Article
Mathematics, Applied
Zhicheng Gao, Simon Kuttner, Qiang Wang
Summary: This paper enumerates irreducible polynomials of degree m and related objects over a finite field F-q with respect to their trace and norm, using generating functions and exponential sums. It improves upon all previously known results in the literature when m > root q.
FINITE FIELDS AND THEIR APPLICATIONS
(2021)
Article
Materials Science, Multidisciplinary
Erica J. Sturm, Matthew R. Carbone, Deyu Lu, Andreas Weichselbaum, Robert M. Konik
Summary: The study shows that neural network models can accurately predict the spectral function of the Anderson Impurity Model, outperforming models based on kernel ridge regression. Trained models demonstrate a significant speedup and the size of the training set can be greatly reduced through specific sampling methods.
Article
Physics, Multidisciplinary
Hiroshi Shinaoka, Markus Wallerberger, Yuta Murakami, Kosuke Nogaki, Rihito Sakurai, Philipp Werner, Anna Kauch
Summary: This study proposes a multiscale space-time ansatz for correlation functions of quantum systems based on quantics tensor trains (QTTs), which can compress high-dimensional tensors into tensor trains with several orders of magnitude compression ratios. The ansatz has been numerically verified and demonstrated for various equilibrium and nonequilibrium systems, as well as for the Dyson and Bethe-Salpeter equations, showing stability and efficiency.
Article
Engineering, Mechanical
Radek Vobejda, Frantisek Sebek, Petr Kubik, Jindrich Petruska
Summary: Accurate material behavior and its response to loading are necessary for reliable calibration of ductile failure criteria. Non-quadratic yield functions are often used for this purpose, but they can lead to inconsistent stress predictions and contradictory deformations when the associated flow rule is adopted. These issues can be resolved by using a less restrictive non-associated flow rule. In this study, an isotropic non-associated non-quadratic phenomenological plasticity model was developed, and it was shown that the non-associated flow rule can resolve the aforementioned problems. Additionally, possible extensions of the proposed yield function to include hydrostatic stress dependence were described.
INTERNATIONAL JOURNAL OF PLASTICITY
(2022)
Article
Physics, Condensed Matter
A. S. Belozerov, A. A. Katanin, V. Anisimov
JOURNAL OF PHYSICS-CONDENSED MATTER
(2020)
Letter
Multidisciplinary Sciences
A. A. Katanin
NATURE COMMUNICATIONS
(2021)
Article
Physics, Condensed Matter
A. S. Belozerov, A. A. Katanin, V. Anisimov
Summary: The electronic and magnetic properties of chromium were studied using a combination of DFT and DMFT, revealing weak electronic correlations and a lack of formation of local magnetic moments. The non-uniform magnetic susceptibility showed sharp maxima at the wave vector Q(H) = (0, 0, 2pi/a), corresponding to Kohn anomalies. These anomalies were preserved by interactions and pressure did not destroy them, leading to a qualitative decrease in the Neel temperature and breakdown of itinerant antiferromagnetism at around 9 GPa.
JOURNAL OF PHYSICS-CONDENSED MATTER
(2021)
Article
Materials Science, Multidisciplinary
A. S. Belozerov, A. A. Katanin, V. I. Anisimov
Summary: This study investigates the electronic correlation effects on the magnetic properties of tetragonally distorted chemically ordered FeCo alloys. The predicted Curie temperature decreases with the increase of lattice parameter ratio c/a. Well-localized magnetic moments are found on Fe sites, while magnetism on Co sites is more itinerant with shorter lifetime of local magnetic moments. The electronic states at Fe sites exhibit a nonquasiparticle form of self-energies, while the ones for Co sites have a Fermi-liquid-like shape.
PHYSICAL REVIEW MATERIALS
(2022)
Article
Chemistry, Physical
Saeed Rahmanian Koshkaki, Zahed Allahyari, Artem R. Oganov, Vladimir L. Solozhenko, Ilya B. Polovov, Alexander. S. Belozerov, Andrey A. Katanin, Vladimir I. Anisimov, Evgeny V. Tikhonov, Guang-Rui Qian, Konstantin V. Maksimtsev, Andrey S. Mukhamadeev, Andrey V. Chukin, Aleksandr V. Korolev, Nikolay V. Mushnikov, Hao Li
Summary: The development of a new algorithm extension for searching half-metals and hard magnetic materials has led to the prediction of promising hard magnets and rediscovery of half-metal phases. Experimental results confirm the robustness of this technique.
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Materials Science, Multidisciplinary
A. A. Katanin, A. S. Belozerov, A. I. Lichtenstein, M. I. Katsnelson
Summary: We analyze possible ways to calculate magnetic exchange interactions within the density functional theory plus dynamical mean-field theory (DFT+DMFT) approach in the paramagnetic phase. Using the susceptibilities obtained within the ladder DMFT approach together with the random phase approximation result for the Heisenberg model, we obtain bilinear exchange interactions. We show that the earlier obtained result of Stepanov individual magnetic moments in each orbital in the leading-order approximation in the nonlocal correlations.
Article
Materials Science, Multidisciplinary
I. A. Goremykin, A. A. Katanin
Summary: We propose a dynamical mean-field theory approach for the study of spiral magnetic order, which includes impurity solvers for the diagonal local Green's function. By considering nonuniform dynamic magnetic susceptibilities in a local coordinate frame, we describe the evolution of magnetic order in the t-t' Hubbard model. We find that with doping, the antiferromagnetic order changes to an incommensurate one and then to the paramagnetic phase.
Article
Materials Science, Multidisciplinary
P. A. Igoshev, A. A. Katanin
Summary: We use the functional renormalization group technique with temperature as a scale parameter to investigate the possibility of ferromagnetic ordering in the nondegenerate Hubbard model on the face-centered cubic lattice. By assuming the relations between hopping parameters, we find that ferromagnetic instability forms with decreasing temperature. We calculate the phase diagrams of chemical potential versus temperature and find that ferromagnetic order only occurs when the density of states diverges and the fillings are near the van Hove singularity. The obtained Curie temperature is significantly smaller compared to the results of the random-phase approximation.
Article
Materials Science, Multidisciplinary
A. S. Belozerov, A. A. Katanin, V. I. Anisimov
Summary: We investigate the effects of electron correlations on the magnetic properties of bcc vanadium using density functional and dynamical mean-field theory. Our calculations demonstrate that the temperature dependence of the magnetic susceptibility in the bcc structure can be qualitatively reproduced without considering the martensitic phase transition. We find that the Curie-Weiss behavior arises from the partial formation of local magnetic moments due to local spin correlations caused by Hund's rule coupling.
Article
Materials Science, Multidisciplinary
T. B. Mazitov, A. A. Katanin
Summary: This study investigates the impact of the formation and screening of local magnetic moments on the temperature and interaction dependencies of spectral functions and resistivity. The results indicate that, at half filling, the maximum resistivity corresponds to the appearance of a central quasiparticle peak in the spectral function and the transition to a metallic regime with well-defined fermionic quasiparticles. The temperature at which the screening of local magnetic moments occurs is lower than the temperature scale of the maximum resistivity, and at half filling, it coincides with the boundary corresponding to the exponent of resistivity.
Article
Materials Science, Multidisciplinary
A. A. Katanin
Summary: We study the electronic, charge, and magnetic properties of twisted bilayer graphene with specific fillings per moire unit cell. The results show the importance of spin exchange between certain lattice spots in introducing charge and spin correlations. The local spectral functions indicate a gapped state at specific fillings, while the nonlocal charge and spin susceptibilities exhibit incommensurate pattern.
Article
Materials Science, Multidisciplinary
T. B. Mazitov, A. A. Katanin
Summary: This study investigates the formation of local magnetic moments in the strongly correlated Hubbard model using dynamical mean-field theory, linking the temperature dependence of local charge and spin susceptibilities to different stages of local moment formation. The relationship between the Kondo temperature and the fingerprint criterion is discussed, with similarities near the Mott transition and slight discrepancies further away. Additionally, the behavior of eigenvectors/eigenvalues of fermionic frequency-resolved charge susceptibility and divergences of irreducible vertices is considered in relation to the observed features.
Article
Materials Science, Multidisciplinary
V. S. Protsenko, A. A. Katanin
Summary: This study investigates the magnetic, charge, and transport properties of hexagonal graphene nanoflakes connected to metallic leads using the functional renormalization group method. The competition between on-site and long-range interactions leads to the emergence of different phases. Realistic screening of Coulomb interaction by sigma bands enhances the stability of the semimetal phase, and the relationship between linear conductance and magnetic or charge states is discussed. Comparisons with other studies on graphene nanoflakes and infinite graphene sheets are presented.
Article
Materials Science, Multidisciplinary
A. A. Katanin
Summary: The study investigates magnetic and charge correlations in graphene using extended dynamical mean-field theory (E-DMFT) for two-sublattice systems. The method maps nonlocal interactions onto effective static interactions between different sublattices and introduces an effective retarded interaction to consider the remaining nonlocal interactions. The study demonstrates the competition of semimetal, spin density wave (SDW), and charge-density-wave (CDW) correlations in graphene.
Article
Materials Science, Multidisciplinary
A. A. Katanin
Summary: This study investigates the momentum dependence of static magnetic susceptibility in the paramagnetic phase of Heisenberg magnets and its relation to critical behavior within the nonlinear sigma model at finite dimension. The research reveals the contribution of anomalous terms to critical exponent nu and the dominance of such terms in determining the 1/N correction to the critical exponent v in certain dimension ranges.
