Scientists at Cornell Engineering have found a way to make a thin film material expand and contract billions of times per second by hitting it with ultrafast pulses of infrared light.
This rapid “breathing,” caused by strain in the material’s atomic structure, could one day be used to switch its electronic, magnetic, or optical properties on and off at incredible speeds.
The study, published in Physical Review Letters, was led by materials science professors Nicole Benedek and Andrej Singer.
Their team wanted to test whether light could be used to manipulate strain in a material—a well-known way to change a material’s properties, but one usually achieved through mechanical means, not light.
“Normally, when you grow a material under strain, that strain is fixed in place forever,” Benedek explained. “With light, we’re creating a dynamic strain—a temporary expansion and contraction that disappears once the light is gone.
That makes it fundamentally different.”
To make this work, the researchers used ultrafast bursts of terahertz light, lasting just trillionths of a second.
Terahertz light vibrates at the same low frequency as phonons—the sound-like vibrations of atoms inside a crystal lattice.
By tuning the light to the right frequency, the scientists could excite a specific atomic motion, like pushing a child on a swing at just the right moment to make the swing soar higher.
The result was a rapid expansion of the material’s lattice structure, creating a state of matter that doesn’t naturally occur.
The material chosen for the experiment was lanthanum aluminate, a simple and stable oxide thin film. “It’s not a flashy material—it doesn’t have many interesting properties on its own,” Benedek said. “But because the theory behind light interactions is so complex, we needed something straightforward to start with.”
The material was synthesized at Cornell by Darrell Schlom, an expert in oxide thin films, using a method called oxide molecular-beam epitaxy. The experiments were then carried out at the Stanford Linear Accelerator Center (SLAC), where the team used a free-electron laser to deliver the necessary bursts of terahertz light.
Analysis confirmed that the predicted breathing effect occurred—but the researchers also stumbled upon something unexpected. The process didn’t just make the material expand and contract; it also permanently improved its internal structure. “We saw a more ordered, crystalline state form at the boundaries between domains,” Singer said. “The light excited phonons that created a new structure, which then spread across the film surface.”
This finding suggests that ultrafast light pulses could be used not only for temporary switching but also for long-lasting improvements in material properties. That opens up possibilities for designing devices where light triggers structural changes that enable superconductivity, alter magnetism, or control electronic states.
All materials have physical limits to how much they can be stretched or compressed. But this method of using low-frequency light adds a new dimension, allowing scientists to explore states of matter that would be impossible to achieve through conventional approaches.
“The combination of theory, synthesis, and characterization really allowed us to understand what light is doing in these complex oxides,” Singer said. “It’s giving us access to properties that go beyond standard methods, and that’s very exciting for the future of materials science.”
