Calculated Momentum Dependence of Zhang-Rice States in Transition Metal Oxides

Abstract

Using a combination of local density functional theory and cluster exact diagonalization based dynamical mean field theory, we calculate many body electronic structures of several Mott insulating oxides including undoped high Tc materials. The dispersions of the lowest occupied electronic states are associated with the Zhang-Rice singlets in cuprates and with doublets, triplets, quadruplets and quintets in more general cases. Our results agree with angle resolved photoemission experiments including the decrease of the spectral weight of the Zhang-Rice band as it approaches k=0.Quasiparticle excitations in insulating transition metal oxides (TMOs) such as classical Mott-Hubbard systems or undoped high temperature superconductors (HTSCs) have been puzzling electronic structure theorists for many years [1,2]. While photoemission experiments in these materials show [3] the existence of the d-states located both right below the Fermi energy and at much higher binding energies (typically ∼10 eV), it is difficult to understand this genuine many-body redistribution of the spectral weight using calculations based on a static mean field theory [4,5], such as the density functional theory (DFT) in its local density approximation (LDA) [6]. Modern approaches, such as LDA+U [7], can differentiate between charge-transfer and Mott-Hubbard natures of these systems [8], but still have difficulties in recovering insulating behavior of the paramagnetic (PM) state and tackling more complicated many-body features such as Zhang-Rice (ZR) singlet of HTSCs [3,9]. Only most recent developments based on a combination of local density approximation (LDA) and dynamical mean field theory (DMFT) [10] have started to address those issues [11,12,13].In the present work, using a novel implementation of LDA plus cluster exact diagonalization based DMFT we demonstrate how to obtain accurate spectra of transition metal oxides and, in particular, describe full momentum dependent low-energy excitations associated in those systems with antiferromagnetic (AFM) Kondo-like coupling between a spin of oxygen hole injected by photoemission process and a local magnetic moment of the transition metal ion. These narrow energy bands are composed from the well known Zhang-Rice singlet states in cuprates [9], which have recently renewed their attention in connection with the disappearance of their spectral weight as the wave vector approaches the Brillouin Zone (BZ) center, and the observed high energy kink entitled as "waterfall" feature [14]. Zhang-Rice doublets have been discussed in NiO [15], and their further generalizations to triplets (CoO), quadruplets (FeO) and quintets (MnO) all naturally emerge from our LDA+DMFT calculations. We find that the ZR states exhibit a similar behavior in all systems including the loss of their spectral weight at the Γ point, which can be understood as the lack of hybridization between transition metal d states and neighboring oxygen p states, the effect most pronounced in HTSCs. There is a generally good agreement between o...

Correlated band structure of NiO, CoO, and MnO by variational cluster approximation

“…Figure 16 compares the k-integrated spectra, Figure 17 shows the dipersion along (100). The DMFT-results are taken from Yin et al [22] which have obatined essentially identical results as Kunes et al [21]. While the k-integrated spectra look similar at first sight, comparison with the band structure shows that there are major differences.…”

“…The distance between the dispersive band complex and the dispersionless bands is underestimated somewhat by VCA. To conclude we compare the results of the VCA for NiO with recent LDA+DMFT calculations [21,22]. Figure 16 compares the k-integrated spectra, Figure 17 shows the dipersion along (100).…”

“…This is also in contradition to LDA calculations which predicts band widths of around 2eV for the TM3d-derived bands. Starting with the work of Hubbard [11] a variety of theoretical methods have been invented to deal with this problem [12,13,14,15,16,17,18,19,20,21,22]. Major progress towards a quantitative description of 3d TM oxides has been made by the cluster method initiated by Fujimori and Minami [23,24,25,26,27] This takes the opposite point of view as compared to band theory, namely to abandon translational invariance and instead treat exactly -by means of atomic multiplet theory [28,29] -the Coulomb interaction in the 3d-shell of a TM-ion in an octahedral 'cage' of nearest-neighbor oxygen atoms.…”

Combined density functional and dynamical cluster quantum Monte Carlo calculations of the three-band Hubbard model for hole-doped cuprate superconductors

“…As the first study of this type we aim to address the following questions: (1) What is the magnitude of T c variation in the Hubbard model following the LDA+DCA scheme, and is this variation realistic? (2) Are there parameters found by LDA-DFT beyond those typically considered in Hubbard-like schemes that are particularly important for determining T c in these materials 25 .…”

Photoelectron spectroscopy of transition metal oxide interfaces

“…Reasonable agreement with the experimental finding was reported in 1990 by Svane and Gunnarsson [12] using a self-consistent version of the self-interacting-corrected local spin density approximation of the spin density functional formalism. For some early and some recent discussion on the issue of NiO see Merlin [13] and Yin et al [14], respectively. While refined calculations are meanwhile able to describe quite well the bandstructure for TMOs such as NiO [15], they still fail predicting or even explaining many of their properties.…”