Electron Spin Dynamics in Semiconductor Quantum Dots

The electron spin is a fundamental digital unit that can be utilized
to store and to process information. Practical applications require
long spin life-times and large spin polarizations without the need
of strong external magnetic fields and at temperatures as high as
possible.

The talk deals with a resident electron in a charged quantum dot.
Since largely isolated from the environment, spin-orbit interaction
that limits the electron spin life-time in bulk semiconductors is
strongly suppressed here. Steady-state single-spin polarizations as
large as 0.5 can be created by optical pumping.

The electron spin is coupled by the contact hyperfine interaction to
the nuclear moments of the lattice atoms in the quantum dot. The
formation of zero-field nuclear spin polarization as well as its
subsequent decay by the dipole-dipole interaction is directly
resolved in time up to about 100 K. The findings demonstrate the
potential of controlling optically the spin state of the nuclear
ensemble and to use it as a long-lived quantum memory as well.