电子-声子问题的累积量方法。II。自洽累积展开
Cumulant methods for electron-phonon problems. II. The self-consistent cumulant expansion
摘要：
在这项工作中，我们提出了一个自洽累积展开（SC-CE），并研究其准确性的一维Holstein模型与声子色散。我们发现，对于有限的晶格尺寸，SC-CE方程的数值积分变得不稳定，在很长的时间。这个缺陷是部分改善时，在热力学极限研究系统，使示范，SC-CE纠正许多赤字的标准微扰CE（非色散）荷斯坦模型。在更现实的分散Holstein模型中出现的自然声子阻尼使得SC-CE稳定，从而允许对该方法进行完整的评估。在这里，我们发现，自我一致性显着纠正了许多故障中发现的微扰CE，但也介绍了一些非物理的功能。最后，我们评论的潜在用途SC-CE作为一种工具，计算格林函数在一般的多体问题。
英文摘要：
In this work we present a self-consistent cumulant expansion (SC-CE) and investigate its accuracy for the one-dimensional Holstein model with and without phonon dispersion. We show that for finite lattices sizes, the numerical integration of the SC-CE equations becomes unstable at long times. This defect is partially ameliorated when studying systems in the thermodynamic limit, enabling the demonstration that the SC-CE corrects many deficits of the standard perturbative CE in the (non-dispersive) Holstein model. The natural phonon damping that arises in the more realistic dispersed Holstein model renders the SC-CE stable, allowing for a complete assessment of the method. Here we find that self-consistency dramatically corrects many of the failures found in the perturbative CE, but also introduces some unphysical features. Finally, we comment on the potential use of SC-CE as a tool for calculating Green's functions in generic many-body problems.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
