Striped or checkered? Magnetic field influences competing electronic patterns in a graphene-like quantum material Sadie Harley Scientific Editor Robert Egan Senior Editor In most everyday materials, such as copper, silver and silicon, the behavior of electrons is relatively predictable. In quantum materials, however, electrons can interact in complex ways, giving rise to collective electronic states with remarkable properties.

Understanding how these states emerge—and, ultimately, how to control them—is one of the central challenges in quantum materials research. Now, researchers from the Okinawa Institute of Science and Technology (OIST) and Hiroshima University have discovered that a small magnetic field switches the layered quantum material CeTe₃ between competing electronic states that appear as striped or checkerboard patterns. Published in Nature Communications, the work reveals how magnetism can reorganize a quantum material's entire electronic state.

CeTe₃, a material formed from cerium and tellurium atoms, has some properties similar to graphene in that it is a two-dimensional layered material with highly mobile electrons. But unlike graphene, electrons on the cerium sites remain localized while the mobile electrons on the tellurium sites naturally self-organize into ordered patterns. Thanks to a quantum property called spin, the localized electrons behave like tiny magnets, allowing CeTe₃'s electronic states to be manipulated with a magnetic field.

Until now, however, no one had directly observed how magnetism influences the evolution of these electronic patterns. "CeTe₃ offers a rare opportunity to watch mobile electrons and localized spins work together," says co-first author Yuita Fujisawa, an assistant professor at Hiroshima University and a former postdoctoral researcher in the Quantum Materials Science Unit at OIST, led by Professor Yoshinori Okada. "We wanted to directly visualize how this cooperation gives rise to collective electronic states." From stripes to checkerboards To begin, the researchers used scanning tunneling microscopy (STM) to map how electrons are arranged within CeTe₃ at the atomic scale.

Once cooled to near absolute zero, the researchers observed a striped electronic pattern. When they then applied a magnetic field, the striped electronic pattern transformed into a checkerboard pattern. "I immediately went to Professor Okada's office and said, 'Look at this!'" recalls Fujisawa.

"We were astonished because it is extremely rare for a material to host multiple competing electronic patterns that can be switched so dramatically by such a small magnetic field." So why can the material adopt such different electronic patterns so easily? The answer lies in a phenomenon physicists call frustration. In CeTe₃, the electrons can organize themselves into several different low-energy patterns, with no single arrangement preferred.

"Imagine placing a ball on a landscape with several nearly identical valleys," Fujisawa explains. "A slight tilt is enough to make the ball roll into a different valley. In CeTe₃, the magnetic field provides that push, shifting the balance between competing electronic states and switching the material from a striped to a checkerboard pattern." Linking magnetic and electronic structures After discovering the competing electronic patterns, the researchers next sought to understand the kind of magnetic structure underlying them.