We show that by illuminating an InGaAs/GaAs self-assembled quantum dot with circularly polarized light, the nuclei of atoms constituting the dot can be driven into a bistable regime, in which either a thresholdlike enhancement or reduction of the local nuclear field by up to 3 T can be generated by varying the pumping intensity. The excitation power threshold for such a nuclear spin “switch” is found to depend on both the external magnetic and electric fields. The switch is shown to arise from the strong feedback of the nuclear spin polarization on the dynamics of the spin transfer from electrons to the nuclei of the dot.
Falko predicted a bistable behaviour of the nuclear spin polarisation in optically pumped semiconductor quantum dots in a magnetic field, which has been observed experimentally by M. Skolnick's group at Sheffield. Bistability is manifested via the polarisation switch and hysteresis which occur when varying the intensity of illumination. RAE_import_type : Journal article RAE_uoa_type : Physics