請用此 Handle URI 來引用此文件:
http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/46116
標題: | 對雙能隙超導體砷化鈮的理論研究 Theoretical Study on NbSe2 as a Two-gap Superconductor |
作者: | Ta Ko 柯達 |
指導教授: | 高英哲(Kao Ying-Jer) |
關鍵字: | 鈮化砷,雙能隙,硼化錳,超流體密度,較高臨界場, two-gap,Ginzburg-Landau theory,Eilenberger equation,NbSe2,MgB2,Superfluid density,upper critical field, |
出版年 : | 2010 |
學位: | 碩士 |
摘要: | NbSe2 has been recognized as a multiband superconductor recently by many experiments, including
the reported Fermi-sheet-dependent superconductivity in angle-resolved photoemission spectroscopy, thus strongly suggesting the multiband nature in NbSe2. It appears that a second energy gap involved can give a plausible explanation for previous experiments. Viewing NbSe2 as a two-gap superconductor, we proposed two possible scenarios to investigate how to locate the large gap and the small gap on the three bands in NbSe2. The two-gap Ginzburg-Landau theory is used to calculate the upper critical field and the corresponding gap ratio near Tc. Also, we apply the two-band Eilenberger equations and the two-gap BCS theory to calculate the superfluid density and the specific heat. The obtained results are fitted to previous experimental data, and it appears that the more plausible scenario is to respectively locate the large gap and the small gap on Nb-derived antibonding band and the Nb-derived bonding band. While previous studies have suggested that the Se-derived band serves as the isotropic small gap, we exclude such role of the Se-derived band for two reasons. One is its bad fit to the superfluid density, and the other is that the gap ratio obtained in the fit to Hc2(ab) is inconsistent with previous ARPES studies. Additionally, we discuss how the upper critical field is affected by the intraband Fermi-velocity anisotropy, interband Fermi-velocity anisotropy, density of states, interband coupling and the transition temperature of the large gap. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/46116 |
全文授權: | 有償授權 |
顯示於系所單位: | 物理學系 |
文件中的檔案:
檔案 | 大小 | 格式 | |
---|---|---|---|
ntu-99-1.pdf 目前未授權公開取用 | 2.28 MB | Adobe PDF |
系統中的文件,除了特別指名其著作權條款之外,均受到著作權保護,並且保留所有的權利。