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Spin gaps in two models of strongly correlated electron systems Sikkema, Arnold Eric
Abstract
Two aspects of strongly correlated electron systems are studied in this thesis. Hubbard-type models are thought to be at the basis of high-critical-temperature superconductivity. One interaction which has not had much study is the nearest-neighbour hopping of on-site singlet pairs. We refine earlier renormalization group arguments and, using the density-matrix renormalization group method, numerically confirm their prediction that a spin gap opens at infinitesimal pair-hopping amplitude V > 0 in the one-dimensional tight-binding model. We also find a phase separation transition at a finite V > 0 as well as a spin-gap transition at a finite V < 0. The exotic magnetic behaviour of heavy-fermion materials involves an interplay between the screening of local moments from each other and the formation of a magnetic state of long range order. While the single-impurity Kondo Hamiltonian is thought to model some aspects of this behaviour, the properties of the Kondo lattice model away from half-filling are largely unknown. We determine the presence of a spin-gap region in the phase diagram of the one-dimensional Heisenberg-Kondo lattice model and make predictions about certain concealed dimerization order parameters.
Item Metadata
Title |
Spin gaps in two models of strongly correlated electron systems
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
1997
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Description |
Two aspects of strongly correlated electron systems are studied in this thesis.
Hubbard-type models are thought to be at the basis of high-critical-temperature superconductivity.
One interaction which has not had much study is the nearest-neighbour
hopping of on-site singlet pairs. We refine earlier renormalization group arguments and,
using the density-matrix renormalization group method, numerically confirm their prediction
that a spin gap opens at infinitesimal pair-hopping amplitude V > 0 in the
one-dimensional tight-binding model. We also find a phase separation transition at a
finite V > 0 as well as a spin-gap transition at a finite V < 0.
The exotic magnetic behaviour of heavy-fermion materials involves an interplay between
the screening of local moments from each other and the formation of a magnetic
state of long range order. While the single-impurity Kondo Hamiltonian is thought to
model some aspects of this behaviour, the properties of the Kondo lattice model away
from half-filling are largely unknown. We determine the presence of a spin-gap region
in the phase diagram of the one-dimensional Heisenberg-Kondo lattice model and make
predictions about certain concealed dimerization order parameters.
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Extent |
5778794 bytes
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Genre | |
Type | |
File Format |
application/pdf
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Language |
eng
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Date Available |
2009-04-03
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0085487
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
1997-05
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Item Media
Item Citations and Data
Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.