Author's School

Graduate School of Arts & Sciences

Author's Department/Program

Physics

Language

English (en)

Date of Award

Spring 4-25-2013

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Chair and Committee

James S. Schilling

Abstract

Superconductivity has been studied extensively since it was first discovered over 100 years ago. High pressure studies, in particular, have been vital in furthering our understanding of the superconducting state. Pressure allows researchers to enhance the properties of existing superconductors, to find new superconductors, and to test the validity of theoretical models. This thesis presents a series of high pressure measurements performed in both He-gas and diamond anvil cell systems on various superconductors and on materials in which pressure-induced superconductivity has been predicted. Under pressure the alkali metals undergo a radical departure from the nearly-free electron model. In Li this leads to a superconducting transition temperature that is among the highest of the elements. All alkali metals have been predicted to become superconducting under pressure. Pursuant to this, a search for superconductivity has been conducted in the alkali metals Na and K. In addition, the effect of increasing electron concentration on Li1−xMgx alloys has been studied. Metallic hydrogen and hydrogen-rich compounds are believed to be good candidates for high temperature superconductivity. High pressure optical studies of benzene: C6H6) have been performed to 2 Mbar to search for pressure-induced metallization. Finally, cuprate and iron-based materials are considered high-Tc superconductors. These layered compounds exhibit anisotropic behavior under pressure. Precise hydrostatic measurements of dTc/dP on HgBa2CuO4+_ have been carried out in conjunction with uniaxial pressure experiments by another group. The results obtained provide insight into the effect of each of the lattice parameters on Tc. Finally, a series of hydrostatic and non-hydrostatic measurements on LnFePO: Ln = La, Pr, Nd) reveal startling evidence that the superconducting state in the iron-based superconductors is highly sensitive to lattice strain.

DOI

https://doi.org/10.7936/K76971QP

Comments

Permanent URL: http://dx.doi.org/10.7936/K76971QP

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Physics Commons

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