Quantum limit for nuclear spin polarization in semiconductor quantum dots.

A recent experiment [E. A. Chekhovich etal., Phys. Rev. Lett. 104,066804 (2010)] has demonstrated that high nuclear spin polarization can be achieved in self-assembled quantum dots by exploiting an optically forbidden transition between a heavy hole and a trion state. However, a fully polarized state is not achieved as expected from a classical rate equation.Here, we theoretically investigate this problem with the help of a quantum master equation and we demonstrate that a fully polarized state cannot be achieved due to formation of a nuclear dark state. Moreover, we show that the maximal degree of polarization depends on structural properties of the quantum dot. [ABSTRACT FROM AUTHOR]