Valence band hard x-ray photoelectron spectroscopy on 
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 transition-metal oxides containing rare-earth elements

Takegami, D.; Nicolaï, Laurent; Koethe, T. C.; Kasinathan, Deepa; Kuo, Chang‐Yang; Liao, Yen Fa; Tsuei, Ku‐Ding; Panaccione, G.; Offi, Francesco; Monaco, G.; Brookes, N. B.; Minář, J.; Tjeng, L. H.

doi:10.1103/physrevb.99.165101

Cited by 31 publications

(19 citation statements)

References 30 publications

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“…The overall energy resolutions for HAXPES and UPS measurements were 200 and 10 meV, respectively. To consider polarization-induced effects in the valence band spectra [16], the measurements were carried out in the normal emission geometry. UPS studies are done only for As 3d emissions and the incident light comes at an incidence angle of 45 • with the sample surface normal.…”

Section: Experimental Techniquementioning

confidence: 99%

Emergence of well-screened states in a superconducting material of the CaFe2As2 family

et al. 2021

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Coupling among conduction electrons (e.g., Zhang-Rice singlet) are often manifested in the core level spectra of exotic materials such as cuprate superconductors, manganites, etc. These states are believed to play key roles in the ground state properties and appear as low binding energy features. To explore such possibilities in the Fe-based systems, we study the core level spectra of a superconductor CaFe 1.9 Co 0.1 As 2 (CaCo122) in the CaFe 2 As 2 (Ca122) family employing high-resolution hard x-ray photoemission spectroscopy. While As core levels show almost no change with doping and cooling, the Ca 2p peak of CaCo122 shows reduced surface contribution relative to Ca122 and a gradual shift of the peak position towards lower binding energies with cooling. In addition, we discover the emergence of a feature at the lower binding energy side of the well-screened Fe 2p signal in CaCo122. The intensity of this feature grows with cooling and indicates additional channels to screen the core holes. The evolution of this feature in the superconducting composition and its absence in the parent compound suggests relevance of the underlying interactions in the ground state properties of this class of materials. These results reveal another dimension in the studies of Fe-based superconductors and the importance of such states in the unconventional superconductivity in general.

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Section: Experimental Techniquementioning

confidence: 99%

Emergence of well-screened states in a superconducting material of the CaFe2As2 family

et al. 2021

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“…Formally Co ion is trivalent (3d 6 ) in LaCoO 3 and LiCoO 2 , while it is tetravalent (3d 5 ) in SrCoO 3 . Due to its small CT energy, SrCoO 3 possesses a dominant d 6 configuration (plus one hole in ligands) in the [62], LaCoO3 (Sr 0.2% doped) [63] and LiCoO2 [64] are shown together. The Co L3-edge XAS and RIXS spectra calculated for (g,j) SrCoO3, (h,k) LaCoO2 and (i,l) LiCoO2, together with the experimental XAS data (dashed lines) [65][66][67].…”

Section: Cobaltitesmentioning

confidence: 99%

LDA+DMFTapproach to resonant inelastic x-ray scattering in correlated materials

et al. 2020

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We present a computational study of L-edge resonant inelastic x-ray scattering (RIXS) in correlated 3d transition-metal oxides using an ab initio method based on local density approximation + dynamical mean-field theory (DMFT). The present method, building on Anderson impurity model with an optimized continuum bath within DMFT, is an extension of the cluster model to include unbound electron-hole pair excitations as well as material-specific charge-transfer excitations with less empirical parameters. We find a good agreement with available experimental data. The relationship between correlated bands and fluorescence-like feature in the RIXS spectra is discussed.

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“…A different approach has been used in the case of lanthanum, based on the calculation of Takegami et al that finds the contribution of the La 6p two orders of magnitude smaller than the one of La 5p in LaCoO 3 . Given the similarity of the two compounds (both are 3d transition metal oxides containing rare-earth elements) we also conclude that the La p density of states in the valence band region originates primarily from the La 5p orbital contribution included in the DFT calculation [17]. Furthermore, in analogy with the La case, we assumed that the Sr p valence states originate from the Sr 4p, although we cannot exclude that such contribution might be related to hybridization effects.…”

Section: Resultsmentioning

confidence: 94%

“…In this framework, the study of the LSMO valence states by hard x-ray photoelectron spectroscopy (HAXPES), with excitation photon energies larger than 2 keV, enhances the sensitivity to specific orbital components usually not achievable for lower excitation photon energies through the more favorable contributions of the sp/d photoionization cross sections and specific experimental geometries [12][13][14][15][16]. This approach has revealed, for example, the importance of the rare-earth-5p contribution in the valence band spectrum of rare-earth compounds containing 3d transition metal oxides [17], and has outlined the similarities in the O 2p and Ir 5d hybridization process in several double perovskites containing Ir [18]. In particular, in the present contribution we show that the joint soft x-ray photoelectron spectroscopy (SXPES)/HAXPES investigation allows to distinguish in detail the orbital distribution of the different element in the LSMO valence band spectra, hence highlighting spectral terms, especially close to the Fermi energy, which are usually hidden and thus overlooked.…”

Section: Introductionmentioning

confidence: 99%

Identification of hidden orbital contributions in the La0.65Sr0.35MnO3 valence band

Offi

Yamauchi

Picozzi

et al. 2021

Phys. Rev. Materials

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Hybridization of electronic states and orbital symmetry in transition metal oxides are generally considered key ingredients in the description of both their electronic and magnetic properties. In the prototypical case of La 0.65 Sr 0.35 MnO 3 (LSMO), a landmark system for spintronics applications, a description based solely on Mn 3d and O 2p electronic states is reductive. We thus analyzed elemental and orbital distributions in the LSMO valence band through a comparison between density functional theory calculations and experimental photoelectron spectra in a photon energy range from soft to hard x rays. We reveal a number of hidden contributions, arising specifically from La 5p, Mn 4s, and O 2s orbitals, considered negligible in previous analyses; our results demonstrate that all these contributions are significant for a correct description of the valence band of LSMO and of transition metal oxides in general.

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Valence band hard x-ray photoelectron spectroscopy on 3d transition-metal oxides containing rare-earth elements

Cited by 31 publications

References 30 publications

Emergence of well-screened states in a superconducting material of the CaFe2As2 family

Emergence of well-screened states in a superconducting material of the CaFe2As2 family

LDA+DMFTapproach to resonant inelastic x-ray scattering in correlated materials

Identification of hidden orbital contributions in the La0.65Sr0.35MnO3 valence band

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