Self-sustained current oscillations in spin-blockaded quantum dots

Self-sustained current oscillations observed in spin-blockaded double quantum dots are explained as a consequence of periodic motion of dynamical nuclear spin polarization (along a limit cycle) under an external magnetic field and a spin-transfer torque. Based on the Landau-Lifshitz-Gilbert equation, it is shown that a sequence of semistable limit cycle, Hopf, and homoclinic bifurcations occur as the external field is tuned. The divergent period near the homoclinic bifurcation explains well why the period in experiments can be many orders of magnitude longer than all microscopic time scales. DOI: 10.1103/PhysRevB.87.035311