This item is only available for download by members of the University of Illinois community. Students, faculty, and staff at the U of I may log in with your NetID and password to view the item. If you are trying to access an Illinois-restricted dissertation or thesis, you can request a copy through your library's Inter-Library Loan office or purchase a copy directly from ProQuest.
Permalink
https://hdl.handle.net/2142/30820
Description
Title
Normal and superconducting many-body systems
Author(s)
Kastrinakis, George
Issue Date
1998
Director of Research (if dissertation) or Advisor (if thesis)
Chang, Yia-Chung
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Fermi liquid model
Superconductors
magnetoresistance
Cuprates
Language
en
Abstract
"This thesis consists of three Chapters. In the first Chapter, based on a planar unconventional
Fermi liquid model, we present several results on the optimally doped and overdoped cuprate
superconductors. For the normal state, we have analytically derived a linear in temperature and
energy scattering rate for the carriers. This scattering rate yields necessarily a linear in temperature
resistivity and a linear in 1/energy optical conductivity. The linearity of the scattering rate requires
that the interacting Fermi liquid has strong peaks in its density of states (van-Hove singularities
in 2 dimensions) near the chemical potential fl· Our results are backed by self-consistent Baym-Kadanoff (BK) numerical calculations, which also show that the interactions tend to pin the van-
Hove singularities close to fl· We show that the low energy dependence of the Millis-Monien-
Pines susceptibility XMMP can have a fermionic origin. We obtain particularly high transition
temperatures Tc from our BK-Eliashberg scheme by introducing an ansatz for the susceptibility
of the carriers. We postulate that the latter is enhanced in an additive manner due to the weak
antiferromagnetic order of the Cu02 planes. Thus we have obtained a dx2_y2 gap with Tc > 120°K
for nearest neighbor hopping t = 250me V.
In the second Chapter we propose a novel mechanism for giant corrections to the transport
quantities, including positive giant magnetoresistance, due to the presence of paramagnons in a
weakly disordered metal. At low temperature and for finite impurity spin scattering, for a certain
value, predicted from our theory, of the material-dependent paramagnon interaction, the total
conductivity becomes highly sensitive to the orbital effects of a finite magnetic field. This is
attributed to certain microscopic processes, otherwise negligibly small, which can be enhanced by
a resonance factor, emanating from· the spin-density channel. We obtain very good agreement between this theory and four (4) different positive giant magnetoresistance experiments, including
very recent ones, while making specific material-dependent predictions. We emphasize that our
theory broadens the 'conventional wisdom' viewpoint that weak disorder would only generate small
corrections to transport quantities.
In the third Chapter we examine the effects of interface roughness and/or planar impurity
doping in a superlattice, under the assumption that a weak disorder description is adequate. We
find that these two types of disorder are equivalent, and that they can be viewed as effective
""bulk"" disorder, with anisotropic diffusion coefficients. This study can offer quantitative insight to
transport properties of multilayers and devices, which contain inadvertently structural disorder at
the interfaces."
Use this login method if you
don't
have an
@illinois.edu
email address.
(Oops, I do have one)
IDEALS migrated to a new platform on June 23, 2022. If you created
your account prior to this date, you will have to reset your password
using the forgot-password link below.