存在相互作用时超导-超导共存相的稳定性
Stability of the coexistent superconducting-nematic phase under the presence of intersite interactions
摘要：
本文分析了正方晶格上扩展的Hubbard模型和$t$ - $J$-$U$模型中，位间相互作用项对共存超连续相（SC+N）稳定性的影响.为了考虑到具有适当精度的相关效应，我们使用基于\textit{diagrammatic expansion of the Gutzwiller wave function}（DE-GWF）的方法，该方法以系统的方式超越了重整化平均场论（RMFT）。作为我们分析的出发点，我们讨论的情况下，哈伯德模型的SC+N相的稳定区域的intrasite库仑排斥空穴掺杂平面。接下来，我们表明，交换相互作用项增强超导性，同时抑制向列性，而位间库仑排斥项的行为在相反的方式。SC和N相相互作用的竞争特征在整个分析中清晰可见。一个普遍的结论是，在$t$ -$U$模型中，在高T $_C$铜酸盐的典型$J$积分值（$J\approx 0.1$ eV）下，结晶相不存在。为了完整起见，还分析了相关跳变项的影响。因此，目前的讨论包含所有相关的双网站的相互作用项出现在参数化的单带模型内的第二个量化方案。最后，通过与RMFT结果的比较，说明了图解展开的高阶项对转动对称破缺的影响。
英文摘要：
We analyze the effect of intersite-interaction terms on the stability of the coexisting superconucting-nematic phase (SC+N) within the extended Hubbard and $t$-$J$-$U$ models on the square lattice. In order to take into account the correlation effects with a proper precision, we use the approach based on the \textit{diagrammatic expansion of the Gutzwiller wave function} (DE-GWF), which goes beyond the renormalized mean field theory (RMFT) in a systematic manner. As a starting point of our analysis we discuss the stability region of the SC+N phase on the intrasite Coulomb repulsion-hole doping plane for the case of the Hubbard model. Next, we show that the exchange interaction term enhances superconductivity while suppresses the nematicity, whereas the intersite Coulomb repulsion term acts in the opposite manner. The competing character of the SC and N phases interplay is clearly visible throughout the analysis. A universal conclusion is that the nematic phase does not survive within the $t$-$J$-$U$ model with the value of $J$ integral typical for the high-T$_C$ cuprates ($J\approx 0.1$eV). For the sake of completeness, the effect of the correlated hopping term is also analyzed. Thus the present discussion contains all relevant two-site interaction terms which appear in the parametrized one-band model within the second quantization scheme. At the end, the influence of the higher-order terms of the diagrammatic expansion on the rotational symmetry breaking is also shown by comparing the DE-GWF results with those corresponding to the RMFT.
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