| 1. |
- Atumi, M.K., et al.
(författare)
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Hyperfine interaction of H-divacancy in diamond
- 2020
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Ingår i: Results in Physics. - : Elsevier. - 2211-3797. ; 16
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Tidskriftsartikel (refereegranskat)abstract
- We present a first principles density functional theory study of microscopic properties of hydrogen defect centres in diamond. Several configurations, involving interstitial hydrogen impurities, have been considered either forming with other defects, such as hydrogen defects and vacancies. The atomic structures, and hyperfine parameters of hydrogen result compared with the experimental data on electrically active centres in synthetic diamond. Based on Local density functional theory our calculations are in excellent agreement with one interpretation of electron paramagnetic resonance of hydrogen in diamond.
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| 2. |
- Barakat, M. M. E., et al.
(författare)
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Superconducting gap and critical behavior in the Iron-Pnictides
- 2023
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Ingår i: RESULTS IN PHYSICS. - : ELSEVIER. - 2211-3797. ; 52
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Tidskriftsartikel (refereegranskat)abstract
- In the phase diagram of iron pnictides, superconductivity arises at the border of antiferromagnetism, which raises the question of the role of symmetry of the gap and quantum criticality. Although more than 15-years of extensive research, the microscopic origin of the pairing symmetry inside the superconducting (SC) dome and its link to quantum criticality still remains elusive. Here, we report two new findings on BaFe2_xNixAs2: (1) A sharp peak in the x-dependence of the lower and upper critical fields, the SC critical current density Jc, the size of the jump in the specific heat Delta Cel/T and the Sommerfeld coefficient (gamma) at the optimum composition x = 0.10, where the SC transition temperature Tc reaches a maximum. Our obtained reliable values as a function of doping of the normal-state Sommerfeld coefficient increase with doping, illustrating the strong competition between magnetism and superconductivity and attributed to closing of spin density wave gap with Ni doping. (2) We show that doping induced a sudden change of the gap structure from nodeless to nodal. Our results imply that the superconductivity in BaFe2_xNixAs2 is closely linked to the quantum criticality and is characterized by a complex order parameter.
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| 3. |
- Baránková, Hana, et al.
(författare)
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Atmospheric pressure plasma conversion of CO2 to solid deposits
- 2015
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Ingår i: Results in Physics. - Elsevier : Elsevier BV. - 2211-3797. ; 5, s. 257-258
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Tidskriftsartikel (refereegranskat)abstract
- Fused Hollow Cathode (FHC) with aerodynamic stabilization was used for the gas conversion processes. During the conversion of NO into NO2 in air mixtures, the CO2 reduction occurs, without forming gaseous CO. In these processes brownish glassy solid deposits are formed in the plasma region. The deposits were analyzed by scanning electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction.
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| 4. |
- Bayani, Amirhossein, et al.
(författare)
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The influence by substrate morphology on the Rashba band splitting in graphene
- 2020
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Ingår i: Results in Physics. - : Elsevier. - 2211-3797. ; 17
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Tidskriftsartikel (refereegranskat)abstract
- The influence of substrate morphology on the Rashba band splitting at the Dirac point of graphene, has been theoretically investigated. More specifically, the possibility for this splitting to be caused by spin–orbit coupling (with the heavy metal substrate) was of a special interest to study. The model system consisted of a 4H-SiC (0 0 0 1)/graphene interface, with an intercalated metal layer (Ag and Au, respectively). These intercalating metal layers were built with two different types of morphologies; either flat or buckled (with different buckling positions). The results show that depending on the position of the buckled metal atom, the size of the bandgap and band splitting (at the Dirac point of graphene) will either increase (or decrease). Moreover, the enlargement of the buckling size was also shown to affect the electronic properties of graphene (i.e., by increasing the bandgap). The sizes of the bandgaps and band splitting for the different intercalating metals (Ag and Au), were also found to be different. Spin-projected band structures was also implemented in the present study, with the purpose to show the spin-texture of graphene. It was thereby shown that the spins pined to the x and y spin components for most of the cases.
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| 5. |
- Chafai, A., et al.
(författare)
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Linear and nonlinear optical properties of donors inside a CdSe/ZnTe core/shell nanodot : Role of size modulation
- 2019
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Ingår i: RESULTS IN PHYSICS. - : ELSEVIER. - 2211-3797. ; 14
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Tidskriftsartikel (refereegranskat)abstract
- The optical absorption coefficient (OAC) and the refractive index (RI), related to a confined donor, were theoretically investigated by the mean of the density matrix formalism. In order to obtain the 1s - 1p donor transition energy a variational calculation, within the context of the effective-mass approach, was deployed. Our numerical results exhibit the possibility to modulate the electronic and optical properties of confined donors by tailoring the inner and outer radii of the core/shell heterodot. Further, we have obtained that the nanodot size shrinking leads, for very small values of core radius, to reduce the magnitude of the total absorption coefficient resonance peak. It was also obtained that the resonance peak position of the absorption coefficient is redshifted with increasing the core radius for a fixed shell thickness. The same situation occurs when reducing the thickness of the shell material for a fixed core size.
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| 6. |
- Fanyaev, Ivan, et al.
(författare)
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Subwavelength imaging amplification via electro-thermally tunable InSb-graphene-based hyperlens in terahertz frequency
- 2023
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Ingår i: Results in Physics. - 2211-3797. ; 52
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Tidskriftsartikel (refereegranskat)abstract
- Subwavelength imaging plays an important role in various fields of science and technology. We propose a electro-thermally tunable hyperlens design featuring alternating graphene/metal/dielectric layers that enables subdiffraction far-field imaging with real-time amplification capabilities at terahertz frequencies. We show that one layer of graphene is able to increase the intensity of the subwavelength image of the hyperlens radiation in the near and far zones by tuning its chemical potential by the applied voltage. The proposed hyperlens is dynamically tunable with temperature changes over a wide frequency range. Simultaneous or independent electro-thermal tunability of the hyperlens opens new multifunctional possibilities for light manipulation. This improves the quality of subwavelength images for new devices in the terahertz range.
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| 7. |
- Fondell, Mattis, 1984-, et al.
(författare)
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HAXPES study of Sn core levels and their plasmon loss features
- 2014
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Ingår i: Results in Physics. - : Elsevier BV. - 2211-3797. ; 4, s. 168-169
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Tidskriftsartikel (refereegranskat)abstract
- Hard X-ray Photoelectron spectra have been recorded for elemental Sn. Electron loss features, prominent in all core level spectra of the metal, are analyzed at several photo energies for the 3p core level. For higher photoelectron kinetic energies the intensity of the plasmonic features follows a simple exponential law. The data and models presented here will aid the modeling of spectra where tin is present and especially if its spectrum overlaps with those from other sources.
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| 8. |
- Han, Yilin, et al.
(författare)
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171 Scandium-based full Heusler compounds : A comprehensive study of competition between XA and L21 atomic ordering
- 2019
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Ingår i: Results in Physics. - : Elsevier. - 2211-3797. ; 12, s. 435-446
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Tidskriftsartikel (refereegranskat)abstract
- The site-preference rule (SPR), which is widely used to design and study the properties of full-Heusler alloys X2YZ, is applied to determine the positions of different transition-metal elements with various numbers of valence electrons in Heusler alloys. The scandium-based full Heusler alloys should form an XA structure according to the SPR, because the transition-metal element Sc with fewer valence electrons tends to occupy the Wyckoff sites A(0, 0, 0) and B(0.25, 0.25, 0.25). As opposed to previous investigations, L21-type scandium-based full Heusler alloys, which do not follow the SPR, are also considered in this work. Theoretical computations are used to study the atomic-site preferences of 171 scandium-based full Heusler alloys, and the results indicate that most of these alloys form L21-type structures rather than XA-type structures. Two possible orderings are also studied in terms of their difference in charge density. Furthermore, the ground state, electronic structure, and magnetic characteristics of these alloys are also investigated in detail in both XA and L21 structures. The results reveal dramatic differences between XA- and L21-type alloys. This study thus presents a counterexample of the SPR rule and should provide significant guidance for the future design of full-Heusler alloys.
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| 9. |
- Höglin, Viktor, et al.
(författare)
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Sample cell for in-field X-ray diffraction experiments
- 2015
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Ingår i: Results in Physics. - : Elsevier BV. - 2211-3797. ; 5, s. 53-54
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Tidskriftsartikel (refereegranskat)abstract
- A sample cell making it possible to perform synchrotron radiation X-ray powder diffraction experiments in a magneticfield of 0.35 T has been constructed. The device is an add-on to an existing sample cell and contains a strong permanentmagnet of NdFeB-type. Experiments have shown that the setup is working satisfactory making it possible to performin-field measurements.
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| 10. |
- Kozlova, Anna P., et al.
(författare)
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Luminescence and vacuum ultraviolet excitation spectroscopy of cerium doped Gd3Ga3Al2O12 single crystalline scintillators under synchrotron radiation excitations
- 2020
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Ingår i: Results in Physics. - : Elsevier BV. - 2211-3797. ; 16
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Tidskriftsartikel (refereegranskat)abstract
- Cerium doped Gd3Ga3Al2O12 (GGAG) single crystals as well as GGAG:Ce single crystals co-doped by divalent (Mg2+, Ca2+), trivalent (Sc3+) or tetravalent (Zr4+, Ti4+) ions have been studied by means of the excitation luminescence spectroscopy in vacuum ultraviolet spectral range. Synchrotron radiation from the undulator beam was utilized for the luminescence excitation in the energy range from 4.5 to 800 eV. The influence of the co-dopant ions on the excitonic transitions as well as on the intrinsic defects in GGAG was revealed examining the luminescence emission and excitation spectra of both Gd3+ and Ce3+ ions in all single crystals studied. Special attention was paid to the analysis of Ce3+ excitation spectra in VUV spectral range (4.5–45 eV) where multiplication of electronic excitation (MEE) processes occur. It was obtained that GGAG:Ce single crystals having different co-dopant ions reveal distinguished efficiency of MEE. The role of intrinsic defects in MEE processes in the co-doped GGAG:Ce single crystals was elucidated.
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