Many-body effects on Cr(001) surfaces: An LDA+DMFT study

Schüler, Malte; Barthel, Stefan; Karolak, M.; Poteryaev, A. I.; Lichtenstein, A. I.; Katsnelson, M. I.; Sangiovanni, Giorgio; Wehling, T. O.

doi:10.1103/physrevb.93.195115

Cited by 6 publications

(12 citation statements)

References 32 publications

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“…These systems allow for a direct experimental manipulation of the Kondo scale and offer a rich playground for the exploration of connections between theoretical models and real-world physics. Section 4.3 is instead devoted to the study on the Cr(001) surface [86], which has been raising a long debate on the many-body nature of its low-energy spectral features. We reveal that the spectral feature observed close to the Fermi level is a consequence of changes in the electronic structure at the surface, as well as complex many-body effects in certain orbitals.…”

Section: Discussionmentioning

confidence: 99%

“…The origin of the peak was so far discussed either to be of single particle nature (surface state, [85]) or of many-body nature (orbital Kondo effect [84]). Here, we review our work from reference [86] where we use the LDA+DMFT method to unravel the nature of the resonance in the electronic spectrum of Cr(001). We show that local electronic correlations play a key role for understanding the electronic structure of Cr(001).…”

Section: Electronic Structure Of the Cr(001) Surfacementioning

confidence: 99%

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Realistic theory of electronic correlations in nanoscopic systems

Schüler

Barthel

Wehling

et al. 2017

Eur. Phys. J. Spec. Top.

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Abstract.Nanostructures with open shell transition metal or molecular constituents host often strong electronic correlations and are highly sensitive to atomistic material details. This tutorial review discusses method developments and applications of theoretical approaches for the realistic description of the electronic and magnetic properties of nanostructures with correlated electrons. First, the implementation of a flexible interface between density functional theory and a variant of dynamical mean field theory (DMFT) highly suitable for the simulation of complex correlated structures is explained and illustrated. On the DMFT side, this interface is largely based on recent developments of quantum Monte Carlo and exact diagonalization techniques allowing for efficient descriptions of general four fermion Coulomb interactions, reduced symmetries and spin-orbit coupling, which are explained here. With the examples of the Cr (001) surfaces, magnetic adatoms, and molecular systems it is shown how the interplay of Hubbard U and Hund's J determines charge and spin fluctuations and how these interactions drive different sorts of correlation effects in nanosystems. Non-local interactions and correlations present a particular challenge for the theory of low dimensional systems. We present our method developments addressing these two challenges, i.e., advancements of the dynamical vertex approximation and a combination of the constrained random phase approximation with continuum medium theories. We demonstrate how non-local interaction and correlation phenomena are controlled not only by dimensionality but also by coupling to the environment which is typically important for determining the physics of nanosystems.a

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Section: Discussionmentioning

confidence: 99%

Section: Electronic Structure Of the Cr(001) Surfacementioning

confidence: 99%

Realistic theory of electronic correlations in nanoscopic systems

Schüler

Barthel

Wehling

et al. 2017

Eur. Phys. J. Spec. Top.

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“…40 In order to use the CTQMC results as a benchmark the Cr(001) surface is modelled in exactly the same way as in Ref. 16. This is a slab of 10 atomic layers with a vacuum of approximately 16 Å stacked in the z-direction and perdiodically continued in the x and y direction.…”

Section: Computational Detailsmentioning

confidence: 99%

“…These newest experiments hint in the direction of a many-body interpretation of the resonance. Also recent dynamical mean-field theory (DMFT) calculations within the continuous-time quantum Monte Carlo (CTQMC) solver hint in this direction 16 . Namely it was 2 observed that the resonance was very robust against artificial shifts in the one-particle energies of the d xz , d yz and d z 2 states, which points towards a dominant many-body contribution.…”

Section: Introductionmentioning

confidence: 99%

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Origin of the quasiparticle peak in the spectral density of Cr(001) surfaces

et al. 2017

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In the spectral density of Cr(001) surfaces a sharp resonance close to the Fermi level is observed in both experiment and theory. For the physical origin of this peak two mechanisms were proposed. A single particle d z 2 surface state renormalised by electron-phonon coupling and an orbital Kondo effect due to the degenerate dxz/dyz states. Despite several experimental and theoretical investigations, the origin is still under debate. In this work we address this problem by two different approaches of the dynamical mean-field theory. First, by the spin-polarized T-matrix fluctuation exchange approximation suitable for weakly and moderately correlated systems. Second, by the non-crossing approximation derived in the limit of weak hybridization (i.e. for strongly correlated systems) capturing Kondo-like processes. By using recent continuous-time quantum Monte Carlo calculations as a benchmark, we find that the high-energy features, everything except the resonance, of the spectrum is captured within the spin-polarized T-matrix fluctuation exchange approximation. More precisely the particle-particle processes provide the main contribution. For the non-crossing approximation it appears that spin-polarized calculations suffer from spurious behavior at the Fermi level. Then, we turned to non spin-polarized calculations to avoid this unphysical behavior. By employing two plausible starting hybridization functions, it is observed that the characteristics of the resonance are crucially dependent on the starting point. It appears that only one of these starting hybridizations could result in an orbital Kondo resonance in the presence of a strong magnetic field like in the Cr(001) surface. It is for a future investigation to first resolve the unphysical behavior within the spin-polarized non-crossing approximation and then check for an orbital Kondo resonance.

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Electronic reconstruction of hexagonal FeS: a view from density functional dynamical mean-field theory

Craco

Faria

Leoni

2017

Mater. Res. Express

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IntroductionStoichiometric FeS is known to be a natural occurring mineral and has been investigated in fields as diverse as space science [1][2][3], geosciences [4], crystal chemistry [5] and condensed matter physics [6-9], because it is a possible core material for the terrestrial planets and one of the fundamental components of meteorites. Hence, similar to the classical Mott-Hubbard insulator FeO [10,11], FeS is considered to be an important material for solid state and earth sciences. Apart from this, hexagonal iron monosulfide has also been investigated in field as diverse as applied surface sciences [12] or as potential material for future energy storage and lithium-ion battery applications [13].As revealed by high-pressure x-ray diffraction measurements [1,3,5,14], FeS undergoes a series of structural phase transitions with increasing pressure (P): a detailed description of the × P T structural phase transformations of FeS can be found, for example, in [2] and [5]. From these studies it is known that under ambient conditions troilite FeS has a hexagonal structure (space group P − 62c) which is derivative of the NiAs unit cell with axis lengths = =å c 3 5.955 A f and =c 2 11.76 A f [14], where c f is the lattice parameter of the fundamental NiAs subcell. The corresponding crystal structure of troilite FeS is shown in figure 1, see also [14]. As seen in this figure, increasing pressure at room temperature results in a structural phase transition close to 3.5 GPa to an hexagonal NiAs-type structure (here dubbed as h-FeS) [2] with space group P mmc 63 /. With further increasing P at temperatures close to room-T results in an additional structural transformation at around 7 GPa to a monoclinic unit cell (space group P2 1 or P2 1 /m) [14]. It is worth noting as well that the change of the sulfur sublattice might transform the layered structure of tetragonal FeS (mackinawite) to the three-dimensional NiAs-type structure of hexagonal pyrrhotite [15]. Thus, it is clear that FeS adopts a variety of crystallographic structures under different sample preparations [15,16] AbstractWe present a detailed study of correlation-and pressure-induced electronic reconstruction in hexagonal iron monosulfide, a system which is widely found in meteorites and one of the components of Earth's core. Based on a perusal of experimental data, we stress the importance of multi-orbital electron-electron interactions in concert with first-principles band structure calculations for a consistent understanding of its intrinsic Mott-Hubbard insulating state. We explain the anomalous nature of pressure-induced insulator-metal-insulator transition seen in experiment, showing that it is driven by dynamical spectral weight transfer in response to changes in the crystal-field splittings under pressure. As a byproduct of this analysis, we confirm that the electronic transitions observed in pristine FeS at moderated pressures are triggered by changes in the spin state which causes orbitalselective Kondo quasiparticle electronic reconstruction at lo...

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Many-body effects on Cr(001) surfaces: An LDA+DMFT study

Cited by 6 publications

References 32 publications

Realistic theory of electronic correlations in nanoscopic systems

Realistic theory of electronic correlations in nanoscopic systems

Origin of the quasiparticle peak in the spectral density of Cr(001) surfaces

Electronic reconstruction of hexagonal FeS: a view from density functional dynamical mean-field theory

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