distribution of a quantum-dot spin valve

We discuss the electronic waiting-time distribution of a quantum-dot spin valve, i.e., a single-level quantum dot coupled to two ferromagnetic electrodes with magnetizations that can point in arbitrary directions. We demonstrate that the rich transport physics of this setup, such as dynamical channel blockade and spin precession in an interaction-driven exchange field, shows up in the waiting-time distribution, and we analyze the conditions necessary to observe the various effects.

Figure 1

Schematic sketch of a quantum-dot spin valve. A single-level quantum dot (blue) with excitation energies $\varepsilon$ and $\varepsilon +U$ is tunnel coupled with coupling strength ${\Gamma }_r$ to two ferromagnetic electrodes (yellow) with noncollinear magnetizations pointing along ${\mathbf{n}}_r$ and enclosing an angle ${\phi }_{\mathrm{L}}+{\phi }_{\mathrm{R}}$.

Figure 2

Waiting-time distribution for a symmetric quantum-dot spin valve, ${\Gamma }_{\mathrm{L}}={\Gamma }_{\mathrm{R}}=\Gamma /2$, in the parallel geometry, ${\phi }_r=0$. The bias voltage is chosen such that transport occurs through the empty and singly occupied state only. For large polarizations a crossover between two different exponential decays indicates bunching of electron transport.

Figure 3

Waiting-time distribution as a function of bias voltage for a quantum-dot spin valve with perpendicular magnetizations, ${\phi }_{\mathrm{L}}=-{\phi }_{\mathrm{R}}=\pi /4$. Parameters are ${\Gamma }_{\mathrm{L}}=10{\Gamma }_{\mathrm{R}},\varepsilon =U/4,p=1$. White dashed lines mark the times after which the spin of the dot has precessed by an angle $(2n+1)\pi$.

Figure 4

Waiting-time distribution for a quantum-dot spin valve with perpendicular magnetizations. $V=3U/4$; other parameters are as in Fig. 3.

Figure 5

Waiting-time distribution as a function of applied bias voltage and time. Parameters are ${\Gamma }_L=10{\Gamma }_R,\varepsilon =-U/4,p=1$, and ${\phi }_L=-{\phi }_R=0.495\pi$. White dashed lines mark again the times after which the spin has precessed by an angle $(2n+1)\pi$ in the exchange field.