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  • 1.
    Aad, G.
    et al.
    Aix Marseille Univ, CPPM, CNRS IN2P3, Marseille, France..
    Leopold, Alexander
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lundberg, Olof
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ohm, Christian
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ripellino, Giulia
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Shaheen, Rabia
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Shope, David R.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    CERN, CH-1211 Geneva 23, Switzerland..
    et al.,
    Study of B-c(+) -> J/psi D-s(+) and B-c(+)-> J/psi D-s*(+)decays in pp collisions at root s=13 TeV with the ATLAS detector2022In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 8, article id 087Article in journal (Refereed)
    Abstract [en]

    A study of B-c(+) -> J/psi D-s(+) and B-c(+)-> J/psi D-s*(+) decays using 139 fb(-1) of in- tegrated luminosity collected with the ATLAS detector from root s = 13 TeV pp collisions at the LHC is presented. The ratios of the branching fractions of the two decays to the branching fraction of the B-c(+) -> J/psi pi(+) decay are measured: B(B-c(+) -> J/psi D-s(+))/B(B-c(+) -> J/psi pi(+)) = 2.76 +/- 0.47 and B(B-c(+)-> J/psi D-s*(+))/B(B-c(+) -> J/psi pi(+)) = 5.33 +/- 0.96. The ratio of the branching fractions of the two decays is found to be B(B-c(+)-> J/psi D-s*(+))/B(B-c(+) -> J/psi D-s(+)) = 1.93 +/- 0.26. For the B-c(+)-> J/psi D-s*(+) decay, the transverse polarization fraction, Gamma(+/-+/-)/Gamma, is measured to be 0.70 +/- 0.11. The reported uncertainties include both the statistical and systematic components added in quadrature. The precision of the measurements exceeds that in all previous studies of these decays. These results supersede those obtained in the earlier ATLAS study of the same decays with root s = 7 and 8 TeV pp collision data. A comparison with available theoretical predictions for the measured quantities is presented.

  • 2. Abanin, D. A.
    et al.
    Bardarson, Jens H.
    KTH, School of Engineering Sciences (SCI), Physics, Condensed Matter Theory.
    De Tomasi, G.
    Gopalakrishnan, S.
    Khemani, V
    Parameswaran, S. A.
    Pollmann, F.
    Potter, A. C.
    Serbyn, M.
    Vasseur, R.
    Distinguishing localization from chaos: Challenges in finite-size systems2021In: Annals of Physics, ISSN 0003-4916, E-ISSN 1096-035X, Vol. 427, article id 168415Article in journal (Refereed)
    Abstract [en]

    We re-examine attempts to study the many-body localization transition using measures that are physically natural on the ergodic/quantum chaotic regime of the phase diagram. Using simple scaling arguments and an analysis of various models for which rigorous results are available, we find that these measures can be particularly adversely affected by the strong finite-size effects observed in nearly all numerical studies of many-body localization. This severely impacts their utility in probing the transition and the localized phase. In light of this analysis, we discuss a recent study (?untajs et al., 2020) of the behaviour of the Thouless energy and level repulsion in disordered spin

  • 3.
    Abbas, Ghazanfar
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology. COMSATS Institute of Information Technology, Pakistan.
    Raza, Rizwan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology. COMSATS Institute of Information Technology, Pakistan.
    Ahmad, M. Ashfaq
    Khan, M. Ajmal
    Hussain, M. Jafar
    Ahmad, Mukhtar
    Aziz, Hammad
    Ahmad, Imran
    Batool, Rida
    Altaf, Faizah
    Zhu, Bin
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Electrochemical investigation of mixed metal oxide nanocomposite electrode for low temperature solid oxide fuel cell2017In: International Journal of Modern Physics B, ISSN 0217-9792, Vol. 31, no 27, article id 1750193Article in journal (Refereed)
    Abstract [en]

    Zinc-based nanostructured nickel (Ni) free metal oxide electrode material Zn-0.60/CU0.20Mn0.20 oxide (CMZO) was synthesized by solid state reaction and investigated for low temperature solid oxide fuel cell (LTSOFC) applications. The crystal structure and surface morphology of the synthesized electrode material were examined by XRD and SEM techniques respectively. The particle size of ZnO phase estimated by Scherer's equation was 31.50 nm. The maximum electrical conductivity was found to be 12.567 S/cm and 5.846 S/cm in hydrogen and air atmosphere, respectively at 600 degrees C. The activation energy of the CMZO material was also calculated from the DC conductivity data using Arrhenius plots and it was found to be 0.060 and 0.075 eV in hydrogen and air atmosphere, respectively. The CMZO electrode-based fuel cell was tested using carbonated samarium doped ceria composite (NSDC) electrolyte. The three layers 13 mm in diameter and 1 mm thickness of the symmetric fuel cell were fabricated by dry pressing. The maximum power density of 728.86 mW/cm(2) was measured at 550 degrees C.

  • 4.
    Abdoshahi, Neda
    et al.
    Univ Leoben, Dept Mat Sci, Franz Josef Str 18, A-8700 Leoben, Austria..
    Dehghani, Mohammad
    Mat Ctr Leoben Forsch GmbH, Roseggerstr 12, A-8700 Leoben, Austria..
    Ruban, Andrei V.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures. Mat Ctr Leoben Forsch GmbH, Roseggerstr 12, A-8700 Leoben, Austria..
    Friak, Martin
    Czech Acad Sci, Inst Phys Mat, Zizkova 22, CZ-61662 Brno, Czech Republic.;Brno Univ Technol, Fac Mech Engn, Inst Mat Sci & Engn, Tech 2896-2, CZ-61669 Brno, Czech Republic..
    Sob, Mojmir
    Czech Acad Sci, Inst Phys Mat, Zizkova 22, CZ-61662 Brno, Czech Republic.;Masaryk Univ, Fac Sci, Dept Chem, Kotlarska 2, CZ-61137 Brno, Czech Republic..
    Spitaler, Juergen
    Mat Ctr Leoben Forsch GmbH, Roseggerstr 12, A-8700 Leoben, Austria..
    Holec, David
    Univ Leoben, Dept Mat Sci, Franz Josef Str 18, A-8700 Leoben, Austria..
    On the energetics of the cubic-to-hexagonal transformations in TiAl plus Mo alloys2022In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 240, article id 118268Article in journal (Refereed)
    Abstract [en]

    Diffusionless transformations allow access to metastable phases and enrich the materials design portfolio. They are well suited for atomistic modeling; nonetheless, they are challenging when involving disordered systems or alloys with complex compositions. This work presents a comprehensive study of transforma-tion energetics between bcc and hcp ordered and disordered phases in the TiAl+Mo model alloy system. By employing two complementary techniques I. VASP-SQS, and II. EMTO-CPA, we can show that chemical disorder flattens the energy landscape but may introduce a small barrier. Unlike that, the energetics of ordered phases are barrier-less and hence would suggest a spontaneous transformation. Finally, we show that Mo stabilizes the bcc phases, leading to a barrier-less transformation hcp -+ bcc for both ordered and disordered states when Mo content exceeds ti 12 at.%.

  • 5. Aberg, D
    et al.
    Hallberg, T
    Svensson, B G
    Lindstrom, J L
    Linnarsson, M K
    KTH, School of Information and Communication Technology (ICT).
    Ultra-shallow thermal donor formation in oxygen-containing ambient1998In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 210, p. 527-532Article in journal (Refereed)
    Abstract [en]

    Czochralski-grown phosphorus-doped (approximate to 2 x 10(14) cm(-3)) silicon wafers have been annealed in nitrogen, wet nitrogen, argon, oxygen, and vacuum ambients at 470 degrees C for times up to 500 h. Sample characterization was made with capacitance-voltage, four-point probe, DLTS, thermally stimulated capacitance, admittance spectroscopy, secondary ion-mass spectrometry, and Fourier transform infrared spectroscopy. This study finds a strong relation between the previously reported ultra-shallow thermal donors (USTDs) and shallow thermal donors (STDs), and it is shown that the net concentration of thermally formed donors is independent on annealing ambient within the experimental accuracy. It was found that the majority of formed donors for long anneals consisted of either STDs or USTDs, however, it was found that oxygen-containing ambient is indispensable for forming USTDs.

  • 6. Aberg, D
    et al.
    Linnarsson, M K
    KTH, School of Information and Communication Technology (ICT).
    Svensson, B G
    Hallberg, T
    Lindstrom, J L
    Ultrashallow thermal donor formation in silicon by annealing in ambient oxygen1999In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 85, p. 8054-8059Article in journal (Refereed)
    Abstract [en]

    Czochralski-grown silicon wafers doped with phosphorus (similar to 10(14) cm(-3)) have been annealed in nitrogen, wet nitrogen, oxygen, argon, and vacuum ambients at 470 degrees C for times up to 500 h. Sample characterization was made using predominantly electrical techniques such as admittance spectroscopy and thermally stimulated capacitance measurements but also secondary ion mass spectrometry (SIMS) and Fourier transform infrared spectroscopy were employed. In all samples, an increasing concentration of free carrier electrons is observed with increasing annealing time, reaching a maximum of similar to 10(16) cm(-3) at 100 h. For durations in excess of 100 h gradual decrease of the free electron concentration takes place except for the samples treated in wet nitrogen and oxygen atmospheres, which display donors stable even after 200 h. These stable centers are found to have shallower donor level positions in the energy band gap (similar to 25 meV below the conduction band edge E-c) than those of the centers formed in vacuum, argon, and nitrogen atmospheres (similar to 35 meV below E-c). The latter centers are associated with the well-established shallow thermal donors (STDs) while the origin of the former ones, which are labeled ultrashallow thermal donors (USTDs) is less known. However, on the basis of a wealth of experimental results we show that the USTDs are most likely perturbated STDs modified through interaction with fast-in diffusing oxygen species, possibly oxygen dimers. Further, comparison between the electrical data and the SIMS measurements reveals unambiguously that neither the STD nor the USTD centers involve nitrogen, in contrast to recent suggestions in the literature. (C) 1999 American Institute of Physics. [S0021-8979(99)06512-3].

  • 7.
    Abergel, David
    et al.
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA.
    Mucha-Kruczynski, Marcin
    Infrared absorption of closely aligned heterostructures of monolayer and bilayer graphene with hexagonal boron nitride2015In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 92, no 11, article id 115430Article in journal (Refereed)
    Abstract [en]

    We model optical absorption of monolayer and bilayer graphene on hexagonal boron nitride for the case of closely aligned crystal lattices. We show that perturbations with different spatial symmetry can lead to similar absorption spectra. We suggest that a study of the absorption spectra as a function of the doping for an almost completely full first miniband is necessary to extract meaningful information about the moire characteristics from optical absorption measurements and to distinguish between various theoretical proposals for the physically realistic interaction. Also, for bilayer graphene, the ability to compare spectra for the opposite signs of electric-field-induced interlayer asymmetry might provide additional information about the moire parameters.

  • 8. Aboulfadl, Hisham
    et al.
    Sopiha, Kostiantyn, V
    Keller, Jan
    Larsen, Jes K.
    Scragg, Jonathan J. S.
    Persson, Clas
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Thuvander, Mattias
    Edoff, Marika
    Alkali Dispersion in (Ag,Cu)(In,Ga)Se-2 Thin Film Solar Cells-Insight from Theory and Experiment2021In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 13, no 6, p. 7188-7199Article in journal (Refereed)
    Abstract [en]

    Silver alloying of Cu(In,Ga)Se-2 absorbers for thin film photovoltaics offers improvements in open-circuit voltage, especially when combined with optimal alkali-treatments and certain Ga concentrations. The relationship between alkali distribution in the absorber and Ag alloying is investigated here, combining experimental and theoretical studies. Atom probe tomography analysis is implemented to quantify the local composition in grain interiors and at grain boundaries. The Na concentration in the bulk increases up to similar to 60 ppm for [Ag]/([Ag] + [Cu]) = 0.2 compared to similar to 20 ppm for films without Ag and up to similar to 200 ppm for [Ag]/([Ag] + [Cu]) = 1.0. First-principles calculations were employed to evaluate the formation energies of alkali-on-group-I defects (where group-I refers to Ag and Cu) in (Ag,Cu)(In,Ga)Se-2 as a function of the Ag and Ga contents. The computational results demonstrate strong agreement with the nanoscale analysis results, revealing a clear trend of increased alkali bulk solubility with the Ag concentration. The present study, therefore, provides a more nuanced understanding of the role of Ag in the enhanced performance of the respective photovoltaic devices.

  • 9. Abrikosov, I. A.
    et al.
    Olsson, Pär
    Department of Materials and Mechanics of Components, EDF RandD, les Renardières, Moret-sur-Loing, France.
    Ponomareva, A. V.
    Correlation between electronic structure, magnetism and physical properties of Fe-Cr alloys: Ab initio modeling2008In: MATERIALS ISSUES FOR GENERATION IV SYSTEMS: STATUS, OPEN QUESTIONS AND CHALLENGES, 2008, p. 153-168Conference paper (Refereed)
    Abstract [en]

    We review recent developments in the field of ab initio electronic structure theory and its application for studies of phase stability of alloy systems. Basic ideas behind state-of-the-art techniques for first-principles theoretical simulations of the phase stabilities and properties of intermetallic compounds and alloys based on the density functional theory are outlined. We concentrate on methods that allow for an efficient treatment of disorder effects, and illustrate their predictive power for the case of Fe-Cr system. We show that in the ferromagnetic alloys there are peculiarities of the mixing enthalpy in the low-Cr region in the bee phase. Thus the stability of the Cr containing steels stems from the negative mixing enthalpy at low concentrations of chromium. We explain the effect by the strong concentration dependence of the interatomic interactions in Fe-Cr system.

  • 10. Achtziger, N
    et al.
    Grillenberger, J
    Witthuhn, W
    Linnarsson, M K
    KTH, School of Information and Communication Technology (ICT).
    Janson, M S
    Svensson, B G
    Hydrogen passivation of silicon carbide by low-energy ion implantation1998In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 73, p. 945-947Article in journal (Refereed)
    Abstract [en]

    implantation of deuterium is performed to investigate the mobility and passivating effect of hydrogen in epitaxial alpha-SiC (polytypes 4H and 6H). To avoid excessive damage and the resulting trapping of hydrogen, the implantation is performed with low energy (600 eV H-2(2)+). The H-2 depth profile is analyzed by secondary ion mass spectrometry. Electrical properties are measured by capacitance-voltage profiling and admittance spectroscopy. In p-type SIG, hydrogen diffuses on a mu m scale even at room temperature and effectively passivates accepters. In n-type SiC, the incorporation of H is suppressed and no passivation is detected. (C) 1998 American Institute of Physics.

  • 11. Achtziger, N
    et al.
    Hulsen, C
    Janson, M
    Linnarsson, M K
    KTH, School of Information and Communication Technology (ICT).
    Svensson, B G
    Witthuhn, W
    Formation of passivated layers in p-type SiC by low energy ion implantation of hydrogen2000In: SILICON CARBIDE AND RELATED MATERIALS - 1999 PTS, 1 & 2, 2000, Vol. 338-3, p. 933-936Conference paper (Refereed)
    Abstract [en]

    The mobility of hydrogen and its passivating effect on accepters in p-type SiC is investigated. Hydrogen (isotope H-1 or H-2 alternatively) is implanted at temperatures between 300 K and 680 K with low energy (300 eV per atom) in order to minimize implantation damage. The depth profiles of 2H and of passivated accepters correspond closely. Up to 500 K, a fully passivated layer with a well defined thickness is formed. Its depth ton the order of 1 micrometer) is investigated as a function of doping level and hydrogen fluence. At higher temperatures, the incorporation drastically increases, but the electrical passivation is partial only. Qualitative explanations are given.

  • 12. Achtziger, N
    et al.
    Hulsen, C
    Witthuhn, W
    Linnarsson, M K
    KTH, School of Information and Communication Technology (ICT).
    Janson, M
    Svensson, B G
    Mobility passivating effect and thermal stability of hydrogen in silicon carbide1998In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 210, p. 395-399Article in journal (Refereed)
    Abstract [en]

    The diffusion and passivating effect of hydrogen (isotope H-2) in epitaxial p-type SiC is studied by secondary ion mass spectrometry and capacitance-voltage profiling on Schottky diodes. The incorporation of hydrogen is achieved by low-energy ion implantation. The influence of implantation energy, temperature and subsequent annealing is presented. Annealing experiments with an electric field applied reveal a reactivation of passivated accepters and a H+ ion drift at a surprisingly low temperature of 530 K.

  • 13.
    Afzal, Muhammad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology. Hubei University, Faculty of Physics and Electronic Science, Wuhan, Hubei, 430062, China.
    Anwar, M.
    Asghar, M. I.
    Lund, P. D.
    Jhamat, N.
    Raza, R.
    Zhu, B.
    Charge transfer, transportation, and simulation2020In: Solid Oxide Fuel Cells: From Electrolyte-Based to Electrolyte-Free Devices, Wiley , 2020, p. 319-246Chapter in book (Refereed)
    Abstract [en]

    This chapter discusses charge transfer and transportation in energy materials and devices, especially focusing on single layer or electrolyte-free fuel cells (EFFCs). Here, charge means electrons and both positive and negative ions, e.g. H+ and O2-. We will study the factors that affect the charges resulting in conduction either externally for electrons or internally for both electrons and ions in EFFCs. Theoretical simulations are carried out by considering specific characteristics EFFC processes. Moreover, the enhancement in ionic conductivity is discussed leading to superionic conduction.

  • 14.
    Agnarsson, Björn
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Surface studies on α–sapphire for potential use in GaN epitaxial growth2009Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This Licentiate thesis summarizes the work carried out by the author the years 2004 to 2008 at the University of Iceland and the Royal Institute of Technology (KTH) in Sweden. The aim of the project was to investigate the structure of sapphire (alpha-Al2O3) surfaces, both for pure scientific reasons and also for potential use as substrate for GaN-growth by molecular beam epitaxy.

    More generally the thesis describes some surface science methods used for investigating the substrates; the general physical back ground, the experi- mental implementation and what information they can give. The described techniques are used for surface analysis on sapphire substrates which have been treated variously in order to optimize them for use as templates for epi- taxial growth of GaN or related III-V compounds.

    The thesis is based on three published papers.

    The first paper focuses on the formation a thin AlN layer on sapphire, which may act as a buffer layer for potential epitaxial growth of GaN or any related III-V materials. Two types of sapphire substrates (reconstructed and non- reconstructed) were exposed to ammonia resulting in the formation of AlN on the surface. The efficiency of the AlN formation (nitridation efficiency) for the two surfaces was then compared as a function of substrate temperature through photoelectron spectroscopy and low electron energy diffraction. The reconstructed surface showed a much higher nitridation efficiency than the non-reconstructed surface.

    In the second paper, the affect of different annealing processes on the sapphire morphology, and thus its capability to act as a template for GaN growth, was studied. Atomic force microscopy, X-ray diffraction analysis together with ellipsometry measurements showed that annealing in H2 ambient and subse- quent annealing at 1300 °C in O2 for 11 hours resulted in high quality and atomically flat sapphire surface suitable for III-V epitaxial growth.

    The third paper describes the effect of argon sputtering on cleaning GaN surfaces and the possibility of using indium as surfactant for establishing a clean and stoichiometric GaN surface, after such sputtering. Soft sputtering, followed by deposition of 2 ML of indium and subsequent annealing at around 500 °C resulted in a well ordered and clean GaN surface while hard sputtering introduced defects and incorporated both metallic gallium and indium in the surface.

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  • 15.
    Agnarsson, Björn
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Olafsson, S.
    Gislason, H. P.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Influence of initial surface reconstruction on nitridation of Al2O3 (0001) using low pressure ammonia2007In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 101, no 1, p. 013519-Article in journal (Refereed)
    Abstract [en]

    The purpose of this study is to investigate the effect of initial surface reconstruction on the nitridation process of Al2O3 (0001). This was done by exposing differently reconstructed sapphire substrates at different temperatures to low pressure ammonia (NH3). Structural and chemical analysis were carried out using low-electron energy diffraction and x-ray photoelectron spectroscopy. The experiments revealed that using low pressure ammonia (P-NH3 < 1 X 10(-5) Torr), no nitridation takes place on (1x1) unreconstructed surfaces. However, when the unreconstructed surface starts to change to a (root 31 x root 31) R +/- 9 degrees reconstructed surface, with increasing substrate temperature, the nitridation becomes successful. When using the initially reconstructed surface, the nitridation is successful even from the lowest temperature used. These results suggest that the initial surface reconstruction has a major effect on the nitridation process. This kinetic behavior has not been reported before, with most nitridation studies mainly focusing on the effect of surface temperature on the resulting surface morphology, rather than the actual kinetics of the process itself.

  • 16.
    Agrawal, Tarun Kumar
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Sustainable production development.
    Angelis, Jannis
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.).
    Thakur, Jagruti
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Energy Systems.
    Wiktorsson, Magnus
    KTH, School of Industrial Engineering and Management (ITM), Sustainable production development, Avancerad underhållsteknik och produktionslogistik.
    Kalaiarasan, Ravi
    KTH, School of Industrial Engineering and Management (ITM), Sustainable production development, Avancerad underhållsteknik och produktionslogistik.
    Enabling circularity of electric vehicle batteries-the need for appropriate traceability2021In: 2021 IEEE International Conference on Technology Management, Operations and Decisions, ICTMOD 2021, Institute of Electrical and Electronics Engineers (IEEE) , 2021Conference paper (Refereed)
    Abstract [en]

    With the increased electrification of transportation, there is a growth in the number of electric vehicles (EV) in use, and hence also discarded EV batteries. It is critical to trace the batteries so that the policy of electrification does not lead to a negative impact on sustainability. To achieve the goals of circular economy, it is necessary to consider the sustainable extended life cycle strategies of reduce, reuse and recycle. Information gathering and sharing through the supply chain is the key driver for enabling the tracking and tracing of materials and services needed. Traceability indicators across the value chain may enable the creation of a comprehensive database that aids the circular economy goals. In this study, we discuss three different circular economy business models and identify the key traceability indicators for enabling circularity in the lithium-ion battery application in the automotive sector. Insights are used to develop a framework for viable EV battery circularity, capturing three key circular economy elements and four traceability characteristics for different circularity types.

  • 17. Agterberg, Daniel F.
    et al.
    Garaud, Julien
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Condensed Matter Theory.
    Checkerboard order in vortex cores from pair-density-wave superconductivity2015In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 91, no 10, article id 104512Article in journal (Refereed)
    Abstract [en]

    We consider competing pair-density-wave (PDW) and d-wave superconducting states in a magnetic field. We show that PDW order appears in the cores of d-wave vortices, driving checkerboard charge-density-wave (CDW) order in the vortex cores, which is consistent with experimental observations. Furthermore, we find an additional CDW order that appears on a ring outside the vortex cores. This CDW order varies with a period that is twice that of the checkerboard CDW and it only appears where both PDW and d-wave order coexist. The observation of this additional CDW order would provide strong evidence for PDW order in the pseudogap phase of the cuprates. We further argue that the CDW seen by nuclear magnetic resonance at high fields is due to a PDW state that emerges when a magnetic field is applied.

  • 18.
    Ahlberg, Martina
    et al.
    Univ Gothenburg, Dept Phys, S-41296 Gothenburg, Sweden..
    Chung, Sunjae
    Univ Gothenburg, Dept Phys, S-41296 Gothenburg, Sweden.;Korea Natl Univ Educ, Dept Phys Educ, Cheongju 28173, South Korea..
    Jiang, Sheng
    KTH, School of Engineering Sciences (SCI), Applied Physics. Univ Gothenburg, Dept Phys.
    Frisk, Andreas
    Univ Gothenburg, Dept Phys, S-41296 Gothenburg, Sweden..
    Khademi, Maha
    Shahid Beheshti Univ, Dept Phys, Tehran 1983969411, Iran..
    Khymyn, Roman
    Univ Gothenburg, Dept Phys, S-41296 Gothenburg, Sweden..
    Awad, Ahmad A.
    Univ Gothenburg, Dept Phys, S-41296 Gothenburg, Sweden..
    Le, Quang Tuan
    KTH, School of Engineering Sciences (SCI), Applied Physics. Univ Gothenburg, Dept Phys.
    Mazraati, Hamid
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics. NanOsc AB, S-16440 Kista, Sweden..
    Mohseni, Majid
    KTH, School of Engineering Sciences (SCI), Applied Physics. Shahid Beheshti Univ, Dept Phys, Tehran 1983969411, Iran..
    Weigand, Markus
    Max Planck Inst Intelligent Syst, Stuttgart, Germany..
    Bykova, Iuliia
    Max Planck Inst Intelligent Syst, Stuttgart, Germany..
    Gross, Felix
    Max Planck Inst Intelligent Syst, Stuttgart, Germany..
    Goering, Eberhard
    Max Planck Inst Intelligent Syst, Stuttgart, Germany..
    Schutz, Gisela
    Max Planck Inst Intelligent Syst, Stuttgart, Germany..
    Grafe, Joachim
    Max Planck Inst Intelligent Syst, Stuttgart, Germany..
    Åkerman, Johan
    KTH, School of Engineering Sciences (SCI), Applied Physics. Univ Gothenburg, Dept Phys.
    Freezing and thawing magnetic droplet solitons2022In: Nature Communications, E-ISSN 2041-1723, Vol. 13, no 1, article id 2462Article in journal (Refereed)
    Abstract [en]

    Magnetic droplets are a type of non-topological magnetic soliton, which are stabilised and sustained by spin-transfer torques for instance. Without this, they would collapse. Here Ahlberg et al show that by decreasing the applied magnetic field, droplets can be frozen, forming a static nanobubble Magnetic droplets are non-topological magnetodynamical solitons displaying a wide range of complex dynamic phenomena with potential for microwave signal generation. Bubbles, on the other hand, are internally static cylindrical magnetic domains, stabilized by external fields and magnetostatic interactions. In its original theory, the droplet was described as an imminently collapsing bubble stabilized by spin transfer torque and, in its zero-frequency limit, as equivalent to a bubble. Without nanoscale lateral confinement, pinning, or an external applied field, such a nanobubble is unstable, and should collapse. Here, we show that we can freeze dynamic droplets into static nanobubbles by decreasing the magnetic field. While the bubble has virtually the same resistance as the droplet, all signs of low-frequency microwave noise disappear. The transition is fully reversible and the bubble can be thawed back into a droplet if the magnetic field is increased under current. Whereas the droplet collapses without a sustaining current, the bubble is highly stable and remains intact for days without external drive. Electrical measurements are complemented by direct observation using scanning transmission x-ray microscopy, which corroborates the analysis and confirms that the bubble is stabilized by pinning.

  • 19. Ahmad, S. A.
    et al.
    Naqvi, S. I.
    Khalid, M.
    Amin, Y.
    Loo, J.
    Tenhunen, Hannu
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Integrated devices and circuits.
    Penta-band antenna with defected ground structure for wireless communication applications2019In: 2019 2nd International Conference on Computing, Mathematics and Engineering Technologies, iCoMET 2019, Institute of Electrical and Electronics Engineers Inc. , 2019Conference paper (Refereed)
    Abstract [en]

    This work proposes a compact, penta-band, slotted antenna with Defected Ground Structure (DGS). The proposed multiband resonator is intended for integration into microwave circuits and portable RF portable devices. The prototype with spurlines and DGS is designed on thin Rogers RT Duroid 5880 substrate having thickness 0.508 mm. The presented radiator is capable to cover the frequency bands 2.46-2.59 GHz, 2.99-3.78 GHz, 5.17-5.89 GHz, 6.86-7.36 GHz, 9.38-11 GHz. The impedance bandwidths of 5.24%, 23.68%, 12.8%, 7.24% and 16.08% is obtained for the covered frequency bands respectively. The antenna proposed in this work thus supports WLAN, WiMAX, ISM, LTE, Bluetooth, C-band and X-band applications. The radiator attains 4.2 dB peak gain. It is apparent from the radiation performance of the prototype, that it is an effective candidate for current and forthcoming multiband wireless applications.

  • 20.
    Ahmadi, Sareh
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Structure-dependent charge transfer at the interafce between organic thin films, and metals and metal oxides2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The purpose of the research work, presented in this thesis is to offer a detailed atomic level study of interfaces created by adsorption of organic molecules on metals and metal oxides to point out significant impact of substrate, dye structure as well as different mediators on the charge transfer at these interfaces, which is proven to influence the device performance to a great extent.

    Adsorption of organic photosensitive molecules on metals and metal-oxides is the main focus of this thesis. Phthalocyanines which are organic semiconductors offer a broad range of properties, such as thermal and chemical stability, high charge mobility and strong absorption coefficient in the visible and near-IR regions, which make them very attractive to be applied in various systems and devices. Fuel cells, organic field-effect transistors (OFETs), organic light emitting diodes (OLEDs) and solar cells are examples of phthalocyanine’s applications. The main focus of this work is to characterize the interfaces of Dye Sensitized Solar Cells (DSSCs).

    DSSC was invented by Michael Grätzel and Brian O’Regan in 1988. At the heart of this cell there is an oxide which is coated by a photosensitive dye. Under illumination, an electron is excited from HOMO to LUMO of the molecule, which can be further transferred to the conduction band of the oxide by a proper energy level alignment. The original state of the dye is regenerated by electron donation via the electrolyte, which usually is an organic solvent containing a redox couple e.g., iodide/triiodide. The iodide is regenerated by reduction of triiodide at the counter electrode. To improve the functionality of the cell, different additives can be added to the electrolyte.

    To mimic the interfaces of this cell, molecular layers of MPc (M: Fe, Zn, Mg) are adsorbed on both metallic surfaces, Au(111) and Pt(111), and rutile TiO2(110). Layers of iodine were inserted between metallic substrates and dyes to investigate the electronic properties and charge transfer at these multi-interface systems. 4-tert-butyl pyridine is a significant additive to the electrolyte and has proven to enhance the cell’s performance. This molecule was also adsorbed on Pt(111) and TiO2(110). Phthalocyanines were deposited by organic molecular beam deposition and 4TBP was evaporated at room temperature. Surface structures and reconstructions were confirmed by LEED measurements. Surface sensitive synchrotron radiation based spectroscopy methods, XPS and NEXAFS were applied to characterize these surfaces and interfaces. STM images directly give a topographical and electronic map over the surface. All measurements were carried out in UHV condition.

    When MPc was adsorbed on Au(111) and TiO2(110), charge transfer from molecule to substrate is suggested, while the opposite holds for MPc adsorbed on Pt(111). Moreover, stronger interaction between MPc and Pt(111) and TiO2(110) compared to Au(111) also demonstrates the effect of substrate on the charge transfer at the interface. The stronger interaction observed for these two substrates disturbed the smooth growth of a monolayer; it also resulted in bending of the molecular plane. Interaction of MPc with metallic surfaces was modified by inserting iodine at the interface. Another substrate-related effect was observed when MgPc was adsorbed on TiO2(110);  and -cross linked surfaces, where the surface reconstruction directly affect the molecular configuration as well as electronic structure at the interface. Besides, it is shown that the d-orbital filling of the central metal atom in MPc plays an important role for the properties of the molecular layer as well as charge transfer at the interface.

    Upon adsorption of 4TBP on Pt(111), C-H bond is dissociatively broken and molecules is adsorbed with N atoms down. Modification of surface by iodine, prevent this dissociation. In the low coverage of iodine, there is a competition between 4TBP and iodine to directly bind to Pt(111). Investigation on the adsorption of 4TBP on TiO2(110) illustrated that these molecules in low coverage regime, prefer the oxygen vacancy sites and their adsorption on these sites, results in a downward band bending at the substrate’s surface. 

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    Thesis
  • 21.
    Ahmed, Aamna
    et al.
    Indian Inst Sci Educ & Res, Dept Phys, Bhopal 462066, Madhya Pradesh, India..
    Ramachandran, Ajith
    Christ Coll, Dept Phys, Irinjalakuda 680125, Kerala, India..
    Khaymovich, Ivan
    Nordita SU; Stockholm Univ, Hannes Alfvens Vag 12, SE-10691 Stockholm, Sweden.
    Sharma, Auditya
    Indian Inst Sci Educ & Res, Dept Phys, Bhopal 462066, Madhya Pradesh, India..
    Flat band based multifractality in the all-band-flat diamond chain2022In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 106, no 20, article id 205119Article in journal (Refereed)
    Abstract [en]

    We study the effect of quasiperiodic Aubry-Andre disorder on the energy spectrum and eigenstates of a one-dimensional all-band-flat (ABF) diamond chain. The ABF diamond chain possesses three dispersionless flat bands with all the eigenstates compactly localized on two unit cells in the zero disorder limit. The fate of the compact localized states in the presence of the disorder depends on the symmetry of the applied potential. We consider two cases here: a symmetric one, where the same disorder is applied to the top and bottom sites of a unit cell and an antisymmetric one, where the disorder applied to the top and bottom sites are of equal magnitude but with opposite signs. Remarkably, the symmetrically perturbed lattice preserves compact localization, although the degeneracy is lifted. When the lattice is perturbed antisymmetrically, not only is the degeneracy is lifted but compact localization is also destroyed. Fascinatingly, all eigenstates exhibit a multifractal nature below a critical strength of the applied potential. A central band of eigenstates continue to display an extended yet nonergodic behavior for arbitrarily large strengths of the potential. All other eigenstates exhibit the familiar Anderson localization above the critical potential strength. We show how the antisymmetric disordered model can be mapped to a pi /4 rotated square lattice with the nearest and selective next-nearest-neighbor hopping and a staggered magnetic field-such models have been shown to exhibit multifractality. Surprisingly, the antisymmetric disorder (with an even number of unit cells) preserves chiral symmetry-we show this by explicitly writing down the chiral operator.

  • 22. Ahola-Tuomi, M.
    et al.
    Punkkinen, Marko Patrick John
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Laukkanen, P.
    Kuzmin, M.
    Lang, J.
    Schulte, K.
    Pietzsch, A.
    Perala, R. E.
    Rasanen, N.
    Vayrynen, I. J.
    Properties of self-assembled Bi nanolines on InAs(100) studied by core-level and valence-band photoemission, and first-principles calculations2011In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 83, no 24, p. 245401-Article in journal (Refereed)
    Abstract [en]

    We have studied self-assembled bismuth (Bi) nanolines on the Bi-terminated InAs(100) surface by core-level and valence-band photoelectron spectroscopy, and ab initio first-principles calculations. A structural model for this intriguing surface is suggested based on the comparison of the measured and calculated core-level shifts. Also, the atomic origins for the core-level shifts are proposed based on the calculations. A clear peak related to this surface was observed in the valence band 0.34 eV below the Fermi level, which can be used as a "fingerprint" of a well-ordered Bi/InAs(100) nanoline surface.

  • 23. Airiskallio, E.
    et al.
    Nurmi, E.
    Heinonen, M. H.
    Vayrynen, I. J.
    Kokko, K.
    Ropo, M.
    Punkkinen, M. P. J.
    Pitkanen, H.
    Alatalo, M.
    Kollar, J.
    Johansson, Börje
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Vitos, Levente
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Third element effect in the surface zone of Fe-Cr-Al alloys2010In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 81, no 3Article in journal (Refereed)
    Abstract [en]

    The third element effect to improve the high temperature corrosion resistance of the low-Al Fe-Cr-Al alloys is suggested to involve a mechanism that boosts the recovering of the Al concentration to the required level in the Al-depleted zone beneath the oxide layer. We propose that the key factor in this mechanism is the coexistent Cr depletion that helps to maintain a sufficient Al content in the depleted zone. Several previous experiments related to our study support that conditions for such a mechanism to be functional prevail in real oxidation processes of Fe-Cr-Al alloys.

  • 24.
    Akan, Rabia
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Parfeniukas, Karolis
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Vogt, Carmen
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Toprak, M. S.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Vogt, Ulrich
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Reaction control of metal-assisted chemical etching for silicon-based zone plate nanostructures2018In: RSC Advances, E-ISSN 2046-2069, Vol. 8, no 23, p. 12628-12634Article in journal (Refereed)
    Abstract [en]

    Metal-assisted chemical etching (MACE) reaction parameters were investigated for the fabrication of specially designed silicon-based X-ray zone plate nanostructures using a gold catalyst pattern and etching solutions composed of HF and H2O2. Etching depth, zone verticality and zone roughness were studied as a function of etching solution composition, temperature and processing time. Homogeneous, vertical etching with increasing depth is observed at increasing H2O2 concentrations and elevated processing temperatures, implying a balance in the hole injection and silica dissolution kinetics at the gold-silicon interface. The etching depth decreases and zone roughness increases at the highest investigated H2O2 concentration and temperature. Possible reasons for these observations are discussed based on reaction chemistry and zone plate design. Optimum MACE conditions are found at HFH2O2 concentrations of 4.7 M:0.68 M and room temperature with an etching rate of ≈0.7 μm min-1, which is about an order of magnitude higher than previous reports. Moreover, our results show that a grid catalyst design is important for successful fabrication of vertical high aspect ratio silicon nanostructures. 

  • 25.
    Akbarnejad, Shahin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Tilliander, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Process.
    Sheng, Dongyuan
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Process.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Process.
    Effect of Batch Dissimilarity on Permeability of Stacked Ceramic Foam Filters and Incompressible Fluid Flow: Experimental and Numerical Investigation2022In: Metals, ISSN 2075-4701, Vol. 12, no 6, p. 1001-, article id 1001Article in journal (Refereed)
    Abstract [en]

    Ceramic foam filters (CFFs) are used to remove inclusions and/or solid particles from molten metal. In general, the molten metal poured on the top of a CFF should reach a certain height to form the pressure (metal head) required to prime the filter. For estimating the required metal head and obtaining the permeability coefficients of the CFFs, permeability experiments are essential. Recently, electromagnetic priming and filtration of molten aluminum with low and high grades of CFF, i.e., 30, 50 and 80 pore per inch (PPI) CFFs, have been introduced. Since then, there has been interest in exploring the possibility of obtaining further inclusion entrapment and aluminum refinement by using electromagnetic force to prime and filter with stacked CFFs. The successful execution of such trials requires a profound understanding concerning the permeability parameters of the stacked filters. Such data were deemed not to exist prior to this study. As a result, this study presents experimental findings of permeability measurements for stacks of three 30, three 50 and three 80 PPI commercial alumina CFFs from different industrial batches and compares the findings to numerically modelled data as well as previous research works. Both experimental and numerical findings showed a good agreement with previous results. The deviation between the experimentally and numerically obtained data lies in the range of 0.4 to 6.3%.

  • 26.
    Akemann, Gernot
    et al.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.).
    Tribe, Roger
    Tsareas, Athanasios
    Zaboronski, Oleg
    Determinantal structure and bulk universality of conditional overlaps in the complex ginibre ensemble2020In: Acta Physica Polonica B, ISSN 0587-4254, E-ISSN 1509-5770, Vol. 51, no 7, p. 1611-1626Article in journal (Refereed)
    Abstract [en]

    In these proceedings, we summarise how the determinantal structure for the conditional overlaps among left and right eigenvectors emerges in the complex Ginibre ensemble at finite matrix size. An emphasis is put on the underlying structure of orthogonal polynomials in the complex plane and its analogy to the determinantal structure of k-point complex eigenvalue correlation functions. The off-diagonal overlap is shown to follow from the diagonal overlap conditioned on k >= 2 complex eigenvalues. As a new result, we present the local bulk scaling limit of the conditional overlaps away from the origin. It is shown to agree with the limit at the origin and is thus universal within this ensemble.

  • 27.
    Aksoy, Omer M.
    et al.
    Paul Scherrer Inst, Condensed Matter Theory Grp, CH-5232 Villigen, Switzerland..
    Chandrasekaran, Anirudh
    Loughborough Univ, Dept Phys, Loughborough LE11 3TU, England..
    Tiwari, Apoorv
    KTH, School of Engineering Sciences (SCI), Physics, Condensed Matter Theory.
    Neupert, Titus
    Univ Zurich, Winterthurerstr 190, CH-8057 Zurich, Switzerland..
    Chamon, Claudio
    Boston Univ, Dept Phys, Boston, MA 02215 USA..
    Mudry, Christopher
    Paul Scherrer Inst, Condensed Matter Theory Grp, CH-5232 Villigen, Switzerland.;EPF Lausanne, Inst Phys, CH-1015 Lausanne, Switzerland..
    Single monkey-saddle singularity of a Fermi surface and its instabilities2023In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 107, no 20, article id 205129Article in journal (Refereed)
    Abstract [en]

    Fermi surfaces can undergo sharp transitions under smooth changes of parameters. Such transitions can have a topological character, as is the case when a higher-order singularity, one that requires cubic or higher-order terms to describe the electronic dispersion near the singularity, develops at the transition. When time-reversal and inversion symmetries are present, odd singularities can only appear in pairs within the Brillouin zone. In this case, the combination of the enhanced density of states that accompanies these singularities and the nesting between the pairs of singularities leads to interaction-driven instabilities. We present examples of single n = 3 (monkeysaddle) singularities when time-reversal and inversion symmetries are broken. We then turn to the question of what instabilities are possible when the singularities are isolated. For spinful electrons, we find that the inclusion of repulsive interactions destroys any isolated monkey-saddle singularity present in the noninteracting spectrum by developing Stoner or Lifshitz instabilities. In contrast, for spinless electrons and at the mean-field level, we show that an isolated monkey-saddle singularity can be stabilized in the presence of short-range repulsive interactions.

  • 28.
    Al Khabouri, Saja
    et al.
    Sultan Qaboos Univ, Dept Phys, POB 36, Muscat 123, Oman..
    Al Harthi, Salim
    Sultan Qaboos Univ, Dept Phys, POB 36, Muscat 123, Oman..
    Maekawa, Toru
    Toyo Univ, Bionano Elect Res Ctr, 2100 Kujirai, Kawagoe, Saitama 3508585, Japan..
    Elzain, Mohamed E.
    Sultan Qaboos Univ, Dept Phys, POB 36, Muscat 123, Oman..
    Kyaw, Htet Htet
    Sultan Qaboos Univ, Nanotechnol Res Ctr, POB 33, Muscat 123, Oman..
    Myint, Myo Tay Zar
    Sultan Qaboos Univ, Dept Phys, POB 36, Muscat 123, Oman..
    Laxman, Karthik
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Structure, composition and enhanced magnetic properties of novel ternary multicore-shell Ni-Co-Cr nanoclusters prepared by one-step inert gas condensation method2021In: Materials Chemistry and Physics, ISSN 0254-0584, E-ISSN 1879-3312, Vol. 271, article id 124858Article in journal (Refereed)
    Abstract [en]

    We have synthesized ternary Ni-Co-Cr nanoclusters using one step method by simultaneous sputtering of metallic targets through inert gas condensation (IGC) deposition process. The difference in surface energy between the component atoms creates a preferential surface phase leading to the formation of multi core/shell structures. Surface structure and composition analysis reveal metallic and oxide phases characterized by extraordinary 1.43 mu m periodicity strong magnetic stripe domains with weak magnetic force microscopy signal attenuation up to a lift height value of 2.5 mu m. In addition, the ternary nanoclusters exhibit strong ferromagnetic behavior below the blocking temperature of 139 K with coercivity of 700 Oe at 4 K. The enhanced magnetic properties are attributed to Volmer-Weber growth mechanism and pave a facile way for preparing ternary core/ shell magnetic structures needed for applications which require strong magnetic anisotropy along their growth direction.

  • 29.
    Albertsson, Dagur Ingi
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems.
    Rusu, Ana
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems.
    Experimental Demonstration of Duffing Oscillator-Based Analog Ising Machines2024In: Experimental Demonstration of Duffing Oscillator-Based Analog Ising Machines / [ed] IEEE, IEEE, 2024Conference paper (Refereed)
  • 30.
    Albrecht, Steffen
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Sigma-delta based techniques for future multi-standard wireless radios2005Doctoral thesis, monograph (Other scientific)
    Abstract [en]

    Improvements in process technology and design innovations have resulted in compact and cost effective digital baseband solutions. The radio part, however, has remained a bottleneck in terms of chip area and power consumption as the feature size of analog devices does not directly benefit from scaling. With the addition of yet more standards into emerging products, the requirements of future radios will extend over characteristic performance features into demands of programmable and reconfigurable hardware for radios covering multiple frequency bands. Hence, a guideline in the design of such radios is a large degree of hardware sharing.

    The thesis investigates the application of sigma-delta modulation to arising multistandard wireless radios. First, it reviews principles in wireless radios, such as selected modulation and access techniques. It also examines several communication standards of personal wireless radios as well as common receiver architectures for their implementation. This is followed by general considerations and background information about sigma-delta modulators. In the third and fourth chapter, implementations to two blocks of a wireless radio receiver system are suggested: An architecture for a frequency synthesizer and an implementation of an analog-to-digital converter.

    In the first contribution, the thesis develops a novel concept for frequency synthesis that is more suitable for multi-band, multi-standard radio architectures, achieving a large amount of hardware sharing among different wireless standards. As a second pillar, the thesis contributes with the design of a dual-standard sigma-delta modulator for data conversion within a radio receiver. Parts of the work concerning the dual-standard modulator are embodied in a granted swedish patent.

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    FULLTEXT01
  • 31. Almessiere, M. A.
    et al.
    Slimani, Y.
    Trukhanov, A. V.
    Sadaqat, A.
    Korkmaz, A. D.
    Algarou, N. A.
    Aydın, H.
    Baykal, A.
    Toprak, Muhammet
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Review on functional bi-component nanocomposites based on hard/soft ferrites: Structural, magnetic, electrical and microwave absorption properties2021In: Nano-Structures and Nano-Objects, ISSN 2352-507X, Vol. 26, article id 100728Article in journal (Refereed)
    Abstract [en]

    Bi-component hard (H) (hexaferrite) and soft (S) (spinel) ferrites nanocomposites are gaining interest scientifically and technically, not only for combining the high magnetization of spinel ferrite nanomaterials and the high coercivity of hexaferrite magnetic nanomaterials but also for the outstanding exchange-coupling behavior among hard and soft magnetic phase. The improved magnetic features lead to produce a new nanocomposite with higher microwave absorption capacity in comparison with ferrites with a single absorption mechanism. Exchange-coupled effect has a potential application based on microwave absorption, recording media, permanent magnets, biomedical and other applications. Intensive studies have been conducted on this topic to produce hard/soft (H/S) ferrite nanocomposites with establishment of exchange coupled effect between the two phases. Preparation methods, microstructure, magnetics features, microwave and dielectric properties, and applications are elaborated. Consequently, a comprehensive effort has been made to contain an original reference investigating in detail the precise outcomes of the published papers. 

  • 32.
    Almessiere, M. A.
    et al.
    Imam Abdulrahman Bin Faisal Univ, Coll Sci, Dept Phys, POB 1982, Dammam 31441, Saudi Arabia.;Imam Abdulrahman Bin Faisal Univ, Inst Res & Med Consultat IRMC, Dept Biophys, POB 1982, Dammam 31441, Saudi Arabia..
    Unal, B.
    Istanbul Univ Cerrahpasa, Inst Forens Sci & Legal Med, Buyukcekmece Campus, TR-34500 Istanbul, Turkey..
    Slimani, Y.
    Imam Abdulrahman Bin Faisal Univ, Inst Res & Med Consultat IRMC, Dept Biophys, POB 1982, Dammam 31441, Saudi Arabia..
    Gungunes, H.
    Hitit Univ, Dept Phys, Cevre Yolu Bulvari, TR-19030 Corum, Turkey..
    Toprak, Muhammet
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Tashkandi, N.
    Imam Abdulrahman Bin Faisal Univ, Inst Res & Med Consultat IRMC, Dept Nanomed Res, POB 1982, Dammam 31441, Saudi Arabia..
    Baykal, A.
    Imam Abdulrahman Bin Faisal Univ, Inst Res & Med Consultat IRMC, Dept Nanomed Res, POB 1982, Dammam 31441, Saudi Arabia..
    Sertkol, M.
    Imam Abdulrahman Bin Faisal Univ, Dept Basic Sci, Preparatory Year & Supporting Studies, POB 1982, Dammam 34212, Saudi Arabia..
    Trukhanov, A. V.
    Yildiz, A.
    Namik Kemal Univ, Corlu Engn Fac, Text Engn Dept, TR-59860 Corlu Tekirdag, Turkey..
    Manikandan, A.
    Bharath Univ, Bharath Inst Higher Educ & Res BIHER, Dept Chem, Chennai 600073, Tamil Nadu, India.;Bharath Inst Higher Educ & Res BIHER, Ctr Catalysis & Renewable Energy, Chennai 600073, Tamil Nadu, India..
    Effects of Ce-Dy rare earths co-doping on various features of Ni-Co spinel ferrite microspheres prepared via hydrothermal approach2021In: Journal of Materials Research and Technology, ISSN 2238-7854, Vol. 14, p. 2534-2553Article in journal (Refereed)
    Abstract [en]

    The effects of Ce-Dy co-doping on the crystal structure, optical, dielectric, magnetic properties, and hyperfine interactions of Ni-Co spinel ferrite microspheres synthesized hydrothermally have been studied. A series of ferrites with the general formula Ni0.5-Co0.5CexDyxFe2-2xO4 were synthesized with x values ranging from 0.00 to 0.10. The phase, crystallinity, and morphology of ferrite microspheres were analyzed by X-ray powder diffractometry (XRD), scanning and transmission electron microscopes (SEM and TEM), respectively. The structural analyses of the synthesized ferrite microspheres confirmed their high purity and cubic crystalline phase. The Diffuse reflectance spectroscopic (DRS) measurements were presented to calculate direct optical energy band gaps (E-g) and is found in the range 1.63 eV - 1.84 eV. Fe-57 Mossbauer spectroscopy showed that the hyperfine magnetic field of tetrahedral (A) and octahedral (B) sites decreased with the substitution of Dy3+-Ce3+ ions that preferrentially occupy the B site. The impact of the rare-earth content (x) on the magnetic features of the prepared NiCo ferrite microspheres was investigated by analyzing M-H loops, which showed soft ferrimagnetism. The magnetic features illustrate a great impact of the incorporation of Ce3+-Dy3+ ions within the NiCo ferrite structure. The saturation magnetization (M-s), remanence (M-r), and coercivity (H-c) increased gradually with increasing Ce-Dy content. At x = 0.04, M-s, M-r, and H-c attain maximum values of about 31.2 emu/g, 11.5 emu/g, and 512.4 Oe, respectively. The Bohr magneton (n(B)) and magneto-crystalline anisotropy constant (K-eff) were also determined and evaluated with correlation to other magnetic parameters. Further increase in Ce3+-Dy3+ content (i.e., x >= 0.06) was found to decrease M-s, M-r, and H-c values. The variations in magnetic parameters (M-s, M-r, and H-c) were largely caused by the surface spins effect, the variations in crystallite/particle size, the distribution of magnetic ions into the different sublattices, the evolutions of magneto-crystalline anisotropy, and the variations in the magnetic moment (n(B)). The squareness ratios were found to be lower than the predicted theoretical value of 0.5 for various samples, indicating that the prepared Ce-Dy substituted NiCo ferrite microspheres are composed of NPs with single-magnetic domain (SMD). Temperature and frequency-dependent electrical and dielectric measurements have been done to estimate the ac/dc conductivity, dielectric constant, and tangent loss values for all the samples. The ac conductivity measurements confirmed the power-law rules, largely dependent on Ce-Dy content. Impedance analysis stated that the conduction mechanisms in all samples are mainly due to the grains-grain boundaries. The dielectric constant of NiCo ferrite microspheres give rise to normal dielectric distribution, with the frequency depending strongly on the Ce-Dy content. The observed variation in tangential loss with frequency can be attributed to the conduction mechanism in ferrites, like Koop's phenomenological model.

  • 33.
    Al-Shammari, Rusul M.
    et al.
    School of Physics, University College Dublin, Belfield, Dublin, 4, Ireland, Belfield; Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin, 4, Ireland, Belfield.
    Kassem, Ahmed
    School of Veterinary Medicine, University College Dublin, Belfield, Dublin, 4, Ireland, Belfield; School of Veterinary Medicine, University of Kufa, Iraq.
    Al-attar, Nebras
    Laser and Optoelectronic Engineering Department, University of Technology -Iraq, Baghdad, Iraq; School of Chemistry, Trinity College Dublin, The University of Dublin, Dublin, 4, Ireland.
    Manzo, Michele
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Gallo, Katia
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Whyte, Paul
    School of Veterinary Medicine, University College Dublin, Belfield, Dublin, 4, Ireland, Belfield.
    Rice, James H.
    School of Physics, University College Dublin, Belfield, Dublin, 4, Ireland, Belfield.
    Rodriguez, Brian J.
    School of Physics, University College Dublin, Belfield, Dublin, 4, Ireland, Belfield; Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin, 4, Ireland, Belfield.
    Antibacterial properties of lithium niobate crystal substrates2023In: International Journal of Optomechatronics, ISSN 1559-9612, Vol. 17, no 1, article id 2250400Article in journal (Refereed)
    Abstract [en]

    The bactericidal properties of chemically patterned lithium niobate substrates under a super-bandgap UV light source is established. UV irradiation of lithium niobate surfaces inoculated with bacteria leads to antimicrobial activity compared to a glass substrate under similar conditions, as determined by surface enhanced Raman spectroscopy and corroborated with a fluorescence-based live/dead assay. This finding may expand the possible biomedical applications of lithium niobate.

  • 34.
    Altmann, Robert
    et al.
    Univ Augsburg, Dept Math, Univ Str 14, D-86159 Augsburg, Germany..
    Henning, Patrick
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Numerical Analysis, NA. Ruhr Univ Bochum, Fac Math, D-44801 Bochum, Germany..
    Peterseim, Daniel
    Univ Augsburg, Dept Math, Univ Str 14, D-86159 Augsburg, Germany..
    Localization And Delocalization Of Ground States Of Bose-Einstein Condensates Under Disorder2022In: SIAM Journal on Applied Mathematics, ISSN 0036-1399, E-ISSN 1095-712X, Vol. 82, no 1, p. 330-358Article in journal (Refereed)
    Abstract [en]

    This paper studies the localization behavior of Bose-Einstein condensates in disorder potentials, modeled by a Gross-Pitaevskii eigenvalue problem on a bounded interval. In the regime of weak particle interaction, we are able to quantify exponential localization of the ground state, depending on statistical parameters and the strength of the potential. Numerical studies further show delocalization if we leave the identified parameter range, which is in agreement with experimental data. These mathematical and numerical findings allow the prediction of physically relevant regimes where localization of ground states may be observed experimentally.

  • 35.
    Al-Zoubi, Noura
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Describing Interstitials in Close-packed Lattices: First-principles Study2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Describing interstitial atoms in intermetallics or simple mono-atomic close-packed metals is a straightforward procedure in common full-potential calculations. One establishes a sufficiently large supercell, introduces the interstitial impurity and performs the electronic structure and total energy calculation. Real systems, however, are rarely mono-atomic or ordered metals. In most of the cases, the matrix is a random or quasirandom mixture of several chemically and/or magnetically distinct components. Because of that a proper computational tool should incorporate advanced alloy theory and at the same time have sufficiently high accuracy to describe interstitial positions in close-packed solids. The purpose of the present thesis is to make a step towards solving this fundamental problem in computational materials science. To this end, in the first part of the thesis a prestudy on some selected metals and compounds was presented, and in the second part tools were applied to investigate the effect of interstitial carbon on the structural properties of steels.

    For the prestudy, the equation of state for the selected Al, Cu and Rh was investigated in two equivalent phases: in conventional face-centered-cubic lattice (fcc, str-I) and in a face-centered-cubic lattice with one atomic and three interstitial empty potentialwells per primitive cell (str-II). A proper basis set of the exact muffin-tin orbitals as well as a proper potential sphere radius were established by calculating the equilibrium Wigner-Seitz radius and bulk modulus of the above elements in str-I and str-II using the exact muffin-tin orbitals (EMTO) first-principle density functional method. It was found that for Al spd orbitals are sufficient to describe the equilibrium bulk properties in both structures, while for str-II Rh and Cu at least five orbitals (spdfg) are needed to get accurate equilibrium volume and bulk modulus. Furthermore, it was shown that in general, for the str-II type of structure (close-packed structure with interstitials) the optimized overlapping muffin-tin potential in combination with spdfg orbitals ensures well converged bulk properties.

    As an application of the above work in alloys, (i) the chemical reaction between hydrogen H2 molecule and ScAl1−xMgx (0≤x≤0.3) random alloys, (ii) the phase stability of the hydrogenated alloys in different structures and (iii) the hydrogen absorption/desorption temperatures were studied by calculating the Gibbs energy for the components of the reaction. Experimental and theoretical studies by Sahlberg et al . showed that the ScAl0.8Mg0.2 compound with CsCl structure absorbs hydrogen by decomposing into ScH2 with CaF2 structure and fcc Al0.8Mg0.2. This reaction was found to be very fast, even without adding catalyst, and fully reversible. The theoretical hydrogen absorption/desorption temperatures agree well with the experimental values. On the other hand, the stability field of the hydrogenated alloys was found to be strongly depends on Mg content and on the microstructure of the hydrogenated alloys. For a given microstructure, the critical temperature for hydrogen absorption/desorption increases with the Mg concentration.

    The second part of the thesis focused on steel materials with special emphases on the effect of interstitial carbon. Steels are considered to be one of the most important engineering materials. They are mainly composed of iron and carbon. Other alloying elements in steel are introduced to get specific properties like microstructure, corrosion resistance, hardness, brittleness, etc. In order to describe the effect of carbon interstitial in iron alloys, it is important to know how the substitutional alloying elements affect the softness and some other properties of iron alloys. For that reason, the alloying effects on the energetic and magnetic structure of paramagnetic Fe0.85Cr0.1M0.05 (M = Cr, Mn, Fe, Co and Ni) alloys along the tetragonal distortion path connecting the body centered cubic (bcc) and the face centered cubic (fcc) phases were investigated. It was shown that Cr stabilizes bcc phase and increases the energy barrier (relative to bcc phase) between fcc and bcc phases. Cobalt and Ni stabilize fcc structure. Cobalt increases whereas Ni slightly decreases the energy barrier relative to fcc structure. Manganese and iron have negligible effect on the structural energy difference as well as on the energy barrier along the Bain path. The local magnetic moments on Fe atoms have maximum values at bcc phase and minimum values at fcc phase. Cobalt atoms possess local magnetic moments only for tetragonal lattices with c/a < 1.30, and the Mn magnetic moments have almost constant value along the Bain path.

    The tetragonality of Fe-C martensite was discovered in 1928. Early experimental works showed that the tetragonality of Fe-C is linearly depends on C content. However, Later many observations indicated that the tetragonality of martensite is influenced also by alloying and interstitial carbon distributions. Very few ab initio studies focus on investigating the tetragonality of Fe-C based alloys. In this thesis the interstitial carbon in ferromagnetic Fe-based alloys and it is impact on the tetragonal lattice ratio of Fe matrix as well as the alloying effect on the tetragonality of Fe-C system were investigated. It was found that the ferromagnetic Fe-C system with C content ∼ 1.3 wt. % has a body-centered tetragonal (bct) structure with c/a ∼ 1.07. Alloying has an impact on the tetragonality; adding 5% Al, Co or Ni enhances while 5% Cr addition decreases the tetragonal lattice ratio.

    The electronic structure and total energy calculations from this thesis are based on firstprinciples exact muffin-tin orbitals method. The chemical and magnetic disorder was treated using coherent-potential approximation and the paramagnetic phase was modeled by the disordered local magnetic moments approach. Some test calculations involved also full-potential tools as implemented in Vienna ab-initio simulation package (VASP).

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  • 36.
    Al-Zoubi, Noura
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Describing interstitials in close-packed lattices: first-principles study2010Licentiate thesis, comprehensive summary (Other academic)
    Download full text (pdf)
    FULLTEXT02
  • 37.
    Al-Zoubi, Noura
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Johansson, Börje
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Nilson, G.
    Uddeholms AB, Hagfors, Sweden.
    Vitos, Levente
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    The bain path of paramagnetic Fe-Cr based alloys2011In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 110, no 1, p. 013708-Article in journal (Refereed)
    Abstract [en]

    Employing the first-principles exact muffin-tin orbital method in combination with the coherent potential approximation, we calculated the total energy and local magnetic moments of paramagnetic Fe-Cr-M (M = Cr, Mn, Fe, Co, Ni) alloys along the tetragonal distortion (Bain) path connecting the body centered cubic (bcc) and the face centered cubic (fcc) structures. The paramagnetic phase is modeled by the disordered local magnetic moment scheme. For all alloys, the local magnetic moments on Fe atoms decrease from the maximum value corresponding to the bcc phase toward the minimum value realized for the fcc phase. Cobalt atoms have non-vanishing local magnetic moments only for tetragonal lattices with c/a < 1.30, whereas the local magnetic moments of Mn show weak crystal structure dependence. We find that Cr stabilizes the bcc lattice and increases the energy barrier as going from the bcc toward the fcc phase. Both Co and Ni favor the fcc lattice and decrease the energy barrier relative to the bcc phase. On the other hand, the tetragonal distortion around the fcc phase is facilitated by Cr and to a somewhat lesser extent also by Ni, but strongly impeded by Co. Manganese has negligible effect on the structural energy difference as well as on the energy barrier along the Bain path. Our findings on the alloying induced softening or hardening of Fe-Cr based alloys against tetragonal distortions are important for understanding the interstitial driven martensitic transformations in alloy steels.

  • 38.
    Al-Zoubi, Noura
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Punkkinen, Marko Patrick John
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Johansson, Börje
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Vitos, Levente
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Completeness of the exact muffin-tin orbitals: application to hydrogenated alloys2010In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 81, no 4Article in journal (Refereed)
    Abstract [en]

    We investigate the basis set convergence of the exact muffin-tin orbitals by monitoring the equation of state for Al, Cu, and Rh calculated in the conventional face-centered-cubic lattice (str-I) and in a face-centered-cubic lattice with one atomic and three empty sites per primitive cell (str-II). We demonstrate that three (spd) muffin-tin orbitals are sufficient to describe Al in both structures, but for str-II Cu and Rh at least five (spdfg) orbitals are needed to get converged equilibrium Wigner-Seitz radius (within <= 0.8%) and bulk modulus (<= 3.3%). We ascribe this slow convergence to the nearly spherical densities localized around the Cu and Rh atoms, which create strongly asymmetric charge distributions within the nearest cells around the empty sites. The potential sphere radius dependence of the theoretical results for structure str-II is discussed. It is shown that a properly optimized overlapping muffin-tin potential in combination with the spdfg basis yields acceptable errors in the equilibrium bulk properties. The basis set convergence is also shown on hydrogenated Sc and Sc-based alloys.

  • 39.
    Al-Zoubi, Noura
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Punkkinen, Marko Patrick John
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Johansson, Börje
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Vitos, Levente
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Influence of Magnesium on hydrogenated ScAl1-xMgx alloys: a theoretical study2011In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 50, no 10, p. 2848-2853Article in journal (Refereed)
    Abstract [en]

    Ab initio total energy calculations, based on the projector augmented wave method and the exact mu±n-tin orbitals method in combination with the coherent-potential approximation, are used to examine the effect of magnesium on hydrogen absorption/desorption temperature and phase stability of hydrogenated ScAl1-xMgx (0 ≤ x ≤ 0:3) alloys. According to the  experiments, ScAl1-xMgx adopts the CsCl structure, and upon hydrogen absorption it decomposes into ScH2 with CaF2 structure and Al-Mg with face centered cubic structure. Here we demonstrate that the stability field of the hydrogenated alloys depends sensitively on Mg content and on the microstructure of the decomposed system. For a given microstructure, the critical temperature for hydrogen absorption/desorption increases with Mg concentration.

  • 40.
    Al-Zoubi, Noura
    et al.
    Tafila Tech Univ, Dept Appl Phys, Tafila, Jordan..
    Schönecker, Stephan
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Li, Xiaoqing
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Li, Wei
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Johansson, Börje
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Vitos, Levente
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Elastic properties of 4d transition metal alloys: Values and trends2019In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 159, p. 273-280Article in journal (Refereed)
    Abstract [en]

    Using the Exact Muffin-Tin Orbitals method within the Perdew-Burke-Ernzerhof exchange-correlation approximation for solids and solid surfaces (PBEso1), we study the single crystal elastic constants of 4d transition metals (atomic number Z between 39 and 47) and their binary alloys in the body centered cubic (bcc) and face centered cubic (fcc) structures. Alloys between the first neighbors Z(Z + 1) and between the second neighbors Z(Z + 2) are considered. The lattice constants, bulk moduli and elastic constants are found in good agreement with the available experimental and theoretical data. It is shown that the correlation between the relative tetragonal shear elastic constant C-fcc'-2C(bcc)' and the structural energy difference between the fcc and bcc lattices Delta E is superior to the previously considered models. For a given crystal structure, the equiatomic Z(Z + 2) alloys turn out to have similar structural and elastic properties as the pure elements with atomic number (Z + 1). Furthermore, alloys with composition Z(1-x)(Z + 2)(x) possess similar properties as Z(1-2x)(Z + 1)(2x). The present theoretical data on the structural and the elastic properties of 4d transition metal alloys provides consistent input for coarse scale modeling of material properties.

  • 41.
    Amundsen, Morten
    et al.
    NORDITA SU.
    Juricic, Vladimir
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA. Univ Tecn Federico Santa Maria, Dept Fis, Casilla 110, Valparaiso, Chile..
    Controlling Majorana modes by p-wave pairing in two-dimensional p2022In: Physical Review Research, E-ISSN 2643-1564, Vol. 4, no 1, article id 013088Article in journal (Refereed)
    Abstract [en]

    We show that corner Majorana zero modes in a two-dimensional p + id topological superconductor can be controlled by the manipulation of the parent p-wave superconducting order. Assuming that the p-wave superconducting order is in either a chiral or helical phase, we find that when a d(x2-y2) wave superconducting order is induced, the system exhibits quite different behavior depending on the nature of the parent p-wave phase. In particular, we find that while in the helical phase, a localized Majorana mode appears at each of the four corners, in the chiral phase, it is localized along only two of the four edges. We furthermore demonstrate that the Majoranas can be directly controlled by the form of the edges, as we explicitly show in the case of circular edges. We argue that the application of strain may provide additional means of fine-tuning the Majorana zero modes in the system; in particular, it can partially gap them out. Our findings may be relevant for probing the topology in two-dimensional mixed-pairing superconductors.

  • 42.
    Amundsen, Morten
    et al.
    Nordita SU.
    Juričić, Vladimir
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA. Departamento de Física, Universidad Técnica Federico Santa María, Casilla 110, Valparaíso, Chile, Casilla 110.
    Grain-boundary topological superconductor2023In: Communications Physics, E-ISSN 2399-3650, Vol. 6, no 1, article id 232Article in journal (Refereed)
    Abstract [en]

    Majorana zero modes (MZMs) are of central importance for modern condensed matter physics and quantum information due to their non-Abelian nature, which thereby offers the possibility of realizing topological quantum bits. We here show that a grain boundary (GB) defect can host a topological superconductor (SC), with a pair of cohabitating MZMs at its end when immersed in a parent two-dimensional gapped topological SC with the Fermi surface enclosing a nonzero momentum. The essence of our proposal lies in the magnetic-field driven hybridization of the localized MZMs at the elementary blocks of the GB defect, the single lattice dislocations, due to the MZM spin being locked to the Burgers vector. Indeed, as we show through numerical and analytical calculations, the GB topological SC with two localized MZMs emerges in a finite range of both the angle and magnitude of the external magnetic field. Our work demonstrates the possibility of defect-based platforms for quantum information technology and opens up a route for their systematic search in future.

  • 43.
    Amundsen, Morten
    et al.
    Nordita SU.
    V. Bobkova, Irina
    Inst Solid State Phys, Chernogolovka, Moscow 142432, Russia.;Moscow Inst Phys & Technol, Dolgoprudny, Moscow 141700, Russia.;Natl Res Univ Higher, Sch Econ, Moscow 101000, Russia..
    Kamra, Akashdeep
    Univ Autonoma Madrid, Dept Fis Teor Mat Condensada, Madrid 28049, Spain.;Condensed Matter Phys Ctr IFIMAC, Madrid 28049, Spain..
    Magnonic spin Joule heating and rectification effects2022In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 106, no 14, article id 144411Article in journal (Refereed)
    Abstract [en]

    Nonlinear devices, such as transistors, enable contemporary computing technologies. We theoretically investigate nonlinear effects, bearing a high fundamental scientific and technical relevance, in magnonics with emphasis on superconductor-ferromagnet hybrids. Accounting for a finite magnon chemical potential, we theoretically demonstrate magnonic spin Joule heating, the spin analog of conventional electronic Joule heating. Besides suggesting a key contribution to magnonic heat transport in a broad range of devices, it provides insights into the thermal physics of nonconserved bosonic excitations. Considering a spin-split superconductor self-consistently, we demonstrate its interface with a ferromagnetic insulator to harbor large tunability of spin and thermal conductances. We further demonstrate hysteretic rectification I-V characteristics in this hybrid, where the hysteresis results from the superconducting state bistability.

  • 44.
    Andersson, Andreas
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics.
    Phase fluctuation phenomena in superconductors2012Doctoral thesis, comprehensive summary (Other academic)
    Download full text (pdf)
    thesis
  • 45.
    Andersson, Andreas
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics.
    Simulations of thermoelectric transport in granularsuperconductors2010Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis presents results from numerical simulations of the Nernst effect dueto phase fluctuations in models of two-dimensional granular superconductors. Inaddition other transport properties, such as thermal conductivity and electrical re-sistivity are calculated. The models are based on a phase only description withLangevin or resistively and capacitively shunted Josephson junction (RCSJ) dy-namics, generalized to be valid for any type of two-dimensional lattice structure.All transport coefficients are evaluated from equilibrium correlation functions usingKubo formulas.

    In Paper I, anomalous sign reversals of the Nernst signal eN , corresponding tovortex motion from colder to hotter regions, are observed. These are attributedto geometric frustration effects close to magnetic fields commensurate with theunderlying lattice structure. The effect is seen also in systems with moderategeometric disorder, and should thus be possible to observe in real two-dimensionalgranular superconductors or Josephson junction arrays.

    Paper II presents two different derivations of an expression for the heat current inLangevin and RCSJ dynamics. The resulting expression is through our simulationsseen to obey the required Onsager relation, as well as giving consistent resultswhen calculating κ and eN via Kubo formulas and through the responses to anapplied temperature gradient. In zero magnetic field and at low-temperatures, thecontribution to the thermal conductivity κ in RCSJ dynamics is calculated usinga spin-wave approximation, and is shown to be independent of temperature anddiverge logarithmically with system size. At higher temperatures, κ shows a non-monotonic temperature dependence. In zero magnetic field κ has a anomalouslogarithmic size dependence also in this regime. The off-diagonal component ofthe thermoelectric tensor αxy is calculated and displays the very same ∼1/T dependence at low temperatures predicted from calculations based on Gaussiansuperconducting fluctuations.

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    FULLTEXT02
  • 46.
    Andersson, Andreas
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics.
    Lidmar, Jack
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics.
    Influence of vortices and phase fluctuations on thermoelectric transport properties of superconductors in a magnetic field2011In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 83, no 17, p. 174502-Article in journal (Refereed)
    Abstract [en]

    We study heat transport and thermoelectric effects in two-dimensional superconductors in a magnetic field. These are modeled as granular Josephson-junction arrays, forming either regular or random lattices. We employ two different models for the dynamics: relaxational model-A dynamics or resistively and capacitively shunted Josephson junction dynamics. We derive expressions for the heat current in these models, which are then used in numerical simulations to calculate the heat conductivity and Nernst coefficient for different temperatures and magnetic fields. At low temperatures and zero magnetic field the heat conductivity in the RCSJ model is calculated analytically from a spin wave approximation, and is seen to have an anomalous logarithmic dependence on the system size, and also to diverge in the completely overdamped limit C -> 0. From our simulations we find at low magnetic fields that the Nernst signal displays a characteristic "tilted hill" profile similar to experiments and a nonmonotonic temperature dependence of the heat conductivity. We also investigate the effects of granularity and randomness, which become important for higher magnetic fields. In this regime geometric frustration strongly influences the results in both regular and random systems and leads to highly nontrivial magnetic field dependencies of the studied transport coefficients.

  • 47.
    Andersson, Andreas
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Lidmar, Jack
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Modeling and simulations of quantum phase slips in ultrathin superconducting wires2015In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 91, no 13, article id 134504Article in journal (Refereed)
    Abstract [en]

    We study quantum phase slips (QPS) in ultrathin superconducting wires. Starting from an effective one-dimensional microscopic model, which includes electromagnetic fluctuations, we map the problem to a (1+1)-dimensional gas of interacting instantons. We introduce a method to calculate the tunneling amplitude of quantum phase slips directly from Monte Carlo simulations. This allows us to go beyond the dilute instanton gas approximation and study the problem without any limitations of the density of QPS. We find that the tunneling amplitude shows a characteristic scaling behavior near the superconductor-insulator transition. We also calculate the voltage-charge relation of the insulating state, which is the dual of the Josephson current-phase relation in ordinary superconducting weak links. This evolves from a sinusoidal form in the regime of dilute QPS to more exotic shapes for higher QPS densities, where interactions are important.

    Download full text (pdf)
    fulltext
  • 48.
    Andersson, Andreas
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics.
    Lidmar, Jack
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics.
    Modeling and simulations of quantum phase slips in ultrathin superconducting wiresManuscript (preprint) (Other academic)
  • 49.
    Andersson, Andreas
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics.
    Lidmar, Jack
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics.
    Scaling, Finite Size Effects, and Crossovers of the Resistivity and Current-Voltage Characteristics in Two-Dimensional SuperconductorsManuscript (preprint) (Other academic)
    Abstract [en]

    We revisit the scaling properties of the resistivity and the current-voltage characteristics at and below the Berezinskii-Kosterlitz-Thouless transition, both in zero and nonzero magnetic field. The scaling properties are derived by integrating the renormalization group flow equations up to a scale where they can be reliably matched to simple analytic expressions. The vortex fugacity turns out to be dangerously irrelevant for these quantities below $T_c$, thereby altering the scaling behavior. We derive the possible crossover effects as the current, magnetic field or system size is varied, and find a strong multiplicative logarithmic correction near $T_c$, all which is necessary to account for when interpreting experiments and simulation data. Our analysis clarifies a longstanding discrepancy between the finite size dependence found in many simulations and the current-voltage characteristics of experiments. We further show that the logarithmic correction can be avoided by approaching the transition in a magnetic field, thereby simplifying the scaling analysis. We confirm our results by large scale numerical simulations, and calculate the dynamic critical exponent $z$, for relaxational Langevin dynamics and for resistively and capacitively shunted Josephson junction dynamics.

  • 50.
    Andersson, David A.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Korzhavyi, Pavel A.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Johansson, Börje
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    First-principles based calculation of binary and multicomponent phase diagrams for titanium carbonitride2008In: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, Vol. 32, no 3, p. 543-565Article in journal (Refereed)
    Abstract [en]

    In this paper we have used a combined first principles and Calphad approach to calculate phase diagrams in the titanium-carbon-nitrogen system, with particular focus on the vacancy-induced ordering of the substoichiometric carbonitride phase, TiCxNy (x + y <= 1). Results from earlier Monte Carlo simulations of the low-temperature binary phase diagrams are used in order to formulate sublattice models for TiCxNy within the compound energy formalism (CEF) that are capable of describing both the low temperature ordered and the high-temperature disordered state. We parameterize these models using first-principles calculations and then we demonstrate how they can be merged with thermodynamic descriptions of the remaining Ti-C-N phases that are derived within the Calphad method by fitting model parameters to experimental data. We also discuss structural and electronic properties of the ordered end-member compounds, as well as short range order effects in the TiCxNy phase.

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