Moiré patterns arise whenever two periodic lattices are overlaid with a slight rotational misalignment, producing a long-wavelength interference superlattice that can profoundly alter electronic behavior. The phenomenon became world-famous with magic-angle twisted bilayer graphene, where twisting two graphene sheets by about 1.1 degrees unleashed unconventional superconductivity. Until now, however, moiré engineering has been pursued almost exclusively as a route to emergent quantum states in atomically thin heterostructures, typically assembled layer by layer under demanding laboratory conditions. The new work demonstrates that the same rotational degree of freedom, when distributed throughout the interior of a bulk crystal, can serve an entirely different purpose: dissipating mechanical stress and preventing catastrophic fracture.

The research team, led by scientists at the Shanghai Institute of Ceramics of the Chinese Academy Sciences together with collaborators at Zhejiang University, concentrated on gallium germanium telluride, GaGeTe, a ternary layered van der Waals semiconductor. Like other van der Waals crystals, GaGeTe consists of robust covalently bonded sheets held together by weak interlayer forces, which allows individual layers to slip relative to one another. In a pristine, perfectly aligned crystal, the layers share a common crystallographic orientation, and under tension the material tends to fail through the initiation and rapid propagation of cracks. The researchers reasoned that if adjacent layers were rotated with respect to each other, the mismatch between their lattices would create moiré superlattices that fundamentally change how stress is accommodated during deformation.

Introducing such twists into a bulk crystal might seem to require assembling it layer by layer, but the team found a remarkably simple route. By applying compression along an axis slightly off the crystal’s principal orientation, they controllably generated interlayer moiré twisting spanning a broad range of angles commensurate with the crystal’s translational symmetry. The magnitude of the twist could be tuned through the degree of pre-compression: samples compressed by 5, 10, and 20 percent developed distinct distributions of twist angles, as revealed by transmission electron microscopy and synchrotron-based diffraction techniques. Three-dimensional precession electron diffraction tomography and Rietveld refinement of synchrotron powder diffraction data confirmed the structural integrity and composition of the treated crystals, while in situ TEM tensile experiments captured the moiré patterns evolving in real time as the material was stretched.

The mechanical consequences were striking. When the pre-compressed, twisted crystals were subsequently pulled in tension at room temperature, their stress–strain curves revealed a transformation from brittle to genuinely ductile behavior. Where untreated GaGeTe fractured after limited elastic and plastic elongation, the twisted crystals sustained tensile strains approaching 30 percent, an increase of up to 360 percent in macroscopic ductility. Critically, the enhancement scaled with the twist angles introduced by compression: higher pre-compression levels produced larger interlayer rotations and correspondingly greater stretchability. The team also verified that the effect persisted across variations in sample thickness and strain rate, underscoring that the mechanism is intrinsic to the twisted architecture rather than an artifact of a particular testing configuration.

The origin of this extraordinary plasticity lies in how moiré superlattices facilitate stress relaxation. Under mechanical loading, the twist angles between neighboring layers continue to increase, allowing the crystal to accommodate deformation through widespread interlayer slipping rather than through the nucleation of fatal cracks. In an untwisted crystal, slipping is constrained by the periodic registry between layers, and once a micro-crack forms, the covalent bonds within a layer offer little resistance to its propagation. In the twisted configuration, the moiré modulation effectively homogenizes and redistributes the interlayer potential energy landscape, lowering the barriers to slip along the basal planes. Density functional theory calculations of generalized stacking fault energies and crystal orbital Hamilton populations supported this picture, showing reduced slip energies and modified Te–Te and Te–Ga bonding along slipping pathways in twisted structures.

Direct atomic-scale imaging told a complementary story. High-angle annular dark-field scanning transmission electron microscopy of deformed samples revealed intralayer bending, ripplocations, and micro-cracks that remained arrested rather than propagating through the entire crystal. In situ TEM tensile videos documented moiré patterns with small twist angles of roughly 1.5 degrees at early deformation stages, growing to approximately 6 degrees as tensile strain accumulated, with the progressive twisting acting as a built-in reservoir for plastic accommodation. The researchers also constructed idealized twist-stacked models, denoted θ-GaGeTe, with alternating layers rotated by specific angles ranging from about 1.5 to nearly 22 degrees; simulated moiré patterns for these structures matched the experimentally observed contrast, validating the structural interpretation of the deformation mechanism.

Perhaps the most important practical feature of the approach is its selectivity. Because moiré twisting occurs only between layers while the atomic arrangement within each layer remains intact, the in-plane electronic properties that make these materials attractive for devices are essentially untouched. This stands in contrast to many toughening strategies that rely on defects, grain boundaries, or alloying, all of which can severely degrade charge transport, optical response, or thermoelectric performance. The authors also demonstrated the generality of the concept beyond GaGeTe: off-axis compression produced comparable enhancements in tensile plasticity across a family of bulk van der Waals crystals including GaS, GaSe, InSe, CrSiTe3, InSiTe3, and SnBi2Te4, suggesting the strategy is broadly applicable to the entire class of layered semiconductors.

The implications reach into several technology areas where mechanical fragility has long limited deployment. Flexible thermoelectrics, which convert waste heat into electricity in conformable formats, depend on semiconductors that can bend and stretch without failing; earlier work by some of the same groups established ductile inorganic semiconductors and exceptional plasticity in materials such as InSe and Bi2Te3-based crystals. The moiré-twisting strategy adds a new, geometrically driven lever to that toolkit, one that is compatible with the demanding electronic requirements of thermoelectric and optoelectronic devices. It may likewise inform the design of two-dimensional-material-based transistors, photodetectors, and silicon photonics components, where GaGeTe itself has recently been integrated into electro-optic devices, by improving the mechanical robustness of bulk crystals used as feedstock or substrates.

From a fundamental standpoint, the study expands the conceptual scope of moiré physics from quantum emergent phenomena to classical mechanics of deformation. It shows that a structural parameter long treated as an electronic tuning knob can double as a mechanical design variable, decoupled from in-plane transport. The work was supported by the National Natural Science Foundation of China, the Chinese Academy of Sciences, and Shanghai municipal programs, with synchrotron experiments performed at the RIKEN BL44B2 beamline of SPring-8 in Japan. As research groups worldwide continue to explore twistronics for superconductivity, magnetism, and correlated electron physics, this result suggests a parallel track: twisting crystals to make them tough. If the strategy can be scaled from laboratory single crystals to manufactured components, the humble rotational misalignment between atomic layers may become one of the most versatile tools in the materials engineer’s repertoire, turning inherently brittle semiconductors into materials that bend, stretch, and survive the demands of real-world flexible technology.

The result also reframes a long-standing dichotomy in materials science. Metals derive their ductility from dislocations, dense arrays of line defects that glide through the crystal lattice and dissipate strain; conventional semiconductors, with their stiff covalent bonding and scarcity of mobile defects, have almost always been relegated to the brittle side of that divide. The moiré-twisting mechanism offers a third route: rather than relying on point or line defects introduced during growth or processing, it exploits a rotational degree of freedom that is deliberately programmed into the stacking sequence itself, effectively designing the deformation pathway in advance.

The approach resonates with recent independent demonstrations that twist can strengthen otherwise fragile solids. Twisted-layer boron nitride ceramics have shown high deformability and strength, and twist-assisted toughening has been reported in two-dimensional transition metal dichalcogenides, indicating that rotational misalignment is emerging as a general design principle spanning scales from atomically thin films to bulk ceramics. The present study extends this principle to ternary van der Waals semiconductors and, crucially, shows that the twist can be introduced after synthesis by a scalable mechanical step rather than during crystal growth.

For practical adoption, the compatibility with existing characterization and processing workflows matters. Off-axis compression requires no epitaxial assembly, no layer-by-layer transfer, and no exotic chemistry, which means the treatment could in principle be applied to crystals grown by conventional bulk methods. Because the twist angles are commensurate with the crystal’s translational symmetry, the resulting superlattices are periodic and well defined, making the deformed crystals amenable to standard diffraction-based quality control before device fabrication.

Open questions remain, including how the twist distributions evolve under cyclic loading, elevated temperature, and long-term operation, and whether the ductility gains persist when crystals are integrated into multilayer device stacks. Answering these will determine whether moiré-twisted semiconductors move from laboratory demonstrations into flexible thermoelectric modules, wearable sensors, and compliant photonic platforms.

Subject of Research: Enhancing tensile plasticity of bulk van der Waals crystals through tunable interlayer moiré twist angles

Article Title: Tuning moiré twist angles enhances tensile plasticity in bulk van der Waals crystals

Article References: Zhou, J., Zou, J., Gao, Z., Zhang, J., Zhang, L., Li, Z., Zhou, Z., Qiu, P., Yang, Y., Yu, Q., Chen, L., & Shi, X. (2026). Tuning moiré twist angles enhances tensile plasticity in bulk van der Waals crystals. Nature Materials. https://doi.org/10.1038/s41563-026-02731-2

Image Credits: AI Generated

DOI: 10.1038/s41563-026-02731-2

Keywords: moiré twisting, van der Waals crystals, tensile ductility, GaGeTe, off-axis compression, plastic deformation, two-dimensional materials, twistronics, semiconductors, flexible electronics, interlayer slipping, Nature Materials

The central material, TaS₂, belongs to the family of van der Waals crystals. Its atoms are strongly bonded within two-dimensional planes, while adjacent planes are held together comparatively weakly. This unusual bonding arrangement allows one layer to shift laterally with respect to another, much like a stack of cards. In conventional three-dimensional solids, such relative motion is generally difficult because atoms are locked into a rigid three-dimensional framework. In layered crystals, however, interlayer sliding can modify orbital overlap, charge transfer, and the effective dimensionality of electronic states. Even a displacement on the scale of a fraction of a nanometer can therefore alter how electrons move through the crystal. The research team set out to determine whether this structural flexibility could be harnessed deliberately in a macroscopic, three-dimensional material rather than only in isolated atomically thin flakes.

The researchers’ earlier experiments provided the first part of that answer. By creating periodic interlayer-sliding superlattices in single crystals of the 1T structural phase of TaS₂, they produced a material referred to as LC-TaS₂. Although the chemical formula and stoichiometry remained unchanged, the altered stacking sequence substantially modified the electronic ground state. The team showed that subtle changes in interlayer coupling could move the system between a three-dimensional band-insulating state and a two-dimensional Mott-insulating state. A band insulator is electrically inactive because filled electronic bands are separated from empty bands by an energy gap. A Mott insulator, by contrast, may be predicted to conduct by conventional band theory but becomes insulating because strong electron-electron repulsion prevents charge carriers from moving freely. The distinction demonstrated that stacking could control correlation-driven physics as powerfully as composition.

That conclusion was not easy to establish. The structural differences created by sliding are extremely small, and their signatures can be comparable to the uncertainty of ordinary measurements. The team relied on advanced spectroscopic techniques and atomic-resolution imaging to connect the arrangement of layers with the resulting electronic behavior. Such sensitivity was essential because the relevant structural information is effectively hidden from conventional crystallographic descriptions that average over many unit cells. Professor Hai Xu of Anhui University, one of the collaborators, emphasized that without sufficiently precise measurements, the electronic consequences of different stacking sequences could easily have been missed. The findings suggested that layered crystals might contain a much larger catalogue of accessible quantum states than their chemical formulas alone would indicate.

The new study pushes the concept further by showing that interlayer sliding does not act in isolation. Under suitable conditions, sliding between layers can cooperate with reconstruction of atoms within a layer, producing what the researchers describe as “two-tier sliding.” This coupled process can drive a layer-resolved transformation from the metastable 1T phase of TaS₂ into the stable 1H phase. The two structures have different atomic arrangements and electronic environments, even though both consist of the same elements in the same overall proportion. The 1T-to-1H conversion therefore represents a structural phase transition rather than a chemical reaction. What makes the observation especially striking is that the transformed regions do not appear as random defects or isolated patches. Instead, they organize into regular, nanoscale patterns that behave as self-adaptive hetero-phase superlattices.

These superlattices combine domains of different crystal phases within a single coherent material. Atomic-resolution aberration-corrected high-angle annular dark-field scanning transmission electron microscopy revealed ladder-like structures as well as more complex arrangements containing alternating 1H and 1T regions. In some cases, the interfaces include a 60-degree-rotated variant of the 1H structure, designated 1H’. The resulting sequences can be described as 1H/1T or 1H/1T/1H’ heterostructures, with atomically sharp boundaries between phases. Rather than being imposed through lithography or assembled from separate crystals, these architectures emerge through the material’s own structural response. Their formation indicates that the crystal can redistribute strain, charge, and local bonding to stabilize a repeating pattern, effectively building a superlattice from within.

Interphase charge transfer appears to play a key role in this self-organization. When two structural phases meet, their electronic bands and local chemical environments need not align. Electrons can therefore move across the interface until the combined system reaches a lower-energy configuration. This redistribution changes the electrostatic landscape and can help stabilize specific domain widths and interface geometries. In TaS₂, the coupling between phase boundaries and charge transfer creates a form of structural feedback: the arrangement of phases influences the electronic distribution, while the electronic distribution helps determine which arrangement is energetically favorable. Such feedback is central to many emergent phenomena in quantum materials, but here it is expressed through a controllable combination of layer sliding and atomic reconstruction.

The electronic consequences are particularly important because the engineered interfaces exhibit different superconducting transition temperatures. Superconductivity occurs when electrons form correlated pairs that can move without electrical resistance below a characteristic temperature. The transition temperature depends sensitively on the electronic structure, lattice vibrations, dimensionality, and interactions between carriers. By creating neighboring phases with distinct local environments, the TaS₂ superlattices provide multiple superconducting settings within one crystal. The research therefore demonstrates that structural reorganization alone can generate differentiated quantum states, without relying on dopants, external chemical pressure, or changes in stoichiometry. This result could prove valuable for designing materials in which superconducting regions, insulating regions, and conducting interfaces are positioned through atomic-scale architecture rather than conventional chemical synthesis.

The broader significance extends beyond TaS₂. In recent years, twisted and slid two-dimensional materials have shown that small changes in relative orientation or displacement can produce dramatic effects such as flat electronic bands, correlated insulating phases, and superconductivity. The new work suggests that related principles can operate in bulk layered crystals, which are generally more robust, scalable, and stable in practical environments than isolated monolayers. A three-dimensional crystal with programmable stacking could combine the mechanical resilience of a bulk material with the electronic tunability associated with two-dimensional systems. It may also allow researchers to investigate how quantum states evolve across interfaces, how charge moves between phases, and how collective behavior changes when superlattice periodicity is varied.

Together, the studies establish stacking sequence as a fundamental materials-design parameter alongside chemical composition and stoichiometry. The ability to coordinate interlayer motion with intralayer reconstruction creates a pathway for building adaptive quantum architectures directly inside a crystal. Although considerable work remains before such structures can be incorporated into devices, the concept points toward a new generation of electronics based on controlled sliding, phase conversion, and interface engineering. Instead of treating atomic rearrangements as unwanted instability, scientists may be able to use them as functional operations—turning layers, interfaces, and phase boundaries into active components. TaS₂ has thus become a model for a broader idea: in layered quantum matter, changing where atoms sit may be nearly as powerful as changing what the material is made of.

Subject of Research: Atomic stacking, interlayer sliding, intralayer reconstruction, hetero-phase superlattices, and superconducting states in TaS₂.

Web References: https://doi.org/10.1093/nsr/nwag246

References: National Science Review, DOI: 10.1093/nsr/nwag246

Image Credits: Ding et al., National Science Review, CC BY 4.0.

Keywords

TaS₂, van der Waals materials, interlayer sliding, stacking engineering, superlattices, superconductivity, Mott insulator, quantum materials, phase transformation, sliding electronics