A. A. Katanin

Moscow Institute of Physics and Technology | MIPT · Center for Photonics and 2D Materials

We study magnetic properties of CrO2 within the density functional theory plus dynamical mean-field theory (DFT+DMFT) approach in the paramagnetic phase. We consider the 3-orbital (per Cr site) model, containing only t_{2g} states, the $5$-orbital model, including all d-states, as well as the model including also the oxygen $p$-states. Using the re...

We reconsider the derivation of Ward identities for spin stiffnesses, which determine the non-linear sigma model of magnetic degrees of freedom of interacting electrons in the presence of antiferromag-netic or incommensurate correlations. We emphasize that in the approaches, which do not break explicitly spin symmetry of the action, the spatial com...

We investigate magnetic properties of CrTe2 within the density functional theory (DFT) approach in ferromagnetic phase and combination of DFT and dynamical mean field theory (DFT+DMFT) approach in paramagnetic phase. We show that few layer CrTe2 possesses well formed local magnetic moments. In the single layer CrTe2 we find antiferromagnetic exchan...

We investigate the magnetic quantum phase-transitions in bulk correlated metals at the level of dynamical mean-field theory. To this end, we focus on the Hubbard model on a simple cubic lattice as a function of temperature and electronic density, determining the different regimes of its magnetic transition - classical, quantum critical, and quantum...

The talk given at the TRIQS meeting (Paris, July 2024)

We study formation and screening of local magnetic moments in the two-band Hubbard model in the presence of Hund exchange interaction using dynamic mean field theory approach. The characteristic temperatures of the formation, beginning and full screening of local magnetic moments are obtained from the analysis of temperature dependence of the orbit...

We reconsider derivation of Ward identities for spin stiffnesses, which determine the non-linear sigma model of magnetic degrees of freedom of interacting electrons in the presence of antiferromagnetic or incommensurate correlations. We emphasize that in the approaches, which do not break explicitly spin symmetry of the action, the spatial componen...

We study formation and screening of local magnetic moments in the two-band Hubbard model in the presence of Hund exchange interaction using dynamic mean field theory approach. The characteristic temperatures of the formation, beginning and full screening of local magnetic moments are obtained from the analysis of temperature dependence of the orbit...

Monolayer Fe$_2$C is expected to possess strong electronic correlations, which can significantly contribute to electronic and magnetic properties. In this study we consider electronic and magnetic properties of MXene Fe$_2$C within the DFT+DMFT approach.~We establish the existence of local magnetic moments $\mu_{\rm loc}=3.3\mu_B$ in this compound,...

We reconsider magnetic properties of fcc and hcp cobalt within the density functional theory plus dynamical mean-field theory (DFT+DMFT) approach in the paramagnetic phase. Using recently proposed approach of calculation of exchange interactions in paramagnetic phase, we extract exchange interaction parameters of fcc and hcp cobalt and show that th...

We study the effect of various configurations of vacancies on the magnetic properties of graphene nanoflake (GNF) with screened realistic long-range electron interaction [T. O. Wehling et al., Phys. Rev. Lett. 106, 236805 (2011)] within the functional renormalization group approach. In agreement with previous studies, the presence of vacancies in G...

We reconsider magnetic properties of fcc and hcp cobalt within the density functional theory plus dynamical mean-field theory (DFT+DMFT) approach in the paramagnetic phase. Using recently proposed approach of calculation of exchange interactions in paramagnetic phase, we extract exchange interaction parameters of fcc and hcp cobalt and show that th...

We study the effect of various configurations of vacancies on the magnetic properties of graphene nanoflake (GNF) with screened realistic long-range electron interaction [T. O. Wehling, et. al., Phys. Rev. Lett. 106, 236805 (2011)] within the functional renormalization group approach. In agreement with previous studies, the presence of vacancies in...

The talk prepared for the French-German WE-Heraeus-Seminar / Exploring New Topics with Functional Renormalisation (01.05.2023 - 05.05.2023)

We investigate the possibility of ferromagnetic ordering in the nondegenerate Hubbard model on the face-centered cubic lattice within the functional renormalization group technique using temperature as a scale parameter. We assume the relations between nearest, next-nearest, and next-next-nearest hopping parameters providing higher-order (giant) va...

We study electron correlations and their impact on magnetic properties of bcc vanadium by a combination of density functional and dynamical mean-field theory. The calculated uniform magnetic susceptibility in bcc structure is of Pauli type at low temperatures, while it obeys the Curie-Weiss law at higher temperatures. Thus, we qualitatively reprodu...

We develop dynamical mean field theory approach for the incommensurate magnetic order, passing to a local coordinate frame with preferable spin alignment along $z$-axis, which can be considered with the standard impurity solvers. We apply this approach to describe the evolution of antiferromagnetic order with doping in the $t$-$t'$ Hubbard model wi...

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 biline...

We investigate a possibility of ferromagnetic ordering in the non-degenerate Hubbard model on the face-centered cubic lattice within the functional renormalization group technique using temperature as a scale parameter. We assume the relations between nearest, next-nearest, and next-next-nearest hopping parameters providing higher order (giant) van...

The discovery of new magnetic materials is a big challenge in the field of modern materials science. We report the development of a new extension of the evolutionary algorithm USPEX, enabling the search for half-metals (materials that are metallic only in one spin channel) and hard magnetic materials. First, we enabled the simultaneous optimization...

We study the effect of the formation and screening of local magnetic moments on the temperature- and interaction dependencies of spectral functions and resistivity in the vicinity of the metal-insulator transition. We use dynamical mean-field theory for the strongly correlated Hubbard model and associate the peculiarities of the above mentioned pro...

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. O...

We study electronic, charge, and magnetic properties of twisted bilayer graphene with fillings $2\leq n\leq 6$ per moire unit cell within the recently introduced formulation of extended dynamical mean-field theory (E-DMFT) for two-sublattice systems. We use the hopping parameters between the spots of AB and BA stacking, obtained previously by the W...

The presentation at the XXIV Ural International School on semiconductor physics

We consider electronic correlation effects and their impact on magnetic properties of tetragonally distorted chemically ordered FeCo alloy (L1$_0$ structure) being a promising candidate to rare-earth-free permanent magnets. We employ a state-of-the-art method combining the density functional (DFT) and dynamical mean-field theory (DMFT). According t...

We investigate magnetic, charge and transport properties of hexagonal graphene nanoflakes (GNFs) connected to two metallic leads by using the functional renormalization group (fRG) method. The interplay between the on-site and long-range interactions leads to a competition of semimetal (SM), spin density wave (SDW), and charge-density-wave (CDW) ph...

We study formation of local magnetic moments in strongly correlated Hubbard model within dynamical mean field theory and associate peculiarities of temperature dependence of local charge $\chi_c$ and spin $\chi_s$ susceptibilities with different stages of local moment formation. Local maximum of temperature dependence of the charge susceptibility $...

We investigate magnetic and charge correlations in graphene by using the formulation of extended dynamical mean-field theory (E-DMFT) for two-sublattice systems. First, we map the average non-local interaction onto the effective static interaction between different sublattices, which is treated together with the local interaction within an effectiv...

We consider electronic and magnetic properties of chromium, a well-known itinerant antiferromagnet, by a combination of density functional theory (DFT) and dynamical mean-field theory (DMFT). We find that electronic correlation effects in chromium, in contrast to its neighbours in the periodic table, are weak, leading to the quasiparticle mass enha...

We consider electronic and magnetic properties of chromium, a well-known itinerant antiferromagnet, by a combination of density functional theory (DFT) and dynamical mean-field theory (DMFT). We find that electronic correlation effects in chromium, in contrast to its neighbours in the periodic table, are weak, leading to the quasiparticle mass enha...

The temperature scales of screening of local magnetic and orbital moments are important characteristics of strongly correlated substances. In a recent paper X. Deng et al. \cite{paper} using dynamic mean-field theory (DMFT) have identified temperature scales of the onset of screening in orbital and spin channels in some correlated metals from the...

The temperature scales of screening of local magnetic and orbital moments are important characteristics of strongly correlated substances. In a recent paper X. Deng et al. using dynamic mean-field theory (DMFT) have identified temperature scales of the onset of screening in orbital and spin channels in some correlated metals from the deviation of t...

The current theoretical and experimental situation is reviewed for low-dimensional (layered and chain-like) insulating systems. Such systems possess a low magnetic transition temperature $T_M$ and pronounced short-range magnetic order above this temperature. Both the standard and self-consistent spin-wave theories are shown to be insufficient to qu...

We study momentum dependence of static magnetic susceptibility $\chi(q)$ in paramagnetic phase of Heisenberg magnets and its relation to critical behavior within nonlinear sigma model (NLSM) at arbitrary dimension $2<d<4$. In the first order of $1/N$ expansion, where $N$ is the number of spin components, we find $\chi(q)\propto[q^{2}+\xi^{-2}(1+f(q...

We study the electronic and magnetic properties of L1$_0$ phase of FeNi, a perspective rare-earth-free permanent magnet, by using a combination of density functional and dynamical mean-field theory. Although L1$_0$ FeNi has a slightly tetragonally distorted fcc lattice, we find that magnetic properties of its constituent Fe atoms resemble those in...

We study Coulomb correlation effects and their role in superconductivity of ɛ-iron under pressure from 12 to 33 GPa by using a combination of density functional and dynamical mean-field theory. Our results indicate a persistence of the Fermi-liquid behavior below the temperature ∼1000K. The Coulomb correlations are found to substantially renormaliz...

We present results of a theoretical study of a prototypical weak ferromagnet ZrZn$_2$. We use the density-functional theory (DFT)+dynamical mean-field theory (DMFT) method to study the electronic and local magnetic properties. The obtained DFT+DMFT electronic self-energies are Fermi-liquid like, indicating a small effective mass enhancement of the...

Strong repulsive interactions between electrons can lead to a Mott metal-insulator transition. The Dynamical Mean-Field Theory (DMFT) explains the critical end-point and hysteresis region with single-particle concepts such as the spectral function and the quasiparticle weight. In this work, we reconsider the critical end point of the metal-insulato...

We study Coulomb correlation effects and their role in superconductivity of $\varepsilon$-iron under pressure from 12 to 33 GPa by using a combination of density functional and dynamical mean-field theory. Our results indicate a persistence of the Fermi-liquid behavior below the temperature $\sim$1000 K. The Coulomb correlations are found to substa...

We reconsider the procedure of calculation of fermion-boson vertices and numerical solution of Bethe-Salpeter equations, used in non-local extensions of dynamical mean-field theory. Because of the frequency dependence of vertices, finite frequency box for matrix inversions is typically used, which often requires some treratment of asymptotic behavi...

We study the phase diagram and quantum critical region of one of the fundamental models for electronic correlations: the periodic Anderson model. Employing the recently developed dynamical vertex approximation, we find a phase transition between a zero-temperature antiferromagnetic insulator and a Kondo insulator. In the quantum critical region we...

We propose new approach for treatment of local and non-local interactions in correlated electronic systems, which is based on the combination of the (extended) dynamical mean-field theory ((E)DMFT) and the two-particle irreducible functional renormaliztion-group (2PI-fRG) method. The considering approach uses self-energy and the two-particle irredu...

We apply the non-equilibrium functional renormalization group approach treating flow of the electronic self-energies, to describe local magnetic moments formation and electronic transport in a quadruple quantum dot (QQD) ring, coupled to leads, with moderate Coulomb interaction on the quantum dots. We find that at zero temperature depending on para...

Some Bravais lattices have a particular geometry that can slow down the motion of Bloch electrons by pre-localization due to the band-structure properties. Another known source of electronic localization in solids is the Coulomb repulsion in partially filled d or f orbitals, which leads to the formation of local magnetic moments. The combination of...

We study the phase diagram and quantum critical region of one of the fundamental models for electronic correlations: the periodic Anderson model. Employing the recently developed dynamical vertex approximation, we find a phase transition between a zero-temperature antiferromagnetically ordered and a Kondo insulating phase. In the quantum critical r...

We study the momentum and temperature dependencies of magnetic susceptibilities and magnetic exchange in paramagnetic fcc iron by a combination of density functional theory and supercell dynamical mean-field theory (DFT+DMFT). We find that in agreement with experimental results the antiferromagnetic correlations with the wave vector close to (0,0,2...

We propose new approach for treatment of local and non-local interactions in correlated electronic systems, which is based on the combination of the (extended) dynamical mean-field theory ((E)DMFT) and the two-particle irreducible functional renormaliztion-group (2PI-fRG) method. The considering approach uses self-energy and the two-particle irredu...

We investigate a possibility of Hund's metal behavior in the Hubbard model with asymmetric density of states having peak(s). Specifically, we consider the degenerate two-band model and compare its results to five-band model with realistic density of states of iron and nickel, showing that the obtained results are more general. We find that quasipar...

We study the momentum- and temperature dependences of magnetic susceptibilities and magnetic exchange in paramagnetic fcc iron by a combination of density functional theory and supercell dynamical mean-field theory (DFT+DMFT). We find that in agreement with experimental results the antiferromagnetic correlations with the wave vector close to $(0,0,...

We analyze the momentum and temperature dependences of the magnetic susceptibilities and magnetic exchange interaction in paramagnetic bcc iron by a combination of density functional theory and dynamical mean-field theory (DFT+DMFT). By considering a general derivation of the orbital-resolved effective model for spin degrees of freedom for Hund's m...

A general understanding of quantum phase transitions in strongly correlated materials is still lacking. By exploiting a cutting-edge quantum many-body approach, the dynamical vertex approximation, we make important progress, determining the quantum critical properties of the antiferromagnetic transition in the fundamental model for correlated elect...

We consider a possibility of realization Kohn points in electronic spectum of some three-dimensional systems, yielding at low temperatures non-analytic momentum dependence of magnetic susceptibility near its maximum. In particular, we consider one-band model on face centered cubic lattice with hopping between nearest and next-nearest neighbors, whi...

Some Bravais lattices have a particular geometry that can slow down the motion of Bloch electrons by pre-localization due to the band-structure properties. Another known source of electronic localization in solids is the Coulomb repulsion in partially filled d- or f-orbitals, which leads to the formation of local magnetic moments. The combination o...

We study properties of magnetic nanoparticles adsorbed on the halloysite surface. For that a distinct magnetic Hamiltonian with random distribution of spins on a cylindrical surface was solved by using a nonequilibrium Monte Carlo method. The parameters for our simulations: anisotropy constant, nanoparticle size distribution, saturated magnetizatio...

We analyze momentum- and temperature dependences of magnetic susceptibilities and magnetic exchange in paramagnetic bcc iron by a combination of density functional theory and dynamical mean-field theory (DFT+DMFT). By considering a general derivation of the orbital-resolved effective model for spin degrees of freedom for Hund metals, we relate mome...

Strong electronic correlations pose one of the biggest challenges to solid state theory. We review recently developed methods that address this problem by starting with the local, eminently important correlations of dynamical mean field theory (DMFT). On top of this, non-local correlations on all length scales are generated through Feynman diagrams...

We explore the effects of asymmetry of hopping parameters between double parallel quantum dots and the leads on the conductance and a possibility of local magnetic moment formation in this system using functional renormalization group approach with the counterterm. We demonstrate a possibility of a quantum phase transition to a local moment regime...

We investigate non-equilibrium properties of the frustrated Heisenberg antiferromagnets on the triangular lattice. Nonequilibrium critical relaxation of frustrated Heisenberg antiferromagnets shows a sharp dynamic topological Berezinskii-Kosterlitz-Thouless transition at the same temperature $T_{\rm BKT}=0.282 J$ as for static properties, due to th...

We consider nonlocal correlations in iron in the vicinity of the α−γ phase transition within the spin rotationally invariant dynamical mean-field theory (DMFT) approach, combined with the recently proposed spin-fermion model of iron. The obtained nonlocal corrections to DMFT yield a decrease of the Curie temperature of the α phase, leading to an ag...

We propose a version of functional renormalization-group (fRG) approach, which is, due to including Litim-type cutoff and switching off (or reducing) the magnetic field during fRG flow, capable describing singular Fermi liquid (SFL) phase, formed due to presence of local moments in quantum dot structures. The proposed scheme allows to describe the...

We consider non-local correlations in iron in the vicinity of $\alpha$-$\gamma$ phase transition within the spin-rotationally-invariant dynamical mean-field theory (DMFT) approach, combined with the recently proposed spin-fermion model of iron. The obtained non-local corrections to DMFT result in a decrease of the Curie temperature of $\alpha$ phas...

We study the effects of electronic interactions on transport through parallel quantum dots connected symmetrically to leads, focusing on the case of an intermediate value of the on-site Coulomb interaction at each quantum dot. We apply both the mean-field (MF) approximation and the functional renormalization group (fRG) approach with using the Liti...

We propose an efficient dual boson scheme, which extends the DMFT paradigm to collective excitations in correlated systems. The theory is fully self-consistent both on the one- and on the two-particle level, thus describing the formation of collective modes as well as the renormalization of electronic and bosonic spectra on equal footing. The metho...

In this paper we consider the possibility of chiral (charge or spin density wave) symmetry breaking in graphene due to long-range Coulomb interaction by comparing the results of the Bethe-Salpeter and functional renormalization-group approaches. The former approach performs summation of ladder diagrams in the particle-hole channel, and reproduces t...

Layered perovskites Sr2IrO4 and Ba2IrO4 are regarded as the key materials for understanding the properties of magnetic relativistic insulators, mediated by the strong spin-orbit (SO) coupling. One of the most fundamental issues is to which extent these properties can be described by the superexchange (SE) model, formulated in the limit of the large...

Thermodynamic properties of cubic Heisenberg ferromagnets with competing exchange interactions are considered near the frustration point where the coefficient $D$ in the spin-wave spectrum $E_{\mathbf{k}}\sim D k^{2}$ vanishes. Within the Dyson-Maleev formalism it is found that at low temperatures thermal fluctuations stabilize ferromagnetism by in...

We consider formulations of the functional renormaliztion-group flow for correlated electronic systems, having the dynamical mean-field theory as a starting point. We classify the corresponding renormalization-group schemes into those neglecting the one-particle irreducible (with respect to the local Green functions) six-point vertices and neglecti...

Applying the local density approximation (LDA) and dynamical mean field theory (DMFT) to paramagnetic $\alpha $-iron, we revisit a problem of theoretical description of its magnetic properties. The analysis of local magnetic susceptibility shows that at sufficiently low temperatures $T<1500K$, both, $e_{g}$ and $t_{2g}$ states equally contribute to...