| Apr 23, 2026 |
New research shows how the organization of electrons can reshape how a material responds to light, opening previously inconceivable possibilities for optical and quantum materials.
(Nanowerk News) In materials science, if you can understand the “texture” of a material – how its internal patterns form and shift – you can begin to design how it behaves. That’s the focus of the work of Zhenglu Li, assistant professor in the Mork Family Department of Chemical Engineering and Materials Science at USC Viterbi School of Engineering.
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Li’s recently published paper in Proceedings of the National Academy of Sciences (“Moiré excitons in generalized Wigner crystals”) demonstrates that the way electrons organize themselves inside a material determines how that material responds to light – and this organization can be engineered.
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From texture to technologies
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“Moiré” is a word that will be familiar to anyone who follows fashion. In the context of textiles, it refers to a larger-scale interference pattern that appears when two repeating patterns are slightly misaligned. Imagine brushing a swatch of velvet in different directions; the material reveals different properties depending on how it is ruffled.
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Likewise, in the context of nanoscale materials science, an independent, shimmering or wavelike pattern is formed when two overlapping atomically thin layers are overlaid at an acute angle. The new pattern, namely moiré superlattice, changes how electrons move, which can give the material unusual properties.
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“The pattern only emerges when two layers are slightly misaligned,” Li explains. “In fact, the pattern actively reshapes how electrons behave and that’s what makes these moiré materials so remarkable. In this paper, we study how the pattern flattens the energy bands, slowing electrons down and amplifying their interactions.”
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The results are highly significant and suggest a new way to think about designing materials for light-based technologies. In addition to changing a material’s chemical composition, researchers may also be able to tune optical behavior by controlling how electrons arrange themselves. In the long term, this could help guide the design of future quantum and optoelectronic materials, including platforms relevant to sensing, energy conversion and quantum information science.
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Predicting complex phenomena
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Li leads the Computational Quantum Materials research group at USC, developing advanced computational methods grounded in many-body quantum mechanics – the framework that describes how large numbers of interacting electrons behave collectively. “Rather than treating electrons as independent particles, this approach accounts for how they influence one another, often producing effects that cannot be understood in isolation,” he explains.
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A defining feature of Li’s approach is the use of “first-principles” methods: calculations that begin from the fundamental laws of quantum mechanics, without relying on experiments with adjustable parameters. These methods make it possible to predict complex phenomena – such as superconductivity or ultrafast energy transfer – by working outwards from the underlying physics.
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Here’s where we’ll encounter so-called “excited states”: conditions under which materials are driven by light, heat or electric fields. These excited states are central to materials’ usefulness and how materials absorb light, transport energy, and function in optical devices. But, as Li notes, these conditions are also among the most difficult to calculate because they depend on the collective behavior of interacting particles.
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From texture, to crystals, to light
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In moiré superlattices where strong interactions arise, electrons arrange themselves into ordered configurations known as generalized Wigner crystals, forming an internal structure defined by how electrons organize – not just by the atoms themselves.
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And then – the plot thickens – the material shimmers – let’s add another factor to the mix. What happens when light interacts with such a system?
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“In most semiconductors, light creates excitons – pairs of an excited electron and the ‘hole’ it leaves behind – and this is largely understood from the material’s band structure,” said Li. “Using large-scale first-principles calculations, our team was able to directly resolve the internal structure of these excitations for the first time.” This is especially challenging because moiré materials involve very large atomic-scale patterns and strong many-electron interactions, making the calculations far more difficult than for ordinary materials.
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Li and primary postdoctoral researchers Jing-Yang You and Chih-En Hsu, together with collaborators including Mauro Del Ben, researcher at Lawrence Berkeley National Laboratory, and Steven G. Louie, professor emeritus in Physics, UC Berkeley, found that the electron and hole remain tightly linked, moving together in a way that follows the underlying Wigner crystal. The excitation does not behave as independent electrons and holes. Rather than behaving like a simple excitation in an ordinary semiconductor, it reflects the strong correlations and charge order already present in the material.
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This is what Li’s team terms a Wigner crystalline exciton: an exciton state shaped by the pre-existing Wigner crystal order of electrons.
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The optics of the possible
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The key insight here is that a material’s responses to light, or excitons, are not determined by its band structure alone. It can be shaped by how electrons organize themselves beforehand along with the strong interactions between the excited electrons and holes.
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“That changes how materials can be designed,” said Li. “Instead of tuning properties only through composition, we can begin to control optical behavior by engineering electronic structure – how electrons arrange and interact.”
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This provides Li’s research group with the grounding they need to develop computational frameworks for predicting these effects in complex materials. And with those predictions in hand, who knows what new technologies could be within arm’s reach?
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While the work is still at the fundamental research stage, it provides a new computational framework for predicting how strongly correlated quantum materials respond to light. That insight could help guide future efforts to design materials with tunable optical and quantum properties.
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The clues to that new world can be found in the prediction frameworks being developed in Li’s lab. For now, we’ll watch and wait – and dream of possible patterns of quantum texture.
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This article may feature some AI-assisted content for clarity, consistency, and to help explore complex scientific concepts with greater depth and creative range.
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