Two-Band-Type Superconducting Instability in MgB2
Two-Band-Type Superconducting Instability in MgB2
复制标题
MgB2 中的双能带型超导不稳定性
DOI：
10.1143/jpsj.70.1476
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发表时间：
2001
影响因子：
1.7
通讯作者：
K. Yamaji
中科院分区：
文献类型：
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作者：
K. Yamaji
利用π能带紧束缚方法，将两个不等价的B-p-z轨道上的Hubbard在位库仑相互作用转化为π能带算符形式。对于波矢Q与{z}平行的散射过程，我们发现它具有相对简单的形式，包括带内库仑散射、带间对散射等，且耦合常数较大。这使得可以得到两个π带之间的带间对散射的幅度的简单表达式，当其中的带间极化函数足够大时，该幅度发散。对后者进行了近似评估，发现其在能带结构上得到了很大程度的增强。这些结果导致了发散的带间对散射，这意味着具有增强的T_c的双带型超导不稳定性。在每个能带中加入一个辅助的BCS吸引相互作用，给出了一个半定量的能隙方程，并给出了T_c和T_a。
Using the tight-binding method for the π-bands in MgB 2 , the Hubbard on-site Coulomb interaction on two inequivalent boron p z -orbitals is transformed into expressions in terms of π-band operators. For scattering processes relevant to the problem in which a wave vector q is parallel to \(\hat{z}\), it is found to take a relatively simple form consisting of intra-band Coulomb scattering, interband pair scattering etc. with large constant coupling constants. This allows to get a simple expression for the amplitude of interband pair scattering between two π-bands, which diverges if the interband polarization function in it becomes large enough. The latter was approximately evaluated and found to be largely enhanced in the band structure in MgB 2 . These results lead to a divergent interband pair scattering, meaning two-band-type superconducting instability with enhanced T c . Adding a subsidiary BCS attractive interaction in each band into consideration, a semi-quantitative gap equation is given, and T c a...