Imagine witnessing a microscopic ballet, where atoms twist and turn in perfect harmony, all triggered by a single pulse of light. But here's where it gets mind-blowing: this atomic dance happens in a trillionth of a second, far too fast for the human eye or even most scientific tools to catch. Thanks to a groundbreaking collaboration between Cornell and Stanford University, researchers have finally captured this fleeting performance using ultrafast electron diffraction—a technique that films matter at its most rapid pace.
A pulse of light sets the stage, and atoms in a crystalline sheet just a few layers thick begin to move. It’s not chaos; it’s choreography. These atoms twist and untwist in sync, like dancers following a beat, all driven by precisely timed bursts of energy. This phenomenon, known as moiré materials, involves stacking ultra-thin layers and twisting them slightly to alter their properties—turning them into superconductors or making electrons behave in entirely new ways.
And this is the part most people miss: until now, scientists could only theorize how these layers responded to light. But in this study, published in Nature, the Cornell-Stanford team revealed that the layers don’t just sit still. They briefly twist tighter, then spring back, like a coiled ribbon releasing its energy. This dynamic motion opens up new possibilities for controlling materials in real time, with potential applications in superconductivity, magnetism, and quantum electronics.
“People have long known that stacking and twisting these layers changes a material’s behavior,” explains Jared Maxson, professor of physics at Cornell and co-corresponding author. “What’s new is that we’re enhancing that twist dynamically with light—and watching it happen live.”
But here’s the controversial part: some researchers previously believed that once moiré materials were stacked at a fixed angle, their structure was locked in place. Fang Liu, project lead at Stanford and co-corresponding author, challenges this notion. “The atoms will move,” she asserts. “In fact, they perform a kind of circle dance within each moiré unit cell.”
To capture this dance, the team used a Cornell-built ultrafast electron diffraction instrument, paired with a high-speed detector called the Electron Microscope Pixel Array Detector (EMPAD). Originally designed for still images, the EMPAD was repurposed to act as a hypersensitive movie camera for atoms. “Most detectors would blur the signal,” Maxson notes. “The EMPAD allowed us to capture incredibly subtle features that could have been lost in the noise.”
This achievement was only possible through collaboration. Cornell provided the cutting-edge tools and expertise in electron-beam technology, while Liu’s lab at Stanford engineered the moiré materials. “Without combining materials understanding with electron-beam mastery, this wouldn’t have happened,” Maxson emphasizes. Liu adds, “Jared’s ultrafast instrument was the only one capable of seeing the moiré pattern, and his team even modified it in real time to make the experiment possible.”
The data, collected by Cameron Duncan, Ph.D. ’22, during his doctoral studies at Cornell, played a central role in reconstructing the atomic motion from complex diffraction patterns. “We customized our hardware to enhance its diffraction-resolving power,” Duncan explains. “Seeing our hard work pay off was incredibly satisfying.”
Looking ahead, Liu’s lab has already created new moiré samples to push the limits of Cornell’s ultrafast instrument even further. The teams plan to explore how different materials and twist angles respond to light, aiming to deepen their understanding of real-time quantum behavior control.
Here’s where you come in: Do you think this research could revolutionize technologies like quantum electronics or superconductivity? Or is there a potential downside to manipulating materials at such a microscopic level? Let’s discuss in the comments—your perspective could spark the next big idea!
