Na₂Mn₃O₇ is a magnetic material that behaves unusually and therefore can provide insight into how magnetism emerges in complex materials. Magnetic materials contain entities known as spins, which can be thought of as tiny magnets with north and south poles. These spins interact with neighbouring spins, and as a material is cooled, they often align into an ordered pattern that extends across the entire material, known as long-range magnetic order.

However, Na₂Mn₃O₇, which contains magnetic Mn⁴⁺ ions, behaves differently. It has strong magnetic interactions, very little disorder, and a two-dimensional arrangement of magnetic ions. Under these conditions, a material with relatively large spins would normally be expected to develop long-range magnetic order at low temperatures. Surprisingly, no magnetic ordering is observed, even at very low temperatures.

The material also exhibits two distinct magnetic crossovers. Around 110-120 K, the magnetic susceptibility reaches a broad maximum, indicating that strong magnetic correlations are developing. Around 60-70 K, a feature appears in the specific heat, showing that the system is undergoing a further internal reorganisation. The presence of two separate temperature scales suggests that the magnetism develops in two stages.

Using theoretical and computational techniques, the researchers showed that this unusual behaviour originates from the crystal structure of Na₂Mn₃O₇. The crystal structure divides the magnetic lattice into strongly connected hexagonal clusters of six Mn ions. These clusters behave like magnetic ‘molecules’, with the spins inside each hexagon becoming strongly correlated. Interactions between different hexagons are much weaker and frustrated, preventing the formation of long-range magnetic order across the material.

This research is important because it demonstrates that even large-spin magnetic materials can exhibit quantum-disordered behaviour. More broadly, it shows that crystal structure can be used as a tool to engineer new magnetic states by organising spins into strongly correlated clusters that suppress conventional magnetic ordering.

“What is striking in Na₂Mn₃O₇ is that the crystal structure does more than slightly distort the magnetic lattice. It reorganises the spins into strongly correlated hexagons that behave as emergent magnetic molecules, while frustration and quantum fluctuations prevent these units from ordering collectively.“ – Yasir Iqbal, Indian Institute of Technology Madras

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Frustrated magnets in high magnetic fields—selected examples by J Wosnitza, S A Zvyagin and S Zherlitsyn (2016)

The post Magnetic molecules explain a puzzling material appeared first on Physics World.

Graphene, an atomically thin material of a single layer of carbon atoms, is a fascinating material for high-speed electronics, spintronic devices, and neuromorphic components due to its exceptional tunable electrical conductivity. One area of research focuses on understanding how electrons flow through graphene to enable the design of advanced devices. For applications, ultrathin metal-oxide layers (e.g., aluminum oxide and titanium oxide) are routinely deposited on graphene, which deliberately alter electron flow and provide greater control over its properties, in devices ranging from transistors to spin valves. However, although the effects of these coatings are known, researchers have not previously been able to directly observe what is happening inside the device. Instead, their understanding has relied primarily on theoretical models, numerical simulations, and indirect electrical measurements.

In this work, the researchers used X-ray Photoelectron Spectroscopy (XPS) to map electrical potentials across devices while they were operating. They examined the electrical landscape, identifying regions with steep slopes corresponding to strong electric fields and flatter regions corresponding to weaker electric fields, to determine how oxide coatings modify this landscape. They found that metal oxides flatten the electrical landscape through a process known as p-type charge-transfer doping. This occurs when the oxide removes some electrons from the graphene, altering its local electrostatic environment and reducing the voltage gradient. As a result, local electric fields become weaker. The oxide layers suppress the electric fields, reducing them by more than 50%, a significant effect for device operation. A key advance of this research is the visualisation of this effect at very high spatial resolution, whereas previously it could only be inferred from electrical resistance measurements. In addition, by making a direct comparison with electrical measurements, the researchers confirmed the observed effects are due solely to electrostatics and charge redistribution.

Modern electronic devices increasingly depend on controlling electricity at very small scales. By locally adjusting electric fields using oxide coatings, researchers gain an additional design tool that enables different regions of a graphene circuit to be tuned independently. This is particularly important for spintronic devices, which are highly sensitive to local electric fields, and neuromorphic computing hardware, which requires precise control of local electrical properties.

This work represents a breakthrough in the ability to directly map charge distributions and electric fields inside operating 2D-material devices, enabling improved device design.

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Phonons and thermal transport in graphene and graphene-based materials byDenis L Nika and Alexander A Balandin (2017)

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Many catalysts are made using core-shell nanoparticles, in which the core is a structurally important or inexpensive material and the thin shell surrounding it is an expensive metal such as platinum. Since catalytic reactions occur on the surface, this helps to reduce the amount of platinum required and therefore lowers costs. Crystal structures are described based on the smallest repeating unit of the crystal (the unit cell) using the Bravais lattice system. Three important crystal structures are face-centred cubic (fcc, atoms at the corners and faces of a cube), body-centred cubic (bcc, atoms at the corners and centre of a cube), and hexagonal close-packed (hcp, a hexagonal arrangement of atoms).

Different materials have different crystal structures; for example, platinum is fcc, many alloys are bcc, and magnesium and zinc are hcp. In core–shell nanoparticles, differences between the crystal structures of the core and shell mean that the atoms do not line up perfectly. This mismatch creates strain, which can significantly affect catalytic performance. In this work, the researchers explored how a platinum shell grows on a different crystal structure in a process known as heteroepitaxy.

They studied platinum shells (Pt, fcc) grown on cores made of ruthenium (Ru, hcp), palladium–copper (PdCu, bcc), and specially synthesised ruthenium with an fcc structure. It was found that each system accommodates the atomic mismatch differently. In hcp/fcc particles, some areas lined up coherently while others contained defects called dislocations, which formed networks in particles smaller than 10 nm. In bcc/fcc particles, both the core and shell stretched or compressed to fit together. In fcc/fcc particles, the matching crystal structures aligned more readily, but twin defects formed in which one region mirrored another.

Overall, this study shows that the way a Pt shell grows on a nanoparticle core is determined by a balance between the energies of the interface, shell, and core, with the system naturally adopting the lowest-energy configuration. These findings could help scientists achieve atomic-precision interfacial engineering, controlling the catalytic, mechanical, and electrical properties of core-shell nanoparticles.

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PLP-Logo-2.png, find out more. Single metal nanoparticles: optical detection, spectroscopy and applications by P Zijlstra and M Orrit (2011)

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Intrinsically disordered proteins (IDPs) do not form stable 3D structures. Instead, they remain flexible, adopt many conformations, and can interact with multiple molecules. Although proteins were once thought to require a fixed structure to function, many IDPs play essential cellular roles. Some IDPs can assemble into biomolecular condensates, membrane-less compartments that help organise processes such as gene expression and stress responses.

Many IDPs contain prion-like low complexity domains (PLCDs), which have defined sequence features known as molecular grammas. These IDPs are multivalent and can form hierarchies of interactions with one another. These interactions promote clustering and, under the right conditions, phase separation into a protein-rich condensate and a surrounding dilute phase. Dysregulation of condensates has been linked to disease.

In this study, researchers used computer simulations to investigate the PLCD known as A1-LCD. Their aims were to accurately identify the critical point where phase separation ceases, map the full phase diagram, and assess methods used to estimate the theta temperature (Tθ), a measure related to solvent quality and protein interactions.

The simulations revealed three distinct phase-separation regimes: a dilute phase containing mostly isolated proteins, an intermediate regime where clusters form before large condensates appear, and a regime near the critical point characterised by system-spanning networks. The study also showed that condensates behave as percolated networks of interconnected proteins. Importantly, the authors found that commonly used methods for estimating theta temperature may be inaccurate for these systems.

Overall, this work provides new insights into the phase behaviour of condensate-forming proteins and highlights the need for more reliable approaches to assessing solvent quality. These findings could improve future studies of biomolecular condensates and their roles in health and disease.

“Comparative assessments of driving forces for phase separation requires knowledge of IDP-specific critical points. Our application of rigorous finite size scaling methods pioneered by Kurt Binder helped us delineate the critical and mean field regimes and demonstrate how the critical point can be converged upon for realistic approximations of IDPs. This revealed several surprises regarding the complex nature of the coexisting dilute phase. Additionally, we found that calculation of the two-body interaction coefficient provides a computationally tractable approach to compute comparative, sequence-encoded driving forces for phase separation of IDPs. This is directly relevant to inferring how changes to molecular grammars influence phase behaviors driven by homotypic associations.” – Rohit V. Pappu, Washington University in St. Louis

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Biomolecular dynamics: order–disorder transitions and energy landscapes by Paul C Whitford, Karissa Y Sanbonmatsu and José N Onuchic (2012)

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According to band theory, materials with partially filled energy bands and unpaired electrons should conduct electricity, but in Mott insulators this rule is broken. In these materials, the repulsion between electrons is so strong that they cannot move freely and become localized. When sufficient energy is supplied (for example by light), electrons can form a doublon (two electrons on one site) and a hole (an empty site). These excitations can move, enabling electrical conductivity.

A key question for Mott insulators is how these charge carriers are created and what controls their production. Traditionally, two regimes were known: multiphoton absorption, where several photons combine their energy, and tunnelling, where a strong electric field drives electrons across the gap.

In this work, the authors show that there are actually four regimes: multiphoton, tunnelling, a cooperative regime where the two processes work together, and an incoherent regime where weak fields and scattering dominate. They also show that the energy gap (the cost to create a doubloon-hole pair) is not fixed, but changes during the process because the generated carriers modify the system. This creates a feedback loop, making the dynamics nonlinear and time-dependent. As a result, carrier production can either slow down or suddenly speed up, even making the system more efficient without changing the driving field.

The behaviour depends on field strength, frequency, dissipation, and time, and each mechanism can be identified by its distinct momentum pattern. By tuning laser parameters, the system’s properties can be controlled in real time. Overall, this work shows that light can be used to dynamically reshape and control strongly interacting materials, opening possibilities for ultrafast, light-driven technologies.

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PLP-Logo-2.png, find out more. Quantum frustration in organic Mott insulators: from spin liquids to unconventional superconductors by B J Powell and Ross H McKenzie (2011)

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Quantum mechanics has two seemingly competing rules. Firstly, a system evolving without measurement follows a continuous, deterministic evolution governed by the Schrödinger equation, with dynamics determined by a Hamiltonian. Secondly, when a measurement occurs, the wavefunction collapses, producing a sudden, discontinuous change that is not derived from a Hamiltonian. Several approaches attempt to reconcile these behaviours, including the Copenhagen interpretation (which does not explain the mechanism of collapse), decoherence theory (which does not provide a single definite outcome), stochastic collapse models, and continuous measurement theory.

In this work, measurement is not treated as fundamentally different. Instead, it is described using stochastic (random) Hamiltonians that generate continuous evolution of the quantum state. In this picture, collapse emerges from noisy dynamics. The authors show that these dynamics can be understood as double-bracket gradient flows, where the system is driven to align with a measured observable, steadily reducing uncertainty until it reaches a definite outcome. Thus, wavefunction collapse can be viewed as coarse-grained continuous dynamics that minimise the variance of the observable. By interpreting this as a gradient flow, the same mechanism can be exploited using feedback to drive a system into desired states, including entangled ones.

This approach provides a continuous and physically interpretable picture of wavefunction collapse. Compared to decoherence theory, it explains the emergence of a single outcome but does not specify when measurement dynamics begin. More broadly, it replaces the notion of collapse with a dynamical process, making the theory more internally consistent, while also offering practical tools for controlling quantum systems, which is important for quantum computing and experiments.

“These geometric connections between Hamiltonian dynamics and quantum measurements open the door to exciting new approaches to quantum algorithm design.” – Aaron Villanueva, Radboud University

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Genuine quantum correlations in quantum many-body systems: a review of recent progress by Gabriele De Chiara and Anna Sanpera (2018)

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Percolation studies how small connections can group together to form a larger connected system, known as a cluster. In a grid where sites can be turned on or off, turning on more sites leads to the formation of clusters, and at a certain point a giant cluster spanning the system emerges. This behaviour is relevant to many real-world systems where local interactions lead to global effects, such as power grids, disease spreading, forest fires, and brain activity. While percolation is often studied using theoretical models or simulations, real systems are more complex. Nonlinear effects, noise, imperfect connections, and time-dependent dynamics can all shift the tipping point and change how clusters form.

In this work, the researchers built a physical system using a 2D array of 100 coupled lasers to study percolation experimentally. Each laser acts as a site that can be turned on and interacts with its neighbours, making the system a controllable realisation of a percolation grid. They found that when a large connected cluster forms, the lasers also begin to phase-lock, meaning that connectivity and synchronisation emerge together. Normally, these effects are studied separately.

At high pump power (the energy supplied to the lasers), the system behaves like an ideal percolation model, with a clear critical threshold and a smooth (second-order) transition, consistent with theory. However, at low pump power, nonlinear effects become important. The lasers compete more strongly, meaning more active sites are needed to form a spanning cluster, and weaker clusters are suppressed. This shifts the percolation threshold and alters the cluster size distribution, contrary to the usual expectation that nonlinear effects are stronger at higher power.

To explain this, the researchers introduced a simple model where a site only remains active if it has enough active neighbours, effectively modifying the connectivity rules. This reproduces the observed behaviour and shows how nonlinear effects can reshape percolation. Overall, the work demonstrates that real physical systems can significantly modify ideal percolation behaviour, and provides a controllable platform for studying how connectivity, competition, and synchronisation interact in complex networks.

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Percolation theory by J W Essam (2018)

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When electrons are placed in a strong magnetic field and cooled to very low temperatures, they stop behaving independently and instead act as a collective fluid. This is known as a fractional quantum Hall (FQH) system. In this regime, the electrons lose their individual behaviour and act as one correlated system. The strong interactions between them produce quasiparticles called anyons. These are not real particles but effective ones that emerge from the collective behaviour, and they have unusual properties that do not occur in ordinary systems.

Anyons exhibit braiding behaviour: when they are moved around each other, the system remembers the path taken. In Abelian braiding, this only adds a simple phase, so the quantum state is effectively unchanged. In contrast, non-Abelian braiding transforms the quantum state into a different one, which can be measured and used to encode information.

To study these systems, physicists must compute measurable properties from complicated wave functions, which is computationally challenging, especially for large systems. The traditional method, Metropolis Monte Carlo, is slow and struggles with large numbers of electrons, limiting system size, accuracy, and the ability to test advanced theories.

In this work, the researchers developed a new simulation method, Hybrid Monte Carlo (HMC), for FQH wave functions. It includes global updates (updating many electrons at once) and double stereographic projection to more accurately sample particle positions, making it much faster and more efficient than the Metropolis method.

Using this improved method, they accurately computed edge properties that reveal the system’s topology, as well as high-quality braiding matrices of non-Abelian quasiholes, which are crucial because such braiding underpins topological quantum computing. Overall, this work enables fast, large-scale simulations, allowing more accurate study of exotic quantum states and their anyon behaviour, advancing both fundamental physics and topological quantum computing.

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A review of the quantum Hall effects in MgZnO/ZnO heterostructures by Joseph Falson and Masashi Kawasaki (2018)

The post Advanced simulations of exotic quantum matter appeared first on Physics World.

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Physical properties and atomic arrangements in crystals by W A Wooster (1953)

The post Controlling glycine polymorphs through nanoconfinement appeared first on Physics World.

Electricity grids need to be carefully balanced, with too low levels of electricity leading to blackouts and too high levels causing damage to grids. Due to the intermittent nature of renewable energy sources such as solar and wind, it is possible for specific regions (e.g. the north of Germany) to have an excess of electricity, while the power lines do not have enough capacity to transport it to higher demand regions such as cities and industrial areas. This is known as a grid bottleneck. To keep the grid running properly, operators redispatch electricity by reducing renewable feed-in in oversupplied areas and increasing generation elsewhere. However, this leads to renewable energy being wasted, and because producers are still compensated and generation increase on demand is costly, it is financially inefficient.

In 2024, Germany created regional redispatch markets so that renewable electricity that would otherwise be curtailed can instead be sold locally. This is particularly useful for hydrogen producers because they do not require a continuous supply of electricity. Because they can operate flexibly, turning on and off depending on electricity availability, they can take advantage of very low-priced electricity. In this work, the researchers ask whether using this electricity source makes producing green hydrogen cheaper and how market prices for otherwise curtailed renewable electricity affect this.

They found that using only redispatch electricity is not cost-effective because of its unreliability. However, combining it with different renewable energy sources does reduce costs. Depending on hydrogen storage costs, using redispatch electricity can reduce hydrogen production costs by €0.9 – €1.96 per kg, if the redispatch electricity is available for 0 €/MWh, compared to typical costs of around €6-8 per kg without redispatch electricity.

Increased redispatch prices reduce the potential for production cost reductions, which, combined with the unreliability of redispatch availability, lowers the incentive for
system beneficial electrolyser siting within the regional market areas. Therefore, the success of these markets depends heavily on keeping prices low, which might necessitate effective price capping but could increase green hydrogen competitiveness and simultaneously decrease renewable energy curtailment.

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Metrics for assessing the economic impacts of power sector climate and clean electricity policies John Bistline (2021)

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Top quarks are the heaviest known elementary particles. They are produced in pairs with their antiparticle equivalent, the antitop quark. Researchers at the Large Hadron Collider (LHC) smash protons together at extremely high energies in the hope of producing these top-quark pairs. The minimum energy required to create a pair is known as the production threshold (approximately twice the top mass). Near this threshold, the particles move relatively slowly and, because of the strong nuclear force, they may briefly interact strongly enough to form a quasi-bound state before each top quark decays individually.

In this work, researchers used a huge dataset collected with the ATLAS detector at the LHC. Top quark pairs decay far too quickly to be observed directly, so the ATLAS team instead studied their decay products. A top quark usually decays into a W boson and a b-quark, while the antitop quark decays into the corresponding antiparticles. The W bosons then decay further, either through leptonic decay (producing an electron, muon or tau plus a neutrino) or through hadronic decay, which produces jets of particles.

The ATLAS analysis focuses on the case where both W bosons decay leptonically into electrons and muons and reconstructs the invariant mass of the system using the energy and momentum of the decay products.

If non-relativistic QCD effects are included, the event rate near threshold is expected to be higher than that predicted by standard perturbative QCD alone, due to contributions such as the formation of quasi-bound states that are not accounted for in the perturbative framework. The analysis also employs spin-correlation observables to enhance the sensitivity to the unique spin structure of the phenomena. If non-relativitic QCD effects occur near the production threshold, including the formation of quasi-bound states, physicists expect to see an excess of events concentrated at masses close to the minimum energy needed to produce the pair.

The researchers observed significantly more events near the production threshold (∼345 GeV) than standard QCD calculations predicted, confirming a previous similar measurement by the CMS collaboration. The excess matches predictions from non-relativistic QCD that the top and antitop quarks briefly perform non-relativistic QCD interaction, including the formation of quasi-bound states, before separating and decaying. This is important because it provides strong evidence for a subtle quantum effect of the strong force and improves our understanding of top-quark behaviour in an extreme regime. This measurement underscores the capacity of LHC experiments at the precision frontier, reinforcing the vital interplay between theory and experiment in these precision studies.

“This is a very exciting finding that pushes our current understanding of top quark physics and its modelling to the extreme. It has only been made possible by recent efforts to connect quantum information theory and collider physics.” – Yoav Afik, an ATLAS physicist affiliated with the Enrico Fermi Institute at the University of Chicago

“With the newly collected Run 3 dataset, which is more than twice as large as the Run 2 dataset used in this first analysis, we will be able to scrutinize this excess in much greater detail and determine whether it can be described solely by non-relativistic QCD effects, or whether there is something more to it.” – Baptiste Ravina, a Senior Research Fellow at CERN

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Towards the identification of new physics through quark flavour violating processes by Andrzej J Buras and Jennifer Girrbach (2014)

The post Observation of top-antitop quark excess appeared first on Physics World.

Proton Exchange Membrane Water Electrolysis is a method to split water into its components, hydrogen (H₂) and oxygen (O₂), using electricity typically sourced from renewables. It is one method for producing so-called green hydrogen. Key benefits are that it can easily start and stop, fitting well with fluctuating renewable energy sources; it produces high purity hydrogen suitable for fuel cells and industrial use; and it has a smaller carbon footprint than some alternatives.

This work explores how much water is used in Proton Exchange Membrane Water Electrolysis, which is significant in regions with low water availability, where hydrogen plants could stress supplies. The researchers looked at all lifecycle stages: manufacturing (building the electrolyser and producing materials), operation (water splitting, cooling, and purification), and end-of-life (disposal or recycling).

Their main conclusion was that most water use occurs during the operational phase, where the greatest opportunity to save water lies. Dry cooling uses much less water than wet cooling, reducing consumption by about a factor of three. In a best-case scenario with dry cooling, about 13 litres of water per kg H₂ is used, of which around 3.5 litres is lost in water treatment. This loss can be reduced by about 50% using a brine recovery system, depending on location and infrastructure.

Proton Exchange Membrane Water Electrolysis has a similar lifecycle water use to fossil hydrogen production, therefore switching to green hydrogen does not significantly increase water demand. Although hydrogen plants use comparable water to agriculture (e.g. corn farming), they generate much higher economic value per unit of water (~700×), making them an efficient use of water.

This research is significant because it shows that while green hydrogen can reduce carbon emissions, its water use must be carefully managed to ensure it is sustainable at scale.

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Research and development of hydrogen carrier based solutions for hydrogen compression and storage Martin Dornheim et al. (2022)

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In 2‑dimensional physics, atomically thin materials (e.g. MoS₂, WS₂, WSe₂) are useful for next‑generation electronics such as flexible devices. Using these materials, scientists can create van der Waals heterostructures, where different 2D materials are stacked in layers and held together by weak intermolecular forces called van der Waals forces. Heterostructures combine different materials to optimise their properties. Unlike single crystals, van der Waals heterostructures are more flexible and less prone to defects. They can also tolerate lattice mismatch, where atoms between layers do not perfectly line up, although this must be controlled to avoid building up strain.

In this work, the researchers studied two systems: MoS₂ on WS₂, where the lattice spacing matches closely, and MoS₂ on WSe₂, where there is a larger mismatch. When the layers fit well together (MoS₂/WS₂), the top layer slightly compresses and the structure remains well aligned. However, when the layers do not fit well (MoS₂/WSe₂), moiré patterns appear, which are large-scale patterns caused by mismatched lattices, and these patterns become bent and irregular. The researchers found that instead of forming defects, the material relieves strain through local rotations and distortions of the lattice.

Previous studies had not clearly explained how strain is relieved at the atomic scale, whether it leads to defect formation or alternative mechanisms, or how these distortions vary across nanoscale regions. This research helps scientists better understand and control the behaviour of stacked 2D materials, which is important for designing future ultra-thin electronics, quantum devices, and optoelectronic technologies.

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Tuning and exploiting interlayer coupling in two-dimensional van der Waals heterostructures by Chenyin Jiao et al. (2023)

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Topological features are important because they give rise to states that cannot easily be destroyed. These robust states give materials special behaviours that enable new kinds of electronics and photonics. Some topological systems can even host exotic quasiparticles such as Majorana modes, which are their own antiparticles and are promising building blocks for quantum computing.

However, existing methods for detecting topological states in materials have significant limitations. They typically probe only the surface, even though topology is a bulk property. Topological transitions can be subtle and difficult to identify, and topological signatures can be obscured by impurities or disorder. In some cases, topological features have no easily measurable experimental signature at all.

In this work, the researchers made a striking discovery: ordinary crystal defects can be used to detect topological behaviour inside a material. When a defect is placed in a material with a topological electronic structure, it produces an additional energy state inside the band gap, known as a mid‑gap mode. This effect is universal and appears for the most common types of imperfections: vacancies, Schottky defects, substitutions, and interstitials.

The defect acts as a marker for topology because a mid‑gap mode forms only when the surrounding material is topological. In a trivial material, no such state appears. This happens because the wavefunctions in a topological material have a global structure that cannot be altered locally; introducing a defect forces the system to compensate by creating a mid‑gap state.

This topological probe is not symmetry‑dependent and works in any spatial dimension, making it relevant to 2D materials, 3D crystals, superconductors, photonic and acoustic lattices, and even non‑Hermitian systems. The researchers confirmed this experimentally by building acoustic Chern lattices, where sound waves behave mathematically like electrons. By introducing controlled defects, they observed mid‑gap states exactly where the theory predicted.

This work shows that ordinary crystal defects can serve as reliable, built‑in indicators of a material’s hidden topological character, offering a simple and universal way to detect topology directly within the bulk.

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Topological order, emergent gauge fields, and Fermi surface reconstruction by Subir Sachdev (2018)

The post Defects as topological sensors appeared first on Physics World.

Spain’s transition to a low‑carbon economy requires expanding renewable technologies such as wind, solar, and electric vehicles. These technologies depend on specific materials, and demand for materials, such as cobalt, lithium, and nickel, already represents a significant share of Spain’s total use.

The researchers analysed how much materials Spain would need up to 2050 under different decarbonisation pathways. They enhanced the MEDEAS‑Spain model by adding sector‑specific material intensities, improving the tracking of material stocks and flows, and expanding coverage to more than forty materials, a comprehensive assessment of the material requirements of decarbonisation.

They evaluated three scenarios: Spain’s official energy and climate plan (PNIEC‑LTDS), a scenario where economic demand stops growing after 2025 (CappedEcon), and a Sufficiency scenario where consumption is reduced in a sectorally explicit manner  to levels consistent with decent living standards.

While low-carbon technologies require large quantities of materials, most material demand comes from wider (unrelated to decarbonisation) economic activities. As a result, and as shown in the figure below, the PNIEC-LTDS, which features a high level of economic growth, increases the material footprint by 51% between 2025 and 2050. In contrast, the Sufficiency scenario reduces the material footprint by over 50% while reducing greenhouse gas emissions by 93%.

The study concludes that a rapid expansion of renewable energy is only environmentally sustainable if overall material and energy demand is reduced. Green‑growth pathways sharply increase material use, whereas sufficiency‑based post‑growth approaches enable deep decarbonisation with far lower resource pressure. Ultimately, consumption levels determine the sustainability of the transition.

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Africa’s critical minerals can power the global low-carbon transition N S Ouedraogo and J M M Kilolo (2024)

The post Material limits of Spain’s energy transition appeared first on Physics World.

Abandoned mining areas are difficult to farm, often unsafe to build on, and expensive to restore. They also pose long‑term environmental risks due to land degradation, water contamination, and unstable ground. However, these hard‑to‑use landscapes are often large, open, and exposed to sunlight, making them promising locations for solar power generation.

In this work, the researchers developed a novel tool called SolarMiner to locate abandoned mining areas and calculate how much solar power they could produce. The tool combines satellite imagery with a computer vision model, a form of artificial intelligence, to identify and classify different types of mining sites. SolarMiner can detect mining areas, determine their type (e.g., open‑pit, subsidence zones, water‑filled pits), measure their surface area, and estimate how much solar capacity could be installed, along with the electricity output and cost.

They tested SolarMiner on a major coal‑mining region in China, Shanxi Province. Focusing only on abandoned mining areas, the model estimated that land‑based solar panels alone could generate over five times the province’s 2023 electricity consumption. Floating solar panels on water‑filled mine pits could generate even more, over six times Shanxi’s usage in the same year.

This research highlights the enormous potential of abandoned mining sites for clean‑energy generation. Using SolarMiner will help direct governments toward smarter planning of solar farms and transmission networks by identifying exactly which mining areas can be transformed into low‑cost, high‑impact renewable‑energy assets.

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A review on modelling methods, tools and service of integrated energy systems in China Nianyuan Wu et al. (2023)

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Twisted bilayer graphene has become a key area of research in 2‑dimensional materials. Two graphene sheets are stacked and rotated slightly so their carbon atoms no longer align, creating an interference pattern called a moiré lattice. At specific magic angles (1.1°, 0.55°, 0.37°), the geometry and interlayer coupling slow the electrons dramatically, nearly reducing their velocity to zero. These slowed electrons form flat bands, where interactions become extremely strong and can give rise to exotic phases such as superconductivity and strange‑metal behaviour.

In this work, the researchers examined what happens as the twist angle varies from 0.35° to 1.30°, using scanning tunnelling microscopy (STM) to image individual atoms and local electronic states. STM measures the tunnelling current between a sharp metal tip and the sample, allowing the researchers to map the electronic structure across regions for the first, second, and third magic angles.

They found that shear strain, a sideways distortion where one graphene layer shifts relative to the other, has a far greater impact on the electronic structure than biaxial stretching or compression. Shear strain strongly controls how far apart the flat bands are, how wide they become, and how electrons distribute between them. It enhances the upper flat band while suppressing the lower one, making it a decisive structural factor rather than a minor defect. They also showed that remote bands depend only on twist angle, not strain, making them reliable markers of the local twist. Strain reshapes flat‑band energies within each moiré unit cell, and only a theoretical model combining strain and electron-electron interactions reproduces the full experimental behaviour.

This research demonstrates that shear strain, not just the twist angle, is a critical factor shaping the flat‑band structure in twisted bilayer graphene, redefining how correlated and superconducting states must be engineered.

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Emergent phases in graphene flat bands by Saisab Bhowmik, Arindam Ghosh and U Chandni (2024)

The post Shear strain reshapes magic angle graphene appeared first on Physics World.

Scientists study how waves move in many systems including sound, light, and even electrons. Normally, waves spread out and change as they travel. But sometimes they form flat bands, where the wave doesn’t spread at all. It’s like dropping a pebble into a lake and seeing no ripples. These flat bands are exciting because they make interactions stronger and can be used for ultra‑precise sensing and energy harvesting. The challenge is that in 3D materials, scientists have never been able to make bands that stay perfectly flat everywhere, they always become wiggly near the edges.

In 2D materials, however, flat bands appear naturally as Landau levels. These are fixed energy states created when a magnetic field forces electrons into tiny circular orbits. Because the electrons can’t move freely, all the states at that energy become perfectly flat. But extending this idea to 3D has been extremely difficult.

In this work, the researchers found a way around that problem by using sound waves instead of electrons. They built a special 3D structure that controls sound, and for the first time created a perfectly flat 3D Landau level across the entire material, not just in the middle. Sound waves are much easier to manipulate than electrons, which made the experiment possible.

They designed a structure called a Fock‑state lattice, which naturally produces a kind of synthetic magnetic field for sound. Unlike a normal magnetic field, this one is spherical-like, spreading evenly in all directions. This special field is what keeps the Landau levels perfectly flat everywhere in 3D.

This result settles a long‑standing debate by proving that truly flat Landau levels can exist in 3D. Even better, the same method can be applied not just to sound, but also to light, electrons, and superconducting circuits, opening the door to new technologies that rely on extremely stable, high‑quality resonances.

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Emergent phases in graphene flat bands by Saisab Bhowmik, Arindam Ghosh and U Chandni (2024)

The post Flat bands go 3D appeared first on Physics World.

Rectification is the process of turning alternating current (AC) signals into direct current (DC), and it underpins technologies such as wireless power transfer, photodetection, terahertz sensing, and energy harvesting. To generate a one-directional current, a material normally needs a built-in directional preference for electron motion. This preference usually arises from broken inversion symmetry, meaning that the material is not identical under spatial inversion. For example, graphene has inversion symmetry, while materials with inequivalent sublattices, intrinsic electric dipoles, surfaces, or interfaces naturally break it. When inversion symmetry is broken, electrons can respond differently to opposite directions of an applied light field, allowing oscillating optical fields to generate a DC current.

In this work, the researchers show that this rule has an important exception. Even centrosymmetric bulk materials can rectify light through third-order nonlinear optical effects. Linear optical responses scale with the applied light field. Second-order responses depend on the square of the electric field and can mix frequencies or generate harmonics, but they are usually forbidden in centrosymmetric bulk materials. Third-order responses, however, are symmetry allowed and can generate DC photocurrents even when inversion symmetry is present. These currents are controlled by the shape of the Fermi surface, disorder, and the geometry of electronic bands. This means that materials once considered unsuitable for bulk optical rectification, including common metals, doped systems, and two-dimensional materials, can be engineered to convert oscillating light into DC electrical signals.

This research expands the material platform for optical rectification. Instead of relying only on noncentrosymmetric crystals, it shows that common centrosymmetric materials can also be used for light-to-DC conversion through third-order nonlinear response. This opens a route to energy-efficient photodetectors, terahertz technologies, and future energy-harvesting devices based on materials such as graphene.

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Balancing selectivity and permeability in nanofluidic membranes for osmotic power generation Han Qian et al. (2025)

The post Rethinking rectification for future energy technology appeared first on Physics World.

In condensed matter physics, driving a material with an external stimulus can push it into new nonequilibrium states that reveal hidden properties or create entirely new, potentially useful behaviours. These stimuli can include optical driving, where strong oscillating light is applied to the material, or periodic forcing, which refers to any repetitive push such as acoustic waves, modulated electric fields, or oscillating magnetic fields. 

In this work, the researchers wanted to understand how shining bright, oscillating light on a material can make it behave in unexpected ways, sometimes even resembling a superconductor. They used a theoretical model to study what happens when the system is periodically driven, allowed to exchange energy with a heat bath, and coupled to electromagnetic fields. When the drive is strong enough, the system can spontaneously organise into different kinds of ordered states: uniform order, spatially patterned order, or time oscillating order. 

Ordered phases can repel magnetic fields in the same way a superconductor does, through the Meissner effect, where the electromagnetic field behaves as if the photon has gained an effective mass and therefore cannot propagate inside the material. In some driven phases, however, not all of the magnetic field is expelled: part of it enters the material but only as a standing wave, forming a hybrid light-matter excitation known as a Meissner polariton. Additionally, strong fluctuations near the onset of ordering can make the material’s optical conductivity appear superconducting, causing experiments to detect superconducting like signals even when no true superconducting phase is present, helping explain why light‑driven systems sometimes show ambiguous signs of superconductivity. 

Overall, the researchers developed a unified theoretical picture showing how periodic driving can create or mimic superconducting behaviour, including predicting a new hybrid light-matter mode (the Meissner polariton), offering insight into puzzling experimental results in light driven materials.

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Laser-induced magnetization dynamics and reversal in ferrimagnetic alloys by Andrei Kirilyuk, Alexey V Kimel and Theo Rasing (2013)

The post Driving matter into new states appeared first on Physics World.