用K边X射线吸收谱测量本征电荷转移带隙
Measuring the intrinsic charge transfer gap using K-edge X-ray absorption spectroscopy
摘要：
X射线吸收光谱中的前边缘特征包含关于最低激发态的关键信息，从而包含关于系统的最感兴趣的物理性质的关键信息。在过渡金属氧化物中，它们特别具有结构，但由于若干计算挑战，通过与计算比较来提取物理参数并不容易。在第一性原理方法中，结合核-空穴吸引和关联效应，计算了NiO中Ni的K边X射线吸收谱。我们获得了一个惊人的，无参数的协议与实验数据表明，偶极前边缘功能以上的相关间隙是由于非本地激发在很大程度上不受影响的核心孔。我们表明，在电荷转移绝缘体，这个属性可以用来测量的相关间隙和探测的上哈伯德带的本征位置。
英文摘要：
Pre-edge features in X-ray absorption spectroscopy contain key information about the lowest excited states and thus on the most interesting physical properties of the system. In transition metal oxides they are particularly structured but extracting physical parameters by comparison with a calculation is not easy due to several computational challenges. By combining core-hole attraction and correlation effects in first principles approach, we calculate Ni K-edge X-ray absorption spectra in NiO. We obtain a striking, parameter-free agreement with experimental data and show that dipolar pre-edge features above the correlation gap are due to non-local excitations largely unaffected by the core-hole. We show that in charge transfer insulators, this property can be used to measure the correlation gap and probe the intrinsic position of the upper-Hubbard band.
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