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1.	Borsato, M., et al. (author) Unleashing the full power of LHCb to probe stealth new physics 2022 In: Reports on Progress in Physics. - : IOP Publishing. - 0034-4885 .- 1361-6633. ; 85:2 Journal article (peer-reviewed)abstract In this paper, we describe the potential of the LHCb experiment to detect stealth physics. This refers to dynamics beyond the standard model that would elude searches that focus on energetic objects or precision measurements of known processes. Stealth signatures include long-lived particles and light resonances that are produced very rarely or together with overwhelming backgrounds. We will discuss why LHCb is equipped to discover this kind of physics at the Large Hadron Collider and provide examples of well-motivated theoretical models that can be probed with great detail at the experiment.
2.	Lindahl, Niklas, 1981, et al. (author) Aluminum Metal-Organic Batteries with Integrated 3D Thin Film Anodes 2020 In: Advanced Functional Materials. - : Wiley. - 1616-301X .- 1616-3028. ; 30:51 Journal article (peer-reviewed)abstract Aluminum 3D thin film anodes fully integrated with a separator are fabricated by sputtering and enable rechargeable aluminum metal batteries with high power performance. The 3D thin film anodes have an approximately four to eight times larger active surface area than a metal foil, which significantly both reduces the electrochemical overpotential, and improves materials utilization. In full cells with organic cathodes, that is, aluminum metal-organic batteries, the 3D thin film anodes provide 165 mAh g(-1)at 0.5 C rate, with a capacity retention of 81% at 20 C, and 86% after 500 cycles. Post-mortem analysis reveals structural degradation to limit the long-term stability at high rates. As the multivalent charge carrier active here is AlCl2+, the realistic maximal specific energy, and power densities at cell level are approximate to 100 Wh kg(-1)and approximate to 3100 W kg(-1), respectively, which is significantly higher than the state-of-the-art for Al batteries.
3.	Fan, Qunping, 1989, et al. (author) Over 14% efficiency all-polymer solar cells enabled by a low bandgap polymer acceptor with low energy loss and efficient charge separation 2020 In: Energy & Environmental Science. - : Royal Society of Chemistry. - 1754-5692 .- 1754-5706. ; 13:12, s. 5017-5027 Journal article (peer-reviewed)abstract Obtaining both high open-circuit voltage (V-oc) and short-circuit current density (J(sc)) has been a major challenge for efficient all-polymer solar cells (all-PSCs). Herein, we developed a polymer acceptor PF5-Y5 with excellent optical absorption capability (onset extending to similar to 880 nm and maximum absorption coefficient exceeding 105 cm(-1) in a film), high electron mobility (3.18 x 10(3) cm(2) V-1 s(-1)) and high LUMO level (-3.84 eV) to address such a challenge. As a result, the PBDB-T:PF5-Y5-based all-PSCs achieved a high power conversion efficiency of up to 14.45% with both a high Voc (0.946 V) and a high Jsc (20.65 mA cm(-2)), due to the high and broad absorption coverage, small energy loss (0.57 eV) and efficient charge separation and transport in the device, which are among the best values in the all-PSC field. In addition, the all-PSC shows a similar to 15% improvement in PCE compared to its counterpart small molecule acceptor (Y5)-based device. Our results suggest that PF5-Y5 is a very promising polymer acceptor candidate for applications in efficient all-PSCs.
4.	Dissanayake, Makl, et al. (author) Optimizing the size and amount of CdS quantum dots for efficiency enhancement in CdS/N719 co-sensitized solar cells 2022 In: Physica E-Low-Dimensional Systems & Nanostructures. - : Elsevier BV. - 1386-9477. ; 144 Journal article (peer-reviewed)abstract Co-sensitization of TiO2 photoanodes in solar cells with Ruthenium dye and quantum dots offer better photovoltaic performance compared to the sensitization by the dye only. In the present study, TiO2 nanostructured photoanode was co-sensitized with CdS quantum dots and N719 dye. CdS quantum dots were deposited using successive ionic layer adsorption and reaction (SILAR). A suitable thin ZnS interfacial layer has been introduced between two sensitizers to prevent the corrosion of CdS quantum dots by the iodide-based liquid electrolyte. In order to get the highest efficiency, the number of SILAR cycles for CdS quantum dot deposition has been optimized. A power conversion efficiency of 6.79% with short-circuit current density of 15.55 mA cm-2 and open circuit voltage of 764.5 mV have been obtained for the co-sensitized solar cell made with TiO2/CdS/ZnS/N719 co-sensitized photoanode under the illumination of 100 mW cm-2 with AM 1.5 spectral filter. Efficiency and short-circuit current density of the solar cell have been enhanced by 11.31% and 6.58% respectively due to the co-sensitization. The optimized co-sensitized solar cell shows a higher incident photon to current conversion efficiency and a reduced electron recombination compared to the solar cell with dye-sensitized photoanode. Higher recombination resistance and longer electron lifetime of the solar cell with CdS/ZnS/N719 co-sensitized TiO2 photoanode have contributed to the increased short circuit current and open circuit voltage leading to the enhanced efficiency of 6.79% which is among the highest for a co-sensitized dye sensitized solar cell.
5.	Manzetti, Sergio, et al. (author) A Korteweg-DeVries type model for helical soliton solutions for quantum and continuum phenomena 2021 In: International Journal of Modern Physics C. - : World Scientific. - 0129-1831. ; 32:03 Journal article (peer-reviewed)abstract Quantum mechanical states are normally described by the Schrödinger equation, which generates real eigenvalues and quantizable solutions which form a basis for the estimation of quantum mechanical observables, such as momentum and kinetic energy. Studying transition in the realm of quantum physics and continuum physics is however more difficult and requires different models. We present here a new equation which bears similarities to the Korteweg–DeVries (KdV) equation and we generate a description of transitions in physics. We describe here the two- and three-dimensional form of the KdV like model dependent on the Plank constant ℏ and generate soliton solutions. The results suggest that transitions are represented by soliton solutions which arrange in a spiral-fashion. By helicity, we propose a conserved pattern of transition at all levels of physics, from quantum physics to macroscopic continuum physics.
6.	Bahrova, O. M., et al. (author) Cooling of nanomechanical vibrations by Andreev injection 2022 In: Low Temperature Physics. - : AIP Publishing. - 1063-777X .- 1090-6517. ; 48:6, s. 476-482 Journal article (peer-reviewed)abstract A nanoelectromechanical weak link composed of a carbon nanotube suspended between two normal electrodes in a gap between two superconducting leads is considered. The nanotube is treated as a movable single level quantum dot in which the position-dependent superconducting order parameter is induced due to the Cooper pair tunneling. We show that electron tunneling processes significantly affect the state of the mechanical subsystem. We found that at a given direction of the applied voltage between the electrodes, the stationary state of the mechanical subsystem has a Boltzmann form with an effective temperature dependent on the parameters of the device. As this takes place, the effective temperature can reach significantly small values (cooling effect). We also demonstrate that nanotube fluctuations strongly affect the dc current through the system. The latter can be used to probe the predicted effects in an experiment. Published under an exclusive license by AIP Publishing.
7.	Parafilo, A. V., et al. (author) Pumping and Cooling of Nanomechanical Vibrations Generated by Cooper-Pair Exchange 2022 In: Journal of Low Temperature Physics. - : Springer Science and Business Media LLC. - 0022-2291 .- 1573-7357. ; 210:1-2, s. 150-65 Journal article (peer-reviewed)abstract We consider a nanoelectromechanical system composed of a carbon nanotube suspended between two normal leads and coupled to a superconducting scanning tunneling microscope (STM) tip via vacuum tunnel barrier. Treating the nanotube as a single-level quantum dot, it is shown that an applied voltage between the superconducting STM tip and normal leads gives rise to a pumping or a cooling of the mechanical subsystem depending on the direction of the electronic flow. It is also demonstrated that the transition between these two regimes is controlled by the strength of the tunnel coupling between the nanotube and superconducting STM tip and the relative position of the electronic level. Such phenomena are realized due to a specific electromechanical coupling that is fully governed by the quantum dynamics of the Cooper pairs. The amplitude of the self-sustained oscillations in the pumping regime is analyzed numerically, and the effective temperature of the mechanical subsystem in the cooling regime is obtained.
8.	Windelius, Olle, 1972, et al. (author) Photoelectron angular distributions in photodetachment from P 2021 In: Physical Review A. - 2469-9926 .- 2469-9934. ; 103:3 Journal article (peer-reviewed)abstract The angular distributions of electrons ejected in laser photodetachment of the P- ion have been studied in the photon energy range of 0.95-3.28 eV using a photoelectron spectrometer designed to accommodate a source consisting of collinearly overlapping photon and negative ion beams. We observe the value of the asymmetry parameter beta starting at zero near the threshold, falling to almost -1 about 0.5 eV above the threshold and eventually rising to a positive value. The experimental data has been fitted to a simplified model of the Cooper-Zare formula which yields a qualitative understanding of the quantum interference between the outgoing s and d waves representing the free electron. The present results are also compared with previous results for other elements involving p-electron photodetachment.
9.	Siminos, Evangelos, 1979, et al. (author) Laser Wakefield Driven Generation of Isolated Carrier-Envelope-Phase Tunable Intense Subcycle Pulses 2021 In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 126:4 Journal article (peer-reviewed)abstract Sources of intense, ultrashort electromagnetic pulses enable applications such as attosecond pulse generation, control of electron motion in solids, and the observation of reaction dynamics at the electronic level. For such applications, both high intensity and carrier-envelope-phase (CEP) tunability are beneficial, yet hard to obtain with current methods. In this Letter, we present a new scheme for generation of isolated CEP tunable intense subcycle pulses with central frequencies that range from the midinfrared to the ultraviolet. It utilizes an intense laser pulse that drives a wake in a plasma, copropagating with a long-wavelength seed pulse. The moving electron density spike of the wake amplifies the seed and forms a subcycle pulse. Controlling the CEP of the seed pulse or the delay between driver and seed leads to CEP tunability, while frequency tunability can be achieved by adjusting the laser and plasma parameters. Our 2D and 3D particle-in-cell simulations predict laser-to-subcycle-pulse conversion efficiencies up to 1%, resulting in relativistically intense subcycle pulses.
10.	Siminos, Evangelos, 1979, et al. (author) Parametric study of laser wakefield driven generation of intense sub-cycle pulses 2022 In: Plasma Physics and Controlled Fusion. - : IOP Publishing. - 0741-3335 .- 1361-6587. ; 64:3 Journal article (peer-reviewed)abstract Intense sub-cycle electromagnetic pulses allow one to drive nonlinear processes in matter with unprecedented levels of control. However, it remains challenging to scale such sources in the relativistic regime. Recently, a scheme that utilizes laser-driven wakes in plasmas to amplify and compress seed laser pulses to produce tunable, carrier-envelope-phase stable, relativistic sub-cycle pulses has been proposed. Here, we present parametric studies of this process using particle-in-cell simulations, showing its robustness over a wide range of experimentally accessible laser-plasma interaction parameters, spanning more than two orders of magnitude of background plasma density. The method is shown to work with different gas-jet profiles, including structured density profiles and is robust over a relatively wide range of driver laser intensities. Our study shows that sub-cycle pulses of up to 10mJ of energy can be produced.
11.	Radic, D., et al. (author) Nanomechanical cat states generated by a dc voltage-driven Cooper pair box qubit 2022 In: npj Quantum Information. - : Springer Science and Business Media LLC. - 2056-6387. ; 8:1 Journal article (peer-reviewed)abstract We study a nanoelectromechanical system consisting of a Cooper pair box qubit performing nanomechanical vibrations between two bulk superconductors. We demonstrate that a bias voltage applied to the superconductors may generate states represented by entanglement between qubit states and quantum 'cat states', i.e. a superposition of the coherent states of the nanomechanical oscillator. We characterize the formation and development of such states in terms of the corresponding Wigner function and entropy of entanglement. Also, we propose an experimentally feasible detection scheme for the effect, in which the average current that attains the specific features created by the entanglement is measured.
12.	Airey, John, 1963-, et al. (author) Making the Invisible Visible : The role of undergraduate textbooks in the teaching and learning of physics and chemistry 2023 In: Designing futures. - London : UCL Press. Conference paper (peer-reviewed)abstract As disciplines, undergraduate physics and chemistry leverage a particularly wide range of semiotic systems (modes) in order to create and communicate their scientific meanings. Examples of the different semiotic systems employed are: spoken and written language, mathematics, chemical formulae, graphs, diagrams, sketches, computer simulations, hands-on work with experimental apparatus, computer simulations, etc. Individual semiotic resources within this range of semiotic systems are coordinated in specific constellations (Airey & Linder, 2009) in order to mediate scientific knowledge. In this Swedish Research Council project, we are interested in the representation of scientific phenomena that cannot be seen. The question we pose is: How is scientific knowledge mediated when we cannot directly interact with the phenomena in question through our senses? We adopt a social semiotic approach (Airey & Linder, 2017; van Leeuwen, 2005), to investigate the ways in which two phenomena—electromagnetic fields and chemical bonds—are presented in undergraduate textbooks. To do this we carried out a semiotic audit (Airey & Erikson, 2019) of eight textbooks (four in each discipline). We note that the individual resources used have a mixture of affordances—whilst the majority retain high disciplinary affordance, others are unpacked (Patron et al. 2021) providing higher pedagogical affordance. We discuss the ways in which the resources have been combined and orchestrated (Bezemer & Jewitt, 2010) in order to attempt to make visible that which is invisible, and identify a number of potential problems. In earlier work, Volkwyn et al. (2019) demonstrated how experimental work with physics devices can make the Earth’s magnetic field accessible to students through chains of transduction. Thus, we propose that encouraging transductions across the semiotic resource systems provided in textbooks may help students to experience the invisible.ReferencesAirey, J. (2006). Physics students' experiences of the disciplinary discourse encountered in lectures in English and Swedish (Licentiate dissertation, Department of Physics, Uppsala University).Airey, J. (2009). Science, language, and literacy: Case studies of learning in Swedish university physics (Doctoral dissertation, Acta Universitatis Upsaliensis).Airey, J. (2015). Social Semiotics in Higher Education: Examples from teaching and learning in undergraduate physics. In In: SACF Singapore-Sweden Excellence Seminars, Swedish Foundation for International Cooperation in Research in Higher Education (STINT) , 2015 (pp. 103). Airey, J., & Eriksson, U. (2019). Unpacking the Hertzsprung-Russell diagram: A social semiotic analysis of the disciplinary and pedagogical affordances of a central resource in astronomy. Designs for Learning, 11(1), 99-107.Goodwin, C. (2015). Professional vision. In Aufmerksamkeit: Geschichte-Theorie-Empirie (pp. 387-425). Wiesbaden: Springer Fachmedien Wiesbaden.O’Halloran, K. (2007). Mathematical and scientific forms of knowledge: A systemic functional multimodal grammatical approach. language, Knowledge and pedagogy: functional linguistic and sociological perspective, 205-236.Patron, E. (2022). Exploring the role that visual representations play when teaching and learning chemical bonding: An approach built on social semiotics and phenomenography(Doctoral dissertation, Linnaeus University Press).
13.	Su, Wenyan, et al. (author) Nonconjugated Terpolymer Acceptors with Two Different Fused-Ring Electron-Deficient Building Blocks for Efficient All-Polymer Solar Cells 2021 In: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 13:5, s. 6442-6449 Journal article (peer-reviewed)abstract The ternary polymerization strategy of incorporating different donor and acceptor units forming terpolymers as photovoltaic materials has been proven advantageous in improving power conversion efficiencies (PCEs) of polymer solar cells (PSCs). Herein, a series of low band gap nonconjugated terpolymer acceptors based on two different fused-ring electron-deficient building blocks (IDIC16 and ITIC) with adjustable photoelectric properties were developed. As the third component, ITIC building blocks with a larger pi-conjugation structure, shorter solubilizing side chains, and red-shifted absorption spectrum were incorporated into an IDIC16-based nonconjugated copolymer acceptor PF1-TS4, which built up the terpolymers with two conjugated building blocks linked by flexible thioalkyl chain-thiophene segments. With the increasing ITIC content, terpolymers show gradually broadened absorption spectra and slightly down-shifted lowest unoccupied molecular orbital levels. The active layer based on terpolymer PF1-TS4-60 with a 60% ITIC unit presents more balanced hole and electron mobilities, higher photoluminescence quenching efficiency, and improved morphology compared to those based on PF1-TS4. In all-polymer solar cells (all-PSCs), PF1-TS4-60, matched with a wide band gap polymer donor PM6, achieved a similar open-circuit voltage (V-oc) of 0.99 V, a dramatically increased short-circuit current density (J(sc)) of 15.30 mA cm(-2), and fill factor (FF) of 61.4% compared to PF1-TS4 = 0.99 V, J(sc) = 11.21 mA cm(-2), and FF = 55.6%). As a result, the PF1-TS4-60-based all-PSCs achieved a PCE of 9.31%, which is similar to 50% higher than the PF1-TS4-based ones (6.17%). The results demonstrate a promising approach to develop high-performance nonconjugated terpolymer acceptors for efficient all-PSCs by means of ternary polymerization using two different A-D-A-structured fused-ring electron-deficient building blocks.
14.	Mishra, K., et al. (author) Ultrafast Demagnetization Control in Magnetophotonic Surface Crystals 2022 In: Nano Letters. - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 22:23, s. 9773-80 Journal article (peer-reviewed)abstract Magnetic memory combining plasmonics and magnetism is poised to dramatically increase the bit density and energy efficiency of light-assisted ultrafast magnetic storage, thanks to nanoplasmon-driven enhancement and confinement of light. Here we devise a new path for that, simultaneously enabling light driven bit downscaling, reduction of the required energy for magnetic memory writing, and a subtle control over the degree of demagnetization in a magnetophotonic surface crystal. It features a regular array of truncated-nanocone-shaped Au-TbCo antennas showing both localized plasmon and surface lattice resonance modes. The ultrafast magnetization dynamics of the nanoantennas show a 3-fold resonant enhancement of the demagnetization efficiency. The degree of demagnetization is further tuned by activating surface lattice modes. This reveals a platform where ultrafast demagnetization is localized at the nanoscale and its extent can be controlled at will, rendering it multistate and potentially opening up so-far-unforeseen nanomagnetic neuromorphic-like systems operating at femtosecond time scales controlled by light.
15.	Volkwyn, Trevor S., 1969-, et al. (author) Learning to use Cartesian coordinate systems to solve physics problems : the case of 'movability' 2020 In: European journal of physics. - : IOP Publishing. - 0143-0807 .- 1361-6404. ; 41:4 Journal article (peer-reviewed)abstract In this paper, we show that introductory physics students may initially conceptualise Cartesian coordinate systems as being fixed in a standard orientation. Giving consideration to the role that experiences of variation play in learning, we also present an example of how this learning challenge can be effectively addressed. Using a fine-grained analytical description, we show how students can quickly come to appreciate coordinate system movability. This was done by engaging students in a conceptual learning task that involved them working with a movable magnetometer with a printed-on set of coordinate axes to determine the direction of a constant field (Earth's magnetic field).
16.	Ziemann, Volker (author) Physics and Finance 2021 Book (peer-reviewed)abstract This book introduces physics students to concepts and methods of finance. Despite being perceived as quite distant from physics, finance shares a number of common methods and ideas, usually related to noise and uncertainties. Juxtaposing the key methods to applications in both physics and finance articulates both differences and common features, this gives students a deeper understanding of the underlying ideas. Moreover, they acquire a number of useful mathematical and computational tools, such as stochastic differential equations, path integrals, Monte-Carlo methods, and basic cryptology. Each chapter ends with a set of carefully designed exercises enabling readers to test their comprehension.
17.	Petrucci, G., et al. (author) Macroscopic magneto-chiroptical metasurfaces 2021 In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 118:25 Journal article (peer-reviewed)abstract Nanophotonic chiral antennas exhibit orders of magnitude higher circular dichroism (CD) compared to molecular systems. When the structural chirality is merged with magnetism at the nanoscale, efficient magnetic control over the dichroic response is achieved, bringing exciting prospects to active nanophotonic devices. Here, we devise macroscopic enantiomeric magnetophotonic metasurfaces of plasmonic-ferromagnetic spiral antennas assembled on large areas via hole-mask colloidal lithography. The simultaneous presence of 3D- and 2D-features in chiral nanoantennas induces large CD response, where we identify reciprocal and non-reciprocal contributions, respectively. Exploring further this type of magnetophotonic metasurfaces might allow the realization of high-sensitivity chiral sensors and prompts the design of advanced macroscopic optical devices operating with polarized light.
18.	Andrén, Daniel, 1991, et al. (author) Microscopic metavehicles powered and steered by embedded optical metasurfaces 2021 In: Nature Nanotechnology. - : Springer Science and Business Media LLC. - 1748-3387 .- 1748-3395. ; 16:9, s. 970-974 Journal article (peer-reviewed)abstract Nanostructured dielectric metasurfaces offer unprecedented opportunities to manipulate light by imprinting an arbitrary phase gradient on an impinging wavefront(1). This has resulted in the realization of a range of flat analogues to classical optical components, such as lenses, waveplates and axicons(2-6). However, the change in linear and angular optical momentum(7) associated with phase manipulation also results in previously unexploited forces and torques that act on the metasurface itself. Here we show that these optomechanical effects can be utilized to construct optical metavehicles-microscopic particles that can travel long distances under low-intensity plane-wave illumination while being steered by the polarization of the incident light. We demonstrate movement in complex patterns, self-correcting motion and an application as transport vehicles for microscopic cargoes, which include unicellular organisms. The abundance of possible optical metasurfaces attests to the prospect of developing a wide variety of metavehicles with specialized functional behaviours.
19.	Gregorcic, Bor, 1988-, et al. (author) Conceptual Blending as an Interpretive Lens for Student Engagement with Technology : Exploring Celestial Motion on an Interactive Whiteboard 2021 In: Research in science education. - : Springer. - 0157-244X .- 1573-1898. ; 51:2, s. 235-275 Journal article (peer-reviewed)abstract We present and analyze video data of upper secondary school students’ engagement with a computer-supported collaborative learning environment that enables them to explore astronomical phenomena (Keplerian motion). The students’ activities have an immersive and exploratory character, as students engage in open-ended inquiry and interact physically with the virtual environment displayed on an interactive whiteboard. The interplay of students’ playful exploration through physical engagement with the simulation environment, their attention to physics concepts and laws, and knowledge about the real planets orbiting the Sun presents an analytical challenge for the researcher and instructor encountering such complex learning environments. We argue that the framework of conceptual blending is particularly apt for dealing with the learning environment at hand, because it allows us to take into account the many diverse mental inputs that seem to shape the student activities described in the paper. We show how conceptual blending can be brought together with theoretical ideas concerned with embodied cognition and epistemology of physics, in order to provide researchers and instructors with a powerful lens for looking critically at immersive technology-supported learning environments.
20.	Samuelsson, Christopher Robin, 1989-, et al. (author) Looking for solutions : students' use of infrared cameras in calorimetry labs 2023 In: Chemistry Education Research and Practice. - : Royal Society of Chemistry. - 1756-1108 .- 1109-4028. ; :24, s. 299-311 Journal article (peer-reviewed)abstract This study adds to the growing body of research on laboratory work. The study involves four pairs of students in a university introductory calorimetry lab of which two pairs, the IR-pairs (infrared camera-pairs), were given access to infrared cameras to use however they liked during their course lab work. Two other pairs, the T-pairs (thermometer-pairs), were not given access to infrared cameras during their course lab work. The IR-pairs were video recorded when they chose to use the IR cameras and the T-pairs were video-recorded during the corresponding sequences. Additionally, all pairs participated in a modified lab after their course lab, in which the pairs had access to IR cameras and were presented with the same phenomena although with equipment modified to better accommodate for the use of IR cameras (thin plastic cups were used instead of calorimeters). Students' practice, communication and reasoning was studied to explore how the IR cameras affect students' activity. The results show that the access to IR cameras led to a reasoning focused on a macroscopic level of chemistry knowledge, involving heat transfer to the surrounding and measurement errors, and that the lab practice of most of the students was continuous (rather than intermittent) when they had access to IR cameras. We conclude by arguing that the access to IR cameras affects students' conceptual and epistemological framing of the lab, i.e. that the students perceive the lab activity differently when they get access to IR cameras (both in a conceptual and epistemological sense). As an implication for teaching, we suggest that giving students access to IR cameras in a chemistry lab may be a way to introduce flexibility in the degree of openness of the lab.
21.	Kapodistrias, Anastasios, 1991-, et al. (author) Rearranging equations to develop physics reasoning 2024 In: European journal of physics. - 0143-0807 .- 1361-6404. ; 45:3 Journal article (peer-reviewed)abstract Researchers generally agree that physics experts use mathematics in a way that blends mathematical knowledge with physics intuition. However, the use of mathematics in physics education has traditionally tended to focus more on the computational aspect (manipulating mathematical operations to get numerical solutions) to the detriment of building conceptual understanding and physics intuition. Several solutions to this problem have been suggested; some authors have suggested building conceptual understanding before mathematics is introduced, while others have argued for the inseparability of the two, claiming instead that mathematics and conceptual physics need to be taught simultaneously. Although there is a body of work looking into how students employ mathematical reasoning when working with equations, the specifics of how physics experts use mathematics blended with physics intuition remain relatively underexplored. In this paper, we describe some components of this blending, by analyzing how physicists perform the rearrangement of a specific equation in cosmology. Our data consist of five consecutive forms of rearrangement of the equation, as observed in three separate higher education cosmology courses. This rearrangement was analyzed from a conceptual reasoning perspective using Sherin's framework of symbolic forms. Our analysis clearly demonstrates how the number of potential symbolic forms associated with each subsequent rearrangement of the equation decreases as we move from line to line. Drawing on this result, we suggest an underlying mechanism for how physicists reason with equations. This mechanism seems to consist of three components: narrowing down meaning potential, moving aspects between the background and the foreground and purposefully transforming the equation according to the discipline's questions of interest. In the discussion section we highlight the potential that our work has for generalizability and how being aware of the components of this underlying mechanism can potentially affect physics teachers' practice when using mathematics in the physics classroom.
22.	Balabanov, Oleksandr, 1991, et al. (author) Topology of critical chiral phases: Multiband insulators and superconductors 2021 In: Physical Review Research. - 2643-1564. ; 3:4 Journal article (peer-reviewed)abstract Recent works have proved the existence of symmetry-protected edge states in certain one-dimensional topological band insulators and superconductors at the gap-closing points which define quantum phase transitions between two topologically nontrivial phases. We show how this picture generalizes to multiband critical models belonging to any of the chiral symmetry classes AIII, BDI, or CII of noninteracting fermions in one dimension.
23.	Husain, Sajid, et al. (author) Emergence of spin-orbit torques in 2D transition metal dichalcogenides: A status update 2020 In: Applied Physics Reviews. - : AIP Publishing. - 1931-9401. ; 7:4 Journal article (peer-reviewed)abstract Spin-orbit coupling (SOC) in two-dimensional (2D) materials has emerged as a powerful tool for designing spintronic devices. On the one hand, the interest in this respect for graphene, the most popular 2D material with numerous fascinating and exciting properties, is fading due to the absence of SOC. On the other hand, 2D transition metal dichalcogenides (TMDs) are known to exhibit rich physics including large SOC. TMDs have been used for decades in a variety of applications such as nano-electronics, photonics, optoelectronics, sensing, and recently also in spintronics. Here, we review the current progress in research on 2D TMDs for generating spin-orbit torques in spin-logic devices. Several challenges connecting to thin film growth, film thickness, layer symmetry, and transport properties and their impact on the efficiency of spintronic devices are reviewed. How different TMDs generate spin-orbit torques in magnetic heterostructures is discussed in detail. Relevant aspects for improving the quality of the thin film growth as well as the efficiency of the generated spin-orbit torques are discussed together with future perspectives in the field of spin-orbitronics.
24.	Ye, Chen, et al. (author) Optimizing photon upconversion by decoupling excimer formation and triplet triplet annihilation 2020 In: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 22:3, s. 1715-1720 Journal article (peer-reviewed)abstract Perylene is a promising annihilator candidate for triplet-triplet annihilation photon upconversion, which has been successfully used in solar cells and in photocatalysis. Perylene can, however, form excimers, reducing the energy conversion efficiency and hindering further development of TTA-UC systems. Alkyl substitution of perylene can suppress excimer formation, but decelerate triplet energy transfer and triplet-triplet annihilation at the same time. Our results show that mono-substitution with small alkyl groups selectively blocks excimer formation without severly compromising the TTA-UC efficiency. The experimental results are complemented by DFT calculations, which demonstrate that excimer formation is suppressed by steric repulsion. The results demonstrate how the chemical structure can be modified to block unwanted intermolecular excited state relaxation pathways with minimal effect on the preferred ones.
25.	Gran, Ulf, 1973, et al. (author) Plasmons in holographic graphene 2020 In: SciPost Physics. - : SCIPOST FOUNDATION. - 2542-4653. ; 8:6 Journal article (peer-reviewed)abstract We demonstrate how self-sourced collective modes - of which the plasmon is a prominent example due to its relevance in modern technological applications - are identified in strongly correlated systems described by holographic Maxwell theories. The characteristic ω ∝ pk plasmon dispersion for 2D materials, such as graphene, naturally emerges from this formalism. We also demonstrate this by constructing the first holographic model containing this feature. This provides new insight into modeling such systems from a holographic point of view, bottom-up and top-down alike. Beyond that, this method provides a general framework to compute the dynamical charge response of strange metals, which has recently become experimentally accessible due to the novel technique of momentum-resolved electron energy-loss spectroscopy (M-EELS). This framework therefore opens up the exciting possibility of testing holographic models for strange metals against actual experimental data.
26.	Hyldgaard, Per, 1964, et al. (author) Screening nature of the van der Waals density functional method: A review and analysis of the many-body physics foundation 2020 In: Journal of Physics Condensed Matter. - 0953-8984 .- 1361-648X. ; 32:39 Journal article (peer-reviewed)abstract We review the screening nature and many-body physics foundation of the van der Waals density functional (vdW-DF) method [Berland K et al 2015 Rep. Prog. Phys. 78 066501], a systematic approach to construct truly nonlocal exchange–correlation energy density functionals. To that end we define and focus on a class of consistent vdW-DF versions that adhere to the Lindhard screening logic of the full method formulation. The consistent-exchange vdW-DF-cx version [Berland K and Hyldgaard P 2014 Phys. Rev. B 89 035412] and its spin extension [Thonhauser T et al 2015 Phys. Rev. Lett. 115 136402] represent the first examples of this class; in general, consistent vdW-DFs reflect a concerted expansion of a formal recast of the adiabatic-connection formula [Hyldgaard P et al 2014 Phys. Rev. B 90 075148], an exponential summation of contributions to the local-field response, and the Dyson equation. We argue that the screening emphasis is essential because the exchange–correlation energy reflects an effective electrodynamics set by a long-range interaction. Two consequences are that (1) there are, in principle, no wiggle room in how one balances exchange and correlation, for example, in vdW-DF-cx, and that (2) consistent vdW-DFs have a formal structure that allows them to incorporate vertex-correction effects, at least in the case of levels that experience recoil-less interactions (for example, near the Fermi surface). We explore the extent to which the strictly nonempirical vdW-DF-cx formulation can serve as a systematic extension of the constraint-based semilocal functionals. For validation, we provide a complete survey of vdW-DF-cx performance for broad molecular processes, for the full set of 55 benchmarks in GMTKN55 [Goerigk L et al 2017 Phys. Chem. Chem. Phys. 19 32184] and comparing to the quantum-chemistry calculations that are summarized in that paper. We also provide new vdW-DF-cx results for metal surface energies and work functions that we compare to experiment. Finally, we use the screening insight to separate the vdW-DF nonlocal-correlation term into pure-vdW-interaction and local-field-susceptibility effects and present tools to compute and map the binding signatures.
27.	Hooton, M.J., et al. (author) Spi-OPS: Spitzer and CHEOPS confirm the near-polar orbit of MASCARA-1 b and reveal a hint of dayside reflection 2022 In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 658 Journal article (peer-reviewed)abstract Context. The light curves of tidally locked hot Jupiters transiting fast-rotating, early-type stars are a rich source of information about both the planet and star, with full-phase coverage enabling a detailed atmospheric characterisation of the planet. Although it is possible to determine the true spin-orbit angle ψ-a notoriously difficult parameter to measure-from any transit asymmetry resulting from gravity darkening induced by the stellar rotation, the correlations that exist between the transit parameters have led to large disagreements in published values of ψ for some systems. Aims. We aimed to study these phenomena in the light curves of the ultra-hot Jupiter MASCARA-1 b, which is characteristically similar to well-studied contemporaries such as KELT-9 b and WASP-33 b. Methods. We obtained optical CHaracterising ExOPlanet Satellite (CHEOPS) transit and occultation light curves of MASCARA-1 b, and analysed them jointly with a Spitzer/IRAC 4.5 μm full-phase curve to model the asymmetric transits, occultations, and phase-dependent flux modulation. For the latter, we employed a novel physics-driven approach to jointly fit the phase modulation by generating a single 2D temperature map and integrating it over the two bandpasses as a function of phase to account for the differing planet-star flux contrasts. The reflected light component was modelled using the general ab initio solution for a semi-infinite atmosphere. Results. When fitting the CHEOPS and Spitzer transits together, the degeneracies are greatly diminished and return results consistent with previously published Doppler tomography. Placing priors informed by the tomography achieves even better precision, allowing a determination of ψ = 72.1-2.4+2.5 deg. From the occultations and phase variations, we derived dayside and nightside temperatures of 3062-68+66 K and 1720 ± 330 K, respectively.Our retrieval suggests that the dayside emission spectrum closely follows that of a blackbody. As the CHEOPS occultation is too deep to be attributed to blackbody flux alone, we could separately derive geometric albedo Ag = 0.171-0.068+0.066 and spherical albedo As = 0.266-0.100+0.097 from the CHEOPS data, and Bond albedoAB = 0.057-0.101+0.083 from the Spitzer phase curve.Although small, the Ag and As indicate that MASCARA-1 b is more reflective than most other ultra-hot Jupiters, where H- absorption is expected to dominate. Conclusions. Where possible, priors informed by Doppler tomography should be used when fitting transits of fast-rotating stars, though multi-colour photometry may also unlock an accurate measurement of ψ. Our approach to modelling the phase variations at different wavelengths provides a template for how to separate thermal emission from reflected light in spectrally resolved James Webb Space Telescope phase curve data.
28.	Aalbers, J., et al. (author) A next-generation liquid xenon observatory for dark matter and neutrino physics 2023 In: Journal of Physics G: Nuclear and Particle Physics. - : IOP Publishing. - 0954-3899 .- 1361-6471. ; 50:1 Research review (peer-reviewed)abstract The nature of dark matter and properties of neutrinos are among the most pressing issues in contemporary particle physics. The dual-phase xenon time-projection chamber is the leading technology to cover the available parameter space for weakly interacting massive particles, while featuring extensive sensitivity to many alternative dark matter candidates. These detectors can also study neutrinos through neutrinoless double-beta decay and through a variety of astrophysical sources. A next-generation xenon-based detector will therefore be a true multi-purpose observatory to significantly advance particle physics, nuclear physics, astrophysics, solar physics, and cosmology. This review article presents the science cases for such a detector.
29.	Kersting, Magdalena, et al. (author) What is the role of the body in science education? A conversation between traditions 2023 In: Science & Education. - : Springer. - 0926-7220 .- 1573-1901. Journal article (peer-reviewed)abstract Bodily engagement with the material and sociocultural world is ubiquitous in doing and learning science. However, science education researchers have often tended to emphasize the disembodied and nonmaterial aspects of science learning, thereby overlooking the crucial role of the body in meaning-making processes. While in recent years we have seen a turn towards embracing embodied perspectives, there persist considerable theoretical and methodological differences within research on embodiment in science education that hamper productive discourse. What is needed is a careful examination of how different traditions and disciplines, among them philosophy, social semiotics, and cognitive science, bear on embodiment in science education research. This paper aims to explore and articulate the differences and convergences of embodied perspectives in science education research in the form of a dialogue between three fictitious personas that stand for the cognitive, social-interactionist, and phenomenological research traditions. By bringing these traditions into dialogue, we aim to better position the role of the body in the science education research landscape. In doing so, we take essential steps towards unifying terminology across different research traditions and further exploring the implications of embodiment for science education research.
30.	Lindberg, Simon, 1987, et al. (author) Charge storage mechanism of α-MnO2 in protic and aprotic ionic liquid electrolytes 2020 In: Journal of Power Sources. - : Elsevier BV. - 0378-7753 .- 1873-2755. ; 460 Journal article (peer-reviewed)abstract In this work we have investigated the charge storage mechanism of MnO2 electrodes in ionic liquid electrolytes. We show that by using an ionic liquid with a cation that has the ability to form hydrogen bonds with the active material (MnO2) on the surface of the electrode, a clear faradaic contribution is obtained. This situation is found for ionic liquids with cations that have a low pKa, i.e. protic ionic liquids. For a protic ionic liquid, the specific capacity at low scan rate rates can be explained by a densely packed layer of cations that are in a standing geometry, with a proton directly interacting through a hydrogen bond with the surface of the active material in the electrode. In contrast, for aprotic ionic liquids there is no interaction and only a double layer contribution to the charge storage is observed. However, by adding an alkali salt to the aprotic ionic liquid, a faradaic contribution is obtained from the insertion of Li+ into the surface of the MnO2 electrode. No effect can be observed when Li+ is added to the protic IL, suggesting that a densely packed cation layer in this case prevent Li-ions from reaching the active material surface.
31.	Catena, Riccardo, 1978, et al. (author) Dark matter-electron interactions in materials beyond the dark photon model 2023 In: Journal of Cosmology and Astroparticle Physics. - : IOP Publishing. - 1475-7516. ; 2023:3 Journal article (peer-reviewed)abstract The search for sub-GeV dark matter (DM) particles via electronic transitions in underground detectors attracted much theoretical and experimental interest in the past few years. A still open question in this field is whether experimental results can in general be interpreted in a framework where the response of detector materials to an external DM probe is described by a single ionisation or crystal form factor, as expected for the so-called dark photon model. Here, ionisation and crystal form factors are examples of material response functions: interaction-specific integrals of the initial and final state electron wave functions. In this work, we address this question through a systematic classification of the material response functions induced by a wide range of models for spin-0, spin-1/2 and spin-1 DM. We find several examples for which an accurate description of the electronic transition rate at DM direct detection experiments requires material response functions that go beyond those expected for the dark photon model. This concretely illustrates the limitations of a framework that is entirely based on the standard ionisation and crystal form factors, and points towards the need for the general response-function-based formalism we pushed forward recently [1,2]. For the models that require non-standard atomic and crystal response functions, we use the response functions of [1,2] to calculate the DM-induced electronic transition rate in atomic and crystal detectors, and to present 90% confidence level exclusion limits on the strength of the DM-electron interaction from the null results reported by XENON10, XENON1T, EDELWEISS and SENSEI.
32.	Eriksson, Jakob, 1996, et al. (author) General Bounds on Electronic Shot Noise in the Absence of Currents 2021 In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 127:13 Journal article (peer-reviewed)abstract We investigate the charge and heat electronic noise in a generic two-terminal mesoscopic conductor in the absence of the corresponding charge and heat currents. Despite these currents being zero, shot noise is generated in the system. We show that, irrespective of the conductor's details and the specific nonequilibrium conditions, the charge shot noise never exceeds its thermal counterpart, thus establishing a general bound. Such a bound does not exist in the case of heat noise, which reveals a fundamental difference between charge and heat transport under zero-current conditions.
33.	Kuttruff, Joel, et al. (author) Magneto-Optical Activity in Nonmagnetic Hyperbolic Nanoparticles 2021 In: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 127 Journal article (peer-reviewed)abstract Active nanophotonics can be realized by controlling the optical properties of materials with external magnetic fields. Here, we explore the influence of optical anisotropy on the magneto-optical activity in nonmagnetic hyperbolic nanoparticles. We demonstrate that the magneto-optical response is driven by the hyperbolic dispersion via the coupling of metallic-induced electric and dielectric-induced magnetic dipolar optical modes with static magnetic fields. Magnetic circular dichroism experiments confirm the theoretical predictions and reveal tunable magneto-optical activity across the visible and near infrared spectral range.
34.	Kilde Löfgren, Sebastian, 1991, et al. (author) Rolling balls or trapping ions? How students relate models to real-world phenomena in the physics laboratory 2023 In: Science Education. - 0036-8326 .- 1098-237X. ; 107:5, s. 1215-37 Journal article (peer-reviewed)abstract The creation and use of models in science is of great importance for knowledge production and communication. For example, toy models are often used as idealized explanatory models in physics education. Models can be a powerful tool for exploring phenomena in ways that facilitate learning. However, careful consideration of instruction and explanations needs to be considered to guide how students relate models to real-world phenomena in subject-correct ways. A design experiment was conducted to investigate how upper secondary school students can use models for learning in the physics laboratory. The intervention used in the study was a laboratory exercise developed over three phases where students worked with a mechanical Paul trap and a simulation to understand the principle behind a real Paul trap. Each phase of the study consisted of three to five laboratory sessions. The data were analyzed using thematic analysis and the learning process was understood using the theoretical framework of variation theory. From the results, it was possible to identify patterns of variation for successful lab groups and critical aspects and features students need to discern to effectively modelize the mechanical Paul trap. The findings also indicate that having students work with models can be a meaningful clarificatory process to develop a deeper understanding of the use and limitations of models in science.
35.	Monsel, Juliette, 1994, et al. (author) Optomechanical cooling with coherent and squeezed light: The thermodynamic cost of opening the heat valve 2021 In: Physical Review A. - 2469-9926 .- 2469-9934. ; 103:6 Journal article (peer-reviewed)abstract Ground-state cooling of mechanical motion by coupling to a driven optical cavity has been demonstrated in various optomechanical systems. In our paper, we provide a thermodynamic performance analysis of optomechanical sideband cooling in terms of a heat valve. As performance quantifiers, we examine not only the lowest reachable effective temperature (phonon number) but also the evacuated-heat flow as an equivalent to the cooling power of a standard refrigerator, as well as appropriate thermodynamic efficiencies, which all can be experimentally inferred from measurements of the cavity output light field. Importantly, in addition to the standard optomechanical setup fed by coherent light, we investigate two recent alternative setups for achieving ground-state cooling: replacing the coherent laser drive by squeezed light or using a cavity with a frequency-dependent (Fano) mirror. We study the dynamics of these setups within and beyond the weak-coupling limit and give concrete examples based on parameters of existing experimental systems. By applying our thermodynamic framework, we gain detailed insights into these three different optomechanical cooling setups, allowing a comprehensive understanding of the thermodynamic mechanisms at play.
36.	Volpe, Giovanni, 1979, et al. (author) Roadmap for optical tweezers 2023 In: Journal of Physics-Photonics. - : IOP Publishing. - 2515-7647. ; 5:2 Journal article (peer-reviewed)abstract Optical tweezers are tools made of light that enable contactless pushing, trapping, and manipulation of objects, ranging from atoms to space light sails. Since the pioneering work by Arthur Ashkin in the 1970s, optical tweezers have evolved into sophisticated instruments and have been employed in a broad range of applications in the life sciences, physics, and engineering. These include accurate force and torque measurement at the femtonewton level, microrheology of complex fluids, single micro- and nano-particle spectroscopy, single-cell analysis, and statistical-physics experiments. This roadmap provides insights into current investigations involving optical forces and optical tweezers from their theoretical foundations to designs and setups. It also offers perspectives for applications to a wide range of research fields, from biophysics to space exploration.
37.	Fan, Qunping, 1989, et al. (author) High-performance all-polymer solar cells enabled by a novel low bandgap non-fully conjugated polymer acceptor 2021 In: Science in China Series B. - : Springer Nature. - 1674-7291 .- 1869-1870. ; 64, s. 1380-1388 Journal article (peer-reviewed)abstract Anon-fully conjugated polymer as a new class of acceptor materials has shown some advantages over its small molecular counterpart when used in photoactive layers for all-polymer solar cells (all-PSCs), despite a low power conversion efficiency (PCE) caused by its narrow absorption spectra. Herein, a novel non-fully conjugated polymer acceptor PFY-2TS with a low bandgap of similar to 1.40 eV was developed, via polymerizing a large pi-fused small molecule acceptor (SMA) building block (namely YBO) with a non-conjugated thioalkyl linkage. Compared with its precursor YBO, PFY-2TS retains a similar low bandgap but a higher LUMO level. Moreover, compared with the structural analog of YBO-based fully conjugated polymer acceptor PFY-DTC, PFY-2TS shows similar absorption spectrum and electron mobility, but significantly different molecular crystallinity and aggregation properties, which results in optimal blend morphology with a polymer donor PBDB-T and better device physical processes in all-PSCs. As a result, PFY-2TS-based all-PSCs achieved a PCE of 12.31% with a small energy loss of 0.56 eV enabled by the reduced non-radiative energy loss (0.24 eV), which is better than that of 11.08% for the PFY-DTC-based ones. Our work clearly demonstrated that non-fully conjugated polymers as a new class of acceptor materials are very promising for the development of high-performance all-PSCs.
38.	Hertzog, Manuel, 1989, et al. (author) Enhancing Vibrational Light-Matter Coupling Strength beyond the Molecular Concentration Limit Using Plasmonic Arrays 2021 In: Nano Letters. - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 21:3, s. 1320-1326 Journal article (peer-reviewed)abstract Vibrational strong coupling is emerging as a promising tool to modify molecular properties by making use of hybrid light-matter states known as polaritons. Fabry-Perot cavities filled with organic molecules are typically used, and the molecular concentration limits the maximum reachable coupling strength. Developing methods to increase the coupling strength beyond the molecular concentration limit are highly desirable. In this Letter, we investigate the effect of adding a gold nanorod array into a cavity containing pure organic molecules using FT-IR microscopy and numerical modeling. Incorporation of the plasmonic nanorod array that acts as artificial molecules leads to an order of magnitude increase in the total coupling strength for the cavity with matching resonant frequency filled with organic molecules. Additionally, we observe a significant narrowing of the plasmon line width inside the cavity. We anticipate that these results will be a step forward in exploring vibropolaritonic chemistry and may be used in plasmon based biosensors.
39.	Kjellander, Roland, 1948 (author) En molekylär introduktion till termodynamik 2020 Book (other academic/artistic)abstract Begreppen entropi och fri energi har genom tiderna visat sig särskilt svåra att få grepp om och att förstå för så gott som alla studenter. Termodynamik framställs vanligen på ett ganska matematiskt och abstrakt sätt, vilket ger upphov till denna sorts svårighet. Denna bok visar dock att det inte alltid krävs en massa matematik för att få en intuitiv förståelse av termodynamikens väsentligaste principer om de belyses utifrån molekylära sammanhang. Framställningen är i stor utsträckning baserad på bilder och enkla resonemang som leder till de korrekta matematiska sambanden. Boken är upplagd så att den kan användas på förstaårsnivå och uppåt inom universitets- och högskolestudier i naturvetenskapliga ämnen. Den kan läsas som en fristående bok eller utgöra ett komplement till den gängse kurslitteraturen.
40.	Larsson, Johanna, 1986-, et al. (author) On the periphery of university physics : trainee physics teachers’ experiences of learning undergraduate physics 2021 In: European journal of physics. - : Institute of Physics Publishing (IOPP). - 0143-0807 .- 1361-6404. ; 42:5 Journal article (peer-reviewed)abstract High school physics teachers have a difficult job to do. On the one hand, they are charged with contributing to the creation of a scientifically literate society, while on the other they play a pivotal role in the recruitment of future physicists. Given the importance of this dual role, one might expect that the training of future physics teachers would be a priority for any physics department. However, research suggests that this is often not the case. While concerns have been raised about future physics teachers' understanding of physics content, less work has focussed on the sociocultural experiences of the learning environments trainees meet when learning undergraduate physics. This case study examines how a sample of trainee physics teachers perceive learning undergraduate physics content together with engineering and physics bachelor students in a large, high-status, research-oriented physics department. The findings aim to be of interest to physics lecturers when examining their own practice. We interviewed 17 trainee physics teachers about their experiences of learning undergraduate physics, how they perceived the relevance of their physics courses for their future role as teachers, and how this affected their physics learning. Here, we identified four central themes of the students' experiences: (1) teacher programme invisibility, (2) passive classroom culture, (3) perceived relevance of physics courses, and (4) no incentive to do well in physics. We discuss how this study illustrates the potential struggles trainee physics teachers may encounter when learning undergraduate physics. We also suggest how our findings may be used to inform the practice of university physics lecturers who come in contact with trainee physics teachers, and comment on the structure and organization of physics teacher education as a whole.
41.	Brookes, Paul, et al. (author) Critical slowing down in circuit quantum electrodynamics 2021 In: Science advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 7:21 Journal article (peer-reviewed)abstract Critical slowing down of the time it takes a system to reach equilibrium is a key signature of bistability in dissipative first-order phase transitions. Understanding and characterizing this process can shed light on the underlying many-body dynamics that occur close to such a transition. Here, we explore the rich quantum activation dynamics and the appearance of critical slowing down in an engineered superconducting quantum circuit. Specifically, we investigate the intermediate bistable regime of the generalized Jaynes-Cummings Hamiltonian (GJC), realized by a circuit quantum electrodynamics (cQED) system consisting of a transmon qubit coupled to a microwave cavity. We find a previously unidentified regime of quantum activation in which the critical slowing down reaches saturation and, by comparing our experimental results with a range of models, we shed light on the fundamental role played by the qubit in this regime.
42.	Holmvall, Patric, 1988, et al. (author) Phase crystals 2020 In: Physical Review Research. - 2643-1564. ; 2:1 Journal article (peer-reviewed)abstract Superconductivity owes its properties to the phase of the electron pair condensate that breaks the U(1) symmetry. In the most traditional ground state, the phase is uniform and rigid. The normal state can be unstable towards special inhomogeneous superconducting states: the Abrikosov vortex state and the Fulde-Ferrell-Larkin-Ovchinnikov state. Here we show that the phase-uniform superconducting state can go into a fundamentally different and more ordered nonuniform ground state, which we refer to as a phase crystal. This state breaks translational invariance through formation of a spatially periodic modulation of the phase, manifested by unusual superflow patterns and circulating currents, that also break time-reversal symmetry. We list the general conditions needed for realization of phase crystals. Using microscopic theory, we then derive an analytic expression for the superfluid density tensor for the case of a nonuniform environment in a semi-infinite superconductor. We demonstrate how the surface quasiparticle states enter the superfluid density and identify phase crystallization as the main player in several previous numerical observations in unconventional superconductors, and predict the existence of a similar phenomenon in superconductor-ferromagnetic structures. This analytic approach provides a unifying aspect for the exploration of boundary-induced quasiparticles and collective excitations in superconductors. More generally, we trace the origin of phase crystallization to nonlocal properties of the gradient energy, which implies the existence of similar pattern-forming instabilities in many other contexts.
43.	Muralidhar, Shreyas, et al. (author) Femtosecond Laser Pulse Driven Caustic Spin Wave Beams 2021 In: Physical Review Letters. - : American Physical Society (APS). - 0031-9007 .- 1079-7114. ; 126:3 Journal article (peer-reviewed)abstract © 2021 authors. Controlling the directionality of spin waves is a key ingredient in wave-based computing methods such as magnonics. In this Letter, we demonstrate this particular aspect by using an all-optical pointlike source of continuous spin waves based on frequency comb rapid demagnetization. The emitted spin waves contain a range of k vectors and by detuning the applied magnetic field slightly off the ferromagnetic resonance (FMR), we observe X-shaped caustic spin wave patterns at 70° propagation angles as predicted by theory. When the harmonic of the light source approaches the FMR, the caustic pattern gives way to uniaxial spin wave propagation perpendicular to the in-plane component of the applied field. This field-controlled propagation pattern and directionality of optically emitted short-wavelength spin waves provide additional degrees of freedom when designing magnonic devices.
44.	Tello Marmolejo, Javier, 1995, et al. (author) Fano Combs in the Directional Mie Scattering of a Water Droplet 2023 In: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 130:4 Journal article (peer-reviewed)abstract When light scatters off a sphere, it produces a rich Mie spectrum full of overlapping resonances. Single resonances can be explained with a quantum analogy and result in Fano profiles. However, the full spectrum is so complex that recognizable patterns have not been found, and is only understood by comparing to numerical simulations. Here we show the directional Mie spectrum of evaporating water droplets arranged in consecutive Fano Combs. We then fully explain it by expanding the quantum analogy. This turns the droplet into an "optical atom"with angular momentum, tunneling, and excited states.
45.	Zhong, Shiyang, et al. (author) Attosecond electron–spin dynamics in Xe 4d photoionization 2020 In: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 11:1 Journal article (peer-reviewed)abstract The photoionization of xenon atoms in the 70–100 eV range reveals several fascinating physical phenomena such as a giant resonance induced by the dynamic rearrangement of the electron cloud after photon absorption, an anomalous branching ratio between intermediate Xe+ states separated by the spin-orbit interaction and multiple Auger decay processes. These phenomena have been studied in the past, using in particular synchrotron radiation, but without access to real-time dynamics. Here, we study the dynamics of Xe 4d photoionization on its natural time scale combining attosecond interferometry and coincidence spectroscopy. A time-frequency analysis of the involved transitions allows us to identify two interfering ionization mechanisms: the broad giant dipole resonance with a fast decay time less than 50 as, and a narrow resonance at threshold induced by spin-flip transitions, with much longer decay times of several hundred as. Our results provide insight into the complex electron-spin dynamics of photo-induced phenomena.
46.	Mony, Jürgen, et al. (author) Photoisomerization Efficiency of a Solar Thermal Fuel in the Strong Coupling Regime 2021 In: Advanced Functional Materials. - : Wiley. - 1616-301X .- 1616-3028. ; 31:21 Journal article (peer-reviewed)abstract Strong exciton-photon coupling is achieved when the interaction between molecules and an electromagnetic field is increased to a level where they cannot be treated as separate systems. This leads to the formation of polaritonic states and an effective rearrangement of the potential energy surfaces, which opens the possibility to modify photochemical reactions. This work investigates how the strong coupling regime is affecting the photoisomerization efficiency and thermal backconversion of a norbornadiene-quadricyclane molecular photoswitch. The quantum yield of photoisomerization shows both an excitation wavelength and exciton/photon constitution dependence. The polariton-induced decay and energy transfer processes are discussed to be the reason for this finding. Furthermore, the thermal back conversion of the system is unperturbed and the lower polariton effectively shifts the absorption onset to lower energies. The reason for the unperturbed thermal backconversion is that it occurs on the ground state, which is unaffected. This work demonstrates how strong coupling can change material properties towards higher efficiencies in applications. Importantly, the experiments illustrate that strong coupling can be used to optimize the absorption onset of the molecular photoswitch norbonadiene without affecting the back reaction from the uncoupled quadricyclane.
47.	Wang, Yanan, et al. (author) The radio detection and accretion properties of the peculiar nuclear transient AT 2019avd 2023 In: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 520:2, s. 2417-2435 Journal article (peer-reviewed)abstract AT 2019avd is a nuclear transient detected from infrared to soft X-rays, though its nature is yet unclear. The source has shown two consecutive flaring episodes in the optical and the infrared bands, and its second flare was covered by X-ray monitoring programs. During this flare, the UVOT/Swift photometries revealed two plateaus: one observed after the peak and the other one appeared similar to 240 d later. Meanwhile, our NICER and XRT/Swift campaigns show two declines in the X-ray emission, one during the first optical plateau and one 70-90 d after the optical/UV decline. The evidence suggests that the optical/UV could not have been primarily originated from X-ray reprocessing. Furthermore, we detected a timelag of similar to 16-34 d between the optical and UV emission, which indicates the optical likely comes from UV reprocessing by a gas at a distance of 0.01-0.03 pc. We also report the first VLA and VLBA detection of this source at different frequencies and different stages of the second flare. The information obtained in the radio band - namely a steep and a late-time inverted radio spectrum, a high brightness temperature and a radio-loud state at late times - together with the multiwavelength properties of AT 2019avd suggests the launching and evolution of outflows such as disc winds or jets. In conclusion, we propose that after the ignition of black hole activity in the first flare, a super-Eddington flaring accretion disc formed and settled to a sub-Eddington state by the end of the second flare, associated with a compact radio outflow.
48.	Sarmad, Shokat, et al. (author) Amine functionalized deep eutectic solvent for CO2 capture : Measurements and modeling 2020 In: Journal of Molecular Liquids. - : Elsevier. - 0167-7322 .- 1873-3166. ; 309 Journal article (peer-reviewed)abstract Deep eutectic solvents (DESs) have gained a great interest among researchers owing to their inherent advantages to become an adaptable alternative to ionic liquids (ILs) and common amine solutions for CO2 capture. In the present study, we prepared five new three-component DESs by functionalization of choline chloride-ethanolamine (1,7, mol,mol) DES using different types of amines: diethanolamine (amine type 2), methyldiethanolamine (amine type 3), piperazine (amine type 2) as well as 1-(2-aminoethyl)piperazine (amine type 1 and 2). All of the prepared DESs are liquid at room temperature and their melting points were in the range of 265–276 K. The solubility of CO2 in the studied DESs was measured at pressures up to 2 MPa and 298.15 K. The obtained experimental data were analyzed by the use of generic Redlich-Kwong equation of state (RK-EOS) model and Henry's law constant have been calculated from the obtained experimental data through the EOS correlation. All the studied DESs show chemical absorption of CO2 which can be approved based on the excess enthalpy and Gibbs energy functions. FT-IR spectroscopy and 13C NMR verified the formation of carbamate in the CO2 absorption process which revealed the chemisorption of CO2 in the studied DESs. The ideal association model has been utilized to describe the excess thermodynamic functions and two different types of the chemical association have been detected AB2 and AB, (A refer to DESs and B to CO2). Based on the obtained solubility data, the amines that enhanced the absorption capacity of choline chloride-ethanolamine (1,7) follow the trend as follows: piperazine > aminoethylpiperazine > methyldiethanolamine > diethanolamine. Therefore, piperazine can be considered as an absorption enhancer. The viscosity of DESs before and after CO2 absorption as well as the thermal behavior of the DESs were also investigated.
49.	Airey, John, 1963- (author) Thinking About English-Medium Instruction: Do We Need Everything Everywhere All at Once? 2023 Conference paper (peer-reviewed)abstract Thinking About English-Medium Instruction: Do We Need Everything Everywhere All at Once? Around the world, more and more university courses are being taught in English. Although there are sound economic, social and political reasons for this trend, many questions remain about the pedagogical effects of EMI at university level: How can teachers be prepared for EMI teaching? Will students cope? Are some forms of teaching less suited to EMI? Do different disciplines have different needs? Etc. etc. In this workshop, I present some of the research I have carried out in Sweden that addresses these questions and make a number of recommendations. I finish the workshop by proposing a disciplinary literacy discussion matrix (Airey, 2011) as a tool for carrying out disciplinary needs analysis for EMI. ReferencesAirey, J. (2011). The disciplinary literacy discussion matrix: A heuristic tool for initiating collaboration in higher education. Across the disciplines, 8(3), 1-9.
50.	Ivanjek, Lana, et al. (author) Enhancing Mathematization in Physics Education by Digital Tools 2024. - 1 In: Physics Education Today. - : Springer. - 9783031486661 - 9783031486678 ; , s. 35-53 Book chapter (peer-reviewed)abstract The GTG Mathematics in Physics Education follows the philosophy of supporting physics understanding by the conscious use of mathematical structures in physics teaching. We discuss the possible roles of digital tools in promoting physics understanding by fostering sense making of computational models, using geometrical visualizations or interpreting app-generated diagrams in a physics context. We look into three types of digital tools: (a) Smartphone apps that allow data collection from the phone’s internal sensors to effortlessly produce graphical representations of the data. (b) GeoGebra, that combines different mathematical representations and allows their visualization and manipulation. (c) Computational modeling via Vpython where students can build or manipulate a computational model and compare it to experimental results. We will describe the potential of these tools to improve understanding of different mathematical features in physics, as well as obstacles that educators should take into account. In addition we present some empirical findings concerning graphs from smartphone apps and experiences from teacher professional development.

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