Dynamical polarization effect of nuclear spin bath dragged by electron spin resonance in double quantum dot integrated with micro-magnet

We studied on Overhauser shift of electron dipole spin resonance (EDSR) peaks by using a double quantum dot integrated with a micro-magnet. Two EDSR peaks are well resolved, reflecting electron spin flip events at different resonance conditions between two dots, which depend on the in-plane field at the two dots produced by a micro magnet. One of the two peaks is significantly higher than the other and shows a larger Overhauser shift, indicating that an electron spin flip process local to the dot causes dynamical polarization of local nuclear spins to the same dot. After the nuclear spin polarization is saturated, we observed the decay of the Overhauser shift by repeatedly measuring the EDSR peak with a minimum microwave power. The decay time constant is much longer than by other groups. We discuss the possible reason for this difference.