Skip to main content

Superconducting electrodynamics of underdoped yttrium barium cuprate

Resource type
Thesis type
(Thesis) Ph.D.
Date created
2010-08-23
Authors/Contributors
Abstract
The cuprate high-temperature (high-Tc) superconductors remain an important open problem in physics, with currently no microscopic theory that allows calculation of their doping-temperature phase diagram from first principles. The difficulty stems from the importance of electronic correlations, which means that interactions between charge carriers cannot be treated in an average way. However, a good phenomenological understanding of the phase diagram has been developed, with the two most prominent phases being the antiferromagnetic Mott insulating state (AFM) of the undoped parent compound, and the d-wave high-Tc superconducting state. Microwave spectroscopy has been used to study the physics of YBa2Cu3O6+x in a range of dopings near the boundary between the AFM and the superconducting state. A special technique for continuously tuning hole doping in underdoped YBa2Cu3O6+x was developed. This takes advantage of the connection between CuO2-plane doping and the oxygen coordination number of chain Cu atoms. The experiments were performed on a high quality YBa2Cu3O6:333 single crystal, prepared by the U.B.C. superconductivity group, in which cation disorder is estimated to be at the 10^-5 to 10^-4 level. Microwave spectroscopy was performed using cavity perturbation of a dielectric resonator at 2.64 GHz, at temperatures ranging from 1 K to 150 K. Measurements of surface impedance were made at approximately 40 dopings for in-plane orientation and 13 dopings for c-axis orientation. Measurements have been used to obtain the doping dependant microwave conductivity and superfluid density. A model was developed to allow an accurate determination of intrinsic c-axis surface impedance in a finite-size spherical sample. The electrodynamic data have been used in a number of separate analyses, including: placing limits on the magnitude of various electronic orders that might be competing with pure d-wave superconductivity; a two-fluid analysis of the microwave conductivity to determine the quasiparticle relaxation rate; a scaling analysis of the doping-dependent superfluid density in the vicinity of the Tc -> 0 quantum critical point; a fluctuation analysis of the normal state paraconductivity; and a determination of the doping dependence of the d-wave gap magnitude, nodal gap slope, and charge-current renormalization factor of the d-wave quasiparticles.
Document
Identifier
etd6185
Copyright statement
Copyright is held by the author.
Permissions
The author granted permission for the file to be printed and for the text to be copied and pasted.
Scholarly level
Supervisor or Senior Supervisor
Thesis advisor: Broun, David
Member of collection
Download file Size
etd6185_WHuttema.pdf 17.88 MB

Views & downloads - as of June 2023

Views: 0
Downloads: 1