标题： CDMFT方法在正方形晶格Hubbard模型反铁磁转变中的研究：光学电导率和电子结构 显示英文标题

标题： A CDMFT study of antiferromagnetic transition in the square-lattice Hubbard model: optical conductivity and electronic structure

摘要： 我们数值研究了在半填充的正方晶格Hubbard模型中"反铁磁"相变附近的光学电导率$\sigma (\omega )$。我们使用簇动力学平均场理论并计算包括顶点修正的电导率，为此，我们重新表述了反铁磁相中的顶点修正。我们发现顶点修正改变了正方晶格中电导率的温度和$\omega$依赖性的各种重要细节，这与受挫三角晶格中的莫特转变情况形成鲜明对比。一般来说，顶点修正增强了$\omega$依赖性的变化，并尖锐化顺磁相中的德鲁德峰和高$\omega$无序峰。它们还增强了反铁磁相中$\sigma (\omega )$在$\omega$=0 处的凹陷。因此，在顺磁相中直流电导率被增强而在反铁磁相中被抑制，但这种变化发生在相变温度稍低处。我们还发现，在相变温度以上存在一个温度区域，其中直流电导率表现出绝缘行为，但$\sigma (\omega )$仍保留德鲁德峰，该区域由顶点修正稳定。我们还研究了哪些涨落对顶点修正很重要，并详细分析了顶点函数的动量依赖性。 显示英文摘要

摘要： We numerically study optical conductivity $\sigma (\omega )$ near the "antiferromagnetic" phase transition in the square-lattice Hubbard model at half filling. We use a cluster dynamical mean field theory and calculate conductivity including vertex corrections, and to this end, we have reformulated the vertex corrections in the antiferromagnetic phase. We find that the vertex corrections change various important details in temperature- and $\omega$-dependencies of conductivity in the square lattice, and this contrasts sharply the case of the Mott transition in the frustrated triangular lattice. Generally, the vertex corrections enhance variations in the $\omega$-dependence, and sharpen the Drude peak and a high-$\omega$ incoherent peak in the paramagnetic phase. They also enhance the dip in $\sigma (\omega )$ at $\omega$=0 in the antiferromagnetic phase. Therefore, the dc conductivity is enhanced in the paramagnetic phase and suppressed in the antiferromagnetic phase, but this change occurs slightly below the transition temperature. We also find a temperature region above the transition temperature in which the dc conductivity shows an insulating behavior but $\sigma (\omega )$ retains the Drude peak, and this region is stabilized by the vertex corrections. We also investigate which fluctuations are important in the vertex corrections and analyze momentum dependence of the vertex function in detail.