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San Sebastián de los Reyes, Spain

Caprara S.,Donostia International Physics Center | Caprara S.,University of Rome La Sapienza | Tugushev V.V.,RAS Research Center Kurchatov Institute | Chulkov E.V.,Donostia International Physics Center | Chulkov E.V.,Centro Mixto CSIC UPV EHU
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

We discuss a model which is apt to describe the appearance of a spin-polarized half-metallic state around a single δ layer of a magnetic transition metal embedded into a nonmagnetic semiconductor host. We show that ferromagnetism in this system can be attributed to the intrinsic physical properties of the δ layer. The relevant physical effects described by our model are the hybridization of the electron states of the metal and semiconductor atoms, the charge redistribution around the δ layer, and the electron-electron correlation on a metal atom, which is the driving force of ferromagnetism. We obtain the mean-field phase diagram of the model at zero and finite temperature, both in the case when the chemical potential is fixed, and when the density of particles on the δ layer is fixed. The relevance of our results in connection with numerical and experimental results on the so-called digital magnetic heterostructures, in the absence and in the presence of a quantum-well carrier channel, is eventually discussed. © 2011 American Physical Society.

Hofer U.,University of Marburg | Hofer U.,Donostia International Physics Center | Echenique P.M.,Donostia International Physics Center | Echenique P.M.,Centro Mixto CSIC UPV EHU
Surface Science | Year: 2015

A theory of image-potential states is presented for the general case where these surface electronic states are resonant with a bulk continuum. The theory extends the multiple scattering approach of Echenique and Pendry into the strong coupling regime while retaining independence from specific forms of surface and bulk potentials. The theory predicts the existence of a well-resolved series of resonances for arbitrary coupling strengths. Surprisingly, distinct image-potential resonances are thus expected to exist on almost any metal surface, even in the limiting case of jellium. © 2015 Elsevier B.V.

Okuda T.,Hiroshima University | Maegawa T.,Hiroshima University | Ye M.,Hiroshima University | Shirai K.,Hiroshima University | And 16 more authors.
Physical Review Letters | Year: 2013

A topological surface state that is protected physically under the Bi 2Te3-like five-layer block has been revealed on the Pb-based topological insulator (TI) PbBi4Te7 by bulk sensitive angle-resolved photoelectron spectroscopy (ARPES). Furthermore, conservation of the spin polarization of the hidden topological surface states is directly confirmed by bulk-sensitive spin ARPES observation. This finding paves the way to realize the real spintronics devices by TIs that are operable in the real environment. © 2013 American Physical Society.

Borisova S.D.,Tomsk State University | Rusina G.G.,Tomsk State University | Eremeev S.V.,Tomsk State University | Chulkov E.V.,Centro Mixto CSIC UPV EHU
JETP Letters | Year: 2016

Equilibrium lengths and binding energies, vibrational frequencies, width of the HOMO–LUMO gap, and the magnetic anisotropy energies for one- and two-component dimers of heavy p elements of Groups IV (Sn, Pb), V (Sb, Bi), and VI (Se, Te) with a pronounced relativistic effect have been calculated with the use of the formalism of the density functional theory. It has been shown that it is necessary to take into account the spin–orbit coupling, which significantly affects the energy parameters of clusters. The analysis of the data obtained has revealed that the Pb–Te, Pb–Se, Sn–Te, and Sn–Se dimers have the widest gap at the Fermi level and the lowest reactivity. The magnetic anisotropy energy has been calculated for all single- and doublecomponent dimers and the direction of the easy magnetization axis has been determined. © 2016, Pleiades Publishing, Inc.

Eremeev S.V.,RAS Institute of Strength Physics and Materials Science | Men'Shov V.N.,RAS Research Center Kurchatov Institute | Tugushev V.V.,RAS A.M. Prokhorov General Physics Institute | Chulkov E.V.,San Sebastian University | Chulkov E.V.,Centro Mixto CSIC UPV EHU
Journal of Magnetism and Magnetic Materials | Year: 2015

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 substrate-induced moments. Recent magnetic and magneto-transport measurements in EuS/Bi2Se3 heterostructure are discussed. © 2014 Published by Elsevier B.V.

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