arXiv subjects

A. I. Poteryaev

Publications and source records attributed to A. I. Poteryaev.

At least 19 recordsLinked to original sources

arXiv2026

Orbital-specific Itinerancy and Localization in a Kagome Magnet

The kagome lattice naturally hosts flat bands, Dirac fermions, and van Hove singularities, yet whether its geometry can stabilize orbital-selective phases - a hallmark of Hund's physics in multi-orbital correlated systems - has remained an open question. Here, we combine resonant inelastic X-ray scattering with density functional theory and dynamical mean-field theory to demonstrate that YMn$_6$Sn$_6$ exhibits a spontaneous orbital differentiation into coexisting itinerant and localized electrons within the same Mn $3d$ manifold. Orbitals directed along Mn-Mn bonds provide coherent quasiparticles and metallic bands, while those pointing toward ligands become strongly correlated and display non-Fermi-liquid behavior. Hund's intra-atomic exchange suppresses orbital fluctuations, stabilizing this dichotomy and providing a natural double-exchange-like mechanism for the observed ferromagnetic bilayer coupling. Our work establishes YMn$_6$Sn$_6$ as a kagome platform where orbital selectivity, flat-band topology, and Hund's metallicity converge - revealing that geometric frustration and correlation-driven orbital differentiation can cooperatively design exotic quantum phases beyond the canonical paradigms of Mott physics or band topology alone.

cond-mat.str-el↗

arXiv2025

Highly correlated electronic state in a ferrimagnetic quadruple perovskite CuCu$_3$Fe$_2$Re$_2$O$_{12}$

Recently synthesized quadruple perovskite CuCu$_3$Fe$_2$Re$_2$O$_{12}$ possesses strong ferromagnetism and unusual electron properties, including enhanced electronic specific heat. Application of the first principles electronic structure approaches unambiguously shows importance of the many-body effects in this compound. While CuCu$_3$Fe$_2$Re$_2$O$_{12}$ is half-metallic ferrimagnet in the DFT+U method, in the density functional theory (DFT) combined with the dynamical mean-field theory (DMFT) it appears to be a metal. Strong correlations lead to a renormalization of electronic spectrum and formation of incoherent states close to the Fermi level. Electronic specific heat and magnetic properties obtained in the DFT+DMFT approach are in better agreement with available experimental data than derived by other band structure techniques.

cond-mat.str-el↗

arXiv2019

XPS evidence of degradation mechanism in hybrid halide perovskites

The paper presents the results of measurements of XPS valence band spectra of SiO2/MAPbI3 hybrid perovskites subjected to irradiation with visible light and annealing at an exposure of 0-1000 hours. It is found from XPS survey spectra that in both cases (irradiation and annealing) a decrease in the I:Pb ratio is observed with aging time, which unambiguously indicates PbI2 phase separation as a photo and thermal product of degradation. The comparison of the XPS valence band spectra of irradiated and annealed perovskites with density functional theory calculations of the MAPbI3 and PbI2 compounds have shown a systematic decrease in the contribution of I 5p-states and allowed us to determine the threshold for degradation, which is 500 hours for light irradiation and 200 hours for annealing.

physics.app-ph↗

arXiv2017

Unexpected 3+ valence of iron in FeO$_2$, a geologically important material lying "in between" oxides and peroxides

Recent discovery of pyrite FeO$_2$, which can be an important ingredient of the Earth's lower mantle and which in particular may serve as an extra source of water in the Earth's interior, opens new perspectives for geophysics and geochemistry, but this is also an extremely interesting material from physical point of view. We found that in contrast to naive expectations Fe is nearly 3+ in this material, which strongly affects its magnetic properties and makes it qualitatively different from well known sulfide analogue - FeS$_2$. Doping, which is most likely to occur in the Earth's mantle, makes FeO$_2$ much more magnetic. In addition we show that unique electronic structure places FeO$_2$ "in between" the usual dioxides and peroxides making this system interesting both for physics and solid state chemistry.

cond-mat.str-el↗

arXiv2016

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

The electronic structure of the Cr(001) surface with its sharp resonance at the Fermi level is a subject of controversial debate of many experimental and theoretical works. To date, it is unclear whether the origin of this resonance is an orbital Kondo or an electron-phonon coupling effect. We have combined ab initio density functional calculations with dynamical mean-field simulations to calculate the orbitally resolved spectral function of the Cr(001) surface. The calculated orbital character and shape of the spectrum is in agreement with data from (inverse) photoemission experiments. We find that dynamic electron correlations crucially influence the surface electronic structure and lead to a low energy resonance in the $d_{z^2}$ and $d_{xz/yz}$ orbitals. Our results help to reconvene controversial experimental results from (I)PES and STM measurements.

cond-mat.str-el↗

arXiv2015

Structural ${γ\textrm{-}\varepsilon}$ phase transition in Fe-Mn alloys from CPA+DMFT approach

We present a computational scheme for total energy calculations of disordered alloys with strong electronic correlations. It employs the coherent potential approximation combined with the dynamical mean-field theory and allows one to study the structural transformations. The material-specific Hamiltonians in the Wannier function basis are obtained by density functional theory. The proposed computational scheme is applied to study the ${γ\textrm{-}\varepsilon}$ structural transition in paramagnetic Fe-Mn alloys for Mn content from 10 to 20 at. %. The electronic correlations are found to play a crucial role in this transition. The calculated transition temperature decreases with increasing Mn content and is in a good agreement with experiment. We demonstrate that in contrast to the ${α\textrm{-}γ}$ transition in pure iron, the ${γ\textrm{-}\varepsilon}$ transition in Fe-Mn alloys is driven by a combination of kinetic and Coulomb energies. The latter is found to be responsible for the decrease of the ${γ\textrm{-}\varepsilon}$ transition temperature with Mn content.

cond-mat.str-el↗

arXiv2014

Electronic correlations determine the phase stability of iron up to the melting temperature

We present theoretical results on the high-temperature phase stability and phonon spectra of paramagnetic bcc iron which explicitly take into account many-body effects. Several peculiarities, including a pronounced softening of the [110] transverse (T$_1$) mode and a dynamical instability of the bcc lattice in harmonic approximation are identified. We relate these features to the $α$-to-$γ$ and $γ$-to-$δ$ phase transformations in iron. The high-temperature bcc phase is found to be highly anharmonic and appears to be stabilized by the lattice entropy.

cond-mat.str-el↗

arXiv2013

Magnetic fluctuations and effective magnetic moments in γ-iron due to electronic structure peculiarities

Applying the local density and dynamical mean field approximations to paramagnetic γ-iron we revisit the problem of theoretical description of magnetic properties in a wide temperature range. We show that contrary to α-iron, the frequency dependence of the electronic self-energy has a quasiparticle form for both, t_{2g} and e_g states. In the temperature range T=1200-1500 K, where γ-iron exist in nature, this substance can be nevertheless characterized by temperature-dependent effective local moments, which yield relatively narrow peaks in the real part of the local magnetic susceptibility. At the same time, at low temperatures γ-iron (which is realized in precipitates) is better described in terms of itinerant picture. In particular, the nesting features of the Fermi surfaces yield maximum of the static magnetic susceptibility at the incommensurate wave vector q_{max} belonging the direction q_X-q_W (q_X=(2π/a)(1,0,0),q_W=(2π/a)(1,1/2,0), a is a lattice parameter) in agreement with the experimental data. This state is found however to compete closely with the states characterized by magnetic wave vectors along the directions q_X-q_L-q_K, where q_L=(2π/a)(1/2,1/2,1/2), q_K=(2π/a)(3/4,3/4,0). From the analysis of the uniform magnetic susceptibility we find that contrary to α-iron, the Curie-Weiss law is not fulfilled in a broad temperature range, although the inverse susceptibility is nearly linear in the moderate-temperature region (1200-1500 K). The non-linearity of the inverse uniform magnetic susceptibility in a broader temperature range is due to the density of states peak located close to the Fermi level. The effective exchange integrals in the paramagnetic phase are estimated on the base of momentum dependent susceptibility.

cond-mat.str-el↗

arXiv2012

Rotationally-Invariant Exchange Interaction: The Case of Paramagnetic Iron

We present a generalization of the spin-fluctuation theory of magnetism which allows us to treat the full rotational invariance of the exchange interaction. The approach is formulated in terms of the local density approximation plus dynamical mean-field theory (LDA+DMFT), providing a systematic many-body treatment of the effect of spin-density fluctuations. This technique is employed to study the electronic and magnetic properties of paramagnetic $α$ iron. Our result for the Curie temperature is in good agreement with experiment, while the calculations with the Ising-type exchange interaction yield almost twice overestimated value.

cond-mat.str-el↗

arXiv2011

Calculated phonon spectra of paramagnetic iron at the alpha-gamma phase transition

We compute lattice dynamical properties of iron at the bcc-fcc phase transition using dynamical mean-field theory implemented with the frozen-phonon method. Electronic correlations are found to have a strong effect on the lattice stability of paramagnetic iron in the bcc phase. Our results for the structural phase stability and lattice dynamical properties of iron are in good agreement with experiment.

cond-mat.mtrl-sci↗

arXiv2011

Electronic correlations at the alpha-gamma structural phase transition in paramagnetic iron

We compute the equilibrium crystal structure and phase stability of iron at the alpha(bcc)-gamma(fcc) phase transition as a function of temperature, by employing a combination of ab initio methods for calculating electronic band structures and dynamical mean-field theory. The magnetic correlation energy is found to be an essential driving force behind the alpha-gamma structural phase transition in paramagnetic iron.

cond-mat.str-el↗

arXiv2010

Evidence for strong Coulomb correlations in metallic phase of vanadium dioxide

The influence of Coulomb correlation on magnetic and spectral properties in metallic rutile phase of vanadium dioxide is studied by state of the art LDA+DMFT method. Calculation results in strongly correlated metallic state with an effective mass renormalization $m^*/m\approx2$. Uniform magnetic susceptibility shows Curie-Weiss temperature dependence with effective magnetic moment, $p_{eff}^{theor} = 1.54 μ_B$, in a good agreement with the experimental value $p_{eff}^{exp} = 1.53 μ_B$ that is close to ideal value for V$^{4+}$ ion with the spin $S=1/2$, $p_{eff} = 1.73 μ_B$. Calculated spectral function shows well developed Hubbard bands observabale in the recent experimental photoemission spectra. We conclude that VO2 in rutile phase is strongly correlated metal with local magnetic moments formed by vanadium $d$-electrons.

cond-mat.str-el↗

arXiv2009

First-principles investigation of uranium monochalcogenides

We present first-principles investigation of the electronic structure and magnetic properties of uranium monochalcogenides: US, USe, UTe. The calculations were performed by using recently developed LDA+U+SO method in which both Coulomb and spin-orbit interactions have been taken into account in rotationally invariant form. We discuss the problem of choice of the Coulomb interaction value. The calculated [111] easy axes agree with those experimentally observed. The electronic configuration 5$f^3$ was found for all uranium compounds under investigation.

cond-mat.str-el↗

arXiv2009

Orbital selective local moment formation in iron: first principle route to an effective model

We revisit a problem of theoretical description of alpha-iron. By performing LDA+DMFT calculations in the paramagnetic phase we find that Coulomb interaction and, in particular Hund exchange, yields the formation of local moments in e_g electron band, which can be traced from imaginary time dependence of the spin-spin correlation function. This behavior is accompanied by non-Fermi-liquid behavior of e_g electrons and suggests using local moment variables in the effective model of iron. By investigating orbital-selective contributions to the Curie-Weiss law for Hund exchange I=0.9 eV we obtain an effective value of local moment of e_g electrons 2p=1.04 mu_B. The effective bosonic model, which allows to describe magnetic properties of iron near the magnetic phase transition, is proposed.

cond-mat.str-el↗

arXiv2009

Electronic structure of V2O3: Wannier orbitals from LDA-$N$MTO calculations

Using muffin-tin orbital (MTO) based NMTO-downfolding procedure within the framework of local density approximation, we construct the Wannier orbitals for the $t_{2g}$ manifold of bands in V2O3 in the paramagnetic phase. The real space representation of the one-electron Hamiltonian in the constructed Wannier function basis shows that, contrary to the popular belief, the in-plane hopping interactions are as important as the vertical pair hopping. Following the language of Di Matteo {\it et.al.} [Phys. Rev. B 65, 054413 (2002)], this implies, the problem of V2O3 falls in the atomic regime rather than in the molecular regime. We have also repeated our construction procedure in the low temperature monoclinic phase, for which the changes in hopping interactions are found not to be dramatic.

cond-mat.mtrl-sci↗

arXiv2007

Enhanced Crystal Field Splitting and Orbital Selective Coherence by Strong Correlations in V_2O_3

We present a study of the paramagnetic metallic and insulating phases of vanadium sesquioxide by means of the $N$th order muffin-tin orbital implementation of density functional theory combined with dynamical mean-field theory. The transition is shown to be driven by a correlation-induced enhancement of the crystal field splitting within the $t_{2g}$ manifold, which results in a suppression of the hybridization between the $a_{1g}$ and $e_g^π$ bands. We discuss the changes in the effective quasi-particle band structure caused by the correlations and the corresponding self-energies. At temperatures of about 400 K we find the $a_{1g}$ orbitals to display coherent quasi-particle behavior, while a large imaginary part of the self-energy and broad features in the spectral function indicate that the $e_g^π$ orbitals are still far above their coherence temperature. The local spectral functions are in excellent agreement with recent bulk sensitive photoemission data. Finally, we also make a prediction for angle-resolved photoemission experiments by calculating momentum-resolved spectral functions.

cond-mat.str-el↗

arXiv2003

Non-local Coulomb interactions and metal-insulator transition in Ti$_2$O$_3$: a cluster LDA+DMFT approach

We present an ab initio quantum theory of the metal-insulator transition in Ti$_2$O$_3$. The recently developed cluster LDA+DMFT scheme is applied to describe the many-body features of this compound. The conventional single site DMFT cannot reproduce a low temperature insulating phase for any reasonable values of the Coulomb interaction. We show that the non-local Coulomb interactions and the strong chemical bonding within Ti-Ti pair is the origin of the small gap insulating ground state of Ti$_2$O$_3$.

cond-mat.str-el↗

arXiv2000

Calculation of photoemission spectra of the doped Mott insulator La_{1-x}Sr_xTiO_3 using LDA+DMFT(QMC)

The spectral properties of La$_{1-x}$Sr$_{x}$TiO$_{3}$, a doped Mott insulator with strong Coulomb correlations, are calculated with the ab initio computational scheme LDA+DMFT(QMC). It starts from the non-interacting electronic band structure as calculated by the local density approximation (LDA), and introduces the missing correlations by the dynamical mean-field theory (DMFT), using numerically exact quantum Monte-Carlo (QMC) techniques to solve the resulting self-consistent multi-band single-impurity problem. The results of the LDA+DMFT(QMC) approach for the photoemission spectra of La$_{1-x}$Sr$_{x}$TiO$_{3}$ are in good agreement with experiment and represent a considerable qualitative and quantitative improvement on standard LDA calculations.

cond-mat.str-el↗