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arXiv 1111.1171cond-mat.supr-con
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电子-电子相互作用驱动的超导不稳定性的多带效应

Multiband Effects on Superconducting Instabilities Driven by Electron-Electron Interactions

Stefan Uebelacker, Carsten Honerkamp

摘要:

我们探讨了电子-电子相互作用驱动的d波超导不稳定性的多带效应。我们在二维正方晶格上的模型由一个扩展费米面的主带和主要的$d_{x^2-y^2}$轨道组成,其轨道特征受其他能量守恒轨道的影响。利用系统超导不稳定性的泛函重整化群描述和不同水平的近似,我们研究了如何配对的能量标度,从而临界温度是由能带结构的影响。我们发现,减少轨道混合作为轨道能量的函数,可以导致一个$T_c$增强,虽然费米面变得更加弯曲,因此不利于反铁磁自旋涨落。虽然我们的研究不能定量了解现实高$T_c$铜酸盐体系中的$T_c$差异,但它可能揭示了导致实际材料趋势的潜在机制。

英文摘要:

We explore multiband effects on d-wave superconducting instabilities driven by electron-electron interactions. Our models on the two-dimensional square lattice consist of a main band with an extended Fermi surface and predominant weight from $d_{x^2-y^2}$ orbitals, whose orbital character is influenced by the admixture of other energetically neighbored orbitals. Using a functional renormalization group description of the superconducting instabilities of the system and different levels of approximations, we study how the energy scale for pairing and hence the critical temperature is affected by the band structure. We find that a reduction of orbital admixture as a function of the orbital energies can cause a $T_c$ enhancement although the Fermi surface becomes more curved and hence less favorable for antiferromagnetic spin fluctuations. While our study does not allow a quantitative understanding of the $T_c$ differences in realistic high-$T_c$ cuprate systems, it may reveal an underlying mechanism contributing to the actual material trends.

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