In this paper we provide an exhaustive study of the photoemission spectrum of paramagnetic FeO under pressure using a refined version of our recently derived many-body effective energy theory (MEET). We show that, within a nonmagnetic description of the paramagnetic phase, the MEET gives an overall good description of the photoemission spectrum at ambient pressure as well as the changes it undergoes by increasing pressure. In particular at ambient pressure the band gap opens between the mixed Fe $t_{2g}$ and O $2p$ states and the Fe $4s$ states and, moreover, a $d\text{−}d$ gap opens, which is compatible with a high-spin configuration (hence nonzero local magnetic moments as observed in experiment), whereas with decreasing pressure the band gap tends to close, $t_{2g}$ states tend to become fully occupied, and $e_g$ states tend to become fully unoccupied, which is compatible with a low-spin configuration (hence a collapse of the magnetic moments as observed in experiment). This is a remarkable result, since, within a nonmagnetic description of the paramagnetic phase, the MEET is capable to correctly describe the photoemission spectrum and the spin configuration at ambient as well as high pressure. For comparison we report the band-gap values obtained using density-functional theory with a hybrid functional containing screened exchange (HSE06) and a variant of the $GW$ method (self-consistent COHSEX), which are reliable for the description of the antiferromagnetic phase. Both methods open a gap at ambient pressure, although, by construction, they give a low-spin configuration; increasing pressure they correctly describe the band-gap closing. We also report the photoemission spectrum of the metallic phase obtained with one-shot fully dynamical $GW$ on top of the local-density approximation, which gives a spectrum very similar to dynamical mean-field theory results from literature.

中文翻译：

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顺磁性FeO在压力下的光发射光谱：朝着ab起始的方向

在本文中，我们使用最新推导的多体有效能量理论（MEET）的改进版，对顺磁性FeO在压力下的光发射光谱进行了详尽的研究。我们表明，在顺磁相的非磁性描述中，MEET可以很好地全面描述环境压力下的光发射光谱及其随着压力的增加而发生的变化。特别是在环境压力下，混合铁之间的带隙打开${Ť}_{2G}$ 和O $2p$ 州和铁 $4s$ 州，此外， $d\text{-}d$ 间隙打开，这与高旋转配置兼容（因此，实验中观察到的局部磁矩为非零），而随着压力的降低，带隙趋于闭合， ${Ť}_{2G}$ 各州趋于完全被占领，并且 ${Ë}_G$态往往变得完全不被占用，这与低旋转配置兼容（因此实验中观察到的磁矩崩溃）。这是一个了不起的结果，因为在顺磁相的非磁性描述中，MEET能够正确描述环境及高压条件下的光发射光谱和自旋构型。为了进行比较，我们报告了使用密度泛函理论与包含屏蔽交换（HSE06）和$G\mathrm{w\; ^}$方法（自洽COHSEX），对于描述反铁磁相是可靠的。两种方法都在环境压力下打开了一个缝隙，尽管通过构造，它们具有低自旋结构。随着压力的增加，他们正确地描述了带隙的闭合。我们还报告了通过一次全动态获得的金属相的光发射光谱$G\mathrm{w\; ^}$ 在局部密度近似的基础上，产生的光谱与文献中的动态平均场理论结果非常相似。