Systematic investigations of transient response of nuclear spins in the presence of polarized electrons

Abstract

We electrically probed the transient response of nuclear spins in an $n$-GaAs channel by performing Hanle signal and spin-valve signal measurements on an all-electrical spin-injection device having a half-metallic spin source of $\mathrm{C}{\mathrm{o}}_{2}\mathrm{MnSi}$. Furthermore, we simulated the Hanle and spin-valve signals by using the time evolution of nuclear-spin polarization under the presence of polarized electron spins by taking both ${T}_{1\mathrm{e}}$ and ${T}_{1}$ into consideration, where ${T}_{1\mathrm{e}}^{\ensuremath{-}1}$ is the polarization rate of nuclear spins through the transfer of angular momentum from polarized electron spins and ${T}_{1}^{\ensuremath{-}1}$ is the depolarization rate of nuclear spins through the interaction with the lattice. The simulation results reproduced our experimental results on all the nuclear-spin-related phenomena appearing in the Hanle and spin-valve signals at different measurement conditions, providing quantitative explanation for the transient response of nuclear spins in GaAs to a change in magnetic fields and an estimate of the time scales of ${T}_{1\mathrm{e}}$ and ${T}_{1}$. These experimental and simulated results will deepen the understanding of nuclear-spin dynamics in semiconductors.