Abstract
Using a singlet-triplet spin qubit as a sensitive spectrometer of the GaAs nuclear spin bath, we demonstrate that the spectrum of Overhauser noise agrees with a classical spin diffusion model over 6 orders of magnitude in frequency, from 1 mHz to 1 kHz, is flat below 10 mHz, and falls as for frequency . Increasing the applied magnetic field from 0.1 to 0.75 T suppresses electron-mediated spin diffusion, which decreases the spectral content in the region and lowers the saturation frequency, each by an order of magnitude, consistent with a numerical model. Spectral content at megahertz frequencies is accessed using dynamical decoupling, which shows a crossover from the few-pulse regime ( pulses), where transverse Overhauser fluctuations dominate dephasing, to the many-pulse regime ( pulses), where longitudinal Overhauser fluctuations with a spectrum dominate.
- Received 6 January 2017
DOI:https://doi.org/10.1103/PhysRevLett.118.177702
© 2017 American Physical Society