Lemon, Christopher P.
(2010).
Neutron Compton scattering from hydrogen and perovskite oxide interfaces.
University of Birmingham.
Ph.D.
Abstract
In this thesis we investigate two independent topics: neutron Compton scattering from hydrogen and perovskite oxide interfaces. Part one is an investigation of the scattering of high energy neutrons from hydrogen compounds. The motivation for this investigation stems from neutron Compton scattering experiments, performed with the VESUVIO neutron spectrometer at the ISIS pulsed neutron source, which report an anomalously reduced cross section for hydrogen. We explore the possibility that electronic excitation is responsible for the discrepancy between conventional theory and experiment. We conclude that the effect of electronic excitation on the scattering is small, at the energies relevant to the experiments, and therefore cannot account for the anomalies. Part two is an investigation of two perovskite oxide interfaces: a cuprate-manganite interface, and the interface between SrTiO\(_3\) and LaAlO\(_3\). Both interfaces are investigated using the techniques of impurity theory. Firstly, a simple model of a cuprate-manganite interface is proposed to explain several recent experiments. By applying the idea that the metallicity of the manganite spills out into the cuprate, we provide a theoretical interpretation of the unusual electronic and magnetic properties observed at the interface. Finally, a simple model of the SrTiO\(_3\)-LaAlO\(_3\) interface is investigated. Two ingredients are contained within this model: the orbital physics of the titanates, and the long range coulomb interactions produced by the polar discontinuity at the interface. From this model, we predict a two dimensional layer of charge confined to the interface, which is consistent with experimental observations.
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