Abstract/Details

Numerical study of spin-fermion models for diluted magnetic semiconductors and high Tc cuprates


2007 2007

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Abstract (summary)

In this dissertation, Spin-Fermion (SF) models for diluted magnetic semiconductors and high temperature superconducting cuprates are constructed and studied with unbiased numerical techniques.

A microscopic model to describe magnetically doped III-V semiconductors is proposed. This model includes the appropriate lattice geometry, as well as, magnetic, spin-orbit, and Coulomb interactions and contains no free parameters. Its study using state-of-the-art numerical techniques provides results in excellent agreement with experimental data for Mn doped GaAs. For the first time, Curie-Weiss behavior of the magnetization is obtained numerically and the values of the Curie temperature are reproduced in a wide range of Mn doping and compensations. We observed that for x ≥ 3%, the holes are doped into the valence band and uniformly distributed in the material. This could support the "valence band" scenario regarding this material.

Phononic degrees of freedom, which are often neglected in studies of high Tc cuprates, are considered in a numerical study of a spin-fermion model. Both diagonal and off-diagonal electron-phonon interactions are considered. While diagonal terms tend to stabilize ordered structures such as stripes, the off-diagonal terms introduce disorder making this structures more dynamical. Our results indicate that phonons play a role in the stabilization of stripe-like states.

Indexing (details)


Subject
Condensation
Classification
0611: Condensation
Identifier / keyword
Pure sciences; Dilute magnetic semiconductors; Electron-phonon interactions; High-temperature cuprates; Spin-fermion models
Title
Numerical study of spin-fermion models for diluted magnetic semiconductors and high Tc cuprates
Author
Yildirim, Yucel
Number of pages
127
Publication year
2007
Degree date
2007
School code
0071
Source
DAI-B 68/09, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
ISBN
9780549252610
University/institution
The Florida State University
University location
United States -- Florida
Degree
Ph.D.
Source type
Dissertations & Theses
Language
English
Document type
Dissertation/Thesis
Dissertation/thesis number
3282680
ProQuest document ID
304875639
Copyright
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
http://search.proquest.com/docview/304875639
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