Double nuclear spin switching in single quantum dots

Hyperfine interaction in a quantum dot produces spin-coupled system between an injected electron and few tens of thousands nuclei the wavefunction. We report here that double bistable phenomenon nuclear spin polarization (NSP) can be observed by sweeping three control parameters. All observations indicate NSP has stable branches under longitudinal magnetic field, whereas number been believed to two at most. The incorporation relaxation due fluctuation enables reproduction features polarization.