The electronic structure of cuprates from high energy spectroscopy

Abstract

We report studies of the electronic structure and elementary excitations of doped and undoped cuprate chains, ladders and planes. Using high energy spectroscopies such as xray absorption, core level photoemission and angle resolved photoemission spectroscopy, important information regarding the charge distribution and hole dynamics can be obtained. The comparison of the experimental data with suitable theoretical models sets constraints on the parameters entering into the model calculations, and offers insight into the important physical quantities governing the electronic structure of these materials. Recurring themes include the importance of the dimensionality of the Cu-O network (1D 2D) and the crucial role played by the spin-background in determining the dynamics of low-lying excitations in these strongly correlated systems.

The distribution of the doped holes in La2−xSrxCu1−yRuyO4−δ

“…This is a result of the fact that to achieve a 3d 8 10 L final state in Cu L 2;3 XAS. A similar spectral feature has also been found in the Cu(III) oxide NaCuO 2 in which a 90°Cu-O-Cu interaction pathway causes the inter-plaquette interaction to be weak, leading to a behavior of analogous that an isolated CuO 4 plaquette [23]. In strong contrast to these quasi isolated Cu(III)O 4 plaquette systems, for the Cu(III) oxide LaCuO 3 which has an 180°Cu-O-Cu interaction pathway leading to stronger inter-plaquette hopping and metallic conductivity, a double-peaked Cu L 3 structure has been found [22].…”

“…For systems built up of corner sharing of CuO 4 plaquettes (180°Cu-O-Cu interaction pathway), the spectral features from a Cu(III) state should lie $10 eV above the main peak as a weak, broad satellite [15,22,23]. In contrast to the preliminary work of some of us [24] -in which only the main peak in Cu L 3 XAS spectra were presented and the satellite structures for the 2p 3d 9 final state were not shown -now we measured both the Cu L 3 and Cu L 2 spectra, thus not missing out on any important information.…”

Defect Engineering in Oxide Heterostructures by Enhanced Oxygen Surface Exchange

“…Therefore, in the context of the issue at hand, the dichroism in the X‐ray absorption between an experiment placing the E ‐vector in and perpendicular to the film plane will provide information on the structure of the cuprate layer. For the infinite layer structure, E ‖ film would yield a strong so‐called white line (2p 6 3d 9 → 2p 5 3d 10 ), and for the E ‐vector pointing out of the film plane, almost no intensity would be expected 35. For the Cu–O chain comprised of edge‐sharing plaquettes, bulk Sr 2 CuO 3 is a good reference material, and again here the Cu–L 3 white line is strong for E in the plane of the plaquettes and ten times weaker for E perpendicular to the plaquettes 36.…”

Formation of Hubbard-like bands as a fingerprint of strong electron-electron interactions in FeSe

“…Generally speaking, at higher binding energy, features can become very broad and incoherent when Σ becomes large, and in particular the formation of Hubbardlike bands is possible [32,33]. While experimental evidence of Hubbard bands has been largely reported for effective oneband systems [17,34], results for multiorbital systems are scarce with only a few well-studied exceptions like transition metal oxides [35][36][37][38].…”