Magnetoswitching of current oscillations in dilute magnetic semiconductor nanostructures

Strongly nonlinear transport through dilute magnetic semiconductor multiquantum wells occurs due to the interplay between confinement, Coulomb, and exchange interaction. Nonlinear effects include the appearance of spin-polarized stationary states and self-sustained current oscillations as possible stable states of the nanostructure, depending on its configuration and control parameters such as voltage bias and level splitting due to an external magnetic field. Oscillatory regions grow in size with well number and level splitting. A systematic analysis of the charge and spin response to voltage and magnetic field switching of II-VI dilute magnetic semiconductor multiquantum wells is carried out. The description of stationary and time-periodic spin-polarized states, the transitions between them and the responses to voltage or magnetic field switching have great importance due to the potential implementation of spintronic devices based on these nanostructures.

Figure 1

(Color online) Central panel: phase diagram of dimensionless voltage $\left(N+1\right)\varphi =V/V_0$ $\left(V_0=0.96\text{mV}\right)$ versus $\Delta$ for different $N$. Lateral panels: same phase diagram but for specific values of $N=4,5,6,7,8,9,10$. The SS is stable in the white region, whereas SSCOs are stable in the shaded (colored) regions. For a given value of $N$, the SSCO regions contain those for all smaller values of $N$.

Figure 2

$J\text{−}V$ characteristic curves for a MQWS with $N=10$ and level splittings of $\Delta =10$, 14, and 18 meV.

Figure 3

$J\text{−}B$ plot for a MQWS with $N=10$ and $\varphi =5$. Inset: same for $\varphi =6$, showing indefinite persistence of SSCOs for large values of $B$.

Figure 4

(Color online) $J\left(t\right)$ curve and density plot of the electric field $F$ showing the response of a $N=10$ MQWS to the abrupt switches marked in Fig. 1. (a) and (b): vertical switch from $\varphi =7$ to 9 with $\Delta =12\text{meV}$. (c) and (d): horizontal switch from $B=2$ to 6 T with $\varphi =5$.