Doctoral Dissertations

Date of Award

12-2012

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Physics

Major Professor

Takeshi Egami

Committee Members

Elbio Dagotto, Jaime Fernandez-Baca, Norman Mannella

Abstract

High temperature superconductivity in iron based compounds has presented a series of complex problems to condensed matter physics since being discovered in 2008. The stalwart basis of condensed matter physics is the “strength in numbers" aspect of crystalline periodicity. Perfect crystalline periodicity has made possible the reduction of the questions of structural and electronic properties to single dimensions, increasing the tractability of these problems. Nevertheless, modern complex materials stretch these assumptions to their limits, and it is at this point where our work starts. Using neutron and x-ray scattering, we have conducted a series of studies on the structural disorder of iron based superconductors and found it to be ubiquitous. Further, we have investigated the lattice dynamics of the iron-based superconducting systems, and found anomalous phonon behavior, with coupling between the spin and lattice degrees of freedom. These findings together raise questions on the role of structural disorder in complex materials, high temperature superconductivity specifically.

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