Modeling Hyperpolarized NMR Phenomena in Optically Pumped Semiconductors

Nuclear magnetic resonance (NMR) is a widely-used technique that measures the local environments of nuclei. It is able to detect small differences in energy, making it a highly-valued tool. However, the technique is challenged by inherently low sensitivities, requiring either large sample volumes or long periods of time to overcome this. In semiconductors, optical pumping (OP) can overcome this low sensitivity by creating incredibly large and dynamic nuclear spin polarizations (``hyperpolarization\u27\u27), which is detectable as a large NMR signal. The combined technique of optically-pumped NMR (OPNMR) is a valuable tool that can explore electronic and nuclear phenomena within semiconductors. In some OPNMR spectra of strained GaAs, asymmetry in the intensity of the two quadrupolar satellites for 75As is present. We seek to understand whether the degree of asymmetry is related to the extent of spin polarization. Knowledge of specific nuclear spin polarization can be an important metric, and we are testing how to best approach that measure. In addition, the semiconductor CdTe is unusual in that the natural abundances of spin-half (NMR-detectable) isotopes leads to a sparse spin system. We test the role of through-space and through-bond nuclear spin-spin interactions and the effects of these on 113Cd spectra. Studying this system gives us a unique opportunity to explore weak dipolar and scalar couplings in a single-crystal material, which is normally infeasible without the use of optical pumping. Pairs of 113Cd-125Te isotopes exhibit specific behavior and dipolar oscillations, and the dynamics of their behavior will be measured