Systematic Analysis of ARPES Spectra of Transition-Metal Oxides: Nature of EffectivedBand

Abstract

We have performed systematic tight-binding (TB) analyses of the angle-resolved photoemission spectroscopy (ARPES) spectra of transition-metal (TM) oxides AM O3 (M = Ti, V, Mn, and Fe) with the perovskite-type structure and compared the obtained parameters with those obtained from configuration-interaction (CI) cluster-model analyses of photoemission spectra. The values of ǫ d −ǫp from ARPES are found to be similar to the charge-transfer energy ∆ from O 2p orbitals to empty TM 3d orbitals and much larger than ∆ − U/2 (U : on-site Coulomb energy) expected for Mott-Hubbardtype compounds including SrVO3. ǫ d − ǫp values from ab initio band-structure calculations show similar behaviors to those from ARPES. The values of the p − d transfer integrals to describe the global electronic structure are found to be similar in all the estimates, whereas additional narrowing beyond the TB description occurs in the ARPES spectra of the d band.PACS numbers: 71.15.Mb, 71.28.+d, 71.30.+h 3d transition-metal (TM) oxides have attracted a lot of interest in these decades because of their intriguing physical properties such as metal-insulator transition, colossal magnetoresistance, and the ordering of spin, charge, and orbitals [1]. Photoemission spectroscopy has greatly contributed to the understanding of the electronic structures of these materials. The local electronic structure of strongly correlated 3d states of the TM atoms hybridizing with ligand p orbitals has been understood in the framework of the Zaanen-Sawatzky-Allen (ZSA) diagram [2] based on the configuration-interaction (CI) cluster-model analyses of core-level and valence-band angle-integrated photoemission spectra [3,4,5]. On the other hand, how the energy band structure of the periodic lattice emerges from the correlated local electronic structure has been an extremely difficult problem as has been extensively discussed in the case of f -electron systems [6,7], and no clear scenario has been established so far. On the experimental side, rather surprisingly Sarma et al. [8] have found that the angle-integrated valence-band photoemission spectra of various perovskite-type 3d TM oxides can be well reproduced by band-structure calculation based on the local spin-density approximation in spite of the strong electron correlation.In order to address the issue of a proper description of the periodic systems with strong correlation, the experimental determination of band dispersions by angleresolved photoemission spectroscopy (ARPES) has been highly required, but such data have been largely limited to low dimensional compounds [9, 10, 11] of limited chemical variety. For three-dimensional perovskite oxides, which have a wide variety of chemical compositions, even when bulk single crystals are available, they do not have cleavage planes required for ARPES measurements. Recently, technological development has made it possible to grow high-quality single-crystal thin films using the pulsed laser deposition method, and a setup has been developed for their film growth followed...

Multiband model for the electronic structure of Sr2TiO4

“…Electronic structure is similar to that of the three‐dimensional SrTiO, and HOMO–LUMO gap G (closely related to experimental band‐gap) comes out within the range eV. This range includes the values published in numerous DFT papers , , but experimental band gap which is 3.8 eV for SrTiO , (for SrTiO it is eV) is here underestimated. Therefore, in what follows, we increase the intraorbital Coulomb element on Ti ions to eV and keep eV.…”

“…; eV for SrTiO in Ref. . Note that there is no reason that is the same for in‐plane and for apical oxygens.…”

“…They may be deduced from previous studies. We have adopted the values of in‐plane hopping elements : eV and eV and also eV and eV which were used in , , and rescaled them (to account for the actual Ti‐O distances and to get out‐of‐plane hopping parameters), using Harrison formulas so they are appropriate for the apical Ti‐O bond lengths in SrTiO.…”

X-ray spectroscopic study ofBaFeO3thin films: AnFe4+ferromagnetic insulator

“…5 [44]. From those results and the set of the parameters for the CI cluster-model calculation, BaFeO 3 is classified as a covalent insulator (negative-charge-transfer-energy insulator) as proposed by Sarma et al (Mizokawa et al) in the modified ZaanenSawatzky-Allen diagram.…”

On the Neglect of Local Coulomb Interaction on Oxygens in Perovskites Described by the Multiband d-p Model

“…The in-plane hopping elements were fixed as (pdσ) = −2.4 eV and (pdπ) = 1.3 eV and also (ppσ) = 0.6 eV and (ppπ) = −0.15 eV [11][12][13]. The choice of the Coulomb elements in d-p model is difficult.…”