Optical control of individual spins in magnetic and charged quantum dots
Résumé
This manuscript is organized as follows: In Part One, the main properties of Mn-doped and singly charged II-VI QDs are presented. In chapter 1 we will describe their energy level structure. We will then analyze in detail the influence of the QD symmetry and of the valence band mixing on the spin structure of QDs containing an individual carrier and one or two Mn atoms. We will finally show how the tuning of the charge state of a QD can be used to control the magnetic properties of a Mn atom. In chapter 2, we will focus on the spin dynamics of these few interacting spins. We will first analyse the dynamics of coupled electron and diluted nuclear spins in these II-VI QDs. We will, in particular, show that the electron spin dephasing by the low density of fluctuating nuclear spins is efficiently suppressed at zero field by a dynamic nuclear spin polarization. We will then focus on the dynamics of coupled carriers and Mn spins. We will first show how the injection of spin polarized carriers can be used to prepare by optical pumping the spin state of one or two Mn atoms. We will then discuss the mechanism controlling the efficiency and the dynamics of this optical pumping. We will finally show how the strong coupling between a laser field and the optical transitions of a Mn-doped QD can be used to optically tune the energy of any spin state of a Mn atom. Part Two (Chapter 3) is devoted to the presentation of ongoing work and perspectives on the coherent dynamics of interacting electron, nuclei and Mn spins in II-VI semiconductor QDs. We will, for instance, discuss the possibility of using the strong coupling with a resonant laser field to control the coherent dynamics of coupled electronic and nuclear spins of a Mn atom.