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A semiconductor quantum dot (QD) containing a single Mn atom is a promising system from the point of view
of future information processing and storage devices. An efficient optical read-out of the single Mn spin state in
a CdTe/ZnTe quantum dot, as well as studies of dynamics of this state, were recently reported by L. Besombes
and co-workers. However, to construct the building blocks of future memory devices basing on single magnetic
atoms the ability to control a single spin is still needed.
This work is focused on the advancement in writing and storing of information on the Mn spin state. We
demonstrate optical writing of information on the spin state of a single Mn ion embedded in a CdTe QD and we
test the storage time in the range of a few tenths of a millisecond. A spin-conserving excitation transfer between
two coupled QDs is used as a tool for optical manipulation of the Mn spin. Excitons resonantly created in a
dot without magnetic atom by circularly polarized light tunnel to the dot with the Mn ion in a few picoseconds.
Then they act on the Mn ion via the sp-d exchange interaction and orient its spin. The orientation is much
more efficient in presence of a magnetic field of about 1T, due to suppression of fast spin relaxation channels.
Dynamics of the Mn spin under polarized excitation as well as the information storage time on the Mn spin was
measured in a time-resolved experiment, in which the intensity and polarization of excitation were modulated.
Observed dynamics can be described with a simple rate equation model. The storage time was enhanced by the
magnetic field and reached about half a millisecond at 1T.
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