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研究生：	范軒豪 Hsuan-Hao Fan
論文名稱：	光電導和磁穿透深度在鐵基超導的理論研究 Theoretical Studies of Optical Conductivity and Penetration Depth in Pnictide Superconductors
指導教授：	吳文欽 Wu, Wen-Chin
學位類別：	碩士 Master
系所名稱：	物理學系 Department of Physics
論文出版年：	2009
畢業學年度：	97
語文別：	英文
論文頁數：	60
中文關鍵詞：	鐵基超導、兩帶模型、光電導、磁穿透深度
英文關鍵詞：	iron-based superconductor, two-orbital model, optical conductivity, penetration depth
論文種類：	學術論文
相關次數：	點閱：187 下載：3
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我們利用兩帶模型去研究光電導以及磁穿透深度。由於晶體的對稱性，所以我們考慮了可能的配對對稱性。對於有節點的配對對稱性，我們發現光電導的實部在頻率為零的附近有一個很強的峰。然而對於沒有節點的能隙，intraband 在光電導實部的貢獻在ω≦2△0時幾乎為零。然而，在很多的情況interband都是有貢獻的。然後在磁穿透深度的研究當中，我們得到以下結果：在接近零溫時，對於沒有能隙節點的情況λ^2(0)/λ^2(T) 會呈現指數地下降；然而對於有能隙節點λ^2(0)/λ^2(T) 與溫度成線性關係。

We studied the optical conductivity and the penetration depth on pnictide superconductors based on the two-orbital model proposed by S. Raghu et al. Taking into account the D4 symmetry of the crystals, various possible pairing symmetries are considered. We have found that the real part of optical conductivity σ1(ω) has a strong peak near zero frequency for the case of nodal gaps. For the case of nodeless gaps, σ1(ω) is essentially zero for ω≦2△0 for the intraband contribution. Nevertheless, interband contribution seems to dominate in most cases in these materials. In the study of the penetration depth, we have obtained that the penetration depth λ^2(0)/λ^2(T) behaves exponentially down to zero temperature for nodeless gaps, while λ^2(0)/λ^2(T) has linear temperature dependence at very low temperature.

Introdction .............................................................................. 1
Model ...................................................................................... 7
1 Introduction ........................................................................................ 7
2 Model Hamiltonian in Normal State ................................................. 7
3 Model Hamiltonian in Superconducting State ................................ 13
Optical Conductivity ........................................................... 22
1 Introduction ...................................................................................... 22
2 Theory .............................................................................................. 23
2.1 Linear Response Theory ............................................................ 23
2.2 Kubo Formula for Optical Conductivity ................................... 26
3 Results .............................................................................................. 34
Penetration Depth ................................................................ 49
1 Introduction ...................................................................................... 49
2 Theory .............................................................................................. 50
3 Results .............................................................................................. 52
Conclusion ............................................................................ 57
References ..................................................................................................................... 59
                                

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