Development of Optically-Pumped and Optically-Detected Nuclear Magnetic Resonance in a Longitudinal Magnetic Field and Studies of GaAs Quantum Wells

Date of Award

Winter 12-15-2014

Author's School

Graduate School of Arts and Sciences

Author's Department

Chemistry

Degree Name

Doctor of Philosophy (PhD)

Degree Type

Dissertation

Abstract

Optically-pumped nuclear magnetic resonance (OPNMR) and optically-detected nuclear magnetic resonance (ODNMR) are valuable techniques to examine the coupling of nuclei to electrons in two dimensional semiconductors. Both techniques probe the polarization of conduction band electrons that have been excited with circularly polarized light. The polarized electrons can both relax radiatively back to the valence band emitting a polarized photon or transfer their polarization to surrounding nuclei via the Fermi-contact hyperfine interaction. The coupling of the nuclei to the electron is monitored by photoluminescence polarization in ODNMR and the nuclear spin orientation is measured through radio frequency (rf) detection in OPNMR.

This dissertation describes the construction of an apparatus that is capable of performing OPNMR and ODNMR simultaneously, which has not been done in any other lab to date. The combination of the two techniques provides the capability to observe both the electron and nuclear spin orientation under the same experimental conditions. GaAs quantum wells were used as a test material due to extensive prior studies by both OPNMR and ODNMR. These studies provided a good foundational launching point for the new studies presented. While GaAs quantum wells have been extensively studied in the past, unanticipated results were discovered that afforded us the capability to extract the exact positons of electronic transitions that agree with theoretical calculations. Preliminary ODNMR measurements of 71Ga and 75As are shown, along with the comparison of 69Ga ODNMR to 69Ga OPNMR profiles. The comparisons show unexpected behavior and more experiments are necessary to elucidate the origin.

Language

English (en)

Chair and Committee

Sophia E Hayes

Committee Members

Richard A Loomis, Jacob Schaefer, Mark S Conradi, Li Yang

Comments

Permanent URL: https://doi.org/10.7936/K7DF6PCX

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