Long-term memory magnetic correlations in the Hubbard model: A dynamical  mean-field theory analysis

Watzenböck, Clemens; Fellinger, Martina; Held, Karsten; Toschi, A.

doi:10.21468/scipostphys.12.6.184

Cited by 16 publications

(10 citation statements)

References 57 publications

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“…53,65 Similarly to observations made in Ref. 66, we find in general that the survival probability decays over longer times, when interactions are stronger. At shorter times, we find that the behavior depends strongly on the type of the initial state, likely related to the average density.…”

Section: Introductionsupporting

confidence: 88%

Fermionic-propagator and alternating-basis quantum Monte Carlo methods for correlated electrons on a lattice

Janković¹,

Vučičević²

2022

Preprint

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We devise and benchmark a numerically exact quantum Monte Carlo (QMC) method for interacting electrons on a lattice, that we dub the alternating-basis QMC (ABQMC). The method is uniquely suited to evaluate charge and spin density and the corresponding correlation functions, in both direct and reciprocal space, imaginary or real time. The formalism applies in and out of thermal equillibrium, described by either the canonical or grand-canonical ensemble. The method relies on Suzuki-Trotter decomposition (STD) and owes flexibility to the representation of the kinetic and interaction terms in the many-body bases in which they are diagonal. We formulate a Monte Carlo (MC) update scheme that respects both the momentum and particle-number conservation laws, to restrict the configuration space and thus improve the efficiency of the sampling. To test the method, we perform various calculations for the Hubbard model on finite square lattices of up to 48 sites. We obtain the equation of state (density vs. chemical potential curve) in agreement with reference methods. We also evaluate the (real-time) dynamics of the survival probability of pure densitywave-like states: At small lattice sizes, where the exact diagonalization results are available, we demonstrate the validity of our method at short times; We then proceed to investigate this dynamics on the 4 × 4 Hubbard cluster. Finally, we discuss the extent of the fermionc sign problem and the current limitations of our method, both primarily related to the number of time-slices that we take in the STD.

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Section: Introductionsupporting

confidence: 88%

Fermionic-propagator and alternating-basis quantum Monte Carlo methods for correlated electrons on a lattice

Janković¹,

Vučičević²

2022

Preprint

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“…The half width of the peak in Reχ dyn (ω) at half of its height yields approximately inverse lifetime of local magnetic moments [66,67]. Therefore, we obtain that Hunds's coupling is responsible for formation of local magnetic moments on Fe sites, while magnetic moments on Co sites are much less localized in line with results on local magnetic susceptibility.…”

Section: B Magnetic Propertiessupporting

confidence: 80%

Coulomb correlations and magnetic properties of L10 FeCo: A DFT+DMFT study

Белозеров

Катанин

Анисимов

2022

Phys. Rev. Materials

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We consider electronic correlation effects and their impact on magnetic properties of tetragonally distorted chemically ordered FeCo alloys (L1 0 structure) being a promising candidate for rare-earthfree permanent magnets. We employ a state-of-the-art method combining density functional and dynamical mean-field theory. According to our results, the predicted Curie temperature reduces with increase of lattice parameters ratio c/a and reaches nearly 850 K at c/a = 1.22. For all considered c/a from 1 to √ 2, we find well-localized magnetic moments on Fe sites, which are formed due to strong correlations originating from Hund's coupling. At the same time, magnetism of Co sites is more itinerant with a much less lifetime of local magnetic moments. However, these short-lived local moments are also formed due to Hund's exchange. Electronic states at Fe sites are characterized by a non-quasiparticle form of self-energies, while the ones for Co sites are found to have a Fermi-liquid-like shape with quasiparticle mass enhancement factor m * /m ∼ 1.4, corresponding to moderately correlated metal. The strong electron correlations on Fe sites leading to Hund's metal behaviour can be explained by peculiarities of the density of states, which has pronounced peaks near the Fermi level, while weaker many-body effects on Co sites can be caused by stronger deviation from half-filling of their 3d states. The obtained momentum dependence of magnetic susceptibility suggests that the ferromagnetic ordering is the most favourable one except for the near vicinity of the fcc structure and the magnetic exchange is expected to be of RKKY type.

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“…A more quantitative estimate of the degree of magnetic moment localization can be obtained from the real part of χ spin (ω) shown in the right panels of figure 5. In particular, the half-width of the peak of Re χ spin (ω) at its half-height is approximately equal to the inverse lifetime of local magnetic moments [8,63]. We thus obtain that lifetime of local magnetic moments in vanadium at U = 4 eV and J H = 0.9 eV is about 20 times less than in iron, but about 5 times larger than in chromium.…”

Section: Magnetic Propertiesmentioning

confidence: 69%

Transition from Pauli paramagnetism to Curie-Weiss behaviour in vanadium

Белозеров¹,

Katanin²,

Anisimov³

2022

Preprint

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We study electron correlations and their impact on magnetic properties of vanadium by a combination of density functional and dynamical mean-field theory. The calculated uniform magnetic susceptibility is of Pauli type at low temperatures, while it obeys the Curie-Weiss law at higher temperatures in a qualitative agreement with experimental data. Our results for local spin-spin correlation function and local susceptibility reveal that the Curie-Weiss behaviour occurs due to partial formation of local magnetic moments. We show that these moments originate from t 2g states and their formation is mainly governed by local spin correlations caused by Hund's rule coupling. The formation of local moments is accompanied by a deviation from the Fermi-liquid behaviour although fermionic quasiparticles remain well-defined. The obtained quasiparticle mass enhancement factor of about 1.5-2 corresponds to a moderately correlated metal. By analyzing the momentum dependence of static magnetic susceptibility, we find incommensurate magnetic correlations which may cause the loss of quasiparticle coherence upon heating.

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Long-term memory magnetic correlations in the Hubbard model: A dynamical mean-field theory analysis

Cited by 16 publications

References 57 publications

Fermionic-propagator and alternating-basis quantum Monte Carlo methods for correlated electrons on a lattice

Fermionic-propagator and alternating-basis quantum Monte Carlo methods for correlated electrons on a lattice

Coulomb correlations and magnetic properties of L10 FeCo: A DFT+DMFT study

Transition from Pauli paramagnetism to Curie-Weiss behaviour in vanadium

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