Laser Flashes Line Up Tiny Electric Islands Inside a Crystal for a Trillionth of a Second

Physicists at Auburn University have used flashes of laser light to bring order to tiny, electrically charged "islands" inside a crystal. The result helps answer a decades-old question about how the material organizes itself, and it shows that light can be used to control its behavior, a step toward new ways of processing and storing information.

The research was led by Wencan Jin, the Thomas and Jean Walter endowed associate professor in Auburn's Department of Physics, and graduate student Mohamed Kandil. Their paper, "Optical Poling of a Quantum Ferroelectric Metal across the Order-Disorder Phase Transition," was selected as an Editors' Suggestion in Physical Review Letters. Collaborators at Japan's National Institute of Advanced Industrial Science and Technology grew the crystals used in the experiments.

The team studied a modified form of strontium titanate, a single crystal with an unusual pairing of properties. It lets electrons move through it like a metal while also containing small regions with distinct positive and negative sides. These regions, called polar nanoregions, can point in different directions or line up in an organized pattern.

For decades, researchers have debated how that organization begins. One possibility is that atoms shift together to create a polarized state. The other is that the tiny polar islands already exist and simply line up as the material cools. Jin's group framed it as the difference between forming a crowd and getting people who are already in a crowd to face the same direction. The question is hard to settle because the islands are so small and their signals so faint.

To look, the team built a highly sensitive laser-based measurement system and tracked how the crystal changed incoming light as the sample was repeatedly warmed and cooled. At higher temperatures the islands pointed in disordered directions. As the crystal cooled, they settled into preferred orientations. The results provided strong evidence that the islands were already present before they lined up.

The researchers then showed that light itself could make them align. Brief laser pulses brought order to regions that would otherwise remain disorganized at warmer temperatures, and an optical measurement detected the resulting pattern. The alignment lasted only a picosecond, which is one trillionth of a second, but creating and reading it with light opens possibilities for investigating extremely fast ways to handle information.

Getting the experiment to work took years. The project began at the 2023 American Physical Society March Meeting, where Jin connected with researchers in Japan who could grow the crystals. The Auburn team then spent nearly a year improving its equipment before it detected the islands' faint optical signal, and another challenge remained in capturing the fleeting moment when laser light brought them into alignment. "The breakthrough came in 2025, when Mohamed finally observed the disordered polar regions becoming aligned under laser illumination," Jin said. "Seeing that signal emerge was a thrilling moment for the team."