Nuclear magnetic resonance in the quantum Hall regime: Skyrmion diffusion model.

摘要

As the Trojans strengthened their defenses, they believed their fortress invulnerable. Taking into the city the Trojan horse, with the easiness and self-praising of an assumed victor, proved to be fatal.; Although not with such a tragic tone to the story, similar events are occurring in the exciting field of quantum Hall ferromagnets (QHF). Once the basis for the theory was settled, a surprisingly excellent agreement with a few experimental results was obtained during the first few years of research. Building on these initial successes, the theory has remained somewhat stationary in the past few years, while the experimentalists have gotten busy building their Trojan horse once again.; The model that we present in this thesis has its origins in the non-disorder theory of the charged excitations in the quantum Hall regime. However, at the time of writing, new experiments are beginning to suggest that our understanding of the QHF needs some rethinking, or at the very least, aspects of the experiments need to be understood better.; We present in this thesis a model for the nuclear magnetic resonance (NMR) line shapes in the absence of these experimental complications. We show that within this model the spectra have a very high sensitivity to nuclear polarization spatial profiles and a weak dependence on the dynamics of the charged excitations. It is plausible that some of the observed experimental features may be due to the specific experimental procedure used. Further work will be needed to settle the matter.; Although this thesis does not attempt to be an exhaustive work on the understanding of NMR in the QHE, considerable effort has been made to lay down the basic experimental and theoretical details in order to understand both the trivial and subtle effects extractable from the experiments.