| 1. |
- Etz, Corina, et al.
(författare)
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Indications of weak electronic correlations in SrRuO3 from first-principles calculations
- 2012
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 86:6, s. 064441-
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Tidskriftsartikel (refereegranskat)abstract
- We provide, by a detailed first-principles investigation, evidence for weak electronic correlations in SrRuO 3. The magnetism in SrRuO 3, in terms of the equilibrium magnetization and critical temperature, is well described by the generalized gradient approximation. Including Hubbard-type correlations results in worse agreement with experiment
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| 2. |
- Gürbüz, Emel, et al.
(författare)
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First-principles prediction of energy band gaps in 18-valence electron semiconducting half-Heusler compounds : Exploring the role of exchange and correlation
- 2023
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Ingår i: Journal of Applied Physics. - : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 134:20
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Tidskriftsartikel (refereegranskat)abstract
- The choice of exchange functional is a critical factor in determining the energy bandgap of semiconductors. Ab initio calculations using different exchange functionals, including the conventional generalized-gradient approximation (GGA) functionals, meta-GGA functionals, and hybrid functionals, show significant differences in the calculated energy bandgap for semiconducting half-Heusler compounds. These compounds, which have 18 valence electrons per unit cell, are of great interest due to their thermoelectric properties, making them suitable for energy conversion applications. In addition, accounting for electronic correlations using the GW method also affects the calculated energy bandgaps compared to standard GGA calculations. The variations in calculated energy bandgaps are specific to each material when using different functionals. Hence, a detailed investigation of the electronic properties of each compound is necessary to determine the most appropriate functional for an accurate description of the electronic properties. Our results indicate that no general rules can be established and a comparison with experimental results is required to determine the most appropriate functional.
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| 3. |
- Gürbüz, Emel, et al.
(författare)
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Spin-polarized two-dimensional electron/hole gas at the interface of nonmagnetic semiconducting half-Heusler compounds : Modified Slater-Pauling rule for half-metallicity at the interface
- 2023
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Ingår i: Physical Review Materials. - : American Physical Society. - 2475-9953. ; 7:5
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Tidskriftsartikel (refereegranskat)abstract
- Half-Heusler compounds with 18 valence electrons per unit cell are well-known nonmagnetic semiconductors. Employing first-principles electronic band-structure calculations, we study the interface properties of the half-Heusler heterojunctions based on FeVSb, CoTiSb, CoVSn, and NiTiSn compounds, which belong to this category of materials. Our results show that several of these heterojunction interfaces become not only metallic but also magnetic. The emergence of spin-polarization is accompanied by the formation of two-dimensional electron gas or hole gas at the interface. A qualitative analysis of the origin of the spin polarization at the interfaces suggests that strong correlations are responsible. For the cases of magnetic interfaces where half-metallicity is also present, we propose a modified Slater-Pauling rule similar to the one for bulk half-metallic half-Heusler compounds. Additionally, we calculate exchange parameters, Curie temperatures, and magnetic anisotropy energies for magnetic interfaces. Our study, along with recent experimental evidence confirming the presence of two-dimensional electron gas at CoTiSb/NiTiSn heterojunctions, may motivate future efforts to explore and realize device applications using these heterojunctions.
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| 4. |
- Maslyuk, Volodymyr V., et al.
(författare)
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Organometallic benzene-vanadium wire : A one-dimensional half-metallic ferromagnet
- 2006
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 97:9, s. 097201-
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Tidskriftsartikel (refereegranskat)abstract
- Using density functional theory we perform theoretical investigations of the electronic properties of a freestanding one-dimensional organometallic vanadium-benzene wire. This system represents the limiting case of multidecker V-n(C6H6)(n+1) clusters which can be synthesized with established methods. We predict that the ground state of the wire is a 100% spin-polarized ferromagnet (half-metal). Its density of states is metallic at the Fermi energy for the minority electrons and shows a semiconductor gap for the majority electrons. We find that the half-metallic behavior is conserved up to 12% longitudinal elongation of the wire. Ab initio electron transport calculations reveal that finite size vanadium-benzene clusters coupled to ferromagnetic Ni or Co electrodes will work as nearly perfect spin filters.
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| 5. |
- Meded, Velimir, 1974-
(författare)
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Electronic Transport in Materials
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Transport properties within the Boltzmann transport equation for metallic multi-layer structures as well as bulk materials, were the prime topic of this work. Ab initio total energy calculations for Hydrogen loaded metallic multi-layers were performed in order to shed some light onto problem of H depleted layers at the interfaces that have been experimentally observed. It was explained in connection with structural relaxation of the interface layers. Further on conductivity behavior of Fe/V vs. Mo/V during Hydrogen load was discussed. The difference in, on first sight, rather similar multi-layer structures was explained by the magnitude of Hydrogen induced Vanadium expansion. Problem of variation of conductivity with changed c/a ratio of metals and semiconductors in general was addressed as well. The variations due to change of the Fermi surface of the corresponding materials were observed as well as some intriguing general patterns. The phenomenon could be regarded as piezoresistivity on electronic structure level. For the 3d transition metals variation of conductivity/resistivity through the period was studied.A possible explanation for anomalous behavior of Manganese resistivity due to its much greater lattice constant in comparison to its neighbors in the period is presented. Field of disordered alloys and low dimensional magnetism was touched by discussing Mo/Ru formation energy as well as magnetic nano-wires grown on surfaces.All total energy calculations as well as band structure calculations were performed by using Density Functional Theory based numerical computations. A short but comprehensive review of most common linear-response electron transport techniques is given.
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| 6. |
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| 7. |
- Tange, A., et al.
(författare)
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Electronic structure and spin polarization of the Fe(001)-p(1X1)O surface
- 2010
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 81:19
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Tidskriftsartikel (refereegranskat)abstract
- We present a combined experimental and theoretical study on electronic and magnetic properties of the Fe(001)-p(1X1)O surface. The ordered p(1X1) surface is investigated with spin-polarized scanning tunneling microscopy and spectroscopy accompanied by first-principles calculations. The atomic registry of the Fe(001)-p(1X1)O surface was confirmed in real space from the atomically resolved images. Tunneling spectroscopy reveals two oxygen induced features in the local density of states, around -0.7 eV and at the Fermi level, the origin of which is discussed based on first-principles calculations. Due to the hybridization of oxygen p(z) states with the Fe states near the Fermi level, the spin polarization in tunneling experiments is inverted upon oxygen adsorption.
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| 8. |
- Thonig, Danny, et al.
(författare)
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Existence of topological nontrivial surface states in strained transition metals : W, Ta, Mo, and Nb
- 2016
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Ingår i: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 94:15
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Tidskriftsartikel (refereegranskat)abstract
- We show that a series of transition metals with strained body-centered cubic lattice-W, Ta, Nb, and Mo-hosts surface states that are topologically protected by mirror symmetry and, thus, exhibits nonzero topological invariants. These findings extend the class of topologically nontrivial systems by topological crystalline transition metals. The investigation is based on calculations of the electronic structures and of topological invariants. The signatures of a Dirac-type surface state in W(110), e.g., the linear dispersion and the spin texture, are verified. To further support our prediction, we investigate Ta(110) both theoretically and experimentally by spin-resolved inverse photoemission: unoccupied topologically nontrivial surface states are observed.
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| 9. |
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