p -shell carrier assisted dynamic nuclear spin polarization in single quantum dots at zero external magnetic field

The authors report the first observation of dynamic nuclear spin polarization (DNP) assisted by p-shell carriers in a single self-assembled InAs/GaAs quantum dot (QD) without application of an external magnetic field. With the ideal case of complete nuclear spin polarization remaining an elusive goal, research to improve the degree and efficiency of DNP or to narrow the nuclear field fluctuation distribution has been getting significant attention. The work here has implications that could lead to breaking the current limit of nuclear spin polarization. Furthering our understanding of the mesoscopic nuclear spins in a self-assembled QD is imperative in the pursuit of a stable nuclear spin environment for prolonging spin qubit coherence time.