Individual Mechanisms of Nuclear Spin Decoherence in a Nanoscale GaAs NMR Device

We study decoherence of nuclear spins in a nanoscale GaAs device based on resistively detected nuclear magnetic resonance (NMR). We demonstrate how the spin echo technique can be modified for our system, and this is compared to the damping of Rabi-type coherent oscillations. By selectively decoupling nuclear-nuclear and electron-nuclear spin, we determine decoherence rates due to individual mechanisms, namely, direct or indirect dipole coupling between different or like nuclides and electron-nuclear spin coupling. The data reveal that the indirect dipole coupling between Ga and As mediated by conduction electrons has the strongest contribution, whereas the direct dipole coupling between them has the smallest, reflecting the magic angle condition between the As-Ga bonds and the applied magnetic field.