Nuclear spin dynamics of donor-bound electrons in GaAs

Abstract

Modern computer processors are nowadays approaching limits due to their quantum limitations. The basic principle of modern electronics is measuring a small electrical charge of electrons passing through electronic circuits. An alternative approach based on novel materials could be the solution, which instead relies on the fundamental quantum- mechanical property – spin. The fundamental requirements that apply to a device based on quantum spin qubits include the ability to scale a quantum system, simplicity of creating and reading of the quantum state, long coherence time, and universal set of quantum gates. Concerning nuclear and electron spin states are of particular interest in the field of solid-state qubits manipulating where individual charge and spin carriers can be strongly decoupled from their environment so that the processes destroying the quantum coherence in bulk are largely suppressed. This work is concentrated on the nuclear spin system in GaAs and contributes to the research field of semiconductor nuclear spin physics. In this work, the nuclear spin dynamics of a donor-bound electron was studied in GaAs with n and p doping via optical spectroscopy technique. Since the optical operation of a mesoscopic nuclear spin ensemble is a complex and nonlinear process that involves transferring the angular momentum and energy between nuclear spins and optically-oriented localized electrons, the fundamental optical methods and initial experimental ideas that were formed a structure of this dissertation trace back to the studies of spin-related phenomena in atomic vapors. The conducted research sheds some more light on the complex interdependent system formed by the electron spin and the ensemble of surrounding nuclear spins in the conventional semiconductor – the bulk GaAs. Special attention was given to the detailed study of the nuclear spin relaxation times under a wide range of controlled physical conditions of the experiments. The developed theoretical models explain the whole set of experimental results. It is assumed that this study is another step towards the understanding of this challenging system that can lead to implementations in future quantum information technologies.