论文标题
Cuprate Ba $ _2 $ CUO $ _ {3+δ} $的超导机制基于多纤维lieb晶格模型
Superconducting mechanism for the cuprate Ba$_2$CuO$_{3+δ}$ based on a multiorbital Lieb lattice model
论文作者
论文摘要
对于最近发现的Cuprate超导体$ \ MATHRM {BA_ {2} CUO_ {3+δ}} $，我们提出了一个晶格结构，类似于Lieb所考虑的模型代表大量的氧气缺陷材料。我们首先研究Lieb-tattice结构的稳定性，然后基于第一原理计算构建多梁哈驼型模型。通过将波动 - 交换近似应用于模型并求解线性化的Eliashberg方程，我们表明$ S $ - 波和$ d $ - 波配对彼此之间会紧密竞争，更有趣的是，Orbital和Orbital和Orbital Inter-Orbital配对配对共存。我们进一步表明，如果$ d_ {3z^2-r^2} $ band的能量被提高，以使其“初步”，并且在逼真的频段填充方面，乐队的下边缘接近费米水平，$ s \ s \ pm pm $ -wave $ -Wave超电导性得到强烈增强。我们揭示了Lieb模型与通常的K $ _2 $ NIF $ _4 $结构之间的两轨模型之间的有趣关系，其中已知$ S-$和$ D $ WAVE配对之间的紧密竞争。在本模型中，增强的超导性进一步证明与先前在带有初期带的双层Hubbard模型中发现的增强功能有关。
For the recently discovered cuprate superconductor $\mathrm{Ba_{2}CuO_{3+δ}}$, we propose a lattice structure which resembles the model considered by Lieb to represent the vastly oxygen-deficient material. We first investigate the stability of the Lieb-lattice structure, and then construct a multiorbital Hubbard model based on first-principles calculation. By applying the fluctuation-exchange approximation to the model and solving the linearized Eliashberg equation, we show that $s$-wave and $d$-wave pairings closely compete with each other, and, more interestingly, that the intra-orbital and inter-orbital pairings coexist. We further show that, if the energy of the $d_{3z^2-r^2}$ band is raised to make it "incipient" with the lower edge of the band close to the Fermi level within a realistic band filling regime, $s\pm$-wave superconductivity is strongly enhanced. We reveal an intriguing relation between the Lieb model and the two-orbital model for the usual K$_2$NiF$_4$ structure where a close competition between $s-$ and $d-$wave pairings is known to occur. The enhanced superconductivity in the present model is further shown to be related to an enhancement found previously in the bilayer Hubbard model with an incipient band.
