Diamond Light Source (or Diamond) is the UK's national synchrotron light source science facility located at the Harwell Science and Innovation Campus in Oxfordshire. Its purpose is to produce intense beams of light whose special characteristics are useful in many areas of scientific research. In particular it can be used to investigate the structure and properties of a wide range of materials from proteins (to provide information for designing new and better drugs), and engineering components (such as a fan blade from an aero-engine) to conservation of archeological artifacts (for example Henry VIII's flagship the Mary Rose).There are more than 50 light sources across the world. With an energy of 3 GeV, Diamond is a medium energy synchrotron currently operating with 32 beamlines.
Sodium iron silicate (NFS) samples were synthesised at initial Fe/Si molar ratios of 0.3 and 0.8 and equilibrated at 50 °C for up to 180 days to elucidate reaction pathways in high-Fe alkaline environments. The resulting solid phases comprised siliceous ferrihydrite, sodium‑iron-silicate-hydrate (N-F-S-H) and nontronite. N-F-S-H was isolated via selective dissolution using citrate-bicarbonate-dithionite (CBD). Its features include a broad X-ray diffraction (XRD) hump centred at ~38° 2θ, a SiOFe stretching band at 965 cm−1 in Fourier transform infrared spectroscopy (FTIR), and a mass-loss feature at ~130 °C corresponding to water release. Mass balance calculations identified the early-age (7 and 28 days) N-F-S-H composition as (Na2O)0.3 (Fe2O3)0.4–0.5(SiO2)·0.7 H2O. Identifying these secondary, poorly crystalline phases preceding nontronite formation advances the understanding of FeSi reaction pathways. These insights are highly relevant for Fe-rich blended cements, nuclear waste disposal, and reinforced concrete.
Photocatalysis offers a promising approach for renewable energy conversion and storage, but short lifetimes of charge-separated states in photocatalysts due to charge recombination limit its utility. Here we report an organic molecule with an acceptor–donor–acceptor configuration that can self assemble into highly crystalline nanoparticles. Transient absorption spectroscopy reveals that these crystalline assemblies can induce an ultra-long-lived charge-separated state of up to 1.2 s, attributed to initial symmetry-breaking charge separation, followed by charge hopping across closely packed molecules. These self-assembled nanoparticles have an impressive photocatalytic H2 evolution rate of 126 mmol g−1 h−1 with an external quantum efficiency of 12 Achieving charge separation with minimal energy loss remains a key challenge in photocatalysis, but traditional approaches often suffer from rapid charge recombination or inefficient energy utilization. Now it has been shown that symmetry-breaking charge separation within organic crystalline nanoparticles can generate long-lived charge-separated states, enabling efficient photocatalytic hydrogen production.
Flat electronic bands, where interactions among electrons overwhelm their kinetic energies, hold the promise for exotic correlation physics. The dice lattice has long been theorized as a host of flat bands with intriguing band topology. However, to date, no material has ever been found to host the characteristic flat bands of a dice lattice. Here, using angle-resolved photoemission spectroscopy (ARPES), we discover a dice-lattice flat band at EF in the van der Waals (vdW) electride [YCl]2+: 2e-. In this system, excess valence electrons from Y deconfine from the cation framework to form an interstitial anionic electron lattice that constitutes the dice lattice. Our ARPES measurements unambiguously identify two sets of dice-lattice bands in YCl, including a nearly dispersionless band at the Fermi level. The near-EF electronic structure observed in ARPES, which consists of the flat bands and other dispersive band features, find excellent agreement with first-principles calculations and is well captured by a simple dice-lattice model. Our findings thus end the long quest of a real dice flat band material and establish vdW electride YCl as a prototype of dice metals. Our results further demonstrate the anionic electron lattice as a novel scheme for realizing lattice geometries and electronic structures rare to find in conventional crystalline systems. Using ARPES, this work identifies dice-lattice flat bands in the electride material YCl. The authors show that anionic electrons act as lattice sites to create this rare electronic structure.
The discovery of superconductivity in square-planar nickelates has offered a rich materials platform to explore the origins of high-temperature superconductivity. However, experimental investigations have largely been limited to the infinite-layer RNiO2 (R, rare earth) nickelates. We constructed a phase diagram of multilayer square-planar Ndn+1NinO2n+2 compounds and found signatures of superconductivity for dimensionality n = 4 to 8. Upon decreasing n, the superconducting anisotropy evolves owing to 4f electron effects, and electronic structure characteristics approach cuprate-like behavior. Magnetic fluctuations persist from within the superconducting regime and into the overdoped, nonsuperconducting regime. The superconducting regime overlaps with that of chemically doped infinite-layer nickelates, demonstrating underlying commonalities as well as differences across varying structural realizations of square-planar nickelates. Our work establishes this layered template for creating new nickel-based superconductors.
The recent discovery of high-temperature superconductivity in hole-doped SmNiO2, exhibiting the record-high transition temperature Tc among infinite-layer (IL) nickelates, has opened a new avenue for exploring design principles of superconductivity. Experimentally determining the electronic structure and magnetic interactions in this new system is crucial to elucidating the mechanism behind the enhanced superconductivity. Here, we report a Ni L-edge resonant inelastic x-ray scattering (RIXS) study of superconducting Sm-based IL nickelate thin films Sm1-x-yEuxCayNiO2 (SECNO). Dispersive paramagnonic excitations are observed in both optimally and overdoped SECNO samples, supporting a spin-fluctuation-mediated pairing scenario. However, despite the two-fold enhancement of Tc in the Sm-based nickelates compared to their Pr-based counterparts, the effective exchange coupling strength is reduced by approximately 20%. This behavior contrasts with hole-doped cuprates, where magnetic interactions correlate positively with Tc, highlighting essential differences in their superconducting mechanisms.
