Self-sustained current oscillations in spin-blockaded quantum dots

TL;DR

This paper explains the phenomenon of self-sustained current oscillations in spin-blockaded quantum dots as resulting from the periodic motion of polarized nuclear spins, modeled through bifurcation theory and the Landau-Lifshtz-Gilbert equation.

Contribution

It introduces a theoretical framework linking nuclear spin dynamics and current oscillations in quantum dots using bifurcation analysis.

Findings

Identification of limit cycles, Hopf, and homoclinic bifurcations as key mechanisms.

Explanation of long oscillation periods near bifurcations.

Agreement with experimental observations of period variation.

Abstract

Self-sustained current oscillation observed in spin-blockaded double quantum dots is explained as a consequence of periodic motion of dynamically polarized nuclear spins (along a limit cycle) in the spin-blockaded regime under an external magnetic field and a spin-transfer torque. It is shown, based on the Landau-Lifshtz-Gilbert equation, that a sequence of semistable limit cycle, Hopf and homoclinic bifurcations occurs as the external field is tuned. The divergent period near the homoclinic bifurcation explains well why the period in the experiment is so long and varies by many orders of magnitudes.