Researchers from Brown University and the University of Michigan College of Engineering have achieved a remarkable milestone in materials science by stabilizing a transient structural phase of matter long predicted by theory but never before physically realized. This breakthrough was accomplished through the precise engineering of custom-shaped silver nanoparticles into superlattices, opening doors to new quantum optical phenomena and the potential development of advanced quantum technologies.
At the heart of this advancement lies the ability to capture and maintain an elusive intermediate phase between two predominant crystal structures found in metals: face-centered cubic (FCC) and body-centered cubic (BCC). These arrangements dictate how atoms pack within metallic crystals, influencing properties like strength, conductivity, and phase transitions. The FCC structure is characterized by particles positioned at each cube corner and at the center of each face, representing the densest packing for spheres. Conversely, the BCC structure features particles at the cube corners and one particle at the center of the cube body, resulting in less dense packing relative to FCC.
Transitions between FCC and BCC structures, such as in iron where heating triggers a shift from BCC to FCC at 912°C, have long intrigued scientists. These transitions are theorized to proceed via complex pathways involving short-lived intermediate phases with lower symmetry, notably described by the Nishiyama-Wassermann pathway. These transient states have remained experimentally inaccessible due to their inherent instability—until now.
The Brown and Michigan research teams synthesized silver nanoparticles shaped as truncated octahedra—termed “mecons”—which combine facets of cubes and spheres. This unique geometry provides an intermediate shape ideal for investigating packing behaviors that could mimic the transient phases predicted by theory. By modulating the growth temperature during synthesis, they produced a spectrum of mecon shapes ranging from more spherical to more cubic forms, subsequently coating them with molecular ligands designed to encourage specific inter-particle interactions.
These ligands act as flexible, hairy extensions on the nanoparticle surfaces, facilitating controlled adhesion and enabling the nanoparticles to self-assemble into superlattices. This self-assembly process mimics atomic arrangements in metals and allows for the stabilization of structural phases that mirror the ephemeral intermediates seen in metallic phase transitions. Combining rigorous experimental characterization with sophisticated simulations performed in collaboration with Sharon Glotzer’s group at the University of Michigan, the team demonstrated that these ligand-coated mecons naturally organize themselves into configurations consistent with the Nishiyama-Wassermann transitional phases.
Beyond the structural achievement, the researchers observed extraordinary optical behavior in these superlattices under illumination. The silver nanoparticles exhibited deep-strong light-matter coupling, a quantum optical regime where the vibrations of electrons within the nanoparticles become entangled in unison with incident light waves. Remarkably, this effect manifested at room temperature—a stark contrast to the cryogenic conditions usually required for such phenomena—indicating the superlattices’ potential for real-world quantum devices.
This discovery not only sheds light on fundamental physics governing phase transitions in metals but also provides a versatile platform for designing materials with bespoke quantum mechanical properties. The ability to control and stabilize transitional crystal phases through nanoparticle shape tuning could lead to advancements in quantum computing, sensing technologies, and other applications leveraging quantum information science.
Associate Professor Ou Chen from Brown University likens the process to assembling with LEGO blocks at the nanoscale. Synthesizing nanoparticles with carefully tuned shapes enables stacking into novel architectures once inaccessible, revealing new phases of matter and unlocking unforeseen functionalities. Lead author Yasutaka Nagaoka led the meticulous synthesis and assembly work, while Tim Moore contributed research expertise from Glotzer’s laboratory in elucidating the intricate self-assembly mechanisms.
The integration of experimental nanochemistry and computational modeling was key to unraveling how subtle variations in nanoparticle shape and inter-particle ligand chemistry govern the formation and stability of these in-transition superlattices. These findings deepen understanding of structural phase transitions that have long been theoretically described but practically unobservable, marking a significant leap in the control of material design at the nanoscale.
Moreover, the observation of deep-strong light-matter interactions at ambient conditions in these superlattices points toward a new class of quantum materials capable of harnessing room-temperature quantum entanglement. Such capabilities are fundamental to progressing quantum computing architectures where maintaining coherence and entanglement at non-cryogenic temperatures remains one of the field’s biggest challenges.
This work exemplifies the burgeoning synergy between nanomaterials synthesis and quantum science, where deliberate shape and surface chemistry modifications at the nanoscale produce emergent properties with vast technological implications. Stabilizing transitional phases of matter via nanoparticle superlattices offers a tantalizing glimpse into the future of quantum-enabled devices engineered from the bottom up.
Funded by the National Science Foundation and the Department of Energy, this research was published in the prestigious journal Science, underscoring its importance to the scientific community. The multidisciplinary collaboration between Brown University and the University of Michigan demonstrates how integrated approaches spanning chemistry, physics, and materials science can unlock new realms of possibility in nanotechnology and quantum engineering.
As Professor Chen summarizes, “Identifying and stabilizing a new phase of matter inherently invites novel applications. These superlattices, born from precise shape control and molecular engineering, are more than a scientific curiosity—they lay the foundation for next-generation materials that can revolutionize quantum technologies.”
Subject of Research: Stabilization of transient intermediate crystal phases using nanoparticle superlattices; quantum optical properties of engineered nanomaterials.
Article Title: Stabilizing in-transition phases of superlattices through shape control of silver nanocrystals
News Publication Date: 28-May-2026
Web References: DOI: 10.1126/science.ady6472
Image Credits: Chen Lab / Brown University
Keywords
Nanotechnology, Nanoparticle Superlattices, Phase Transitions, Face-Centered Cubic, Body-Centered Cubic, Silver Nanocrystals, Nishiyama-Wassermann Pathway, Quantum Optics, Light-Matter Coupling, Quantum Entanglement, Materials Engineering, Nanomaterials
