SwePub - sökning: WFRF:(Katsnelson M I)

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1.	Bischoff M. M. J., Fang C. M. , De Groot R. A. , Heijnen G. M. M. , Katsnelson M. I. , Kolesnychenko O. Yu. , De Kort R. , Lichtenstein A. I. , Quinn A. J. , de Parma A. L. V. , Yamada T. K. , and Van Kempen H. (författare) Scanning tunneling spectroscopy study of surface states of 3d metals: Chemical identification, magnetic contrast and orbital Kondo resonance states 2003 Ingår i: Acta Physica Polonica A. ; , s. 231- Konferensbidrag (refereegranskat)
2.	Ferrari, A. C., et al. (författare) Science and technology roadmap for graphene, related two-dimensional crystals, and hybrid systems 2015 Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3372 .- 2040-3364. ; 7:11, s. 4598-4810 Tidskriftsartikel (refereegranskat)abstract We present the science and technology roadmap for graphene, related two-dimensional crystals, and hybrid systems, targeting an evolution in technology, that might lead to impacts and benefits reaching into most areas of society. This roadmap was developed within the framework of the European Graphene Flagship and outlines the main targets and research areas as best understood at the start of this ambitious project. We provide an overview of the key aspects of graphene and related materials (GRMs), ranging from fundamental research challenges to a variety of applications in a large number of sectors, highlighting the steps necessary to take GRMs from a state of raw potential to a point where they might revolutionize multiple industries. We also define an extensive list of acronyms in an effort to standardize the nomenclature in this emerging field.
3.	Boukhvalov D. W., Kurmaev E. Z. , Moewes A. , Zatsepin D. A., Cherkashenko V. M., Nemnonov S. N., Finkelstein L. D. , Yarmoshenko Yu. M., Neumann M., Dobrovitski V. V. , Katsnelson M. I. , Lichtenstein A. I. , Harmon B. N. , Kögerler P. (författare) Electronic structure of magnetic molecules V15: LSDA+U calculations, X-ray emission and photoelectron spectra 2003 Ingår i: Physical Review B. ; 67, s. 134408- Tidskriftsartikel (refereegranskat)
4.	Boukhvalov, D. W., et al. (författare) Electronic structure of a Mn-12 molecular magnet : Theory and experiment 2007 Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 75:1, s. 014419- Tidskriftsartikel (refereegranskat)abstract We used site-selective and element-specific resonant inelastic x-ray scattering (RIXS) to study the electronic structure and the electron interaction effects in the molecular magnet [Mn12O12(CH3COO)(16)(H2O)(4)]center dot 2CH(3)COOH center dot 4H(2)O, and compared the experimental data with the results of local spin density approximation +U electron structure calculations which include the on-site Coulomb interactions. We found a good agreement between theory and experiment for the Coulomb repulsion parameter U = 4 eV. In particular, the p-d band separation of 1.8 eV has been found from the RIXS spectra, which is in accordance with the calculations. Similarly, the positions of the peaks in the XPS spectra agree with the calculated densities of p and d states. Using the results of the electronic structure calculations, we determined the intramolecular exchange parameters, and used them for diagonalization of the Mn-12 spin Hamiltonian. The calculated exchanges gave the correct ground state with the total spin S = 10.
5.	Colarieti-Tosti, M., et al. (författare) First-Principles Theory of Intermediate Valence f-electron systems Ingår i: Physical Review Letters. Tidskriftsartikel (refereegranskat)
6.	Dubrovinsky, L., et al. (författare) The most incompressible metal osmium at static pressures above 750 gigapascals 2015 Ingår i: Nature. - : NATURE PUBLISHING GROUP. - 0028-0836 .- 1476-4687. ; 525:7568, s. 226- Tidskriftsartikel (refereegranskat)abstract Metallic osmium (Os) is one of the most exceptional elemental materials, having, at ambient pressure, the highest known density and one of the highest cohesive energies and melting temperatures(1). It is also very incompressible(2-4), but its high-pressure behaviour is not well understood because it has been studied(2-6) so far only at pressures below 75 gigapascals. Here we report powder X-ray diffraction measurements on Os at multi-megabar pressures using both conventional and double-stage diamond anvil cells(7), with accurate pressure determination ensured by first obtaining self-consistent equations of state of gold, platinum, and tungsten in static experiments up to 500 gigapascals. These measurements allow us to show that Os retains its hexagonal close-packed structure upon compression to over 770 gigapascals. But although its molar volume monotonically decreases with pressure, the unit cell parameter ratio of Os exhibits anomalies at approximately 150 gigapascals and 440 gigapascals. Dynamical mean-field theory calculations suggest that the former anomaly is a signature of the topological change of the Fermi surface for valence electrons. However, the anomaly at 440 gigapascals might be related to an electronic transition associated with pressure-induced interactions between core electrons. The ability to affect the core electrons under static high-pressure experimental conditions, even for incompressible metals such as Os, opens up opportunities to search for new states of matter under extreme compression.
7.	Glazyrin, K., et al. (författare) Importance of Correlation Effects in hcp Iron Revealed by a Pressure-Induced Electronic Topological Transition 2013 Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 110:11, s. 117206- Tidskriftsartikel (refereegranskat)abstract We discover that hcp phases of Fe and Fe0.9Ni0.1 undergo an electronic topological transition at pressures of about 40 GPa. This topological change of the Fermi surface manifests itself through anomalous behavior of the Debye sound velocity, c/a lattice parameter ratio, and Mossbauer center shift observed in our experiments. First-principles simulations within the dynamic mean field approach demonstrate that the transition is induced by many-electron effects. It is absent in one-electron calculations and represents a clear signature of correlation effects in hcp Fe.
8.	Link, S., et al. (författare) Introducing strong correlation effects into graphene by gadolinium intercalation 2019 Ingår i: Physical Review B. - 2469-9950. ; 100:12 Tidskriftsartikel (refereegranskat)abstract Exotic ordered ground states driven by electronic correlations are expected to be induced in monolayer graphene when doped to the Van Hove singularity. Such doping levels are reached by intercalating Gd in graphene on SiC(0001), resulting in a strong homogeneity and stability. The electronic spectrum now exhibits severe renormalizations. Flat bands develop which are driven by electronic correlations according to our theoretical studies. Due to strong electron-phonon coupling in this regime, polaron replica bands develop. Thus, interesting ordered ground states should be made accessible.
9.	Locht, Inka L. M., et al. (författare) Standard model of the rare earths analyzed from the Hubbard I approximation 2016 Ingår i: PHYSICAL REVIEW B. - : American Physical Society. - 2469-9950. ; 94:8 Tidskriftsartikel (refereegranskat)abstract In this work we examine critically the electronic structure of the rare-earth elements by use of the so-called Hubbard I approximation. From the theoretical side all measured features of both occupied and unoccupied states are reproduced, without significant deviations between observations and theory. We also examine cohesive properties like the equilibrium volume and bulk modulus, where we find, in general, a good agreement between theory andmeasurements. In addition, we have reproduced the spin and orbital moments of these elements as they are reflected from measurements of the saturation moment. We have also employed the Hubbard I approximation to extract the interatomic exchange parameters of an effective spin Hamiltonian for the heavy rare earths. We show that the Hubbard I approximation gives results which are consistent with calculations where 4f electrons are treated as core states for Gd. The latter approach was also used to address the series of the heavy/late rare earths. Via Monte Carlo simulations we obtained ordering temperatures which reproduce measurements within about 20%. We have further illustrated the accuracy of these exchange parameters by comparing measured and calculated magnetic configurations for the heavy rare earths and the magnon dispersion for Gd. The Hubbard I approximation is compared to other theories of the electronic structure, and we argue that it is superior. We discuss the relevance of our results in general and how this makes it possible to treat the electronic structure of materials containing rare-earth elements, such as permanent magnets, magnetostrictive compounds, photovoltaics, optical fibers, topological insulators, and molecular magnets.
10.	Mazurenko V. V., Lichtenstein A. I., Katsnelson M. I., Dasgupta I., Saha-Dasgupta T., Anisimov V. I. (författare) Nature of insulating state in NaV2O5 above charge-ordering temperature: A cluster dynamical mean-field study 2002 Ingår i: Physical Review B (Rapid Communications). ; 66, s. 081104 (R)- Tidskriftsartikel (refereegranskat)
11.	McArdle, P. F., et al. (författare) Agreement between TOAST and CCS ischemic stroke classification: The NINDS SiGN Study 2014 Ingår i: Neurology. - 0028-3878 .- 1526-632X. ; 83:18, s. 1653-60 Tidskriftsartikel (refereegranskat)abstract OBJECTIVE: The objective of this study was to assess the level of agreement between stroke subtype classifications made using the Trial of Org 10172 Acute Stroke Treatment (TOAST) and Causative Classification of Stroke (CCS) systems. METHODS: Study subjects included 13,596 adult men and women accrued from 20 US and European genetic research centers participating in the National Institute of Neurological Disorders and Stroke (NINDS) Stroke Genetics Network (SiGN). All cases had independently classified TOAST and CCS stroke subtypes. Kappa statistics were calculated for the 5 major ischemic stroke subtypes common to both systems. RESULTS: The overall agreement between TOAST and CCS was moderate (agreement rate, 70%; κ = 0.59, 95% confidence interval [CI] 0.58-0.60). Agreement varied widely across study sites, ranging from 28% to 90%. Agreement on specific subtypes was highest for large-artery atherosclerosis (κ = 0.71, 95% CI 0.69-0.73) and lowest for small-artery occlusion (κ = 0.56, 95% CI 0.54-0.58). CONCLUSION: Agreement between TOAST and CCS diagnoses was moderate. Caution is warranted when comparing or combining results based on the 2 systems. Replication of study results, for example, genome-wide association studies, should utilize phenotypes determined by the same classification system, ideally applied in the same manner.
12.	Niklasson, A. M. N., et al. (författare) Modeling the actinides with disordered local moments 2003 Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 67, s. 235105- Tidskriftsartikel (refereegranskat)
13.	Sokolewicz, R. J., et al. (författare) Gilbert damping in two-dimensional metallic antiferromagnets 2024 Ingår i: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 109:13 Tidskriftsartikel (refereegranskat)abstract A finite spin life-time of conduction electrons may dominate Gilbert damping of two-dimensional metallic antiferromagnets or antiferromagnet / metal heterostructures. We investigate the Gilbert damping tensor for a typical low-energy model of a metallic antiferromagnet system with honeycomb magnetic lattice and Rashba spinorbit coupling for conduction electrons. We distinguish three regimes of spin relaxation: exchange-dominated relaxation for weak spin -orbit coupling strength, Elliot-Yafet relaxation for moderate spin -orbit coupling, and Dyakonov-Perel relaxation for strong spin -orbit coupling. We show, however, that the latter regime takes place only for the in -plane Gilbert damping component. We also show that anisotropy of Gilbert damping persists for any finite spin -orbit interaction strength provided we consider no spatial variation of the N & eacute;el vector. Isotropic Gilbert damping is restored only if the electron spin -orbit length is larger than the magnon wavelength. Our theory applies to MnPS 3 monolayer on Pt or to similar systems.
14.	Boukhvalov D. W., Lichtenstein A. I., Dobrovitski V. V., Katsnelson M. I., Harmon B. N., Mazurenko V. V., Anisimov V. I. (författare) Effect of local Coulomb interactions on the electronic structure and exchange interactions in Mn12 magnetic molecules 2002 Ingår i: Physical Review B. ; 65, s. 184435- Tidskriftsartikel (refereegranskat)
15.	Carbone, C., et al. (författare) Correlated Electrons Step by Step : Itinerant-to-Localized Transition of Fe Impurities in Free-Electron Metal Hosts 2010 Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 104:11, s. 117601- Tidskriftsartikel (refereegranskat)abstract High-resolution photoemission spectroscopy and ab initio calculations have been employed to analyze the onset and progression of d-sp hybridization in Fe impurities deposited on alkali metal films. The interplay between delocalization, mediated by the free-electron environment, and Coulomb interaction among d electrons gives rise to complex electronic configurations. The multiplet structure of a single Fe atom evolves and gradually dissolves into a quasiparticle peak near the Fermi level with increasing host electron density. The effective multiorbital impurity problem within the exact diagonalization scheme describes the whole range of hybridizations.
16.	Chioncel, L., et al. (författare) Ab initio electronic structure calculations of correlated systems : An EMTO-DMFT approach 2003 Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 67:23 Tidskriftsartikel (refereegranskat)abstract We propose a self-consistent method for electronic structure calculations of correlated systems, which combines the local spin-density approximation (LSDA) and the dynamical mean field theory (DMFT). The LSDA part is based on the exact muffin-tin orbital approach, meanwhile the DMFT uses a perturbation scheme that includes the T matrix with fluctuation exchange approximation. The current LSDA+DMFT implementation fulfills both self-energy and charge self-consistency requirements. We present results on the electronic structure calculations for bulk 3d transition metals (Cr, Fe, and Ni) and for Fe/Cr magnetic multilayers. The latter demonstrates the importance of the correlation effects for the properties of magnetic heterostructures.
17.	Colarieti-Tosti, Massimiliano, et al. (författare) First-principles theory of intermediate-valence f-electron systems 2004 Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 93:9, s. 096403- Tidskriftsartikel (refereegranskat)abstract We propose a first-principles based method for calculating the electronic structure and total energy of solids in an intermediate-valence configuration. The method takes into account correlation effects (d-f Coulomb interaction) and many-body renormalization of the effective hybridization parameter of the f system. As an example, the formation of a pressure-induced intermediate-valence state in Yb is considered and its electronic structure and equation of state are calculated and compared to experimental data. The agreement is found to be excellent for both properties, and we argue that the developed method, which applies to any element or compound, provides for the first time a quantitative theoretical treatment of intermediate-valence materials.
18.	Isaev, E. I., et al. (författare) Phonon related properties of transition metals, their carbides, and nitrides : A first-principles study 2007 Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 101:12 Forskningsöversikt (refereegranskat)abstract Lattice dynamics of body-centered cubic (bcc) V-b-VIb group transition metals (TM), and B1-type monocarbides and mononitrides of IIIb-VIb transition metals are studied by means of first-principles density functional perturbation theory, ultra soft pseudopotentials, and generalized gradient approximation to the exchange-correlation functional. Ground state parameters of transition metals and their compounds are correctly reproduced with the generated ultrasoft pseudopotentials. The calculated phonon spectra of the bcc metals are in excellent agreement with results of inelastic neutron scattering experiments. We show that the superconductivity of transition metal carbides (TMC) and transition metal nitrides (TMN) is related to peculiarities of the phonon spectra, and the anomalies of the spectra are connected to the number of valence electrons in crystals. The calculated electron-phonon interaction constants for TM, TMC, and TMN are in excellent agreement with experimentally determined values. Phonon spectra for a number of monocarbides and mononitrides of transition metals within the cubic NaCl- and hexagonal WC-type structures are predicted. Ideal stoichiometric B1 crystals of ScC, YC, and VC are predicted to be dynamically stable and superconducting materials. We also conclude that YN is a semiconductor.
19.	Locht, Inka L. M., et al. (författare) The standard model of the rare-earths, analyzed from the Hubbard-Iapproximation Annan publikation (övrigt vetenskapligt/konstnärligt)
20.	Ruban, A.V., et al. (författare) Origin of magnetic frustrations in Fe-Ni Invar alloys 2005 Ingår i: Physical Review B. - : American Physical Society. - 1098-0121. ; 71, s. 054402- Tidskriftsartikel (refereegranskat)
21.	Shick, A. B., et al. (författare) Unified character of correlation effects in unconventional Pu-based superconductors and delta-Pu 2013 Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 87:2, s. 020505- Tidskriftsartikel (refereegranskat)abstract Electronic structure calculations combining the local-density approximation with an exact diagonalization of the Anderson impurity model show an intermediate 5 f(5)-5 f(6)-valence ground state and delocalization of the 5 f(5) multiplet of the Pu atom 5f shell in PuCoIn5, PuCoGa5, and delta-Pu. The 5f local magnetic moment is compensated by a moment formed in the surrounding cloud of conduction electrons. For PuCoGa5 and delta-Pu the compensation is complete, and the Anderson impurity ground state is a singlet. For PuCoIn5 the compensation is partial, and the Pu ground state is magnetic. We suggest that the unconventional d-wave superconductivity is likely mediated by the 5 f-state antiferromagnetic fluctuations in PuCoIn5 and by valence fluctuations in PuCoGa5.
22.	Sotnikov, O. M., et al. (författare) Certification of quantum states with hidden structure of their bitstrings 2022 Ingår i: NPJ QUANTUM INFORMATION. - : Springer Nature. - 2056-6387. ; 8:1 Tidskriftsartikel (refereegranskat)abstract The rapid development of quantum computing technologies already made it possible to manipulate a collective state of several dozens of qubits, which poses a strong demand on efficient methods for characterization and verification of large-scale quantum states. Here, we propose a numerically cheap procedure to distinguish quantum states which is based on a limited number of projective measurements in at least two different bases and computing inter-scale dissimilarities of the resulting bit-string patterns via coarse-graining. The information one obtains through this procedure can be viewed as a 'hash function' of quantum state-a simple set of numbers which is specific for a concrete wave function and can be used for certification. We show that it is enough to characterize quantum states with different structure of entanglement, including the chaotic quantum states. Our approach can also be employed to detect phase transitions in quantum magnetic systems.
23.	Wessely, O., et al. (författare) Comparison of X-ray absorption spectroscopy calculations on water and ice using transition-potential and Mahan-Nozières-De Dominicis theory Annan publikation (övrigt vetenskapligt/konstnärligt)
24.	Baglai, Mikhail, et al. (författare) Giant anisotropy of Gilbert damping in a Rashba honeycomb antiferromagnet 2020 Ingår i: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 101:10 Tidskriftsartikel (refereegranskat)abstract Giant Gilbert damping anisotropy is identified as a signature of strong Rashba spin-orbit coupling in a two-dimensional antiferromagnet on a honeycomb lattice. The phenomenon originates in spin-orbit-induced splitting of conduction electron subbands that strongly suppresses certain spin-flip processes. As a result, the spin-orbit interaction is shown to support an undamped nonequilibrium dynamical mode that corresponds to an ultrafast in-plane Neel vector precession and a constant perpendicular-to-the-plane magnetization. The phenomenon is illustrated on the basis of a two-dimensional s-d-like model. Spin-orbit torques and conductivity are also computed microscopically for this model. Unlike Gilbert damping, these quantities are shown to reveal only a weak anisotropy that is limited to the semiconductor regime corresponding to the Fermi energy staying in the close vicinity of the antiferromagnetic gap.
25.	Beutier, G., et al. (författare) Band Filling Control of the Dzyaloshinskii-Moriya Interaction in Weakly Ferromagnetic Insulators 2017 Ingår i: Physical Review Letters. - : AMER PHYSICAL SOC. - 0031-9007 .- 1079-7114. ; 119:16 Tidskriftsartikel (refereegranskat)abstract We observe and explain theoretically a dramatic evolution of the Dzyaloshinskii-Moriya interaction (DMI) in the series of isostructural weak ferromagnets, MnCO3, FeBO3, CoCO3, and NiCO3. The sign of the interaction is encoded in the phase of the x-ray magnetic diffraction amplitude, observed through interference with resonant quadrupole scattering. We find very good quantitative agreement with first-principles electronic structure calculations, reproducing both sign and magnitude through the series, and propose a simplified "toy model" to explain the change in sign with 3d shell filling. The model gives insight into the evolution of the DMI in Mott and charge transfer insulators.
26.	Boukhvalov D. W., Dobrovitski V. V., Katsnelson M. I. , Lichtenstein A. I., Harmon B. N., Kögerler P. (författare) Electronic structure and exchange interactions in V15 magnetic molecules 2003 Ingår i: Journal of Applied Physics. ; , s. 7080- Konferensbidrag (refereegranskat)
27.	Boukhvalov, D.W., et al. (författare) Testing the magnetism of polymerized fullerene 2004 Ingår i: Physical Review B. ; 69:11, s. 115425- Tidskriftsartikel (refereegranskat)
28.	Bručas, R., et al. (författare) Magnetic anisotropy and evolution of ground state domain structure in bcc Fe81Ni19/Co (001) superlattices Annan publikation (populärvet., debatt m.m.)
29.	Brucas, R., et al. (författare) Magnetic anisotropy and evolution of ground-state domain structures in bcc Fe81Ni19/Co(001) superlattices 2008 Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : The American Physical Society. - 1098-0121 .- 1550-235X. ; 78:2, s. 024421- Tidskriftsartikel (refereegranskat)abstract The magnetic anisotropy and evolution of striped magnetic domain structures in bcc Fe81Ni19/Co(001) superlattices with the total thickness ranging from 85 to 1370 nm has been studied by magneto-optical Kerr effect and magnetic force microscopy. At a thickness of about 85 nm [25 bilayers (BL)] the domains appear as stripe domains, typical for perpendicular anisotropy films, with the weak cubic anisotropy of the in-plane magnetization component stabilizing the stripe direction. The magnetic domain period strongly depends on the thickness of the superlattice. As the thickness increases, the equilibrium magnetization orients at oblique angles with respect to the film plane and continuously varies with the thickness from in-plane to out-of-plane. We first apply a simple phenomenological model which correctly predicts the transition from in-plane to out-of-plane magnetization as well as increasing domain period and saturation field with increasing BL number. The results indicate the presence of partial flux-closure domains at the film surface with the tilt angle continuously varying with the superlattice thickness. By solving a linearized Landau–Lifshitz equation together with Maxwell’s equations in magnetostatic approximation for samples consisting of up to 1000 individual layers, we calculate the spin-wave dispersion and determine the stability conditions for the saturated ferromagnetic state. From these results the dependence of the saturation field on the number of layers is inferred and agrees well with the experiment. The uniaxial bulk anisotropy is attributed to distortions along the c axis and the results further show evidence for the presence of an easy-plane interface anisotropy in these samples.
30.	Bručas, R., et al. (författare) Magnetization transitions and ground state domain phases in bcc Fe81Ni19/Co superlattices : On interface induced magnetic anisotropy Annan publikation (populärvet., debatt m.m.)
31.	Cardias, R., et al. (författare) The Bethe-Slater curve revisited; new insights from electronic structure theory 2017 Ingår i: Scientific Reports. - : NATURE PUBLISHING GROUP. - 2045-2322. ; 7 Tidskriftsartikel (refereegranskat)abstract The Bethe-Slater (BS) curve describes the relation between the exchange coupling and interatomic distance. Based on a simple argument of orbital overlaps, it successfully predicts the transition from antiferromagnetism to ferromagnetism, when traversing the 3d series. In a previous article [Phys. Rev. Lett. 116, 217202 (2016)] we reported that the dominant nearestneighbour (NN) interaction for 3d metals in the bcc structure indeed follows the BS curve, but the trends through the series showed a richer underlying physics than was initially assumed. The orbital decomposition of the inter-site exchange couplings revealed that various orbitals contribute to the exchange interactions in a highly non-trivial and sometimes competitive way. In this communication we perform a deeper analysis by comparing 3d metals in the bcc and fcc structures. We find that there is no coupling between the E-g orbitals of one atom and T-2g orbitals of its NNs, for both cubic phases. We demonstrate that these couplings are forbidden by symmetry and formulate a general rule allowing to predict when a similar situation is going to happen. In gamma-Fe, as in alpha-Fe, we find a strong competition in the symmetry-resolved orbital contributions and analyse the differences between the high-spin and low-spin solutions.
32.	Chioncel, L, et al. (författare) Ab initio electronic structure calculations of correlated 2003 Ingår i: Phys. Rev. B. ; 67, s. 235106- Tidskriftsartikel (refereegranskat)
33.	Chioncel L., Katsnelson M. I., de Groot R. A., Lichtenstein A. I. (författare) Nonquasiparticle states in the half-metallic ferromagnet NiMnSb 2003 Ingår i: Physical Review B. ; 68, s. 144425- Tidskriftsartikel (refereegranskat)
34.	Costa, Marcio, et al. (författare) Correlated electronic structure of Fe in bulk Cs and on a Cs surface 2013 Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 87:11, s. 115142- Tidskriftsartikel (refereegranskat)abstract We have investigated the spectral properties of Fe impurities in a Cs host, for both surface and bulk systems, by means of a combination of density functional theory in the local density approximation and dynamical mean-field theory (LDA + DMFT). The effective impurity model arising in LDA + DMFT was solved via two different techniques, i.e., the Hubbard I approximation and the exact diagonalization. It is shown that noticeable differences can be seen in the unoccupied part of the spectrum for different positions of Fe atoms in the host, despite the fact that hybridization between Fe d-states and Cs is low. Our calculations show good agreement with the experimental photoemission spectra reported by Carbone et al. [Carbone, Veronese, Moras, Gardonio, Grazioli, Zhou, Rader, Varykhalov, Krull, Balashov, Mugarza, Gambardella, Lebegue, Eriksson, Katsnelson, and Lichtenstein, Phys. Rev. Lett. 104, 117601 (2010)].
35.	Dallera, C., et al. (författare) Understanding mixed valent materials : Effects of dynamical core-hole screening in high-pressure x-ray spectroscopy 2006 Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 74:8, s. 081101- Tidskriftsartikel (refereegranskat)abstract Changes in the electronic structure of Yb, a material whose valence is modified under pressure, are observed with remarkable detail in x-ray absorption and emission data measured between ambient conditions and 20 GPa. These changes are reproduced by a theory that essentially does not rely on experimental parameters, and includes dynamical core-hole screening. From the combined experimental and theoretical data we can firmly establish on a quantitative level how the valency of an intermediate valence material is modified by pressure. In metallic Yb it increases from 2 to 2.55 +/- 0.05 between 0 and 20 GPa.
36.	de Raedt H. A., Hams A. H., Dobrovitski V. V., Al-Sager M., Katsnelson M. I., Harmon B. N. (författare) Many-spin effects and tunneling splittings in Mn12 magnetic molecules 2002 Ingår i: Journal of Magnetism and Magnetic Materials. ; 246, s. 392- Tidskriftsartikel (refereegranskat)
37.	De Raedt, H.A., et al. (författare) Many-spin calculation of tunneling splittings in Mn12 magnetic molecules 2002 Ingår i: J. Appl. Phys.. ; 91, s. 7152- Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
38.	Di Marco, I., et al. (författare) Electron correlations in Mn(x)Ga(1–x)As as seen by resonant electron spectroscopy and dynamical mean field theory 2013 Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 4, s. 6-2645 Tidskriftsartikel (refereegranskat)abstract After two decades since the discovery of ferromagnetism in manganese-doped gallium arsenide, its origin is still debated, and many doubts are related to the electronic structure. Here we report an experimental and theoretical study of the valence electron spectrum of manganese-doped gallium arsenide. The experimental data are obtained through the differences between off- and on-resonance photo emission data. The theoretical spectrum is calculated by means of a combination of density-functional theory in the local density approximation and dynamical mean field theory, using exact diagonalization as impurity solver. Theory is found to accurately reproduce measured data and illustrates the importance of correlation effects. Our results demonstrate that the manganese states extend over a broad range of energy, including the top of the valence band, and that no impurity band splits-off from the valence band edge, whereas the induced holes seem located primarily around the manganese impurity.
39.	Di Marco, Igor, et al. (författare) gamma-Mn at the border between weak and strong correlations 2009 Ingår i: European Physical Journal B. - : Springer Science and Business Media LLC. - 1434-6028 .- 1434-6036. ; 72:4, s. 473-478 Tidskriftsartikel (refereegranskat)abstract We investigate the role of magnetic fluctuations in the spectral properties of paramagnetic gamma-Mn. Two methods are employed. The Local Density Approximation plus Dynamical Mean-Field Theory together with the numerically exact quantum Monte-Carlo solver is used as a reference for the spectral properties. Then the same scheme is used with the computationally less demanding perturbative spin-polarized fluctuation-exchange solver in combination with the Disordered Local Moment approach, and photoemission spectra are calculated within the one-step model. It is shown that the formation of local magnetic moments in gamma-Mn is very sensitive to the value of Hund's exchange parameter. Comparison with the experimental photoemission spectra demonstrates that gamma-Mn is a strongly correlated system, with the Hubbard band formation, which cannot be described by the perturbative approach. However, minor change of parameters would transform it into a weakly correlated system.
40.	Gornostyrev Yu. N., Karkin I. N. , Katsnelson M. I., and Trefilov A. V. (författare) Evolution of the atomic structure of metal clusters upon heating and cooling. Computer simulation of FCC metals 2003 Ingår i: Physics of Metals and Metallography. ; 96, s. 135- Tidskriftsartikel (refereegranskat)
41.	Grechnev, Alexei, et al. (författare) Theory of bulk and surface quasiparticle spectra for Fe, Co, and Ni 2007 Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 76:3, s. 035107- Tidskriftsartikel (refereegranskat)abstract The correlated quasiparticle band structure of iron, cobalt, and nickel is investigated within the dynamical mean-field theory formalism using the recently developed full-potential linear-muffin-tin-orbital-based local-density approximation plus dynamical mean-field theory (LDA+DMFT) code. Detailed analysis of the calculated electron self-energy, density of states, and the spectral density is presented for these metals. It has been found that all these elements show strong correlation effects for majority-spin electrons, such as strong damping of quasiparticles and formation of a satellite state below the bottom of d bands. In particular, our work clearly predicts the existence of a photoemission satellite for bcc iron. The LDA+DMFT data for fcc nickel and cobalt (111) surfaces and bcc iron (001) surface are also presented. The electron self-energy is found to depend strongly on the number of nearest neighbors, and it practically reaches the bulk value already in the second layer from the surface. The dependence of correlation effects on the dimensionality of the problem is also discussed.
42.	Katsnelson, M. I. and Lichtenstein A. I. (författare) The problem of iron 2003 Ingår i: Proc. of Third School "Phase and Structural Transformations in Steels". - : Magnitogorsk. ; , s. 8- Konferensbidrag (refereegranskat)
43.	Katsnelson M. I., Lichtenstein A. I. (författare) Electronic structure and magnetic properties of correlated metals. A local self-consistent perturbation scheme 2002 Ingår i: European Physical Journal B. ; 30, s. 9- Tidskriftsartikel (refereegranskat)
44.	Keshavarz, Samara, et al. (författare) Layer-resolved magnetic exchange interactions of surfaces of late 3d elements : Effects of electronic correlations 2015 Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 92:16 Tidskriftsartikel (refereegranskat)abstract We present the results of an ab initio study of the magnetic properties of Fe, Co, and Ni surfaces. In particular, we discuss their electronic structure and magnetic exchange interactions (J(ij)), as obtained bymeans of a combination of density functional theory and dynamical mean-field theory. All studied systems have a pronounced tendency to ferromagnetism both for bulk and surface atoms. The presence of narrowband surface states is shown to enhance the magnetic moment as well as the exchange couplings. The most interesting results were obtained for the Fe surface where the atoms have a tendency to couple antiferromagnetically with each other. This interaction is relatively small when compared to interlayer ferromagnetic interaction, and it depends strongly on the lattice parameter. Local correlation effects are shown to lead to strong changes of the overall shape of the spectral functions. However, they seem not to play a decisive role in the overall picture of magnetic couplings studied here. We have also investigated the influence of correlations on the spin and orbital moments of bulklike and surface atoms. We found that dynamical correlations in general lead to enhanced values of the orbital moment.
45.	Kolesnichenko O. Yu., de Kort R., Katsnelson M. I., Lichtenstein A. I., van Kempen H. (författare) Real-space imaging of the orbital Kondo resonance on the Cr(001) surface 2002 Ingår i: Nature. ; 415, s. 507- Tidskriftsartikel (refereegranskat)
46.	Kurmaev, E Z, et al. (författare) Half-metallic electronic structure of CrO2 in resonant scattering 2003 Ingår i: Physical Review B. ; 67:15, s. 155105- Tidskriftsartikel (refereegranskat)
47.	Kvashnin, Yaroslav O., et al. (författare) Exchange parameters of strongly correlated materials : Extraction from spin-polarized density functional theory plus dynamical mean-field theory 2015 Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 91:12 Tidskriftsartikel (refereegranskat)abstract In this paper we present an accurate numerical scheme for extracting interatomic exchange parameters (J(ij)) of strongly correlated systems, based on first-principles full-potential electronic structure theory. The electronic structure is modeled with the help of a full-potential linear muffin-tin orbital method. The effects of strong electron correlations are considered within the charge self-consistent density functional theory plus dynamical mean-field theory. The exchange parameters are then extracted using the magnetic force theorem; hence all the calculations are performed within a single computational framework. The method allows us to investigate how the Jij parameters are affected by dynamical electron correlations. In addition to describing the formalism and details of the implementation, we also present magnetic properties of a few commonly discussed systems, characterized by different degrees of electron localization. In bcc Fe, treated as a moderately correlated metal, we found a minor renormalization of the Jij interactions once the dynamical correlations are introduced. However, generally, if the magnetic coupling has several competing contributions from different orbitals, the redistribution of the spectral weight and changes in the exchange splitting of these states can lead to a dramatic modification of the total interaction parameter. In NiO we found that both static and dynamical mean-field results provide an adequate description of the exchange interactions, which is somewhat surprising given the fact that these two methods result in quite different electronic structures. By employing the Hubbard-I approximation for the treatment of the 4f states in hcp Gd we reproduce the experimentally observed multiplet structure. The calculated exchange parameters result in being rather close to the ones obtained by treating the 4f electrons as noninteracting core states.
48.	Kvashnin, Yaroslav O., et al. (författare) Microscopic Origin of Heisenberg and Non-Heisenberg Exchange Interactions in Ferromagnetic bcc Fe 2016 Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 116:21 Tidskriftsartikel (refereegranskat)abstract By means of first principles calculations, we investigate the nature of exchange coupling in ferromagnetic bcc Fe on a microscopic level. Analyzing the basic electronic structure reveals a drastic difference between the 3d orbitals of E-g and T-2g symmetries. The latter ones define the shape of the Fermi surface, while the former ones form weakly interacting impurity levels. We demonstrate that, as a result of this, in Fe the T-2g orbitals participate in exchange interactions, which are only weakly dependent on the configuration of the spin moments and thus can be classified as Heisenberg-like. These couplings are shown to be driven by Fermi surface nesting. In contrast, for the E-g states, the Heisenberg picture breaks down since the corresponding contribution to the exchange interactions is shown to strongly depend on the reference state they are extracted from. Our analysis of the nearest-neighbor coupling indicates that the interactions among E-g states are mainly proportional to the corresponding hopping integral and thus can be attributed to be of double-exchange origin. By making a comparison to other magnetic transition metals, we put the results of bcc Fe into context and argue that iron has a unique behavior when it comes to magnetic exchange interactions.
49.	Kvashnin, Yaroslav, et al. (författare) Relativistic exchange interactions in CrX3 (X = Cl, Br, I) monolayers 2020 Ingår i: Physical Review B. - : AMER PHYSICAL SOC. - 2469-9950 .- 2469-9969. ; 102:11 Tidskriftsartikel (refereegranskat)abstract It has been predicted theoretically and indirectly confirmed experimentally that single-layer CrX3 (X = Cl, Br, I) might be the prototypes of topological magnetic insulators (TMI). In this work, by using first-principles calculations combined with atomistic spin dynamics, we provide a complete picture of the magnetic interactions and magnetic excitations in CrX3. The focus is here on the two most important aspects for the actual realization of TMI, namely the relativistic magnetic interactions and the finite-size (edge) effects. We compute the full interaction tensor, which includes both Kitaev and Dzyaloshinskii-Moriya (DM) terms, which are considered as the most likely mechanisms for stabilizing topological magnons. First, we instigate the properties of bulk CrI3 and compare the simulated magnon spectrum with the experimental data [Phys. Rev. X 8, 041028 (2018)]. Our results suggest that a large size of topological gap, seen in experiment (approximate to 14 meV), cannot be explained by considering pair-wise spin interactions only. We identify several possible reasons for this disagreement. The magnetic interactions in the monolayers of CrX3 are also investigated. The strength of the anisotropic interactions is shown to scale with the position of halide atom in the periodic table, the heavier the element the larger is the anisotropy, in agreement with prior studies. Comparing the magnons for the bulk and single-layer CrI3, we find that the size of the topological gap becomes smaller in the latter case. The obtained next nearest-neighbor DM vector is oriented primarily in-plane of the monolayer and has relatively small z component, which results in a small value of the topological gap. Finally, we investigate finite-size effects in monolayers and demonstrate that the anisotropic couplings between Cr atoms close to the edges are much stronger than those in ideal periodic structure. This should have impact on the dynamics of the magnon edge modes in Cr halides.
50.	Lebègue, Sebastien, et al. (författare) Multiplet effects in the electronic structure of heavy rare-earth metals 2006 Ingår i: JOURNAL OF PHYSICS-CONDENSED MATTER. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 18, s. 6329- Tidskriftsartikel (refereegranskat)abstract The spectroscopic properties of elemental terbium, dysprosium, holmium, and erbium are investigated using first-principles calculations taking into account intra-atomic correlation effects. In order to describe the strongly localized f electrons together with the conduction bands, we have used the multiband Hubbard-I approximation to reproduce the multiplet features present in the experimental spectra. A comparison with available experimental data is made and the overall agreement is found to be good.

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