论文标题
除了对谐振非弹性X射线散射光谱的电子 - 光子耦合效应的单位近似模型之外
Beyond the single-site approximation modeling of electron-phonon coupling effects on resonant inelastic X-ray scattering spectra
论文作者
论文摘要
共振非弹性X射线散射（RIX）越来越多地用于表征材料中低能的集体激发。 RIX是一个强大的探测器，通常需要复杂的理论描述来解释数据。特别是，随着仪器分辨率的改善，对电子phonon（$ e $ -p）耦合的影响的准确理论的需求正在及时及时，并且这种能量状态正在迅速访问。迄今为止，仅针对此类问题进行了相当探索性的理论工作。我们通过提出一个多功能变化近似来计算弱掺杂材料中的RIX光谱，以弥补这一差距，以计算各种不同$ e $ -P耦合的型号。在这里，我们通过研究电子迁移率的作用来说明其潜力，这在基于Lang-Firsov理论的广泛使用的局部近似中被完全忽略了。假设电子 - 音波耦合是最简单的荷斯坦类型，我们讨论了局部近似失败的机制，并证明其不当使用可能会严重\ textit {低估} $ e $ e $ -p耦合强度。
Resonant inelastic X-ray scattering (RIXS) is used increasingly for characterizing low-energy collective excitations in materials. RIXS is a powerful probe, which often requires sophisticated theoretical descriptions to interpret the data. In particular, the need for accurate theories describing the influence of electron-phonon ($e$-p) coupling on RIXS spectra is becoming timely, as instrument resolution improves and this energy regime is rapidly becoming accessible. To date, only rather exploratory theoretical work has been carried out for such problems. We begin to bridge this gap by proposing a versatile variational approximation for calculating RIXS spectra in weakly doped materials, for a variety of models with diverse $e$-p couplings. Here, we illustrate some of its potential by studying the role of electron mobility, which is completely neglected in the widely used local approximation based on Lang-Firsov theory. Assuming that the electron-phonon coupling is of the simplest, Holstein type, we discuss the regimes where the local approximation fails, and demonstrate that its improper use may grossly \textit{underestimate} the $e$-p coupling strength.
