The research, published in Nature Materials, examined crystal formation in nanoparticles made from high- and medium-entropy alloys. These materials contain several metallic elements in roughly comparable proportions, unlike conventional alloys such as steel, which are dominated by one principal element. Their chemically complex and highly disordered atomic environments make them challenging systems for studying how crystals emerge. They also offer an unusually revealing setting because the atoms do not begin in a simple, uniform arrangement. By observing thousands of nuclei at different stages of development, the researchers were able to test whether the classical model’s assumption of a uniform crystal core and abrupt interface accurately reflects what happens in real materials.

The team developed a strategy for effectively freezing the nucleation process in place. The nanoparticles were heated to temperatures above 3,000 degrees Fahrenheit and then supercooled, dropping from extreme heat to room temperature within a few hundredths of a second. During this rapid thermal journey, crystal nuclei began to form, but the sudden cooling arrested them at different stages of growth. This created a collection of atomic snapshots representing early, intermediate and more advanced nuclei. Because the actual nucleation event occurs far faster than conventional data acquisition, directly watching a single nucleus form is extraordinarily difficult. By stopping many particles at different moments, however, the researchers transformed a fleeting process into a large statistical dataset.

They then used atomic electron tomography, an advanced three-dimensional imaging technique capable of mapping the positions of individual atoms within a nanoparticle. The method allowed the researchers to reconstruct each particle atom by atom and calculate how strongly ordered different regions were. In total, the study analyzed more than 8,000 nuclei, ranging from clusters containing fewer than 10 atoms to structures containing more than 1,000. Rather than finding a consistent crystalline region with a clean outer surface, the researchers observed a striking gradient. The innermost portion of each nucleus displayed the highest degree of crystallinity, while atomic order gradually declined with distance from the center. The transition into the surrounding disordered material was diffuse rather than sharply defined.

“The crystals were not uniform with a sharp boundary from the disordered atoms around them, as predicted by classical nucleation theory,” said corresponding author Jianwei “John” Miao, a professor of physics and astronomy at UCLA and a member of the California NanoSystems Institute. “Instead, we saw a gradient. Every nucleus had a core of highest crystallinity and then became more disordered as you go from that core to the boundary.” The observation challenges one of the most familiar visual images in materials science: a small, perfectly formed crystal embryo surrounded by atoms that have not yet joined it. In the new picture, the nucleus is more like a continuously evolving landscape, in which the distinction between crystal and non-crystal becomes progressively less certain as one moves outward.

To describe this behavior, the researchers introduced what they call the gradient nucleation pathways model. The model extends classical nucleation theory by allowing the degree of atomic order to vary throughout a nucleus. Classical theory remains within the new framework as a special limiting case: if the gradient is replaced by a perfectly uniform crystalline interior and a sharp interface, the classical results are recovered. Yet the experiments indicate that this idealized condition may rarely occur in the systems examined. The revised model therefore treats nucleation not as the sudden appearance of a finished miniature crystal, but as a multistep pathway through intermediate structures whose atomic order changes gradually.

This distinction also alters the way scientists think about the energy barrier involved in nucleation. In classical theory, forming a stable nucleus requires a system to overcome a sharply defined energetic obstacle. Small clusters are energetically unfavorable because creating an interface between ordered and disordered matter costs energy; only clusters that surpass a critical size can continue growing. The UCLA-led analysis suggests that the transition may instead involve a series of intermediate states. Miao compared the conventional energy barrier to a wall that must be climbed, while the gradient pathway resembles a ladder that allows matter to move upward through multiple smaller steps. If the system can pass through partially ordered configurations, nuclei may overcome the overall barrier more efficiently than the classical picture predicts.

The study also uncovered an unexpected pattern in how nuclei grow and eventually combine. As nuclei increased in size, their central regions became more highly ordered, indicating that crystallinity strengthens from the inside outward rather than appearing all at once. When separate nuclei approached one another, many were already oriented in nearly the same direction, even before they merged. Crystal orientation describes the alignment of atomic planes and axes, and matching orientations can make the final coalescence energetically easier. The observation suggests that neighboring nuclei may interact over short distances or follow correlated low-energy pathways during formation. Instead of growing independently and colliding randomly, they may become partially coordinated before joining into a larger crystal.

The implications extend well beyond the particular alloys used in the experiments. Nucleation is a universal step in processes ranging from cloud formation and ice growth to pharmaceutical crystallization, food production, semiconductor fabrication and the manufacture of structural metals. A more realistic description of how nuclei form could help scientists control when and where materials crystallize, as well as the size, orientation and properties of the resulting crystals. High- and medium-entropy alloys are especially attractive for engineering because their unusual compositions can produce combinations of strength, flexibility, thermal stability and catalytic activity. Understanding their earliest structural transformations could guide the design of more durable components, more efficient catalysts and advanced materials for demanding environments.

The researchers emphasize that their model is intended to apply broadly to nucleation systems, not only complex metallic nanoparticles. If gradients in order are common, they could influence models of freezing, condensation, precipitation and phase separation across physics, chemistry, Earth science and engineering. The ability to map atomic structures in three dimensions also opens a new experimental route for testing theories that previously relied heavily on indirect measurements. Classical nucleation theory is not discarded by the findings; rather, it is placed within a more general framework that recognizes the complexity of real atomic arrangements. “We believe this work will change how researchers think about nucleation,” Miao said, expressing hope that textbooks will eventually be revised. By revealing that crystals may begin not as sharply bounded objects but as smoothly evolving patterns of order, the study offers a fresh view of one of nature’s most fundamental transformations.

Subject of Research: Crystal nucleation and growth in high- and medium-entropy alloy nanoparticles; atomic-scale mechanisms of phase transitions.

Article Title: Crystal nucleation and growth in high-entropy alloys revealed by atomic electron tomography

News Publication Date: 25-Aug-2026

Web References: https://www.nature.com/articles/s41563-026-02727-y

References: Nature Materials; UCLA; California NanoSystems Institute; U.S. Department of Energy, Office of Science, Basic Energy Sciences program.

Image Credits: Miao Lab/UCLA

Keywords

Crystal nucleation, phase transitions, atomic electron tomography, high-entropy alloys, medium-entropy alloys, crystallography, materials science, nanotechnology, solid-state physics, UCLA, crystal growth, nucleation theory

At the core of this groundbreaking study is the utilization of hafnium dichalcogenides, a new class of layered materials composed of hafnium and chalcogen elements, such as sulfur and selenium. The research team focused on a unique quasiparticle known as phonon polaritons, which arise from the coupling of photons with the lattice vibrations within a crystal. This coupling phenomenon allowed the researchers to achieve unprecedented levels of confinement for THz light, compressing its wavelengths, which typically exceed 50 microns, to dimensions below 250 nanometers. This remarkable achievement was accomplished while minimizing energy loss, signaling a potential breakthrough in developing energy-efficient THz devices that could reshape various industries.

Caldwell likened the transformation of THz light confinement to a dramatic analogy: compressing light waves akin to confining ocean waves into a teacup. Such a significant reduction in wavelength has profound implications for the future of compact THz technology, which often struggles with large-scale integration due to constraints imposed by traditional materials. The team’s findings challenge the prevailing assumptions about THz light confinement, indicating that fundamental changes can be harnessed to facilitate miniaturization without compromising performance.

The implications of the research extend far beyond academic curiosity. The team’s focus on exploring the interactions between light and matter at the nano to atomic scale has the potential to revolutionize nonlinear optics and the design of nanoscale optical components. Through these studies, the researchers are aiming to reveal how these interactions differ from those in bulk materials. The study delves into intricate details regarding the sub-diffractional confinement of light and the characteristics of novel optical and electronic materials, ultimately paving the way for innovations in opto-electronic integration.

This ambitious research project initially began as a summer undertaking for a high school student, quickly evolving into a pioneering initiative that captured the attention of scientists worldwide. Such unexpected breakthroughs underscore the importance of fostering collaborations between academic institutions and researchers across various domains. The collaborative effort between the Free Electron Laser user facility FELBE at the Helmholtz-Zentrum Dresden-Rossendorf and researchers from both the Fritz Haber Institute and Vanderbilt University emphasizes the invaluable role of interdisciplinary teamwork in driving scientific advancements.

An essential aspect of the research involved utilizing advanced imaging techniques through near-field optical microscopy. This cutting-edge technology provided the necessary nanoscale imaging capabilities essential for exploring the effects of ultra-high THz light compression via phonon polaritons. The results indicate that hafnium dichalcogenides can serve not only as promising platforms for THz applications but also as gateways to exploring new frontiers in light-matter coupling.

Should these findings translate into practical applications, the research could facilitate the design of ultra-compact THz resonators and waveguides, which are critical components for a myriad of applications, including environmental sensing and security imaging. The successful integration of these materials into van der Waals heterostructures—assemblies formed by stacking layers of two-dimensional materials—holds the promise of reinforcing the capabilities of 2D materials research, promoting innovative approaches towards nanoscale opto-electronic integration.

As the scientific community continues to explore the properties of hafnium dichalcogenides, new physics may emerge through ultra-strong or even deep-strong light-matter coupling. The implications of these discoveries reach beyond the immediate research; they pave the way for high-throughput materials screening techniques that could potentially identify even more effective materials for THz technology applications.

The publication of this research represents not just a validation of the team’s hard work but also a stepping stone towards applying theoretical discoveries in practical scenarios. As Paarmann aptly stated, the research underscores the vital question of how far one can push the envelope of THz technology. The future may be bright for opto-electronic integration, which will consequently transform how various industries approach the integration of novel materials into functional devices.

In conclusion, this collaborative research not only broadens our understanding of the interactions between light and matter at unprecedented scales but also encourages future innovations that can arise from this exciting field. As researchers continue to unravel the complexities of terahertz technology, it appears we are only beginning to scratch the surface of what is possible.

Subject of Research: The confinement of terahertz light using hafnium dichalcogenides.
Article Title: Ultraconfined terahertz phonon polaritons in hafnium dichalcogenides.
News Publication Date: 15-Sep-2025.
Web References: Research Article.
References: None at this moment.
Image Credits: Ryan Kowalski and Niclas Mueller.

Keywords

Terahertz technology, hafnium dichalcogenides, phonon polaritons, nanoscale confinement, opto-electronic devices.

The synthesis process utilized in this research involved cutting-edge metal-organic chemical vapor deposition (MOCVD) techniques on a gallium nitride (GaN) substrate, which is known for its abrupt crystalline structure and compatibility with two-dimensional materials. The research team employed a meticulous method where they arranged the layers of hBN in an AA configuration, where identical atoms line up directly as opposed to the more unstable AA’ configuration where boron and nitrogen atoms alternate. This spatial arrangement is crucial for enhancing the material’s insulating properties, which are essential in a range of future electronic applications.

As the researchers conducted their experiments, they discovered that step-edges on the vicinal GaN substrates served as pivotal nucleation sites. These step-edges played a fundamental role in guiding the growth of hBN layers, effectively promoting their unidirectional alignment while reducing any rotational disorder. This remarkable step-edge guided growth mechanism enabled the team to produce high-quality AA-stacked hBN films that maintained an exceptional level of structural uniformity and crystallinity. Such characteristics are vital for the successful integration of hBN into next-generation electronic and photonic devices.

Another significant aspect of this research is the influence of charge incorporation as a result of carbon doping during the MOCVD process. The addition of carbon atoms into the hBN lattice effectively altered the interactions between layers, creating excess charge carriers that mitigated the strong interlayer electrostatic repulsion that typically destabilizes the AA stacking configuration. Hence, this innovative approach does not only demonstrate a new stacking technique but also introduces a previously unconsidered mechanism for tuning the properties and stacking order of van der Waals materials efficiently.

The theoretical assumptions governing the stacking configurations of van der Waals materials have been substantially challenged by this study. For years, scientists have operated under the belief that stacking arrangements in materials like hBN are predominantly controlled by thermodynamic preferences. However, Professors Jong Kyu Kim and Si-Young Choi from POSTECH, along with Guillaume Cassabois from the University of Montpellier, assert that the characteristics of the substrate and the inclusion of charge carriers are equally influential. Such revelations expand the horizons for customizing the architectures of two-dimensional materials, allowing for the engineering of materials with distinct and targeted electronic and optical properties.

Subsequent optical characterization of the synthesized AA-stacked hBN films revealed heightened second-harmonic generation (SHG), which serves as a hallmark for identifying non-centrosymmetric crystal structures. The implications of this feature are wide-ranging, pointing towards its applications in nonlinear optics, which has been an area of intense research interest due to the unique properties offered by such materials. Moreover, the material exhibited sharp band-edge emissions in the deep-ultraviolet (DUV) region, indicating its applicability in developing high-efficiency optoelectronic devices.

The implications of achieving wafer-scale control over the stacking order of hBN are substantial for the future of scalable, high-performance electronic and photonic systems. Seokho Moon, a postdoctoral researcher in Professor Kim’s lab and the lead author of the study, emphasized the importance of their findings by noting that the ability to precisely engineer stacking configurations is a significant step forward. This ability not only enhances the understanding of two-dimensional materials but also opens new pathways for research into their implementation in functional devices.

Furthermore, the funding backing this pioneering research demonstrates a commitment to advancing material science technologies. The research was supported by several programs including the Global Ph.D. Fellowship Program and the Basic Science Research Capacity Enhancement Program by the Ministry of Education, as well as other initiatives from the Ministry of Science and ICT, and Samsung Electronics. This collaborative effort showcases the importance of cross-institutional and governmental support in leading to discoveries that redefine the boundaries of materials engineering.

The synthesis of wafer-scale AA-stacked hBN presents a significant breakthrough in the field of materials science, particularly in the engineering of van der Waals materials. Understanding the mechanisms behind stacking configurations and how they can be manipulated opens a new frontier for research and application in various sectors, including quantum computing, advanced electronic devices, and photonic technologies. This work illustrates how the integration of fundamental science with innovative engineering techniques can create transformative effects in the world of nanomaterials, potentially leading to improvements in the performance and capability of future technologies.

In summary, the successful synthesis of wafer-scale AA-stacked hBN represents not just a scientific accomplishment but a pivotal moment in the exploration of new materials with tailored functionalities. The insights gained from this research contribute significantly to our understanding of two-dimensional materials, promising to spur advances across industries reliant on both electronic and optical applications in their future developments.

Subject of Research: Synthesis of wafer-scale hexagonal boron nitride with AA-stacking configuration
Article Title: Wafer-scale AA-stacked hexagonal boron nitride grown on a GaN substrate
News Publication Date: 19-Mar-2025
Web References: http://dx.doi.org/10.1038/s41563-025-02173-2
References: Nature Materials
Image Credits: Credit: POSTECH

Keywords: hexagonal boron nitride, AA-stacking configuration, metal-organic chemical vapor deposition, van der Waals materials, optoelectronics, quantum photonics, nanoscale materials, electronic devices, crystal structure, photonic systems, non-centrosymmetric crystal structures, deep ultra-violet region.

Historically, the properties that make quantum materials so remarkable often dissipate when scaled to macroscopic dimensions. As quantum behavior is typically observed in two-dimensional (2D) systems, the quest to extend these functionalities into 3D materials has proven difficult. Created from a thin layer of atoms, 2D materials, such as graphene, provide a unique playground for quantum phenomena. Yet the challenge has always been their stable integration into practical applications that necessitate bulk materials.

At the core of this research lies the examination of excitons, quasiparticles with fascinating optical properties that are essential to the transport of energy without electrical charge. These excitons are generally produced in semiconductors when light interacts with the material, energizing electrons and generating excitons comprised of an excited electron and the associated hole it leaves behind. While excitons reveal optimal performance in 2D configurations, their stability tends to diminish within bulk materials like silicon, where the binding energy is relatively weak.

The conventional methods employed to achieve 2D materials often involve labor-intensive processes such as mechanical exfoliation. This technique, notable for its role in isolating graphene, requires meticulous handling; however, this technique doesn’t lend itself well to the mass production of stable excitons in larger, practical formats. Recognizing this limitation, the research team sought an alternative by leveraging the principles of magnetism, targeting chromium sulfide bromide (CrSBr), a unique layered magnetic semiconductor.

CrSBr operates as a normal semiconductor at room temperature, reminiscent of silicon, but exhibits remarkable changes under cooled conditions. By lowering its temperature to approximately -223 degrees Fahrenheit, this material transitions to an antiferromagnetic state. This transformation enables a distinctive arrangement wherein the magnetic moments or spins of its constituent particles align in a consistent and alternating pattern across the layers. The innovative aspect of this research is that the antiferromagnetic ordering in CrSBr forms a boundary that effectively confines excitons to layers with identical spin directions, thus preventing them from traversing neighboring layers that possess opposite spins.

Through advanced optical spectroscopy techniques coupled with theoretical modeling, the researchers demonstrated that the confinement of excitons remains robust regardless of the number of layers present in the semiconductor system. This intriguing approach empowers the researchers to achieve the desired quantum confinement effects akin to those seen in traditional 2D materials, but within the vastly greater context of bulk materials.

Further validation of these findings came from a collaborative effort with researchers from Germany. Florian Dirnberger and Alexey Chernikov at TUD Dresden University of Technology independently studied the same magnetic semiconductors. Upon comparison of results, both research groups found remarkable agreement, lending credence to their findings and suggesting a deeper, perhaps universal, understanding of exciton behavior in magnetic semiconductors.

The implications of this breakthrough cannot be overstated. As we stand on the brink of a technology-driven era, the ability to confine and control excitons in bulk materials opens doors to new methodologies in advanced optical systems and quantum technologies. Applications could include next-generation lasers, energy-efficient optics, and revolutionary quantum computing methods that maximize efficiency through enhanced exciton stability.

In essence, the marriage of magnetism, quantum dynamics, and advanced semiconductor physics embodies the essence of this pioneering work. By revealing the underlying interactions and behaviors of excitons within a layered magnetic framework, researchers have not only advanced the field but potentially charted a course towards unprecedented developments in technology.

As momentum builds around this groundbreaking study, it’s noteworthy to highlight that the research received substantial backing from esteemed organizations, including the U.S. Department of Energy and the National Science Foundation. With such strong institutional support, the future of quantum technology looks exceptionally promising.

The journey to unravel the complexities of quantum behaviors continues, with multi-disciplinary approaches being crucial for future explorations. The collaboration across institutions and countries stands as a testament to the collective effort that is essential in navigating the intricacies of advanced materials and their behaviors. As researchers push the envelope of what is known, the fusion of ideas and innovations in this realm will undoubtedly shape the next wave of technological advancements.

This collaboration between notable universities not only demonstrates the importance of global scientific dialogue but also sets a precedent for future research endeavors. By effectively capturing and controlling the dynamics of excitons, the implications extend far beyond fundamental physics; they resonate through a variety of fields poised for disruption.

The integration of insights from disparate fields exemplifies how interconnected the fabric of scientific inquiry has become. As researchers delve deeper into the intersection of magnetism and excitonic behavior, they will inevitably yield findings that could transform our understanding of materials at both fundamental and applied levels. With each significant discovery, we inch closer to realizing the full potential of quantum technologies.

As we look towards the future, the synergy of innovative research, inter-institutional collaboration, and the unyielding pursuit of knowledge will be the driving forces behind the next generation of scientific breakthroughs.

Subject of Research:
Article Title: Magnetically confined surface and bulk excitons in a layered antiferromagnet
News Publication Date: 19-Feb-2025
Web References: Nature Materials
References:
Image Credits: Yinming Shao and team/Penn State

Keywords

The remarkable findings of this study, published in the esteemed journal Nature Materials, unveil the innovative use of blood-brain barrier-crossing lipid nanoparticles (BLNPs). These specially engineered nanoparticles not only overcome the inherent obstacles posed by the BBB but also carry substantial implications for the future of mRNA-based therapies, marking a transformational shift in therapeutic delivery systems. The meticulous research conducted on mouse models and isolated human brain tissue provides a robust foundation for further exploration and eventual application in clinical settings.

Indeed, the need for brain-targeted therapies has surged in recent years, fueled by the rising incidence of conditions such as Alzheimer’s disease, brain cancer, and amyotrophic lateral sclerosis. Traditional treatment modalities often fail to yield satisfactory outcomes, prompting the scientific community to explore alternative methods such as gene therapy, which offers the potential to replace, repair, or even augment the body’s innate biological processes. The new lipid nanoparticle system represents a pivotal advancement in this quest, showcasing the capability to deliver therapeutic mRNAs efficiently across the BBB.

What makes this research particularly fascinating is its dual focus: it not only introduces a novel delivery system but also sheds light on how this technology can instruct brain cells to synthesize critical therapeutic proteins. By leveraging mRNA, the researchers aim to target neuronal pathways and provide a means to restore normal function in affected areas of the brain, thereby offering hope for patients suffering from previously difficult-to-treat conditions.

Dr. Yizhou Dong, a co-corresponding senior author of the study and a prominent figure in immunology and immunotherapy, emphasizes the significance of these lipid nanoparticles in mRNA therapy. The formulation known as MK16 BLNP was specifically optimized through extensive structural and functional analyses, leading to its identification as a superior carrier with markedly higher mRNA delivery efficiency compared to existing FDA-approved lipid nanoparticles. This innovative system is designed to exploit natural transcytosis mechanisms within the BBB, effectively facilitating the transport of therapeutic payloads into the central nervous system.

Evidence of the impressive efficacy of the BLNP platform was demonstrated in well-designed studies that utilized disease models in mice. The results affirm the nanoparticle system’s capacity to deliver therapeutic mRNAs specifically to brain tissues, providing a pivotal proof-of-concept that such a strategy is not only viable but potentially scalable to human applications. As the research progresses, it is anticipated that the technology could be adapted for various neurological disorders, expanding the therapeutic landscape for mRNA-based interventions.

While the early findings are remarkably encouraging, the research team acknowledges that further studies are essential to comprehensively assess the long-term safety and efficacy of this novel delivery system. There are potential toxicology assessments and additional evaluations under FDA guidelines that will be critical in ensuring the BLNP technology’s clinical applicability. The current focus on refining the formulation underscores the research group’s commitment to translating these scientific innovations into tangible therapies for patients in need.

The excitement surrounding these findings is further amplified by the insights of Dr. Eric J. Nestler, another prominent figure in the research. He articulates that the emergence of lipid nanoparticles is indicative of a new era in tackling one of the most significant barriers in treating central nervous system disorders. With ongoing evaluations of this cutting-edge platform, the team is enthusiastic about its broader therapeutic implications and potential applications in the realm of biomedical science.

As the exploration continues into lipid nanoparticles, researchers are poised to unlock further innovations that could offer novel therapeutic options across a spectrum of brain-related diseases. This work not only signifies a monumental leap in our understanding of mRNA delivery but also serves as a beacon of hope for countless individuals grappling with debilitating conditions that adversely affect their quality of life.

In light of these developments, there is an array of scientific and ethical considerations that must be tackled moving forward. Researchers must tread carefully as they navigate the waters of translational medicine, ensuring that all safety protocols are followed rigorously. The collective goal remains to not only create effective therapies but also to do so in a manner that prioritizes patient safety above all else.

The research conducted at the Icahn School of Medicine exemplifies the potential of pioneering scientific thought when paired with rigorous experimentation. The innovative lipid nanoparticle system stands as a testament to what can be achieved when brilliance meets determination, and the future holds great promise as the team delves deeper into the myriad possibilities that this technology may unlock in the realms of neurology and pharmacotherapy.

This study, along with others like it, heralds a renewed sense of optimism in the medical community regarding the treatment of brain disorders. As more data emerges from subsequent investigations, the hope is that revolutionary therapies will come to fruition, paving the way for a future where neurological and psychiatric conditions can be effectively managed or even cured with newfound vigor.

Subject of Research: Human tissue samples
Article Title: Blood–brain-barrier-crossing lipid nanoparticles for mRNA delivery to the central nervous system
News Publication Date: February 17, 2025
Web References: Nature Materials
References: 10.1038/s41563-024-02114-5
Image Credits: Created with BioRender.com in the lab of Yizhou Dong, PhD, Icahn School of Medicine at Mount Sinai
Keywords: Nanoparticles