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Title: An exploratory study of QED3 with velocity anisotropies
Author: Thomas, I. O.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 2006
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Quantum electrodynamics in 2 + 1 dimensions, or QED3, has been suggested as an effective field theory that might accurately describe the low temperature behaviour of underdoped cuprate superconductors. The insulating, spin-density wave phase of the cuprate corresponds to the breaking of chiral symmetry in QED3, whereas the pseudogap phase corresponds to a chirally symmetric phase of QEDS. In condensed matter systems, there is no a priori reason why Lorentz invariance should be respected; this manifests itself in the existence of velocity anisotropies in the spatial directions of the theory, whose magnitudes are dependent on the doping of the cuprate with impurities, and which reflect the structure of the underlying Fermi surface. This thesis presents evidence obtained from the first, exploratory study of the effects of varying the anisotropy of the system, which suggests that once the ratio of the anisotropies, k, exceeds a critical value kc there is a transition into a chiraiiy symmetric phase. In addition, we perform measurements of the fermion propagator in Landau gauge, and from this obtain evidence that the fermion retains a dynamically generated mass in the symmetric phase, consistent with a scenario suggested by Witten. This raises questions as to the applicability of QED3 to the study of cuprate superconductors; more research will be needed before definite conclusions can be reached. Finally, we discuss the finite size scaling of the system and attempt to take account of the intrinsic anisotropy introduced by k, and also present a simple model of the system which my account for some of its behaviour.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available