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Optical control and dynamics of a single Mn spin in a CdTe/ZnTe quantum dot

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A Manganese Atom is added in the CdTe crystal of a II-VI quantum dot, forming a 5/2 localised spin. The spd-exchange interactions between this Mn atom and a photo-created electron-hole pair results in the emission of a photon at a given energy depending on the spin-state of the Mn atom [1]. In other words, it is possible to access optically the Mn spin-state. We will show in this talk that it is possible to control the orientation of the Mn spin optically using quasi-resonant excitation [2] or resonant excitation [3]. The pumping process is directly observed through time-resolved experiments. Relaxation of the Mn spin can be accessed optically and T1 is found to be much longer than 10 micro-seconds. We will discuss the physics ruling this process: the observed Mn optical orientation can be explained by carrier spin-relaxation towards dark states as proposed by L. Cyvinsky in [4], in conjunction with a strained-induced crystal field along the growth axis that guarantees the conservation of the Mn spin-state Sz between the injection of two excitons even at B=0T. At last, we will report on the observation of optically dressed states and optical stark effect performed on any given spin-state of the Mn atom [5], which is a first step toward a coherent control of the Mn spin.

[1] L. Besombes, Y. Leger, L. Maingault, D. Ferrand, H. Mariette “Probing the spin state of a single Magnetic ion in an individual quantum dot” Phys Rev Lett 93, 207403 (2004)

[2] C. Le Gall, L. Besombes, H. Boukari, R. Kolodka, J. Cibert, and H. Mariette “Optical Spin Orientation of a Single Manganese Atom in a Semiconductor Quantum Dot Using Quasiresonant Photoexcitation”, Phys Rev Lett 102, 127402 (2009)

[3] C. Le Gall, R. S. Kolodka, C. L. Cao, H. Boukari, H. Mariette, J. Fern├índez-Rossier, and L. Besombes “Optical initialization, readout, and dynamics of a Mn spin in a quantum dot” Phys Rev B 81 , 245315 (2010)

[4] L. Cyvinski, “Optical orientation of a single Mn spin in a quantum dot: Role of carrier spin relaxation”, Phys Rev B 82 , 075321 (2010)

[5] C. Le Gall, A. Brunetti, H. Boukari, L. Besombes, “Optical Stark Effect and Dressed Excitonic States in a Mn-doped Quantum Dot” http://arxiv.org/abs/1104.3026

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