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研究生： 李晏榛
Yen-Chen Lee
論文名稱： Flat-Band Ferromagnetism in the Armchair Graphene Nanoribbon
指導教授： 林秀豪
Hsiu-Hau Lin
口試委員:
學位類別： 碩士
Master
系所名稱： 理學院 - 物理學系
Department of Physics
論文出版年： 2008
畢業學年度： 96
語文別： 英文
論文頁數： 54
中文關鍵詞： 奈米帶 、碳 、鐵磁性
外文關鍵詞： nanoribbon, graphene, ferromagnetism, armchair
相關次數： 點閱：2  下載：0 
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    • We study the electronic correlation e ects in armchair graphene nanoribbons that have been recently proposed to be the building blocks of spin qubits. The armchair edges give rise to peculiar quantum interferences and lead to quenched
    kinetic energy of the itinerant carriers at appropriate doping level. This is a beautiful one-dimensional analogy of the Landau level formation in two dimensions except the
    magnetic eld is not needed here. Combining the techniques of e ective eld theory and variational wave function approach, we found that the ground state exhibits a
    new type of at-band ferromagnetism that hasn't been found before. At the end, we address practical issues about realization of this novel magnetic state in experiments.

    1 Introduction 2 The Ferromagnetism for 1-D Hubbard Model 2.1 Model 2.2 Variational Wave Function Approach 2.2.1 The Trial Wave Function 2.2.2 The Hopping Term 2.2.3 The Interaction Term 2.2.4 The Phase Diagram 2.3 Remarks 3 Flat Band in the Armchair Graphene Nanoribbon 3.1 Tight-Binding Model 3.2 Generalized Block Theorem 3.3 Flat Band 4 The Flat-Band Induced Ferromagnetism for the Armchair GNR 4.1 Hubbard Model for Armchair Graphene Nanoribbon 4.2 Variational Energy 4.2.1 Kinetic Energy 4.2.2 Interaction 4.3 The Ly = 3 Case 4.4 The Ly = 5 Case 4.5 Remarks 5 Edwards Ansatz for Spin Wave Excitation 39 5.1 The Ansatz 5.1.1 Two Special Cases 5.1.2 Normalization Factor 5.2 Apply to 1-D Hubbard Model Ring 5.2.1 On-site Interaction 5.2.2 Kinetic Energy 5.3 Eigenvalue Equation 6 Conclusions and Outlook

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