LaFeAsO单晶各向异性光学性质的第一性原理研究

使用密度泛函第一性原理研究了高温超导体LaFeAsO各向异性的光学性质。在描述光学性质的计算原理和计算方法的基础上, 计算了LaFeAsO的态密度、光电导谱、反射谱以及电子能量损失谱。光电导谱中, x方向与z方向有着很大差别, 在沿x方向的第一个带间吸收峰出现在1.3 eV处, 沿z方向出现在1.5 eV处; 在反射谱与电子能量损失谱中, x方向与z方向的特征峰位置在能量较高处都是相互吻合的。分析认为, 主要是电子在Fe原子之间的各个态间的跃迁所引起。考虑到温度效应对其光学性质的影响, 在计算光学矩阵元时, 加入Lorentz展宽δ=0.10 eV。本文的研究结果, 可为实验制备以及材料性质的研究提供有价值的参考。

Ab-initio Investigation of Anisotropic Optical Properties of LaFeAsO

The anisotropic optical properties for superconductor LaFeAsO have been studied by full-potentiallinearized augmented plane wave(FLAPW) method based on density functional theory.In order to simulate the temperature effects,Lorentzian broadening(set as δ = 0.10 eV) is added into optical matrix elements during the calculation in these spectra.The optical conductivity spectra σ(ω),the reflectivity spectra R(ω) and electron energy loss spectra have been calculated.LaFeAsO is an anisotropic single crystal.The optical conductivity spectra along x-axis display quite different features in comparison with those of z-axis entirely,and the reflectivity spectra coincide well with the corresponding electron energy loss spectra especially about the characteristic peaks.In the optic conductivity spectra,the first intraband absorption along x-axis appear at 1.3 eV while it is at1.5 eV along z-axis.By further analysis,the properties are mainly caused by electronic transitions between the various states of the Fe atom.