光電導和磁穿透深度在鐵基超導的理論研究

Abstract

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.