Addressing electron-hole correlation in core excitations of solids: An all-electron many-body approach from first principles

Vorwerk, Christian; Cocchi, Caterina; Draxl, Claudia

doi:10.1103/physrevb.95.155121

Cited by 51 publications

(86 citation statements)

References 67 publications

(95 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The experimental φ and θ angular evolution of the A2 amplitude (Figure 5b and 6a in the SI) matches a quadrupolar transition, qualitatively consistent with the dominant quadrupolar cross-section obtained from FDMNES calculations in the region of peak A2 ( Figure 2b, inset and Figure 3b). Recent calculations accounting for the electron-hole interaction in the Bethe-Salpeter equation have reproduced peak A2, although with an underestimated amplitude as in our FDM calculations [31]. Peaks A1 and A2 are found to exhibit their maximum amplitude when the electric field is parallel to the (a, b) and c axes, respectively.…”

Section: B Origin Of Peak A2supporting

confidence: 65%

“…This explains the relatively intense A2 peak in amorphous TiO 2 [24] or upon electron trapping at defects after photoexcitation of anatase or rutile TiO 2 [25,26,29]. The unprecedented quantitative agreement provided in this work is made possible by the continued improvement of computational codes including full potentials [18][19][20] and the more accurate description of the core-hole interaction in Bethe-Salpeter calculations [31,55]. Experiments are on-going to extend this work to rutile TiO 2 .…”

Section: Discussionmentioning

confidence: 66%

See 1 more Smart Citation

X-ray absorption linear dichroism at the Ti K edge of anatase TiO2 single crystals

et al. 2019

View full text Add to dashboard Cite

Anatase TiO 2 (a-TiO 2 ) exhibits a strong X-ray absorption linear dichroism with the X-ray incidence angle in the pre-edge, the XANES and the EXAFS at the titanium K-edge. In the pre-edge region the behaviour of the A1-A3 and B peaks, originating from the 1s-3d transitions, is due to the strong p-orbital polarization and strong p − d orbital mixing. An unambiguous assignment of the pre-edge peak transitions is made in the monoelectronic approximation with the support of ab initio finite difference method calculations and spherical tensor analysis in quantitative agreement with the experiment. Our results suggest that previous studies relying on octahedral crystal field splitting assignments are not accurate due to the significant p-d orbital hybridization induced by the broken inversion symmetry in a-TiO 2 . It is found that A1 is mostly an on-site 3d-4p hybridized transition, while peaks A3 and B are non-local transitions, with A3 being mostly dipolar and influenced by the 3d-4p intersite hybridization, while B is due to interactions at longer range. Peak A2 which was previously assigned to a transition involving pentacoordinated titanium atoms is shown for the first time to exhibit a quadrupolar angular evolution with incidence angle which implies that its origin is primarily related to a transition to bulk energy levels of a-TiO 2 and not to defects, in agreement with theoretical predictions (Vorwerk et al , Phys. Rev. B, 95, 155121 (2017)). Finally, ab initio calculations show that the occurence of an enhanced absorption at peak A2 in defect rich a-TiO 2 materials is a coincidence of a blue shifted peak A1 due to the chemical shift induced by oxygen vacancies on quadrupolar transitions in the pre-edge. These novel results pave the way to the use of the pre-edge peaks at the Ti K-edge of a-TiO 2 to characterize the electronic structure of related materials and in the field of ultrafast X-ray absorption spectroscopy (XAS) where the linear dichroism can be used to compare the photophysics along different axes.

show abstract

Section: B Origin Of Peak A2supporting

confidence: 65%

Section: Discussionmentioning

confidence: 66%

X-ray absorption linear dichroism at the Ti K edge of anatase TiO2 single crystals

et al. 2019

View full text Add to dashboard Cite

show abstract

“…The adopted theoretical formalism, based on all-electron DFT 25 , allows to access the energies of all the electrons in the core. Although core energies are systematically underestimated by 10–20% in DFT 26 , relative core shifts referred to the same levels in different materials can be correlated with XPS data in a meaningful way. The calculated core level energies of each state in all the investigated materials are reported in Table 2.…”

Section: Resultsmentioning

confidence: 99%

Electronic structure and core electron fingerprints of caesium-based multi-alkali antimonides for ultra-bright electron sources

Cocchi

Mistry

Schmeißer

et al. 2019

Sci Rep

Self Cite

View full text Add to dashboard Cite

The development of novel photocathode materials for ultra-bright electron sources demands efficient and cost-effective strategies that provide insight and understanding of the intrinsic material properties given the constraints of growth and operational conditions. To address this question, we propose a viable way to establish correlations between calculated and measured data on core electronic states of Cs-K-Sb materials. To do so, we combine first-principles calculations based on all-electron density-functional theory on the three alkali antimonides Cs3Sb, Cs2KSb, and CsK2Sb with x-ray photoemission spectroscopy (XPS) on Cs-K-Sb photocathode samples. Within the GW approximation of many-body perturbation theory, we obtain quantitative predictions of the band gaps of these materials, which range from 0.57 eV in Cs2KSb to 1.62 eV in CsK2Sb and manifest direct or indirect character depending on the relative potassium content. Our theoretical electronic-structure analysis also reveals that the core states of these systems have binding energies that depend only on the atomic species and their crystallographic sites, with largest shifts of the order of 2 eV and 0.5 eV associated to K 2p and Sb 3d states, respectively. This information can be correlated to the maxima in the XPS survey spectra, where such peaks are clearly visible. In this way, core-level shifts can be used as fingerprints to identify specific compositions of Cs-K-Sb materials and their relation with the measured values of quantum efficiency. Our results represent the first step towards establishing a robust connection between the experimental preparation and characterization of photocathodes, the ab initio prediction of their electronic structure, and the modeling of emission and beam formation processes.

show abstract

“…In fact, recent ab initio studies using the Green's function approach showed the accurate prediction of core electron binding energy in XPS simulations [34][35][36] . Especially, the GW+Bethe-Salpeter equation (GW + BSE) method has been widely used for simulating the XAS spectra in molecule, cluster, and solid systems [37][38][39][40] . The success of the Green's-function approach in XPS and XAS simulations results from the accurate descriprtion of the screening ef-fect due to the core hole state within the GW approximation (GWA) [41][42][43][44] .…”

Section: Introductionmentioning

confidence: 99%

Ab initio simulations of x-ray emission spectroscopy with the GW+ Bethe-Salpeter equation method

Aoki

Ohno

2019

Phys. Rev. B

View full text Add to dashboard Cite

In order to calculate x-ray emission spectroscopy (XES) spectra, we apply the GW + Bethe-Salpeter equation (GW + BSE) method on a basis of extended quasiparticle theory which enables one to treat an arbitrary excited state as an initial state, because the initial state in the XES process is a highly excited state with a core hole. Compared to the preexisting experimental data of XES fluorescence photon energy, the calculated GW + BSE results give values with about 1-eV accuracy, which is comparable to the previous results using the time dependent density functional theory with the SRC exchange-correlation functional, the equation of motion-coupled cluster single and double, and delta self-consistent field methods. Our GW + BSE results reproduce corresponding experimental XES spectra without missing any peak. The method can assign the excitonic configuration of each peak in XES spectra with the quasiparticle levels. As a result, the analysis of excitonic structure for each peak gives obvious interpretation concerning the relation between excitonic states and valence states.

show abstract

Addressing electron-hole correlation in core excitations of solids: An all-electron many-body approach from first principles

Cited by 51 publications

References 67 publications

X-ray absorption linear dichroism at the Ti K edge of anatase TiO2 single crystals

X-ray absorption linear dichroism at the Ti K edge of anatase TiO2 single crystals

Electronic structure and core electron fingerprints of caesium-based multi-alkali antimonides for ultra-bright electron sources

Ab initio simulations of x-ray emission spectroscopy with the GW+ Bethe-Salpeter equation method

Contact Info

Product

Resources

About