Obtaining X-ray absorption near-edge structure for transition metal oxides via the Bethe-Salpeter equation

Transition metal oxides are an important class of materials featured with strongly correlated effects. Most interesting and yet to-be-unveiled physics is associated with the metal 3d orbitals, which can be probed by X-ray absorption near-edge spectroscopy. A thorough interpretation of the x-ray spectroscopy is often accompanied with first-principles simulations of structures, electronic properties and the corresponding x-ray spectra. However, the simulation for TMOs is particularly challenging with the localized 3d orbitals. Most previous studies relied on the ground-state calculations without the core-hole as a compromise. Other treated the excited atom as a charged impurity but the calculated spectra turn out to be even more deviated from experiments [1]. Here, we present the first study for the O K-edge for several typical TMOs via solving the Bethe-Salpeter equation (BSE). We have found that electron-core-hole interactions can alter the absorption spectra significantly. Our study helps to disentangle core-hole effects from the intrinsic electron correlations and hence facilitates the development of more advanced many-electron theories. [1] Isao Tanaka, Teruyasu Mizoguchi, and Tomoyuki Yamamoto J. Am. Ceram. Soc., 88 [8] 2013–2029 (2005)