二维Fe $_{n}$ GeTe $_{2}$（n= 3，4，5）电子关联效应的动力学平均场论解
Unraveling effects of electron correlation in two-dimensional Fe$_{n}$GeTe$_{2}$ (n=3, 4, 5) by dynamical mean field theory
摘要：
Fe $_{n}$ GeTe $_{2}$系统是一种新发现的二维范德华材料，在室温下具有磁性。属于Fe $_{n}$ GeTe $_{2}$类的子系统是特殊的，因为它们表现出位置相关的磁性行为。本文采用第一性原理计算对Fe $_{n}$ GeTe $_{2}$（$n$ = 3，4，5）（FGT）体系的磁性和电子关联效应进行了临界评价.已经使用了三种不同的从头算方法，即，i）标准密度泛函理论（DFT），ii）结合静态电子相关（DFT+U）和iii）包括动态电子相关效应（DFT+DMFT）。我们的结果表明，DFT+DMFT是最准确的技术，正确地再现磁相互作用和实验观察到的转变温度。由于DFT+U方法得到的结构参数、磁矩和交换相互作用值不准确，因此该方法不适用于FGT族。这类材料的磁性的正确测定是重要的，因为它们是有前途的候选人在室温下的自旋输运和自旋电子学应用。
英文摘要：
The Fe$_{n}$GeTe$_{2}$ systems are newly discovered two-dimensional van-der-Waals materials, exhibiting magnetism at room temperature. The sub-systems belonging to Fe$_{n}$GeTe$_{2}$ class are special because they show site-dependent magnetic behavior. We focus on the critical evaluation of magnetic properties and electron correlation effects in Fe$_{n}$GeTe$_{2}$ ($n$= 3, 4, 5) (FGT) systems performing first-principles calculations. Three different ab-initio approaches have been used, viz., i) standard density functional theory (DFT), ii) incorporating static electron correlation (DFT+U) and iii) inclusion of dynamic electron correlation effect (DFT+DMFT). Our results show that DFT+DMFT is the most accurate technique to correctly reproduce the magnetic interactions and experimentally observed transition temperatures. The inaccurate values of structural parameters, magnetic moments and exchange interactions obtained from DFT+U make this method inapplicable for the FGT family. Correct determination of magnetic properties for this class of materials is important since they are promising candidates for spin transport and spintronic applications at room temperature.
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