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Title: Quantum coherence effects in electronic, photonic and atomic structures
Author: Acton, J. M.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2005
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Light propagating through a disordered dielectric exhibits mesoscopic phenomena, such as coherent back scattering. In electronic systems, equivalent phenomena have been successfully described by the non-linear s-model. Starting from Maxwell’s equation in its full vector form, it is shown that disordered photonic systems, in two and three dimensions, can also be described by a non-linear s-model. The quasi classical approximation on which this theory is based is found to be valid in a window of frequencies. Numerical simulations of these systems are consistent with the s-model predictions. The mathematical equivalence between disordered photonic and electronic systems shows that the mechanisms for localization in the electronic and photonic band gaps are the same; numerical simulations to demonstrate this are presented. An investigation into the interplay of s-wave superconductivity and itinerant antiferromagnetism in disordered metals is presented. First, a s-model to describe this interplay is derived. It is used to obtain the phase diagram for the mean field phase transition between superconductivity and antiferromagnetism. The suppression of antiferromagnetism by disorder (which is analogous to the effect of magnetic disorder on superconductivity) culminates in a quantum critical point. The bilayer proximity effect is also investigated and the density of states inside an antiferromagnet coupled to a superconductor is obtained. Feshback resonance phenomena in ultracold Fermi gases are normally described by a Fermi-Bose model in which the Feshback molecule is treated as a point-like boson. We consider an alternative model of the 6Li system, in which a spin state is shared between the open and closed channels. In contrast to the Fermi-Bose model, a critical coupling in the open channel is required to induce a Feshback resonance, even at small detuning.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available