Magnitude and Origin of the Band Gap in NiO

Sawatzky, G. A.; Allen, J. W.

doi:10.1103/physrevlett.53.2339

Cited by 921 publications

(550 citation statements)

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“…A consecutive tetrahedron integration over the entire Brillouin zone then results in the lattice Green's function, from which the partial spectrum A ν (ω) can be obtained. If we use the same definition of the band gap from experimental physics, i.e., the distance between the midpoints of the top of the peaks, we obtain a band gap of 4.4 eV, in good agreement with the experimental value of 4.3 eV obtained by Sawatsky and Allen [35]. These midpoints are represented by the horizontal dotted lines in Fig.…”

Section: B Electronic Structure Of Niosupporting

confidence: 74%

“…NiO is a prototypical material with strong electronic correlations that has been 245114-8 extensively studied both experimentally [34][35][36] and theoretically [37][38][39][40]. The experimental results from the literature for this compound are the next best thing compared to the exact solution of the impurity model of a multiband system.…”

Section: B Electronic Structure Of Niomentioning

confidence: 99%

“…As such, it is not surprising to reproduce the correct band gap of NiO around the Fermi energy. To further benchmark the CPE, we will compare the calculated spectrum with the experimental spectrum obtained by Sawatzky and Allen [35]. In this way, we want to explore how the CPE behaves over the entire real axis and whether it can capture the essential physics far from the Fermi energy, as we claimed in the exact diagonalization section.…”

Section: B Electronic Structure Of Niomentioning

confidence: 99%

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Continuous-pole-expansion method to obtain spectra of electronic lattice models

et al. 2014

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We present a new algorithm to analytically continue the self-energy of quantum many-body systems from Matsubara frequencies to the real axis. The method allows straightforward, unambiguous computation of electronic spectra for lattice models of strongly correlated systems from self-energy data that has been collected with state-of-the-art continuous time solvers within dynamical mean-field simulations. Using well-known analytical properties of the self-energy, the analytic continuation is cast into a constrained minimization problem that can be formulated as a quadratic programmable optimization with linear constraints. The algorithm is validated against exactly solvable finite-size problems, showing that all features of the spectral function near the Fermi level are very well reproduced and coarse features are reproduced for all energies. The method is applied to two well-known lattice problems, the two-dimensional Hubbard model at half filling, where the momentum dependence of the gap formation is studied, as well as a multiband model of NiO, for which the spectral function can be directly compared to experiment. Agreement with published results is very good.

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Section: B Electronic Structure Of Niosupporting

confidence: 74%

Section: B Electronic Structure Of Niomentioning

confidence: 99%

Section: B Electronic Structure Of Niomentioning

confidence: 99%

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Continuous-pole-expansion method to obtain spectra of electronic lattice models

et al. 2014

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“…The electronic structure of NiO has been extensively investigated. [5][6][7] There are strong indications that NiO is a charge-transfer insulator 5 in which the top of the valence band is primarily formed by oxygen 2p states, while the bottom of the conduction band is Ni-3d like. The insulating state is characterized by a band gap of about 4 eV.…”

mentioning

confidence: 99%

Antiferromagnetic phase transition and spin correlations in NiO

2009

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We have investigated the antiferromagnetic ͑AF͒ phase transition and spin correlations in NiO by hightemperature neutron diffraction below and above T N . We show that AF phase transition is a continuous second-order transition within our experimental resolution. The spin correlations manifested by the strong diffuse magnetic scattering persist well above T N Ϸ 530 K and could still be observed at T = 800 K which is about 1.5T N . We argue that the strong spin correlations above T N are due to the topological frustration of the spins on a fcc lattice. The Néel temperature is substantially reduced by this process. We determined the critical exponents ␤ = 0.328Ϯ 0.002 and = 0.64Ϯ 0.03 and the Néel temperature T N = 530Ϯ 1 K. These critical exponents suggest that NiO should be regarded as a 3dXY system. DOI: 10.1103/PhysRevB.79.172403 PACS number͑s͒: 75.25.ϩz Transition-metal oxides have been the subject of renewed interest ever since high-temperature superconductivity was discovered in cuprate materials. The transition-metal oxides with narrow d bands form strongly correlated electron systems or a Mott-Hubbard system in which Coulomb interactions between electrons lead to a breakdown of the conventional band theory. In such a system, hole or electron doping may transform an insulating antiferromagnet into a highly correlated metal. 1,2 In selected copper oxides, the metal can superconduct, while in others it is a strongly renormalized Fermi liquid. In manganites for example the doping transforms the insulating antiferromagnet into a ferromagnetic metal with colossal magnetoresistive properties. 3 Among the transition-metal oxides the antiferromagnetic NiO plays a key role in the studies of the electronic and magnetic properties of correlated 3d-electron system. NiO, along with other transition-metal oxides MnO, FeO, and CoO, crystallizes with the face-centered-cubic ͑space group Fm3m͒ NaCl-type structure. The magnetic properties of pure NiO are well known. Ni 2+ ions in NiO are in an S = 1 state and order at T N = 530 K in the type-II antiferromagnetic structure with the propagation vector k = ͑ 1 2 , 1 2 , 1 2 ͒. Ferromagnetic ͑111͒ layers are antiferromagnetically stacked along the ͓111͔ direction. The magnetic moments of Ni lie in the ͑111͒ plane and there is now considerable evidence that they lie in the ͓1,1,−2͔ direction. 4 There is a rhombohedral distortion at T N which increases as the temperature is lowered. The electronic structure of NiO has been extensively investigated. [5][6][7] There are strong indications that NiO is a charge-transfer insulator 5 in which the top of the valence band is primarily formed by oxygen 2p states, while the bottom of the conduction band is Ni-3d like. The insulating state is characterized by a band gap of about 4 eV. Magnetic exchange interactions in NiO have been calculated 7-9 and have also been determined by measuring the spin-wave dispersion by inelastic neutron scattering. 10 The spin-wave dispersion in NiO could be described by a nearest-neighbor ͑NN͒ ferromag...

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“…At ambient temperature, NiO is a type-II antiferromagnetic insulator with a local magnetic moment of between 1.64 µ B and 1.9 µ B 18 . Due to the persistence of its magnetic moment and optical gap, which is approximately 4 eV, above the Néel temperature, it falls broadly into the category of a Mott insulator 25 with a charge-transfer insulating gap of predominantly oxygen 2p to nickel 3d-orbital character 25,28 . It has long been recognised that LDA-type exchange correlation functionals 29 qualitatively fail to reproduce the physics of this material, grossly under-estimating the local magnetic moment, the Kohn-Sham gap and assigning an incorrect fully nickel 3d-orbital character to the valence band edge.…”

Section: Bulk Nickel Oxidementioning

confidence: 99%

Subspace Representations in Ab Initio Methods for Strongly Correlated Systems

O’Regan

Payne²,

Mostofi³

2011

Optimised Projections for the Ab Initio Simulation of Large and Strongly Correlated Systems

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We present a generalized definition of subspace occupancy matrices in ab initio methods for strongly correlated materials, such as DFT+U and DFT+DMFT, which is appropriate to the case of nonorthogonal projector functions. By enforcing the tensorial consistency of all matrix operations, we are led to a subspace projection operator for which the occupancy matrix is tensorial and accumulates only contributions which are local to the correlated subspace at hand. For DFT+U in particular, the resulting contributions to the potential and ionic forces are automatically Hermitian, without resort to symmetrization, and localized to their corresponding correlated subspace. The tensorial invariance of the occupancies, energies and ionic forces is preserved. We illustrate the effect of this formalism in a DFT+U study using self-consistently determined projectors.

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Magnitude and Origin of the Band Gap in NiO

Cited by 921 publications

References 18 publications

Continuous-pole-expansion method to obtain spectra of electronic lattice models

Continuous-pole-expansion method to obtain spectra of electronic lattice models

Antiferromagnetic phase transition and spin correlations in NiO

Subspace Representations in Ab Initio Methods for Strongly Correlated Systems

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