Publications (444)1435.88 Total impact
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ABSTRACT: We present a theoretical study of lifetimes of interface states (IS) on metalorganic interfaces PTCDA/Ag(111), NTCDA/Ag(111), PFP/Ag(111), and PTCDA/Ag(100), describing and explaining the recent experimental data. By means of unfolding the band structure of one of the interfaces under study onto the Ag(111) Brillouin zone we demonstrate, that the Brillouin zone folding upon organic monolayer deposition plays a minor role in the phase space for electron decay, and hence weakly affects the resulting lifetimes. The presence of the unoccupied molecular states below the IS gives a small contribution to the IS decay rate mostly determined by the change of the phase space of bulk states upon the energy shift of the IS. The calculated lifetimes follow the experimentally observed trends. In particular, we explain the trend of the unusual increase of the IS lifetimes with rising temperature. 
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ABSTRACT: We develop a theory of energy relaxation in semiconductors and insulators highly excited by the longacting external irradiation. We derive the equation for the nonequilibrium distribution function of excited electrons. The solution for this function breaks up into the sum of two contributions. The lowenergy contribution is concentrated in a narrow range near the bottom of the conduction band. It has the typical form of a Fermi distribution with an effective temperature and chemical potential. The effective temperature and chemical potential in this lowenergy term are determined by the intensity of carriers' generation, the speed of electronphonon relaxation, rates of interband recombination and electron capture on the defects. In addition, there is a substantial highenergy correction. This highenergy 'tail' covers largely the conduction band. The shape of the highenergy 'tail' strongly depends on the rate of electronphonon relaxation but does not depend on the rates of recombination and trapping. We apply the theory to the calculation of a nonequilibrium distribution of electrons in irradiated GaN. Probabilities of optical excitations from the valence to conduction band and electronphonon coupling probabilities in GaN were calculated by the density functional perturbation theory. Our calculation of both parts of distribution function in gallium nitride shows that when the speed of electronphonon scattering is comparable with the rate of recombination and trapping then the contribution of the nonFermi 'tail' is comparable with that of the lowenergy Fermilike component. So the highenergy contribution can affect essentially the charge transport in the irradiated and highly doped semiconductors. 
Article: Universal properties of materials with the Dirac dispersion relation of lowenergy excitations
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ABSTRACT: The Nterminal scheme is considered for studying the contribution of edge states to the response of a twodimensional topological insulator. A universal distribution of the nonlocal resistance between terminals is determined in the ballistic transport approach. The calculated responses are identical to experimentally observed values. The spectral properties of surface electronic states in Weyl semimetals are also studied. The density of surface states is accurately determined. The universal behavior of these characteristics is a distinctive feature of the considered Dirac materials which can be used in practical applications.  [Show abstract] [Hide abstract]
ABSTRACT: We have investigated plasmonic excitations at the surface of Bi2Se3 (0001) via highresolution electron energy loss spectroscopy. For low parallel momentum transfer q∥, the loss spectrum shows a distinctive feature peaked at 104 meV. This mode varies weakly with q∥. The behavior of its intensity as a function of primary energy and scattering angle indicates that it is a surface plasmon. At larger momenta (q∥ ∼ 0.04 Å−1), an additional peak, attributed to the Dirac plasmon, becomes clearly defined in the loss spectrum. Momentumresolved loss spectra provide evidence of the mutual interaction between the surface plasmon and the Dirac plasmon of Bi2Se3. The proposed theoretical model accounting for the coexistence of threedimensional doping electrons and twodimensional Dirac fermions accurately represents the experimental observations. The results reveal novel routes for engineering plasmonic devices based on topological insulators.  [Show abstract] [Hide abstract]
ABSTRACT: The modification of the graphene spin structure is of interest for novel possibilities of application of graphene in spintronics. The most exciting of them demand not only high value of spinorbit splitting of the graphene states, but nonRashba behavior of the splitting and spatial modulation of the spinorbit interaction. In this work we study the spin and electronic structure of graphene on Ir(111) with intercalated Pt monolayer. Pt interlayer does not change the 9.3 × 9.3 superlattice of graphene, while the spin structure of the Dirac cone becomes modified. It is shown that the Rashba splitting of the π state is reduced, while hybridization of the graphene and substrate states leads to a spindependent avoidedcrossing effect near the Fermi level. Such a variation of spinorbit interaction combined with the superlattice effects can induce a topological phase in graphene.  [Show abstract] [Hide abstract]
ABSTRACT: We propose a way to break the timereversal symmetry at the surface of a threedimensional topological insulator that combines features of both surface magnetic doping and magnetic proximity effect. Based on the possibility of organizing an ordered array of local magnetic moments by inserting them into a twodimensional matrix of organic ligands, we study the magnetic coupling and electronic structure of such metalorganic coordination networks on a topological insulator surface from first principles. In this way, we find that both Co and Cr centers, linked by the tetracyanoethylenelike organic ligand, are coupled ferromagnetically and, depending on the distance to the topological insulator substrate, can yield a magnetic proximity effect. This latter leads to the Dirac point gap opening indicative of the timereversal symmetry breaking. 
Dataset: SSP.190.494
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ABSTRACT: Ab initio study of the adsorption, diffusion, and intercalation of alkali metal adatoms on the (0001) step surface of the topological insulator Bi2Se3 has been performed for the case of low coverage. The calculations of the activation energies of diffusion of adatoms on the surface and in van der Waals gaps near steps, as well as the estimate of diffusion lengths, have shown that efficient intercalation through steps is possible only for Li and Na. Data obtained for K, Rb, and Cs atoms indicate that their thermal desorption at high temperatures can occur before intercalation. The results have been discussed in the context of existing experimental data. 
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ABSTRACT: We report the bulk and surface electronic properties and spin polarization of a rich family of Snbased ternary topological insulators studied by means of firstprinciples calculations within the framework of density functional theory. These compounds exist with the following stoichiometries: SnX2Te4,SnX4Te7, and SnBi6Te10 (X = Sb and Bi). Where a septuple layer or a quintuple layer and septuple layer blocks alternate along the hexagonal axis. We reveal that the bulk band gap in these compounds is about 100 meV and recognize a strong dependence of the spin polarization on the cleavage surface. The calculated spin polarization reaches 85% in some cases, that is one of the highest predicted values hitherto. Since the electron spin polarization is a relevant parameter for spintronics technology, this new family is suitable for applications within this field. © 2015 American Physical Society.  [Show abstract] [Hide abstract]
ABSTRACT: The atomic structure of ultrathin iron films deposited on the (0001) surface of the topological insulator Bi2Se3 is analyzed by surface xray absorption spectroscopy. Iron atoms deposited on a Bi2Se3 (0001) surface kept at 160 K substitute bismuth atoms within the first quintuple layer. Iron atoms are neighbored by six selenium atoms at a distance in the 2.4 Å range indicating substantial atomic relaxations. Mild annealing up to 520 K leads to the formation of αFeSe, characterized by a local order extending up to the sixth shell (5.80 Å). Ab initio calculations predict a noncollinear magnetic ordering with a transition temperature of 3.510 K depending on the iron concentration and the number of the layers in which Fe is located.  [Show abstract] [Hide abstract]
ABSTRACT: An exotic type of topological spinhelical surface state was found in layered van der Waals bonded (SnTe)n=2,3(Bi2Te3)m=1 compounds which comprise two covalently bonded band inverted sublattices, SnTe and Bi2Te3, within a building block. This topological state demonstrates unusual dispersion within the band gap. The dispersion of the surface state has two linear sections of different slope with a shoulder feature between them. Such a dispersion of the topological surface state enables an effective switch of the velocity of topological carriers by means of applying an external electric field.  [Show abstract] [Hide abstract]
ABSTRACT: By means of relativistic density functional theory (DFT) calculations we study electron band structure of the topological insulator (TI) Bi2Se3 thin films deposited on the ferromagnetic insulator (FMI) EuS substrate. In the Bi2Se3/EuS heterostructure, the gap opened in the spectrum of the topological state has a hybridization character and is shown to be controlled by the Bi2Se3 film thickness, while magnetic contribution to the gap is negligibly small. We also analyzed the effect of Eu doping on the magnetization of the Bi2Se3 film and demonstrated that the Eu impurity induces magnetic moments on neighboring Se and Bi atoms an order of magnitude larger than the substrateinduced moments. Recent magnetic and magnetotransport measurements in EuS/Bi2Se3 heterostructure are discussed.  [Show abstract] [Hide abstract]
ABSTRACT: We report firstprinciples GW results on the dispersion of the bulk bandgap edges in the threedimensional topological insulator Sb2Te3. We find that, independently of the reference densityfunctionaltheory band structure and the crystallattice parameters used, the oneshot GW corrections enlarge the fundamental band gap, bringing its value in close agreement with experiment. We conclude that the GW corrections cause the displacement of the valenceband maximum (VBM) to the Γ point, ensuring that the surfacestate Dirac point lies above the VBM. We extend our study to the analysis of the electronenergyloss spectrum (EELS) of bulk Sb2Te3. In particular, we perform energyfiltered transmission electron microscopy and reflection EELS measurements. We show that the randomphase approximation with the GW quasiparticle energies and taking into account virtual excitations from the semicore states leads to good agreement with our experimental data.  [Show abstract] [Hide abstract]
ABSTRACT: A new type of topological spinhelical surface states was discovered in layered van der Waals bonded (SnTe)$_{n=2,3}$(Bi$_2$Te$_3$)$_{m=1}$ compounds which comprise two covalently bonded band inverted subsystems, SnTe and Bi$_2$Te$_3$, within a building block. This novel topological states demonstrate nonDirac dispersion within the band gap. The dispersion of the surface state has two linear sections of different slope with shoulder feature between them. Such a dispersion of the topological surface state enables effective switch of the velocity of topological carriers by means of applying an external electric field.  [Show abstract] [Hide abstract]
ABSTRACT: A bilayer of bismuth is recognized as a prototype twodimensional topological insulator. Here we present a simple and well reproducible topdown approach to prepare a flat and well ordered bismuth bilayer with a lateral size of several hundred nanometers on ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$(0001). Using scanning tunneling microscopy, surface xray diffraction, and Auger electron spectroscopy we show that exposure of ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$(0001) to atomic hydrogen completely removes selenium from the top quintuple layer. The band structure of the system, calculated from first principles for the experimentally derived atomic structure, is in excellent agreement with recent photoemission data. Our results open interesting perspectives for the study of topological insulators in general.  [Show abstract] [Hide abstract]
ABSTRACT: The binding energy, equilibrium geometry, and vibration frequencies in bimetallic clusters Ni13 − nAln (n = 0–13) have been calculated using the embedded atom method potentials. It has been shown that the icosahedral structure is the most stable in monoatomic and bimetallic clusters. A tendency of Al atoms to segregate on the cluster surface has been revealed in agreement with the experimental data. The calculations of the atomic vibrations have shown the nonmonotonic dependence of the minimum and maximum vibration frequencies of cluster atoms on its composition and the coupling of their extreme values with the most stable atomic configuration. The increase in the number of Al atoms leads to the shift of the frequency spectrum and the substantial redistribution of the localization of vibrations on the cluster atoms.  [Show abstract] [Hide abstract]
ABSTRACT: The dielectric and optical properties of semiconductor compounds BiTeI and BiTeCl have been studied the� oretically within time dependent density functionaltheory and experimentally by spectral ellipsometry. Anisotropy of dielectric constants in the long�wavelength limit and dispersion of the σand σ+ πbulk plas� mons in the longitudinal and transverse directions of the crystals have been discovered. It has been shown that the inclusion of the spin–orbit interaction is necessary for agreement between the theory and the results of optical measurements.  [Show abstract] [Hide abstract]
ABSTRACT: Modifications in dielectric properties of palladium upon absorption of hydrogen are investigated theoretically in the lowenergy (02 eV) region. The calculations were performed with full inclusion of the electronic band structure obtained within a selfconsistent pseudopotential approach. In particular, we trace the evolution of the acousticlike plasmon (AP) found previously in clean Pd with increasing hydrogen concentration. It exists in PdHx up to the hydrogen content x corresponding to the complete filling of the 4d Pdderived energy bands because of the presence of two kinds of carriers at the Fermi surface. At higher H concentration the AP disappears since only one kind of carrier within the splike energy band exists at the Fermi level. Additionally, we investigate the spatial distribution inside the crystal of a potential caused by a timedependent external perturbation and observe drastic modifications in the screening properties in the PdHx systems with energy and with hydrogen concentration.
Publication Stats
9k  Citations  
1,435.88  Total Impact Points  
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Institutions

2015

Saint Petersburg State University
SanktPeterburg, St.Petersburg, Russia 
Tomsk Polytechnical University
Tomsk, Tomsk, Russia


19942015

Universidad del País Vasco / Euskal Herriko Unibertsitatea
 • Departamento de Física de Materiales
 • Facultad de Química
Leioa, Basque Country, Spain


19792015

Tomsk State University
Tomsk, Tomsk, Russia


20012014

Donostia International Physics Center
San Sebastián, Basque Country, Spain


2011

Novosibirsk State University
 Department of Physics
NovoNikolaevsk, Novosibirsk, Russia


2010

Università degli Studi di MilanoBicocca
 Department of Materials Science
Milano, Lombardy, Italy 
Ikerbasque  Basque Foundation for Science
Bilbo, Basque Country, Spain


20072010

Center of Materials Physics
San Sebastián, Basque Country, Spain


2009

Aarhus University
 Department of Physics and Astronomy
Aarhus, Central Jutland, Denmark


2002

Philipps University of Marburg
 Faculty of Physics
Marburg, Hesse, Germany


19871998

Russian Academy of Sciences
 Institute of Strength Physics and Materials Science of the Siberian Branch
Moscow, Moscow, Russia
