“Pioneering on single-sludge nitrification/denitrification at 50 °C”. Vandekerckhove TGL, Boon N, Vlaeminck SE, Chemosphere 252, 126527 (2020). http://doi.org/10.1016/J.CHEMOSPHERE.2020.126527
Abstract: Thermophilic nitrification has been proven in lab-scale bioreactors at 50 °C. The challenge is now to develop a solution for thermophilic nitrogen removal, integrating nitrification with denitrification and aerobic carbon removal. This pioneering study aimed at a single-sludge nitrification/denitrification process at 50 °C, through exposing nitrification in a step by step approach to anoxia and/or organics. Firstly, recurrent anoxia was tolerated by a nitrifying community during long-term membrane bioreactor (MBR) operation (85 days), with high ammonium oxidation efficiencies (>98%). Secondly, five organic carbon sources did not affect thermophilic ammonium and nitrite oxidation rates in three-day aerobic batch flask incubations. Moving to long-term tests with sequencing batch reactors (SBR) and MBR (>250 days), good nitrification performance was obtained at increasing COD/Ninfluent ratios (0, 0.5, 1, 2 and 3). Thirdly, combining nitrification, recurrent anoxia and presence of organic carbon resulted in a nitrogen removal efficiency of 92–100%, with a COD/Nremoved of 4.8 ± 0.6 and a nitrogen removal rate of 50 ± 14 mg N g−1 VSS d−1. Overall, this is the first proof of principle thermophilic nitrifiers can cope with redox fluctuations (aerobic/anoxic) and the aerobic or anoxic presence of organic carbon, can functionally co-exist with heterotrophs and that single-sludge nitrification/denitrification can be achieved.
Keywords: A1 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
Impact Factor: 8.8
DOI: 10.1016/J.CHEMOSPHERE.2020.126527
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Heijkers S (2020) Plasma chemistry modelling for CO2 and CH4 conversion in various plasma types. 316 p
Keywords: Doctoral thesis; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
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“Prevalence of oxygen defects in an in-plane anisotropic transition metal dichalcogenide”. Plumadore R, Baskurt M, Boddison-Chouinard J, Lopinski G, Modarresi M, Potasz P, Hawrylak P, Sahin H, Peeters FM, Luican-Mayer A, Physical Review B 102, 205408 (2020). http://doi.org/10.1103/PHYSREVB.102.205408
Abstract: Atomic scale defects in semiconductors enable their technological applications and realization of different quantum states. Using scanning tunneling microscopy and spectroscopy complemented by ab initio calculations we determine the nature of defects in the anisotropic van der Waals layered semiconductor ReS2. We demonstrate the in-plane anisotropy of the lattice by directly visualizing chains of rhenium atoms forming diamond-shaped clusters. Using scanning tunneling spectroscopy we measure the semiconducting gap in the density of states. We reveal the presence of lattice defects and by comparison of their topographic and spectroscopic signatures with ab initio calculations we determine their origin as oxygen atoms absorbed at lattice point defect sites. These results provide an atomic-scale view into the semiconducting transition metal dichalcogenides, paving the way toward understanding and engineering their properties.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.7
Times cited: 9
DOI: 10.1103/PHYSREVB.102.205408
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“Probing the chemistry of CdS paints in The Scream by in situ noninvasive spectroscopies and synchrotron radiation x-ray techniques”. Monico L, Cartechini L, Rosi F, Chieli A, Grazia C, De Meyer S, Nuyts G, Vanmeert F, Janssens K, Cotte M, De Nolf W, Falkenberg G, Sandu ICA, Tveit ES, Mass J, De Freitas RP, Romani A, Miliani C, Science Advances 6, eaay3514 (2020). http://doi.org/10.1126/SCIADV.AAY3514
Abstract: The degradation of cadmium sulfide (CdS)-based oil paints is a phenomenon potentially threatening the iconic painting The Scream (ca. 1910) by Edvard Munch (Munch Museum, Oslo) that is still poorly understood. Here, we provide evidence for the presence of cadmium sulfate and sulfites as alteration products of the original CdS-based paint and explore the external circumstances and internal factors causing this transformation. Macroscale in situ noninvasive spectroscopy studies of the painting in combination with synchrotron-radiation x-ray microspectroscopy investigations of a microsample and artificially aged mock-ups show that moisture and mobile chlorine compounds are key factors for promoting the oxidation of CdS, while light (photodegradation) plays a less important role. Furthermore, under exposure to humidity, parallel/secondary reactions involving dissolution, migration through the paint, and recrystallization of water-soluble phases of the paint are associated with the formation of cadmium sulfates.
Keywords: A1 Journal article; Engineering sciences. Technology; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 13.6
Times cited: 4
DOI: 10.1126/SCIADV.AAY3514
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“Proton and Li-Ion permeation through graphene with eight-atom-ring defects”. Griffin E, Mogg L, Hao G-P, Kalon G, Bacaksiz C, Lopez-Polin G, Zhou TY, Guarochico V, Cai J, Neumann C, Winter A, Mohn M, Lee JH, Lin J, Kaiser U, Grigorieva I V, Suenaga K, Ozyilmaz B, Cheng H-M, Ren W, Turchanin A, Peeters FM, Geim AK, Lozada-Hidalgo M, Acs Nano 14, 7280 (2020). http://doi.org/10.1021/ACSNANO.0C02496
Abstract: Defect-free graphene is impermeable to gases and liquids but highly permeable to thermal protons. Atomic-scale defects such as vacancies, grain boundaries, and Stone-Wales defects are predicted to enhance graphene's proton permeability and may even allow small ions through, whereas larger species such as gas molecules should remain blocked. These expectations have so far remained untested in experiment. Here, we show that atomically thin carbon films with a high density of atomic-scale defects continue blocking all molecular transport, but their proton permeability becomes similar to 1000 times higher than that of defect-free graphene. Lithium ions can also permeate through such disordered graphene. The enhanced proton and ion permeability is attributed to a high density of eight-carbon-atom rings. The latter pose approximately twice lower energy barriers for incoming protons compared to that of the six-atom rings of graphene and a relatively low barrier of similar to 0.6 eV for Li ions. Our findings suggest that disordered graphene could be of interest as membranes and protective barriers in various Li-ion and hydrogen technologies.
Keywords: A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT)
Impact Factor: 17.1
Times cited: 53
DOI: 10.1021/ACSNANO.0C02496
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“Purple non-sulphur bacteria and plant production: benefits for fertilization, stress resistance and the environment”. Sakarika M, Spanoghe J, Sui Y, Wambacq E, Grunert O, Haesaert G, Spiller M, Vlaeminck SE, Microbial biotechnology 13, 1336 (2020). http://doi.org/10.1111/1751-7915.13474
Abstract: Purple non-sulphur bacteria (PNSB) are phototrophic microorganisms, which increasingly gain attention in plant production due to their ability to produce and accumulate high-value compounds that are beneficial for plant growth. Remarkable features of PNSB include the accumulation of polyphosphate, the production of pigments and vitamins and the production of plant growth-promoting substances (PGPSs). Scattered case studies on the application of PNSB for plant cultivation have been reported for decades, yet a comprehensive overview is lacking. This review highlights the potential of using PNSB in plant production, with emphasis on three key performance indicators (KPIs): fertilization, resistance to stress (biotic and abiotic) and environmental benefits. PNSB have the potential to enhance plant growth performance, increase the yield and quality of edible plant biomass, boost the resistance to environmental stresses, bioremediate heavy metals and mitigate greenhouse gas emissions. Here, the mechanisms responsible for these attributes are discussed. A distinction is made between the use of living and dead PNSB cells, where critical interpretation of existing literature revealed the better performance of living cells. Finally, this review presents research gaps that remain yet to be elucidated and proposes a roadmap for future research and implementation paving the way for a more sustainable crop production.
Keywords: A1 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
Impact Factor: 5.7
Times cited: 10
DOI: 10.1111/1751-7915.13474
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“Purple phototrophic bacteria for resource recovery : challenges and opportunities”. Capson-Tojo G, Batstone DJ, Grassino M, Vlaeminck SE, Puyol D, Verstraete W, Kleerebezem R, Oehmen A, Ghimire A, Pikaar I, Lema JM, Hülsen T, Grassino M, Hulsen T, Biotechnology Advances 43, 107567 (2020). http://doi.org/10.1016/J.BIOTECHADV.2020.107567
Abstract: Sustainable development is driving a rapid focus shift in the wastewater and organic waste treatment sectors, from a “removal and disposal” approach towards the recovery and reuse of water, energy and materials (e.g. carbon or nutrients). Purple phototrophic bacteria (PPB) are receiving increasing attention due to their capability of growing photoheterotrophically under anaerobic conditions. Using light as energy source, PPB can simultaneously assimilate carbon and nutrients at high efficiencies (with biomass yields close to unity (1 g CODbiomass·g CODremoved−1)), facilitating the maximum recovery of these resources as different value-added products. The effective use of infrared light enables selective PPB enrichment in non-sterile conditions, without competition with other phototrophs such as microalgae if ultraviolet-visible wavelengths are filtered. This review reunites results systematically gathered from over 177 scientific articles, aiming at producing generalized conclusions. The most critical aspects of PPB-based production and valorisation processes are addressed, including: (i) the identification of the main challenges and potentials of different growth strategies, (ii) a critical analysis of the production of value-added compounds, (iii) a comparison of the different value-added products, (iv) insights into the general challenges and opportunities and (v) recommendations for future research and development towards practical implementation. To date, most of the work has not been executed under real-life conditions, relevant for full-scale application. With the savings in wastewater discharge due to removal of organics, nitrogen and phosphorus as an important economic driver, priorities must go to using PPB-enriched cultures and real waste matrices. The costs associated with artificial illumination, followed by centrifugal harvesting/dewatering and drying, are estimated to be 1.9, 0.3–2.2 and 0.1–0.3 $·kgdry biomass−1. At present, these costs are likely to exceed revenues. Future research efforts must be carried out outdoors, using sunlight as energy source. The growth of bulk biomass on relatively clean wastewater streams (e.g. from food processing) and its utilization as a protein-rich feed (e.g. to replace fishmeal, 1.5–2.0 $·kg−1) appears as a promising valorisation route.
Keywords: A1 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
Impact Factor: 16
Times cited: 6
DOI: 10.1016/J.BIOTECHADV.2020.107567
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Eliaerts J (2020) Qualitative and quantitative determination of cocaine using mid-infrared spectroscopy and chemometrics. 184 p
Keywords: Doctoral thesis; Law; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
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“Quantum properties and applications of 2D Janus crystals and their superlattices”. Yagmurcukardes M, Qin Y, Ozen S, Sayyad M, Peeters FM, Tongay S, Sahin H, Applied Physics Reviews 7, 011311 (2020). http://doi.org/10.1063/1.5135306
Abstract: Two-dimensional (2D) Janus materials are a new class of materials with unique physical, chemical, and quantum properties. The name “Janus” originates from the ancient Roman god which has two faces, one looking to the future while the other facing the past. Janus has been used to describe special types of materials which have two faces at the nanoscale. This unique atomic arrangement has been shown to present rather exotic properties with applications in biology, chemistry, energy conversion, and quantum sciences. This review article aims to offer a comprehensive review of the emergent quantum properties of Janus materials. The review starts by introducing 0D Janus nanoparticles and 1D Janus nanotubes, and highlights their difference from classical ones. The design principles, synthesis, and the properties of graphene-based and chalcogenide-based Janus layers are then discussed. A particular emphasis is given to colossal built-in potential in 2D Janus layers and resulting quantum phenomena such as Rashba splitting, skyrmionics, excitonics, and 2D magnetic ordering. More recent theoretical predictions are discussed in 2D Janus superlattices when Janus layers are stacked onto each other. Finally, we discuss the tunable quantum properties and newly predicted 2D Janus layers waiting to be experimentally realized. The review serves as a complete summary of the 2D Janus library and predicted quantum properties in 2D Janus layers and their superlattices.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 15
Times cited: 158
DOI: 10.1063/1.5135306
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“Real-time wood behaviour : the use of strain gauges for preventive conservation applications”. Anaf W, Cabal A, Robbe M, Schalm O, Sensors 20, 305 (2020). http://doi.org/10.3390/S20010305
Abstract: Within the heritage field, the application of strain gauges on wood surfaces is a little-explored but inexpensive and effective method to analyse the environmental appropriateness of rooms for the wooden heritage collections they contain. This contribution proposes a wood sensor connected to a data logger to identify short moments with an elevated risk of harm. Two experiments were performed to obtain insights pertaining to the applicability of wood sensors to evaluate preservation conditions. (1) The representativeness of strain gauges on dummies was tested for their use in evaluating the preservation conditions of a range of wooden objects exposed to the same environment. For this, three situations were mimicked: a bare wood surface, a wood surface covered with a preparation layer, and a wood surface covered with a preparation and varnish layer. (2) The usability of strain gauges to monitor the wood behaviour in real-time measurements was tested with a monitoring campaign of almost two years in a church where a new heating system was installed. The results of both experiments are promising, and the authors encourage a broader application of strain gauges in the heritage field.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Antwerp Cultural Heritage Sciences (ARCHES)
DOI: 10.3390/S20010305
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“Relativistic photoeffect for s states in a central field”. Drukarev E, Mikhailov A, Rakhimov KY, Yusupov H, European Physical Journal D 74, 166 (2020). http://doi.org/10.1140/EPJD/E2020-10264-7
Abstract: We study the photoionization of the s states in the systems bound by sufficiently weak central fields V(r) for the large photon energies corresponding to the relativistic photoelectrons. We demonstrate that the energy dependence of the photoionization cross section can be obtained without solving the wave equation. We show that the shape of the energy dependence of the cross section is determined by analytical properties of the binding potential V(r). We find the cross sections for the potentials V(r) which have singularities in the origin, on the real axis and in the complex plane.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 1.8
DOI: 10.1140/EPJD/E2020-10264-7
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“Reply to “Comment on `Excitons, trions, and biexcitons in transition-metal dichalcogenides: Magnetic-field dependence'””. Van der Donck M, Zarenia M, Peeters FM, Physical Review B 101, 127402 (2020). http://doi.org/10.1103/PHYSREVB.101.127402
Abstract: In the Comment, the authors state that the separation of the relative and center of mass variables in our work is not correct. Here we point out that there is a typographical error, i.e., qi instead of -e, in two of our equations which, when corrected, makes the Comment redundant. Within the ansatzes mentioned in our paper all our results are correct, in contrast to the claims of the Comment.
Keywords: Editorial; Condensed Matter Theory (CMT)
Impact Factor: 3.7
DOI: 10.1103/PHYSREVB.101.127402
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“Research frontiers in energy-related materials and applications for 2020-2030”. Blay V, Galian RE, Muresan LM, Pancratov D, Pinyou P, Zampardi G, Advanced sustainable systems 4, 1900145 (2020). http://doi.org/10.1002/ADSU.201900145
Abstract: This article delineates the state of the art for several materials used in the harvest, conversion, and storage of energy, and analyzes the challenges to be overcome in the decade ahead for them to reach the market and benefit society. The materials covered have had a special interest in recent years and include perovskites, materials for batteries and supercapacitors, graphene, and materials for hydrogen production and storage. Looking at the common challenges for these different systems, scientists in basic research should carefully consider commercial requirements when designing new materials. These include cost and ease of synthesis, abundance of precursors, recyclability of spent devices, toxicity, and stability. Improvements in these areas deserve more attention, as they can help bridge the gap for these technologies and facilitate the creation of partnerships between academia and industry. These improvements should be pursued in parallel with the design of novel compositions, nanostructures, and devices, which have led most interest during the past decade. Research groups are encouraged to adopt a cross-disciplinary mindset, which may allow more efficient use of existing knowledge and facilitate breakthrough innovation in both basic and applied research of energy-related materials.
Keywords: A1 Journal article; Engineering sciences. Technology; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 7.1
Times cited: 2
DOI: 10.1002/ADSU.201900145
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“Return-sludge treatment with endogenous free nitrous acid limits nitrate production and N₂O emission for mainstream partial nitritation/anammox”. Peng L, Xie Y, Van Beeck W, Zhu W, Van Tendeloo M, Tytgat T, Lebeer S, Vlaeminck SE, Environmental Science &, Technology 54, 5822 (2020). http://doi.org/10.1021/ACS.EST.9B06404
Abstract: Nitrite oxidizing bacteria (NOB) and nitrous oxide (N2O) hinder the development of mainstream partial nitritation/anammox. To overcome these, endogenous free ammonia (FA) and free nitrous acid (FNA), which can be produced in the sidestream, were used for return-sludge treatment for two integrated-film activated sludge reactors containing biomass in flocs and on carriers. The repeated exposure of biomass from one reactor to FA shocks had a limited impact on NOB suppression but inhibited anammox bacteria (AnAOB). In the other reactor, repeated FNA shocks to the separated flocs failed to limit the system’s nitrate production since NOB activity was still high on the biofilms attached to the unexposed carriers. In contrast, the repeated FNA treatment of flocs and carriers favored aerobic ammonium-oxidizing bacteria (AerAOB) over NOB activity with AnAOB negligibly affected. It was further revealed that return-sludge treatment with higher FNA levels led to lower N2O emissions under similar effluent nitrite concentrations. On this basis, weekly 4 h FNA shocks of 2.0 mg of HNO2-N/L were identified as an optimal and realistic treatment, which not only enabled nitrogen removal efficiencies of ∼65% at nitrogen removal rates of ∼130 mg of N/L/d (20 °C) but also yielded the lowest cost and carbon footprint.
Keywords: A1 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
Impact Factor: 11.4
Times cited: 1
DOI: 10.1021/ACS.EST.9B06404
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“Seasonality of ship emission related atmospheric pollution over coastal and open waters of the North Sea”. Bencs L, Horemans B, Buczyńska AJ, Deutsch F, Degraeuwe B, Van Poppel M, Van Grieken R, Atmospheric Environment: X 7, 100077 (2020). http://doi.org/10.1016/J.AEAOA.2020.100077
Abstract: The seasonal changes of a large set of atmospheric pollutants (i.e., gases, water-soluble aerosols, metallic/elemental components and black carbon (BC) content) have been studied over the southern bight of the North Sea (the Belgian Continental Shelf) and the English Channel during several marine sampling campaigns, carried out in 2010-2011. A coastal research station at De Haan, Belgium was concurrently used as a background air monitoring site. Size-segregated aerosols (PM1, PM2.5-1, PM10-2.5) were analyzed for particulate mass, elemental content and water-soluble (ionic) compounds, while the equivalent BC content in PM10 was monitored with an Aethalometer. The results clearly demonstrated that the aerosols originating from ship exhaust emissions contributed mostly to fine fraction (PM1), and to a lesser extent to medium-sized fraction (PM2.5-1), whereas components of sea spray and of mineral/soil origin were dominating in the medium-size and coarse aerosol fractions. Looking at seasonal differences, more ship emission related components occurred in the fine and medium-sized PM during winter. Mineral aerosol components were more apparent in coarse PM and especially during the cold season, increased levels were noted. Similarly, higher concentrations of marine fine PM were found during winter, likely due to more extensive ship emissions and/or calm weather conditions. Gaseous pollutants (e.g., HNO2, HNO3, HCl, SO2, NH3) originating from exhaust fumes of ocean-going ships mostly reached the maximum levels in the cold season as well, thus supporting the more intense formation of secondary aerosols. The seasonal trends of total (inorganic) ionic species sampled on the open sea and at the coastal station were usually similar to those of the corresponding PM masses, peaking in the cold season. Sea salt bound fine sulfate and nitrate peaked in spring or the cold season for marine areas, whereas for the coastal site they clearly reached the maximum in the cold season. Ammonium-bound nitrates and sulfates in each PM fraction reached their peak air levels in the cold season over marine sites. Similar seasonal trends could be observed for the coastal station. The general tendency of aerosol distribution over the study areas was independent of the sampling site: the higher the aerosol mass on the open sea with ship traffic, the higher the suspended particulate mass sampled at the coast.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
DOI: 10.1016/J.AEAOA.2020.100077
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“Signature of ballistic band-tail tunneling current in tunnel FET”. Bizindavyi J, Verhulst AS, Sorée B, Groeseneken G, Ieee Transactions On Electron Devices 67, 3486 (2020). http://doi.org/10.1109/TED.2020.3004119
Abstract: To improve the interpretation of the tunnel field-effect transistor (TFET) measurements, we theoretically identify the signatures of the ballistic band-tail (BT) tunneling (BTT) current in the transfer and output characteristics of the TFETs. In particular, we demonstrate that the temperature dependence of a BTT-dominated subthreshold swing (SS) is in agreement with the reported experimental results. We explain how the temperature dependence of the output characteristics can be used to distinguish between a current dominated by BTT and a current dominated by trap-assisted tunneling. Finally, we propose an expression that relates the energetic extension of the quasi-extended BT states in the bandgap to the onset voltage for tunneling.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.1
DOI: 10.1109/TED.2020.3004119
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“Single-layer Janus black arsenic-phosphorus (b-AsP): optical dichroism, anisotropic vibrational, thermal, and elastic properties”. Li LL, Bacaksiz C, Nakhaee M, Pentcheva R, Peeters FM, Yagmurcukardes M, Physical Review B 101, 134102 (2020). http://doi.org/10.1103/PHYSREVB.101.134102
Abstract: By using density functional theory (DFT) calculations, we predict a puckered, dynamically stable Janus single-layer black arsenic-phosphorus (b-AsP), which is composed of two different atomic sublayers, arsenic and phosphorus atoms. The calculated phonon spectrum reveals that Janus single-layer b-AsP is dynamically stable with either pure or coupled optical phonon branches arising from As and P atoms. The calculated Raman spectrum indicates that due to the relatively strong P-P bonds, As atoms have no contribution to the highfrequency optical vibrations. In addition, the orientation-dependent isovolume heat capacity reveals anisotropic contributions of LA and TA phonon branches to the low-temperature thermal properties. Unlike pristine single layers of b-As and b-P, Janus single-layer b-AsP exhibits additional out-of-plane asymmetry which leads to important consequences for its electronic, optical, and elastic properties. In contrast to single-layer b-As, Janus single-layer b-AsP is found to possess a direct band gap dominated by the P atoms. Moreover, real and imaginary parts of the dynamical dielectric function, including excitonic effects, reveal the highly anisotropic optical feature of the Janus single-layer. A tight-binding (TB) model is also presented for Janus single-layer b-AsP, and it is shown that, with up to seven nearest hoppings, the TB model reproduces well the DFT band structure in the low-energy region around the band gap. This TB model can be used in combination with the Green's function approach to study, e.g., quantum transport in finite systems based on Janus single-layer b-AsP. Furthermore, the linear-elastic properties of Janus single-layer b-AsP are investigated, and the orientation-dependent in-plane stiffness and Poisson ratio are calculated. It is found that the Janus single layer exhibits strong in-plane anisotropy in its Poisson ratio much larger than that of single-layer b-P. This Janus single layer is relevant for promising applications in optical dichroism and anisotropic nanoelasticity.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.7
Times cited: 39
DOI: 10.1103/PHYSREVB.101.134102
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“Skyrmion spin transfer torque due to current confined in a nanowire”. Osca J, Sorée B, Physical Review B 102, 125436 (2020). http://doi.org/10.1103/PHYSREVB.102.125436
Abstract: In this work we compute the torque field present in a ferromagnet in contact with a metallic nanowire when a skyrmion is present. If the nanowire is narrow enough, then the current is carried by a single conduction band. In this regime the classical torque model breaks down and we show that a skyrmion driven by spin transfer torque moves in a different direction than predicted by the classical model. However, the amount of charge current required to move a skyrmion with a certain velocity in the single-band regime is similar to a classical model of torque where it is implicitly assumed current transport by many conduction bands. The single-band regime is more efficient creating spin current from charge current because of the perfect polarization of the single band but is less efficient creating torque from spin current. Nevertheless, it is possible to take profit of the single-band regime to move skyrmions even with no net charge or spin current flowing between the device contacts. We have also been able to recover the classical limit considering an ensemble of only a few electronic states. In this limit we have discovered that electron diffusion needs to be considered even in ballistic nanowires due the effect of the skyrmion structure on the electron current.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.7
DOI: 10.1103/PHYSREVB.102.125436
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“Skyrmionic chains and lattices in s plus id superconductors”. Zhang L, Zhang Y-Y, Zha G-Q, Milošević, MV, Zhou S-P, Physical Review B 101, 064501 (2020). http://doi.org/10.1103/PHYSREVB.101.064501
Abstract: We report characteristic vortex configurations in s + id superconductors with time-reversal symmetry breaking, exposed to magnetic field. A vortex in the s + id state tends to have an opposite phase winding between s- and d-wave condensates. We find that this peculiar feature together with the competition between s- and d-wave symmetry results in three distinct classes of vortical configurations. When either s or d condensate absolutely dominates, vortices form a conventional lattice. However, when one condensate is relatively dominant, vortices organize in chains that exhibit skyrmionic character, separating the chiral components of the s +/- id order parameter into domains within and outside the chain. Such skyrmionic chains are found stable even at high magnetic field. When s and d condensates have comparable strength, vortices split cores in two chiral components to form full-fledged skyrmions, i.e., coreless topological structures with an integer topological charge, organized in a lattice. We provide characteristic magnetic field distributions of all states, enabling their identification in, e.g., scanning Hall probe and scanning SQUID experiments. These unique vortex states are relevant for high-T-c cuprate and iron-based superconductors, where the relative strength of competing pairing symmetries is expected to be tuned by temperature and/or doping level, and can help distinguish s + is and s + id superconducting phases.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.7
Times cited: 7
DOI: 10.1103/PHYSREVB.101.064501
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“Source apportionment and seasonal variation in particulate PAHs levels at a coastal site in Belgium”. Ravindra K, Dirtu AC, Mor S, Wauters E, Van Grieken R, Environmental Science And Pollution Research (2020). http://doi.org/10.1007/S11356-020-07881-7
Abstract: In the present study, estimation of the atmospheric polycyclic aromatic hydrocarbons (PAHs) was done in particulate samples collected from De Haan, Belgium, during different seasons. The sampling site was situated very close to the north sea and far from the influence of local or industrial activities. The levels of PAHs depicted a distinct seasonal trend, being highest during the spring season. The observations of the study indicated a mean value of 2.6 ng m(-3) for concentration of all the 16 US EPA PAHs, thus being significantly lower when compared to results of previous studies focused on other sites. The dominating PAHs species reported were naphthalene, fluoranthene, benzo[a]anthracene, chrysene, and indeno[1,2,3c,d] pyrene. Assessment of the seasonal variation of the PAH levels was also done with respect to diagnostic ratio-based source identification, analysis of back trajectories, and principle component analysis. Burning of fossil fuels was observed to be the prominent source of atmospheric PAHs in the study area. Further, lifetime cancer risk assessment was performed to assess the detrimental health impacts on humans on being exposed to atmospheric PAHs. Particulate PAHs present in the ambient air of Belgium shows no carcinogenic health impacts. However, considering the industrial expansion in the region, efforts are required to prevent the environmental contamination of PAHs.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 5.8
DOI: 10.1007/S11356-020-07881-7
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“Source/drain materials for Ge nMOS devices: phosphorus activation in epitaxial Si, Ge, Ge1-xSnx and SiyGe1-x-ySnx”. Vohra A, Makkonen I, Pourtois G, Slotte J, Porret C, Rosseel E, Khanam A, Tirrito M, Douhard B, Loo R, Vandervorst W, Ecs Journal Of Solid State Science And Technology 9, 044010 (2020). http://doi.org/10.1149/2162-8777/AB8D91
Abstract: This paper benchmarks various epitaxial growth schemes based on n-type group-IV materials as viable source/drain candidates for Ge nMOS devices. Si:P grown at low temperature on Ge, gives an active carrier concentration as high as 3.5 x 10(20) cm(-3) and a contact resistivity down to 7.5 x 10(-9) Omega.cm(2). However, Si:P growth is highly defective due to large lattice mismatch between Si and Ge. Within the material stacks assessed, one option for Ge nMOS source/drain stressors would be to stack Si:P, deposited at contact level, on top of a selectively grown n-SiyGe1-x-ySnx at source/drain level, in line with the concept of Si passivation of n-Ge surfaces to achieve low contact resistivities as reported in literature (Martens et al. 2011 Appl. Phys. Lett., 98, 013 504). The saturation in active carrier concentration with increasing P (or As)-doping is the major bottleneck in achieving low contact resistivities for as-grown Ge or SiyGe1-x-ySnx. We focus on understanding various dopant deactivation mechanisms in P-doped Ge and Ge1-xSnx alloys. First principles simulation results suggest that P deactivation in Ge and Ge1-xSnx can be explained both by P-clustering and donor-vacancy complexes. Positron annihilation spectroscopy analysis, suggests that dopant deactivation in P-doped Ge and Ge1-xSnx is primarily due to the formation of P-n-V and SnmPn-V clusters. (C) 2020 The Author(s). Published on behalf of The Electrochemical Society by IOP Publishing Limited.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.2
DOI: 10.1149/2162-8777/AB8D91
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“Spin polarization in monolayer MoS₂, in the presence of proximity-induced interactions”. Zhao XN, Xu W, Xiao YM, Van Duppen B, International Journal Of Modern Physics C 31, 2050143 (2020). http://doi.org/10.1142/S0129183120501430
Abstract: When monolayer (ML) MoS2 is placed on a substrate, the proximity-induced interactions such as the Rashba spin-orbit coupling (RSOC) and exchange interaction (EI) can be introduced. Thus, the electronic system can behave like a spintronic device. In this study, we present a theoretical study on how the presence of the RSCO and EI can lead to the band splitting, the lifting of the valley degeneracy and to the spin polarization in n- and p-type ML MoS2. We find that the maxima of the in-plane spin orientation in the conduction and valence bands in ML MoS2 depend on the Rashba parameter and the effective Zeeman field factor. At a fixed Rashba parameter, the minima of the split conduction band and the maxima of the split valence band along with the spin polarization in ML MoS2 can be tuned effectively by varying the effective Zeeman field factor. On the basis that the EI can be induced by placing the ML MoS2 on a ferromagnetic substrate or by magnetic doping in ML MoS2, we predict that the interesting spintronic effects can be observed in n- and p-type ML MoS2. This work can be helpful to gain an in-depth understanding of the basic physical properties of ML MoS2 for application in advanced electronic and optoelectronic devices.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 1.9
DOI: 10.1142/S0129183120501430
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“Spin textures in chiral magnetic monolayers with suppressed nearest-neighbor exchange”. Menezes RM, de Souza Silva CC, Milošević, MV, Physical Review B 101, 214429 (2020). http://doi.org/10.1103/PHYSREVB.101.214429
Abstract: High tunability of two-dimensional magnetic materials (by strain, gating, heterostructuring, or otherwise) provides unique conditions for studying versatile magnetic properties and controlling emergent magnetic phases. Expanding the scope of achievable magnetic phenomena in such materials is important for both fundamental and technological advances. Here we perform atomistic spin-dynamics simulations to explore the (chiral) magnetic phases of atomic monolayers in the limit of suppressed first-neighbors exchange interaction. We report the rich phase diagram of exotic magnetic configurations, obtained for both square and honeycomb lattice symmetries, comprising coexistence of ferromagnetic and antiferromagnetic spin cycloids, as well as multiple types of magnetic skyrmions. We perform a minimum-energy path analysis for the skyrmion collapse to evaluate the stability of such topological objects and reveal that magnetic monolayers could be good candidates to host the antiferromagnetic skyrmions that are experimentally evasive to date.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.7
Times cited: 1
DOI: 10.1103/PHYSREVB.101.214429
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Vanherck J (2020) Spontaneous and induced magnetisation in two-dimensional and bulk Heisenberg ferromagnets : a quantum mechanical treatment. 160 p
Keywords: Doctoral thesis; Condensed Matter Theory (CMT)
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“Spontaneous emergence of Josephson junctions in homogeneous rings of single-crystal Sr₂RuO₄”. Yasui Y, Lahabi K, Fernández Becerra V, Fermin R, Anwar MS, Yonezawa S, Terashima T, Milošević, MV, Aarts J, Maeno Y, npj Quantum Materials 5, 21 (2020). http://doi.org/10.1038/S41535-020-0223-7
Abstract: The chiral p-wave order parameter in Sr2RuO4 would make it a special case amongst the unconventional superconductors. A consequence of this symmetry is the possible existence of superconducting domains of opposite chirality. At the boundary of such domains, the locally suppressed condensate can produce an intrinsic Josephson junction. Here, we provide evidence of such junctions using mesoscopic rings, structured from Sr2RuO4 single crystals. Our order parameter simulations predict such rings to host stable domain walls across their arms. This is verified with transport experiments on loops, with a sharp transition at 1.5 K, which show distinct critical current oscillations with periodicity corresponding to the flux quantum. In contrast, loops with broadened transitions at around 3 K are void of such junctions and show standard Little-Parks oscillations. Our analysis demonstrates the junctions are of intrinsic origin and makes a compelling case for the existence of superconducting domains.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Times cited: 10
DOI: 10.1038/S41535-020-0223-7
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“Stable single layer of Janus MoSO: strong out-of-plane piezoelectricity”. Yagmurcukardes M, Peeters FM, Physical Review B 101, 155205 (2020). http://doi.org/10.1103/PHYSREVB.101.155205
Abstract: Using density functional theory based first-principles calculations, we predict the dynamically stable 1H phase of a Janus single layer composed of S-Mo-O atomic layers. It is an indirect band gap semiconductor exhibiting strong polarization arising from the charge difference on the two surfaces. In contrast to 1H phases of MoS2 and MoO2, Janus MoSO is found to possess four Raman active phonon modes and a large out-of-plane piezoelectric coefficient which is absent in fully symmetric single layers of MoS2 and MoO2. We investigated the electronic and phononic properties under applied biaxial strain and found an electronic phase transition with tensile strain while the conduction band edge displays a shift when under compressive strain. Furthermore, single-layer MoSO exhibits phononic stability up to 5% of compressive and 11% of tensile strain with significant phonon shifts. The phonon instability is shown to arise from the soft in-plane and out-of-plane acoustic modes at finite wave vector. The large strain tolerance of Janus MoSO is important for nanoelastic applications. In view of the dynamical stability even under moderate strain, we expect that Janus MoSO can be fabricated in the common 1H phase with a strong out-of-plane piezoelectric coefficient.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.7
Times cited: 66
DOI: 10.1103/PHYSREVB.101.155205
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“Stable single-layers of calcium halides (CaX₂, X = F, Cl, Br, I)”. Baskurt M, Yagmurcukardes M, Peeters FM, Sahin H, Journal Of Chemical Physics 152, 164116 (2020). http://doi.org/10.1063/5.0006011
Abstract: By means of density functional theory based first-principles calculations, the structural, vibrational, and electronic properties of 1H- and 1T-phases of single-layer CaX2 (X = F, Cl, Br, or I) structures are investigated. Our results reveal that both the 1H- and 1T-phases are dynamically stable in terms of their phonon band dispersions with the latter being the energetically favorable phase for all single-layers. In both phases of single-layer CaX2 structures, significant phonon softening occurs as the atomic radius increases. In addition, each structural phase exhibits distinctive Raman active modes that enable one to characterize either the phase or the structure via Raman spectroscopy. The electronic band dispersions of single-layer CaX2 structures reveal that all structures are indirect bandgap insulators with a decrease in bandgaps from fluorite to iodide crystals. Furthermore, the calculated linear elastic constants, in-plane stiffness, and Poisson ratio indicate the ultra-soft nature of CaX2 single-layers, which is quite important for their nanoelastic applications. Overall, our study reveals that with their dynamically stable 1T- and 1H-phases, single-layers of CaX2 crystals can be alternative ultra-thin insulators.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 4.4
Times cited: 14
DOI: 10.1063/5.0006011
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“Strain and electric field tuning of semi-metallic character WCrCO₂, MXenes with dual narrow band gap”. Bafekry A, Akgenc B, Ghergherehchi M, Peeters FM, Journal Of Physics-Condensed Matter 32, 355504 (2020). http://doi.org/10.1088/1361-648X/AB8E88
Abstract: Motivated by the recent successful synthesis of double-M carbides, we investigate structural and electronic properties of WCrC and WCrCO2 monolayers and the effects of biaxial and out-of-plane strain and electric field using density functional theory. WCrC and WCrCO2 monolayers are found to be dynamically stable. WCrC is metallic and WCrCO2 display semi-metallic character with narrow band gap, which can be controlled by strain engineering and electric field. WCrCO2 monolayer exhibits a dual band gap which is preserved in the presence of an electric field. The band gap of WCrCO2 monolayer increases under uniaxial strain while it becomes metallic under tensile strain, resulting in an exotic 2D double semi-metallic behavior. Our results demonstrate that WCrCO2 is a new platform for the study of novel physical properties in two-dimensional Dirac materials and which may provide new opportunities to realize high-speed low-dissipation devices.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.7
Times cited: 45
DOI: 10.1088/1361-648X/AB8E88
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Hendrickx M (2020) Study of the effect of cation substitution on the local structure and the properties of perovskites and Li-ion battery cathode materials. 208 p
Keywords: Doctoral thesis; Electron microscopy for materials research (EMAT)
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“Study of the influence of water and oxygen on the morphology and chemistry of pyritized lignite: Implications for the development of a preventive drying protocol”. Odin GP, Belhadj O, Vanmeert F, Janssens K, Wattiaux A, Francois A, Rouchon V, Journal Of Cultural Heritage 42, 117 (2020). http://doi.org/10.1016/J.CULHER.2019.08.004
Abstract: Lignite constitutes a unique testimony of past diversity and evolution of land plants. This material, usually waterlogged, is particularly difficult to dry because of its mechanical sensitivity to moisture changes. In addition, lignite may contain organic and inorganic sulfides, which are susceptible to oxidation once excavated. As a result, the conservation of lignite is particularly complicated and lignite remains scarce in paleobotanical collections. We experimentally test different drying protocols on waterlogged pyritized lignite, while documenting the respective role of water and oxygen on their morphology and chemistry. The results reveal that inorganic sulfides (pyrite) are more prone to oxidation than organic sulfides (thioethers). Critically, water is the main factor responsible for this oxidation, provoking sulfate efflorescence when samples are further exposed to oxygen. On the other hand, an abrupt removal of water provokes significant mechanical damage while sulfur remains mostly present as reduced compounds. The control of water and oxygen exchanges is thus critical for conserving lignite without physical damage and efflorescence. We successfully achieved this by storing the samples in hermetically sealed plastic bags made of semi-permeable films, which slowly release humidity while allowing a gradual influx of oxygen. We advise curators to quickly handle lignite once removed from its waterlogged environment because of the fast kinetics of oxidation, and to choose a drying protocol according to the purpose of the lignite treated. Finally, once dried, we advise to store the lignite in an anhydrous environment. (C) 2019 Elsevier Masson SAS. All rights reserved.
Keywords: A1 Journal article; Art; History; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 3.1
DOI: 10.1016/J.CULHER.2019.08.004
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