| 1. |
- Filianina, M. V., et al.
(författare)
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Spin and electronic structure of the topological insulator Bi1.5Sb0.5Te1.8Se1.2
- 2018
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Ingår i: Materials Chemistry and Physics. - : Elsevier BV. - 0254-0584. ; 207, s. 253-258
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Tidskriftsartikel (refereegranskat)abstract
- Electronic and spin structure of the Dirac-cone-like topological surface and valence band states were studied experimentally and theoretically for topological insulator with fractional stoichiometry Bi1.5Sb0.5Te1.8Se1.2 which is considered as one of the best candidates for efficient spin-polarized current generation. By means of spin- and angle-resolved photoelectron spectroscopy we demonstrate the separation of the Dirac point from the bulk states and the helical spin structure of the Dirac cone. For the freshly cleaved surface the Fermi level is located in the bulk band gap and an exposure in residual gases shifts the Fermi level towards the bulk conduction band. Results of the theoretical calculations are in a good agreement with the experimental data. Surface morphology study shows a well-structured atomically sharp surface after cleavage. The transport measurements confirm that this topological insulator has relatively high resistance with semiconductor-like temperature dependence at low temperatures. The studied Bi1.5Sb0.5Te1.8Se1.2 crystals demonstrated a quite large Seebeck coefficient values reaching −400 μV/K at room temperature.
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| 2. |
- Gogina, A. A., et al.
(författare)
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Adsorption of Na Monolayer on Graphene Covered Pt(111) Substrate
- 2023
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Ingår i: JETP Letters. - 0021-3640 .- 1090-6487. ; 117:2, s. 138-146
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Tidskriftsartikel (refereegranskat)abstract
- Modification of graphene electronic properties via contact with atoms of different kind allows for designing a number of functional post-silicon electronic devices. Specifically, 2D metallic layer formation over graphene is a promising approach to improving the electronic properties of graphene-based systems. In this work we analyse the electronic and spin structure of graphene synthesized on Pt(111) after sodium monolayer adsorption by means of angle-resolved photoemission spectroscopy and ab initio calculations. Here, we show that sodium layer formation leads to a shift of the graphene pi states towards higher binding energies, but the most intriguing property of the studied system is the appearance of a partially spin-polarized Kanji symbol-like feature resembling the graphene Dirac cone in the electronic structure of adsorbed sodium. Our findings reveal that this structure is caused by a strong interaction between Na orbitals and Pt 5d spin-polarized states, where the graphene monolayer between them serves as a mediator of such interaction.
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| 3. |
- Lytvynenko, Y., et al.
(författare)
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Control of the asymmetric band structure in Mn2Au by a ferromagnetic driver layer
- 2023
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Ingår i: Physical Review B. - 2469-9950 .- 2469-9969. ; 108:10
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Tidskriftsartikel (refereegranskat)abstract
- Hard x-ray angle-resolved photoemission spectroscopy reveals the momentum-resolved band structure in an epitaxial Mn2Au(001) film capped by a 2-nm-thick ferromagnetic permalloy layer. By magnetizing the permalloy capping layer, the exceptionally strong exchange bias aligns the Néel vector in the Mn2Au(001) film accordingly. Uncompensated interface Mn magnetic moments in Mn2Au were identified as the origin of the exchange bias using x-ray magnetic circular dichroism in combination with photoelectron emission microscopy. Using time-of-flight momentum microscopy, we measure the asymmetry of the band structure, E(k)≠E(-k), in Mn2Au resulting from the homogeneous orientation of the Néel vector. Comparison with theory shows that the Néel vector, determined by the magnetic moment of the top Mn layer, is antiparallel to the permalloy magnetization. The experimental results demonstrate that hard x-ray photoemission spectroscopy can measure the band structure of epitaxial layers beneath a metallic capping layer and corroborate the asymmetric band structure in Mn2Au that was previously inferred only indirectly.
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