Effective crystal field and Fermi surface topology: A comparison of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>d</mml:mi></mml:math>- and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>d</mml:mi><mml:mi>p</mml:mi></mml:mrow></mml:math>-orbital models

Parragh, N.; Sangiovanni, Giorgio; Hansmann, P.; Hummel, Stefan; Held, Karsten; Toschi, A.

doi:10.1103/physrevb.88.195116

Cited by 41 publications

(35 citation statements)

References 81 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, if the O 2p degrees of freedom are explicitly taken into account, then the orbital polarization is not so considerable as in the two-band model and the FS topology does not change [15]. Such behavior was examined by thorough comparison of both models, and attributed to the Hund's coupling between two d electrons that plays an important role when about one electron is transferred from the O 2p orbitals [16]. Our ARPES results strongly suggest that the chargetransfer energy in LNO is so small or negative that the O 2p degrees of freedom cannot be integrated out.…”

Section: B Electronic Analogue To High-t C Cuprates?mentioning

confidence: 99%

See 1 more Smart Citation

Thickness-dependent electronic structure in ultrathinLaNiO3films under tensile strain

et al. 2016

View full text Add to dashboard Cite

We investigated electronic-structure changes of tensile-strained ultrathin LNO films from 10 to 1 unit cells (UC) using angle-resolved photoemission spectroscopy (ARPES). We found that there is a critical thickness t c between 4 and 3 UC below which Ni e g electrons are confined in two-dimensional space. Furthermore, the Fermi surfaces (FSs) of LNO films below t c consist of two orthogonal pairs of one-dimensional (1D) straight parallel lines. Such a feature is not accidental as observed in constant-energy surfaces at all binding energies, which is not explained by first-principle calculations or the dynamical mean-field theory. The ARPES spectra also show anomalous spectral behaviors, such as no quasiparticle peak at Fermi momentum but fast band dispersion comparable to bare-band one, which is typical in a 1D system. As its possible origin, we propose 1D FS nesting, which also accounts for FS superstructures observed in ARPES.

show abstract

Section: B Electronic Analogue To High-t C Cuprates?mentioning

confidence: 99%

“…has not yet been realized and theoretical controversy has been provoked [15,16], other interesting results have been reported upon reducing its dimensionality. Among them, observation of a metal-insulator transition (MIT) [17][18][19] and a spin/charge ordering [20][21][22] below a critical thickness t c have drawn much attention.…”

Section: Introductionmentioning

confidence: 99%

Thickness-dependent electronic structure in ultrathinLaNiO3films under tensile strain

et al. 2016

View full text Add to dashboard Cite

show abstract

“…Strong d-p hybridization in transition-metal oxides makes orbital occupancies (such as n z 2 , n x 2 −y 2 ) quite sensitive to the choice of the local basis 31,33 with respect to which these occupancies are calculated. This is particularly pronounced in systems with a small charge-transfer energy, such as nickelates, in which the orbital character of states close to the Fermi level is determined by a mixture of d 7 and d 8 L states, 53-56 each of these states obviously having a different d-electron count.…”

Section: A Definition Of Occupanciesmentioning

confidence: 99%

Orbital polarization in strainedLaNiO3: Structural distortions and correlation effects

2014

View full text Add to dashboard Cite

Transition-metal heterostructures offer the fascinating possibility of controlling orbital degrees of freedom via strain. Here, we investigate theoretically the degree of orbital polarization that can be induced by epitaxial strain in LaNiO3 films. Using combined electronic structure and dynamical mean-field theory methods we take into account both structural distortions and electron correlations and discuss their relative influence. We confirm that Hund's rule coupling tends to decrease the polarization and point out that this applies to both the d 8 L and d 7 local configurations of the Ni ions. Our calculations are in good agreement with recent experiments, which revealed sizable orbital polarization under tensile strain. We discuss why full orbital polarization is hard to achieve in this specific system and emphasize the general limitations that must be overcome to achieve this goal.

show abstract

“…Since our DFT approach makes use of a plane-wave basis, we implement this step by means of the wannierization [13] technique. Up to this point, the methodology is very similar to previous work [14][15][16][17][18][19][20][21]. In the third step we add to the Hubbard model the intra-atomic Coulomb repulsion and the spin-orbit coupling for the electrons in the open-shell.…”

mentioning

confidence: 95%

Derivation of the spin Hamiltonians for Fe in MgO

Ferrón¹,

Delgado²,

Fernández-Rossier³

2015

New J. Phys.

View full text Add to dashboard Cite

A method to calculate the effective spin Hamiltonian for a transition metal impurity in a nonmagnetic insulating host is presented and applied to the paradigmatic case of Fe in MgO. In the first step we calculate the electronic structure employing standard density functional theory (DFT), based on generalized gradient approximation (GGA), using plane waves as a basis set. The corresponding basis of atomic-like maximally localized Wannier functions is derived and used to represent the DFT Hamiltonian, resulting in a tight-binding model for the atomic orbitals of the magnetic impurity. The third step is to solve, by exact numerical diagonalization, the N electron problem in the open shell of the magnetic atom, including both effects of spin-orbit and Coulomb repulsion. Finally, the low energy sector of this multi-electron Hamiltonian is mapped into effective spin models that, in addition to the spin matrices S, can also include the orbital angular momentum L when appropriate. We successfully apply the method to Fe in MgO, considering both the undistorted and Jahn-Teller (JT) distorted cases. Implications for the influence of Fe impurities on the performance of magnetic tunnel junctions based on MgO are discussed.which is fundamentally different from the multiplet nature of the real system. In this context, we find it convenient to have a constructive theoretical approach to derive the effective spin Hamiltonian, starting from an atomistic DFT description of the electronic properties of the system, but describing the electronic properties of the system with a multi-electron approach that captures the multiplet nature of the relevant electronic states.Here we propose a method to obtain an effective spin Hamiltonian for a magnetic atom in an insulating host, starting from density functional calculations, in four well-defined steps. First, a density functional calculation of the electronic properties of the magnetic atom inside the non-magnetic host is performed. The second step is to represent the effective DFT Hamiltonian with a basis of localized atomic orbitals, which allows us to obtain the crystal and ligand fields terms of the atomic orbitals of the relevant open shell of the magnetic atom, defining thereby a multi-orbital Hubbard Hamiltonian. Since our DFT approach makes use of a plane-wave basis, we implement this step by means of the wannierization [13] technique. Up to this point, the methodology is very similar to previous work [14][15][16][17][18][19][20][21]. In the third step we add to the Hubbard model the intra-atomic Coulomb repulsion and the spin-orbit coupling for the electrons in the open-shell. The final step is a symmetry analysis of the spectrum and wave functions, obtained by numerical diagonalization of the effective Hubbard model. The resulting multi-electron state analysis permits the construction of an effective spin Hamiltonian for the system.Below we describe in more detail the method and apply it to the paradigmatic case of Fe 2+ as a substitutional impurity of Mg in MgO [1], a band insu...

show abstract

Effective crystal field and Fermi surface topology: A comparison ofd- anddp-orbital models

Cited by 41 publications

References 81 publications

Thickness-dependent electronic structure in ultrathinLaNiO3films under tensile strain

Thickness-dependent electronic structure in ultrathinLaNiO3films under tensile strain

Orbital polarization in strainedLaNiO3: Structural distortions and correlation effects

Derivation of the spin Hamiltonians for Fe in MgO

Contact Info

Product

Resources

About