In this thesis, we develop a novel ab-initio technique to study transport in atomic scale devices based on a self-consistent solution of the Kohn-Sham equations for open systems in and out of equilibrium. Starting from the central motivating theorems of density functional theory, we introduce the basis of the ab-initio technique as currently practiced in condensed matter physics. The Kohn-Sham Hamiltonian is solved numerically by employing a Fireball atomic orbital basis set to transform the problem into matrix form. In order to study open systems, a natural screening approximation is introduced and it is demonstrated that, for the systems studied in this work, the Kohn-Sham potential is effectively screened and the screening approximation is appropriate for the study of atomic scale devices. The method developed in this thesis is contrasted with previous studies of transport in atomic scale devices and it is argued that it presents a significant advance and makes it possible to solve problems which could not previously be studied. / A few representative studies were undertaken in order to illustrate the advantage of using a self-consistent ab-initio method to study quantum transport in open systems. Several short carbon chains were coupled to Al electrodes and it was found that charge transfer plays a role in aligning the Fermi level with standing wave resonance peaks inside the atomic chain. Our study of a C60 molecular junction predicts a substantial equilibrium conductance due to charge transfer doping of three extra electrons inside the C60. Furthermore, these extra electrons may be depleted by an external gate voltage, reducing the conductance and thus producing a field-effect molecular switch. Transport and charge transfer were studied in a number of nanotube devices. Preliminary results are in agreement with recent experimental and theoretical results.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.37848 |
| Date | January 2000 |
| Creators | Taylor, Jeremy, 1974- |
| Contributors | Guo, Hong (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Physics.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001811109, proquestno: NQ70165, Theses scanned by UMI/ProQuest. |
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