SOLARIS – Page 2 – Lightsources.org

Perovskite phase symmetry influence the cobalt modifier position

2024/12/302025/01/09

A research group from the AGH University of Krakow, specializing in material chemistry, in collaboration with the SOLARIS Center, has published findings on the impact of phase symmetry in the CaTiO₃ – SrTiO₃ perovskite system on the incorporation of cobalt into the perovskite structure. These cobalt-modified materials are promising for applications in energy conversion technologies and environmental catalysis. The findings, published in Materials Chemistry and Physics, revealed distinct behaviors between calcium-rich (Ca-rich) and strontium-rich (Sr-rich) perovskite materials. The study also examined the impact of non-stoichiometry on both, the position occupied by cobalt in the structure and its oxidation state. A comprehensive understanding of the structural changes in the system was achieved through an innovative approach combining X-ray absorption spectroscopy (XAS) analysis, conducted at the ASTRA beamline, with results from temperature-programmed reduction (TPR) studies.

Ca-rich materials, characterized by orthorhombic symmetry, more effectively incorporate cobalt into the perovskite structure but also tend to form a secondary phase – CoTiO₃. In contrast, Sr-rich materials with tetragonal symmetry predominantly lead to the formation of cobalt oxides, particularly Co₃O₄. The slight deviations from stoichiometry (a deficiency of atoms in the Ca/Sr sublattice) intensify these effects: in Ca-rich materials, they increase the proportion of the CoTiO₃ phase in the system, while in Sr-rich materials, they result in a higher content of cobalt oxides. Additionally, XAS and TPR results revealed that Ca-rich materials contain more cobalt in the +II oxidation state, while Sr-rich materials contain more cobalt in the +III oxidation state.

These findings open new possibilities for designing materials and optimizing their properties for potential applications in catalysis and electrochemical devices. At the same time, they significantly enhance the understanding of solid-state chemistry, particularly the chemistry of materials with a perovskite-type structure.

Designed, pH-reversible synthetic protein cage

2024/12/202025/01/09

In this study published in Macromolecular Rapid Communications, a team of researchers from Centre for Programmable Biological Matter (Durham University), Malopolska Centre of Biotechnology and NSRC SOLARIS lead by prof. Jonathan Heddle designed a programmable artificial protein cage build from TRAP protein, that is sensitive to pH and can be disassembled on demand.

The rational design and production of a novel series of engineered protein cages are presented, which have emerged as versatile and adaptable platforms with significant applications in biomedicine. These protein cages are assembled from multiple protein subunits, and precise control over their interactions is crucial for regulating assembly and disassembly, such as the on-demand release of encapsulated therapeutic agents.

This approach employs a homo-undecameric, ring-shaped protein scaffold with strategically positioned metal binding sites. These engineered proteins can self-assemble into highly stable cages in the presence of cobalt or zinc ions. Furthermore, the cages can be disassembled on demand by employing external triggers such as chelating agents and changes in pH. Interestingly, for certain triggers, the disassembly process is reversible, allowing the cages to reassemble upon reversal or outcompeting of triggering conditions/agents.

This work offers a promising platform for the development of advanced drug delivery systems and other biomedical applications.

Image: Artistic representation of the designed protein cage geometry

Credit: Izabela Czernecka

Striking structural similarities in RNA of four Betacoronaviruses

2024/11/192024/11/22

In a study published in Nucleic Acids Research, a team from the International Institute of Molecular and Cell Biology in Warsaw (IIMCB), led by Prof. Janusz Bujnicki, in collaboration with the Spanish National Research Council (CSIC) in Madrid and the Jagiellonian University in Krakow, made a significant discovery regarding the four main types of betacoronaviruses, including the deadly viruses SARS-CoV-2 and MERS, as well as the OC43 virus that causes colds. The research was carried out using the research infrastructure of the SOLARIS National Synchrotron Radiation Centre.

The scientists analyzed the ribonucleic acid (RNA) molecules – the genetic material of betacoronaviruses. The RNA nucleotide sequences of coronaviruses, which are about 30,000 nucleotides long, differ significantly from each other. In this work, detailed analyses focused on examining the spatial structure and dynamics of about 500 nucleotides at the very beginning of the viral RNA (the “5′ end”), which plays a crucial role in the replication of viruses in infected cells.

The 5′ ends of the genomic RNA of four different coronaviruses were examined using advanced biochemical, biophysical, and bioinformatics techniques, including chemical probing, cryo-electron microscopy, atomic force microscopy, and computer modeling. The results revealed the presence of very similar structural elements, despite being formed by different nucleotide sequences in the RNA of various betacoronaviruses.

“This discovery is fundamental for understanding the similarities in the functioning of betacoronaviruses,” says Prof. Janusz Bujnicki from the IIMCB, the project leader. “The spatial structures we have identified in the RNA molecules of viruses may contribute to the development of new antiviral drugs in the future.”

The significance of the published discovery goes beyond understanding the SARS-CoV-2 virus responsible for the COVID-19 pandemic and sheds new light on the molecular mechanisms of how all coronaviruses function.

This research was possible thanks to the international collaboration of scientists from Warsaw, Krakow, and Madrid. The project was initiated as part of the COVID-19 research program, funded by the National Science Centre (grant 2020/01/0/NZ1/00232), and then continued with support from other national and international sources. Key to success was the effective cooperation of experts from various fields of science.

Image: Evolutionarily conserved structures of SL5 regulatory elements in Betacoronavirus RNA genomes

MCB JU researchers discovered a mechanism regulating the essential process of hypusination

2024/10/302024/10/30

A research team from the Malopolska Centre of Biotechnology at Jagiellonian University (MCB UJ), led by dr hab. Przemysław Grudnik, in collaboration with scientists from the Medical College of Wisconsin, has uncovered an unusual role of the ERK1/2 kinases in the regulation of a unique post translational modification, hypusination. This breakthrough not only bridges a gap in our understanding of the mechanisms controlling hypusination, an essential process for the human body, but also reveals a surprising function of ERK1/2. These findings have recently been published in the scientific journal “Cell Reports”.

Hypusination is a highly specific modification of eukaryotic translation factor 5A (eIF5A), and deoxyhypusine synthase (DHPS) is responsible for catalyzing the first and limiting step of this process. Hypusination enables eIF5A to facilitate the synthesis of other proteins in the cells, which is a fundamental process. Despite its critical function in cellular homeostasis, the regulation of hypusination remains elusive. Researchers at MCB have started to unravel the mechanisms controlling hypusination and have shown the new unexpected finding that the extracellular signal regulated kinases 1/2 (ERK1/2) perform a non kinase function by directly interacting with DHPS to regulate hypusination. ERK1/2 are key enzymes in a signaling pathway, which is crucial in regulating cell growth, differentiation, and cell survival in human bodies. Until now, these proteins have been studied for their enzymatic (kinase) activity, which allows them to activate other proteins through phosphorylation (adding phosphate groups).

Researchers at MCB employed cryo-electron microscopy (cryo EM) to study the structure of the DHPS ERK2 complex. The data revealed that ERK2 binds to DHPS at the entrance to its active site, effectively blocking access for eIF5A. The findings also highlight how cellular signaling via the Raf/MEK/ERK pathway modulates ERK1/2 association with DHPS. When this pathway is activated, the interaction between ERK1/2 and DHPS decreases, allowing eIF5A to be hypusinated. Moreover, ERK1/2’s kinase activity controls how much DHPS and eIF5A the cell produces. This discovery provides fresh insights into how cells regulate essential processes such as protein synthesis in response to external signals.

Image: Dr hab. Przemysław Grudnik (on the right) and Paweł Kochanowski (on the left) are holding a model of the DHPS-ERK2 complex.

Study Unveils Local Geometry of Copper Cations inside the channels of Mesoporous Silica

2024/10/302024/10/30

A group of researchers from the Institute of Nuclear Physics Polish Academy of Sciences and the University of Lorraine, CNRS in France, conducted studies on the ASTRA line at the SOLARIS Centre. In their publication “Revealing the molecular structure of copper phosphonate groups anchored inside SBA-15 silica channels: Theoretical and experimental study,” they described the local geometry of copper cations immobilized by phosphonate groups in the mesoporous silica pores.

Mesoporous silica provides a versatile platform for creating a new generation hybrid inorganic organic mesoporous materials with pores accommodate distinct organometallic moieties,SBA-15 with propyl phosphonic acid, which serves as anchoring units for two-valent metal ions like copper can be considered a potential candidate in many industrial applications. Rerearchers have demonstrated previously that SBA-propyl-Cu can exhibit quite good Non-linear optical (NLO) response that can be tuned by changing the concentration of the functional unit inside the silica scaffold more over the same material exhibits strong biocidal properties which can be explained by the catalytic action of the copper ion that effectively converts O2 into the O2* radical,this radical promotes oxidative damage to biomolecules.

Image: Magnitude of Fourier transform of the EXAFS plotted vs radial distance of the central copper atom to other elements (R). The presented experimental spectrum was juxtaposed with the theoretical fit draw based on two theoretical models (presented at the right) with the assumed contribution and the signals typical for the assumed paths (a).

The search for the optimal anode material for Na-ion batteries

2024/10/302024/11/07

One of the most demanding challenges for Na-ion batteries is finding a suitable anode material that will provide high capacity, while at the same time its structure will not degrade during repeated sodiation and desodiation (processes that occur during the operation of cells). A group of researchers from the AGH University of Science and Technology and the Paul Scherrer Institute in Switzerland, conducting research on the ASTRA line, undertook an attempt to find a suitable material, and their studies were published in the journal “Energy Storage Materials”.

Among the many proposed anode materials, antimony attracts the attention of scientists because of its high theoretical capacity and good electrical conductivity. However, at the same time, its significant volume changes during operation can lead to the destruction of the material’s microstructure. A solution to the problem of volume changes can be the application of composite materials, where the matrix alleviates stresses. A research team has obtained a composite material Sb/Sb₄O₅Cl₂/C in which the Sb grains are characterized by a unique shape, branches. This morphology is advantageous for materials characterized by large volume changes when voids between branches are filled during operation. Electrochemical characterization results indicate that the composite material works in a more stable manner than individual phases that work separately.

Through measurements by multiple techniques, it was possible to determine the exact mechanism of sodiation and desodiation of this composite material. Unique operando XAS measurements during cell operation with the proposed anode material and metallic sodium were carried out on the ASTRA line. Measurements at the SOLARIS synchrotron made it possible to observe and understand the incomplete reversibility of the reaction in the first cycle of the material and to identify the source of the additional capacitance observed in sodiation below 0.4 V and in desodiation above 1.0 V.

The activity of three phases was observed in the proposed composite material: Sb, Sb₄O₅Cl₂, and C, and demonstrated high mechanical integrity of the electrode by providing space for volume changes in the branch-like shape. At the same time, the presence of an amorphous matrix (originating from the products of the sodiated Sb₄O₅Cl₂ phase) allowed for buffer expansion and contraction of the material during operation.

Image: SEM picture of examined material.

SOLARIS International Projects – NEPHEWS

2024/10/282024/10/28

NEPHEWS (NEutrons and PHotons Elevating Worldwide Science), led by SOLARIS, is a project designed to provide scientists with access to world-class European research infrastructures.

The NEPHEWS project integrate two European Users Organisations: ESUO (European Synchrotron and Free Electron Laser User Organisation) and ENSA (European Neutron Scattering Association), with two largest and most advanced consortia, LEAPS (League of European Accelerator-based Photon Sources) and LENS (League of advanced European Neutron Sources). This initiative aims to develop a new way of cooperation, where neutron facilities work side by side with LEAPS Infrastructures. Additionally, NEPHEWS empowers users through an innovative User-to-User approach, granting ESUO and ENSA a pivotal role in project development.

The NEPHEWS project offers:

Experienced Users: Access to 38,290 hours of beamtime for conducting experiments on project-provided beamlines (TNA Programme);
New Users: Opportunities to join experienced user groups, allowing them to collaborate on measurements and enhance their knowledge (Twinning Programme);
Young Scientists: Week-long internships at large-scale research centres affiliated with the project, providing essential scientific and research training (ESR Programme);
Training Courses: Covering topics such as:
Implementing research using synchrotron facilities, neutron facilities, and free electron lasers, along with their complementary roles;
Infrastructure access procedures, including guidelines for successful beamtime applications.
Training for African Scientists: Selected scientists will receive training and attend the HERCULES school to advance their scientific expertise.

Furthermore, the project aims to establish collaboration with ministries and national funding agencies in developing countries. The objectives include raising awareness about the importance of research funding and fostering cooperation with user communities.

Dirac dispersions and Fermi surface nesting in LaCuSb2

2024/08/202024/08/22

A team composed of scientists from the National Synchrotron Radiation Centre SOLARIS, the Institute of Physics of the Jagiellonian University, the Institute of Nuclear Physics of the Polish Academy of Sciences (PAN), and the Institute of Low Temperature and Structure Research of the Polish Academy of Sciences (PAN), has published the results of their research on the superconducting compound LaCuSb₂. The experiment was conducted using the URANOS beamline at the SOLARIS synchrotron.

In the studies conducted on LaCuSb₂, a material from the RTSb₂ family (where R is a rare earth metal and T is a transition metal), interesting properties of its electronic structure were identified. This material is a superconductor with a transition temperature of approximately 0.9 K. To investigate its electronic structure, angle-resolved photoemission spectroscopy (ARPES) and density functional theory (DFT) calculations were employed.

The analysis of the Fermi surface and energy bands of LaCuSb₂ revealed the presence of linear dispersion relations corresponding to Dirac dispersions and nodal lines along the M–A and X–R directions. The Fermi surface of LaCuSb₂ is composed of four branches, with two inner branches having a more three-dimensional character. A significant finding was that the Fermi surface nesting in LaCuSb₂ is stronger than in the related material LaAgSb₂. Despite this, no charge density waves (CDW) were observed in LaCuSb₂, but they are present in LaAgSb₂, what makes an interesting contrast between these two compounds.

Image: Electronic structure of LaCuSb2 along the “X” ̅”-” “Γ” ̅”-” “X” ̅ direction, collected using 66 and 54 eV with LH and LV light polarizations. Green arrows indicate linear bands, and red arrows indicate Dirac-like band crossings. Calculated surface spectra for La-Sb and Sb terminations, using the surface Green function technique, are presented for comparison.

Structure and Mechanism of Human Elongator revealed

2024/08/072024/08/22

Scientists from the Max Planck Research Group at the MCB of the Jagiellonian University in Krakow fulfilled their longtime goal of understanding how human Elongator works. The research of dr hab. Sebastian Glatt’s team was performed in collaboration with the scientists from Kassel University and Berlin Technical University.
The multi-subunit Elongator complex is composed of two distinct subcomplexes, namely Elp123 and Elp456. The carboxymethyl group (cm5) introduced by Elongator serves as the basis for other enzymes for the synthesis of subsequent modifications. tRNAs with fully modified wobble uridines bind to translating ribosomes in an optimal manner and thus facilitate effective co-translational folding of emerging proteins. Structural biology and in vitro experiments were performed at MCB, with the assistance of the Structural Biology and Proteomics and Mass Spectrometry Core Facilities at MCB. Cryo-EM data was collected on the Titan Krios G3i, a high-end cryo-electron microscope located at SOLARIS National Synchrotron Radiation Centre. The team from Kassel conducted in vivo analyses, while the team from Berlin performed crosslinking mass spectrometry experiments.
The MCB team resolved the structure of the human Elongator complex at the highest resolution among all Elongator structures (2.9 Å), which is published so far. The structure shows human ELP123, in complex with tRNA and acetyl-CoA molecule. It precisely depicts the organization of the active site together with the tRNA anticodon stem loop, and modification target, namely the wobble uridine. The structure allowed to identify the unforeseen role of another universally conserved uridine adjacent to the wobble position which is important for the activity of ELP123. This collaborative work presents structural snapshots of the complex during intermediate stages of modification reaction. The authors also identified a series of conserved amino acid residues located in the active site of the catalytic subunit, which are necessary for the chemical reaction. All these findings were verified and supported by in vivo and in vitro experiments.

Image: Cryo-EM density map (left) and atomic model (right) of ELP123 subcomplex bound to tRNA and acetyl-CoA at a resolution of 2.87 Å

Relationship between enhanced electrochemical performance and partially amorphous material structure

2024/07/262024/07/29

A research team under the leadership of Sebastian Molin D.Sc., from the Faculty of Electronics, Telecommunications and Informatics at Gdańsk University of Technology (as part of a joint project with scientists from the Warsaw University of Technology and Kaunas University of Technology), in collaboration with ASTRA beamline scientists, characterised the perovskite oxide La_0.6Sr_)0.4CoO_3-δ as an oxygen electrode for solid oxide fuel cell technology. This material showed enhanced electrochemical efficiency for the reduction of oxygen when present in a partially amorphous form. Using X-ray absorption spectroscopy (XAS) at the SOLARIS synchrotron. The results of the study have been published in the journal of Applied Surface Science, published by Elsevier.

Image: Wavelet Transform calculated from EXAFS for La_0.6Sr_0.4CoO_3-δannealed at range 400 °C–700 °C.

Electronic Marvel of Tin

2024/07/182024/07/18

An international team of scientists has investigated the topological properties of grey tin (α-Sn), a low-temperature form of tin. They have successfully stabilized this form at room temperature by applying small compressive forces. Through a combination of complementary experimental techniques, the researchers demonstrated that α-Sn belongs to the class of Dirac topological semimetals and, under the influence of an external magnetic field, transforms into a Weyl semimetal phase. A significant part of the experiments exploring the fascinating electronic properties of this material was conducted at the URANOS beamline of the SOLARIS National Synchrotron Radiation Centre.

Tin, a seemingly ordinary and well-known material, reveals unique electronic properties under extreme conditions. Historically, α-Sn caused problems during harsh winters by destroying organ pipes in churches. However, this form now shows fascinating electronic properties. Scientists from the International Research Centre MagTop at the Institute of Physics of the Polish Academy of Sciences have stabilized and strained grey tin at room temperature on insulating substrates. The unusual electronic structure of α-Sn has been experimentally visualized using angle-resolved photoemission spectroscopy at the URANOS beamline at the SOLARIS Synchrotron Centre. The electron energy spectrum of α-Sn resembles a Dirac spectrum, typically observed in particles accelerated to speeds close to the speed of light. This discovery was further supported by magneto-optical experiments and theoretical calculations conducted by researchers from Johannes Kepler Universität in Linz and Ecole Normale Supérieure in Paris. Electrical transport measurements at the MagTop center revealed that applying a magnetic field parallel to the electrical current results in an unusual drop in resistance, manifesting the chiral anomaly, a phenomenon known from high-energy physics. The unique electronic structure of grey tin paves the way for its application as a functional material in novel spintronic devices.

Image: Left panel: Crystal structure of the α-Sn layer grown by molecular beam epitaxy on CdTe/GaAs substrate is subject to in-plane biaxial compressive strain (black arrows) and thus uniaxial tensile strain along normal to the layer. Magnetic field B can be applied in the layer plane; Middle panel: Dirac-like surface states revealed by Angle Resolved Photoemission Spectroscopy studies of α-Sn in Dirac semimetal phase induced by strain for B=0. Right panel: negative longitudinal magnetoresistance (current I ǁ B, see right inset) indicative of chiral anomaly in Weyl semimetal phase induced by an in-plane B. At low temperature, Shubnikov-de Hass oscillations are also visible. Insets to middle and right panels show calculated band structure of Dirac and Weyl semimetal phases, respectively.

Credit: Jakub Polaczyński, Valentine V. Volobuev

Effective and environmentally friendly removal of pharmaceuticals from wastewater under visible light

2024/06/272024/07/18

The research team working under the leadership of Prof. Anna Zielińska-Jurek from the Faculty of Chemistry at Gdańsk University of Technology, in cooperation with scientists from ASTRA beamline, developed and characterized a new semiconductor material based on bismuth orthovanadate (BiVO₄) and copper oxide sub-nanoclusters (CuO_x). This material, when exposed to visible light, is able to effectively remove pharmaceuticals in water. Measurements made at the SOLARIS synchrotron using X-ray absorption spectroscopy (XAS) revealed the oxidation state of copper oxides. The research results were published in the journal “Separation and Purification Technology” from Elsevier publisher.

The rapid development of medicine and the pharmaceutical industry has made pharmaceutical pollution one of the greatest environmental dangers. Some of the most frequently detected pharmaceuticals in Polish sewage are naproxen, a popular painkiller, and ofloxacin, an antibiotic. These compounds, found in rivers, lakes or seas, are persistent and not susceptible to biological degradation, and conventional methods used in sewage treatment plants are insufficient to remove them.

A promising way to remove pharmaceuticals from the aqueous phase is their degradation in the process of heterogeneous photocatalysis supported by peroxymonosulfate ions (HSO₅−, PMS). These processes are based on the generation of highly reactive radicals under sunlight, which, as a result of reaction with pollutants, are able to purify water.

Unusual switching mechanism of memristors based on nickel complexes

2024/06/262024/06/26

A group of scientists from the Academic Centre for Materials and Nanotechnology of the AGH University of Kraków, led by prof. dr. hab. Konrad Szaciłowski, with the help of specialists from the SOLARIS National Synchrotron Radiation Center, published the results of research on the unusual switching mechanism of memristors based on nickel complexes with dibenzotetraase annulenes. The work was published in the journal Advanced Electronic Materials published by Wiley.

The 21st century is undoubtedly marked by a revolution in the computerisation of humankind. The growing demand for computing computer power and Internet traffic results in an increasing electricity demand, which is also related to increasing carbon dioxide emissions by humans. However, some impassable limitations affect the further development of this technology, namely the heat wall and the memory wall. The heat wall is caused by transistor downscaling, which increases power density but leads to excessive heat production that cannot be efficiently dissipated from the chip. The memory wall is associated with long latency and high power consumption when transferring data between the memory and the CPU.

Image: Schematics of the structure and operation of the tested memristor.

Calculate the orientation of macromolecules in three-dimensional space

2024/06/132024/06/13

Scientists from the CIRI beamline are developing a method to calculate the orientation of macromolecules in three-dimensional space based on microscopic measurements using mid-infrared light polarized linearly at different angles. Reconstructing the experimental shape of the absorption dependency on polarization by fitting a nonlinear function to the data points obtained from the measurements allows for determining the angles that define the orientation of macromolecules in three-dimensional space, as well as a parameter describing the degree of sample organization. The measurements were conducted using an FPA array detector available at the FT-IR microscopy end-station on the CIRI beamline.

This method is non-destructive and does not require labeling, making it particularly useful for imaging and quantitatively determining the order parameters in various types of anisotropic polymer and biological samples.

The study focuses on the structural characterization of poly(lactic acid) (PLLA), a biodegradable polymer known for its polymorphism and significant potential in various applications due to its environmentally friendly nature. Scientists prepared thin PLLA films and, through thermal treatment, obtained a sample with varied morphology, including an amorphous phase, isolated spherulites, and larger clusters of the semi-crystalline phase. The reconstruction of the three angles of macromolecule orientation revealed that the morphological organization in the amorphous phase is random, and the molecular orientation differs from the semi-crystalline phase also in the third dimension in thin films.

Strain-control over the valley degree of freedom

2024/05/162024/05/16

Department of the Ecole Normale Supérieure Paris, France in collaboration with scientists from URANOS SOLARIS Centre have published in Physical Review Letters the results of their research on the Valley-Polarized Quantum Hall Phase Dirac System. The different local band minima – called valleys – of a multivalley 2D topological insulator have been independently characterized using ARPES experiments. An efficient control over their electronic population using mechanical strain has been demonstrated.

In a semiconductor multivalley system, local electronic band minima occur at different momenta of the Brillouin zone. These valleys embody a new degree of freedom for the electrons and can be seen as pseudospins. Controlling the valley populations independently from each other is of prime interest to develop valleytronics – the technology of controlling the valley degree of freedom – and investigate interesting pseudospin phenomena such as skyrmions, charge density waves or quantum Hall ferromagnetism.

Using the URANOS beamline, we demonstrate a full control over the valley energy splitting as a function of in-plane biaxial strain in the IV-VI system Pb_1-xSn_xSe. The strain is determined by the lattice mismatch between the buffer and film layer, which depends on the Sn content. The band structure of several Pb_1-xSn_xSe 20 nm quantum wells have been measured near the two types of valleys in these materials, at the Γ ̅ and M ̅ points. As shown in Fig. 1, a huge amount of subband dispersions is observed, witnessing the high-resolution experiments at the URANOS beamline and the high-quality of the samples.

ARPES is one of the rare experimental techniques to independently assess band structure properties near selected momenta of the Brillouin zone. In this way, the relative energy position of the band minima near the Γ ̅-point and the M ̅-point can be measured with respect to the Fermi energy. As strain is increased, the bands at the M ̅-point are seen to shift upward in energy compared to the bands near the Γ ̅-point (see Fig. 1). The valley energy splitting, represented by Δ _l-o, is found to be very sensitive to strain and varies as 160 meV per 1 % strain, twice than the AlAs system for instance.

This work has shown the very efficient valley control using strain in the IV-VI materials, and has allowed for studying valley-polarized quantum Hall phases in tra nsport experiments, where chiral edge states of only one valley or the other are observed. This ARPES study demonstrates a key properties for the development of valleytronics devices based on Pb_1-xSn_xSe system.

The relationship between the structure of polyurethane frameworks and the structural and superconducting properties of Y-123 foams

2024/04/162024/04/24

A Polish team of researchers led by Dr. Paweł Pęczkowski from the Institute of Physical Sciences, Faculty of Mathematics and Natural Sciences, Cardinal Stefan Wyszyński University used the PIRX beam to study the properties of the electronic structure of superconducting foams obtained on the basis of polyurethane foams. The research results were published in the Journal of the European Ceramic Society published by Elsevier.

High-temperature superconductors (HTS) are most often produced in one of three varieties – thin film, wire (tape) and loose. This division results from the properties of these superconductors, which originate from their microstructure. High-temperature superconductors can be produced in a fourth variant with a foam structure. Superconductors with a foam structure have a much shorter cooling time, so the transition or return to the superconducting state from the normal state is much faster than in the case of solid samples manufactured using the top-seeded infiltration-growth (TSIG) method. Additionally, they are lightweight and exhibit fewer micro-cracks, which are the main factor limiting the critical current density in solid superconducting samples. These unique features make superconducting foams an excellent material for space applications, where it is necessary to use strong and light sources of magnetic fields to build, for example, docking mechanisms for space vehicles and ion engines. However, before superconducting foams are used, several basic questions need to be answered: what is the impact of changes in the foam structure (e.g. size and shape of pores) on superconducting properties, how does current flow in the three-dimensional structure of the foam and what is its impact on the properties related to ability to anchor vortexes (pinning centers).

Image: (a) Y-211 foam before and (b) after Y-035 infiltration process; (c) Y-123 – final foam levitation in a magnetic field