Optical probing of the spin state of a single magnetic atom in a quantum dot

The magnetic state of a single magnetic ion (Mn2+) embedded in an individual quantum dot is optically probed using microspectroscopy. The fine structure of a confined exciton in the exchange field of a single Mn2+ ion ( S = 5 / 2 ) is analyzed in detail. The exciton–Mn2+ exchange interaction shifts the energy of the exciton depending on the Mn2+ spin component and six emission lines are observed at zero magnetic field. The QD exciton emission is then a direct probe of the Mn spin state. The limiting factors of such detection are then presented: they are mainly due to the influence of geometrical effects such as the anisotropic strain distribution into the QD and its shape anisotropy. In the last part, we show how we can manipulate and understand quantitatively the interaction between the single Mn spin and a confined carrier by controlling the charge state of a quantum dot ( 0 , ± 1 electron) with an electrostatic (and optical) gate. This opens the way to an electrical or optical control of the magnetic properties of a single atom. To cite this article: L. Besombes et al., C. R. Physique 9 (2008).