There is currently interest in developing control over the spin of a single Manganese (Mn) ion, the atomic limit of magnetic memory, in semiconductor quantum dots (QDs). In this work we present theoretical results showing how one can manipulate the spin of Mn ion with light in a QD by engineering Mn-multi-exciton interactions through quantum interference, design of exciton and bi-exciton states and application of the magnetic field. We develop a fully microscopic model of correlated exciton and bi-exciton interacting with the Mn ion. The electrons and heavy holes, confined in the QD, approximated as a two-dimensional harmonic oscillator (HO), interact via direct and short- and long-range exchange Coulomb interactions. The matrix elements of the exchange interaction are computed for the first time in the harmonic oscillator basis and for arbitrary magnetic fields. The exciton and bi-exciton energies and states are computed using the configuration interaction method. The interaction between carriers and the Mn spin is accounted for by the Heisenberg electron-Mn and Ising hole-Mn exchange interactions. For a single exciton confined in a magnetic dot, a novel quantum interference (QI) effect between the electron-hole Coulomb scattering and the scattering by Mn ion is obtained. The QI significantly affects the exciton-Mn coupling, modifying the splitting of the emission/absorption lines from the exciton-Mn complex depending on the degree of electronic correlations in the exciton state. The second signature of the QI are the nonuniform energy gaps between the consecutive emission peaks due to the scattering of carriers by Mn among single-particle orbitals. Magneto-photoluminescence experiments show that the coupling between the exciton and Mn ion does not change in the magnetic field. We report that electron-hole correlations counteract the magnetic squeezing of the single-particle wave functions strengthening the carrier-Mn interactions. As a result, the rate of change of the magneto-photoluminescence spectra with magnetic field is reduced as observed in the experiment. We develop here for the first time a microscopic theory of bi-exciton-Mn complex, and report the presence of the fine structure of bi-exciton-Mn complex, even though as a spin-singlet it is expected to decouple from the localized spin. Theoretical results are compared with experiments in Grenoble and Warsaw.

There is currently interest in developing control over the spin of a single Manganese (Mn) ion, the atomic limit of magnetic memory, in semiconductor quantum dots (QDs). In this work we present theoretical results showing how one can manipulate the spin of Mn ion with light in a QD by engineering Mn-multi-exciton interactions through quantum interference, design of exciton and bi-exciton states and application of the magnetic field. We develop a fully microscopic model of correlated exciton and bi-exciton interacting with the Mn ion. The electrons and heavy holes, confined in the QD, approximated as a two-dimensional harmonic oscillator (HO), interact via direct and short- and long-range exchange Coulomb interactions. The matrix elements of the exchange interaction are computed for the first time in the harmonic oscillator basis and for arbitrary magnetic fields. The exciton and bi-exciton energies and states are computed using the configuration interaction method. The interaction between carriers and the Mn spin is accounted for by the Heisenberg electron-Mn and Ising hole-Mn exchange interactions. For a single exciton confined in a magnetic dot, a novel quantum interference (QI) effect between the electron-hole Coulomb scattering and the scattering by Mn ion is obtained. The QI significantly affects the exciton-Mn coupling, modifying the splitting of the emission/absorption lines from the exciton-Mn complex depending on the degree of electronic correlations in the exciton state. The second signature of the QI are the nonuniform energy gaps between the consecutive emission peaks due to the scattering of carriers by Mn among single-particle orbitals. Magneto-photoluminescence experiments show that the coupling between the exciton and Mn ion does not change in the magnetic field. We report that electron-hole correlations counteract the magnetic squeezing of the single-particle wave functions strengthening the carrier-Mn interactions. As a result, the rate of change of the magneto-photoluminescence spectra with magnetic field is reduced as observed in the experiment. We develop here for the first time a microscopic theory of bi-exciton-Mn complex, and report the presence of the fine structure of bi-exciton-Mn complex, even though as a spin-singlet it is expected to decouple from the localized spin. Theoretical results are compared with experiments in Grenoble and Warsaw.

xvi, 143 p. : ill. (some col.) / Electron spins form a two-level quantum system in which the remarkable properties of quantum mechanics can be probed and utilized for many applications. By learning to manipulate these spins, it may be possible to construct a completely new form of technology based on the electron spin degree of freedom, known as spintronics. The most ambitious goal of spintronics is the development of quantum computing, in which electron spins are utilized as quantum bits, or qubits, with properties that are not possible with classical bits. Before these ideas can become reality, a system must be found in which spin lifetimes are long enough and in which spins can be completely controlled. Semiconductors are an excellent candidate for electron spin control since they can be integrated into on-chip devices and produced on a scalable level. The focus of this dissertation is on electron spin control in two different semiconductor systems, namely a two-dimensional electron gas in a modulation-doped quantum well and donor-bound electrons in bulk semiconductors. Both systems have been studied extensively for a variety of purposes. However, the ability to manipulate spins has been elusive. In this dissertation, the first experimentally successful demonstration of electron spin control in a two-dimensional electron gas is presented, in which ultrafast optical pulses induce spin rotations via the optical Stark effect. Donor-bound electron spin manipulation in bulk semiconductors is also investigated in this dissertation. Important information was obtained on the limiting factors that serve to prohibit spin control in this system. By taking these new factors into account, it is our hope that full electron spin control can eventually be accomplished in this system. Finally, through the course of investigating electron spin dynamics, a strange nonlinear optical behavior was observed in a bilayer system, which was determined to result from a coupling of optical interactions with tunneling rates between layers. The data suggest that there is a strong interplay between interlayer and intralayer correlations in this system. Investigations into the nature of this interaction were undertaken and are presented in the last part of this dissertation. This dissertation includes previously published and unpublished co-authored material. / Committee in charge: Dr. Daniel Steck, Chair; Dr. Hailin Wang, Advisor; Dr. Jens Nockel, Inside; Dr. John Toner, Inside; Dr. Andrew Marcus, Outside