Voltage-controlled nuclear polarization switching in a singleInxGa1−xAsquantum dot

Abstract

Sharp thresholdlike transitions between two stable nuclear-spin polarizations are observed in optically pumped individual ${\text{In}}_{x}{\text{Ga}}_{1\ensuremath{-}x}\text{As}$ self-assembled quantum dots embedded in a Schottky diode when the bias applied to the diode is tuned. The abrupt transitions lead to the switching of the Overhauser field in the dot by up to 3 T. The bias-dependent photoluminescence measurements reveal the importance of the electron-tunneling-assisted nuclear-spin pumping. We also find evidence for the resonant LO-phonon-mediated electron cotunneling, the effect controlled by the applied bias and leading to the reduction of the nuclear-spin pumping rate.