Ultrafast Coherent Electron Spin Control and Correlated Tunneling Dynamics of Two-Dimensional Electron Gases
Phelps, Carey E., 1982-
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Phelps, Carey E., 1982-
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.