论文标题
低维材料中响应函数的批判分析
Critical analysis of the response function in low dimensional materials
论文作者
论文摘要
在静态介电响应函数的实际部分中存在尖峰的存在通常被接受为材料中电荷或自旋不稳定性的指示。但是，存在误解，即费米表面（FS）嵌套保证了像一维系统一样的响应函数的峰值，此外，在空和占用状态之间的响应函数矩阵元素通常被认为是次要的重要性，通常将其设置为Unity，并且像自由电子气体情况一样设置为Unity。在这项工作中，我们在密度功能理论的框架内通过模型系统和真实材料明确显示了有关响应函数峰的预测，使用FS嵌套和恒定矩阵元素会得出错误的结论。我们发现矩阵元素的包含完全改变了响应函数的结构。在所有研究的情况下，除了一维情况以外，我们都发现矩阵元素的包含均用恒定基质元素清洗了结构。我们的结论是，在对新材料中的不稳定性进行预测时，必须使用基质元素来计算完整的响应函数。
The presence of sharp peaks in the real part of the static dielectric response function are usually accepted as indication of charge or spin instabilities in a material. However, there are misconceptions that Fermi surface (FS) nesting guarantees a peak in the response function like in one-dimensional systems, and, in addition, response function matrix elements between empty and occupied states are usually considered of secondary importance and typically set to unity like in the free electron gas case. In this work, we explicitly show, through model systems and real materials, within the framework of density functional theory, that predictions about the peaks in the response function, using FS nesting and constant matrix elements yields erroneous conclusions. We find that the inclusion of the matrix elements completely alters the structure of the response function. In all the cases studied other than the one-dimensional case we find that the inclusion of matrix elements washes out the structure found with constant matrix elements. Our conclusion is that it is imperative to calculate the full response function, with matrix elements, when making predictions about instabilities in novel materials.
