Inhomogeneous dynamic nuclear polarization and suppression of electron polarization decay in a quantum dot

•Nuclear spin polarization is highly inhomogeneous after a dynamic nuclear polarization (DNP) process.•The DNP process is well described by an analytical model based on the independent spin approximation.•The highly inhomogeneous nuclear polarization significantly prolongs the electron spin coherence time.

We investigate the dynamic nuclear polarization in a quantum dot. Due to the suppression of direct dipolar and indirect electron-mediated nuclear spin interactions by frequently injected electron spins, our analytical results under independent spin approximation agree well with quantum numerical simulations for a small number of nuclear spins. We find that the acquired nuclear polarization is highly inhomogeneous, proportional to the square of the local electron-nuclear hyperfine interaction constant. Starting from the inhomogeneously polarized nuclear spins, we further show that the electron polarization decay time can be extended 100 times even at a relatively low nuclear polarization.