Plate Nº 82 · recorded October 10, 2026
PhysicsReported finding
Electrons Crawl Together in a New Quantum State of Fe5GeTe2
A University of Chicago team reports that electrons in Fe5GeTe2 form a coherent slow-motion charge-ordered state up to 100 kelvin, contradicting current theory and hinting at future memory devices.
By Elena Vasquez3 min read656 words
In brief
- Results published October 1, 2026 in Science Advances
- Coherent collective electron motion persists at temperatures up to 100 kelvin (-173 °C)
- ARPES laser spot measured just 10 micrometers across
- Co-author and UChicago physicist Peter Littlewood died on June 15, 2026
- Funded by U.S. DOE Grant DE-SC0022960 and Gordon and Betty Moore Foundation Grant GBMF12763
A University of Chicago team has found that electrons in the layered magnetic material Fe5GeTe2 can move together in coherent slow motion at temperatures up to 100 kelvin, a quantum behavior that contradicts existing theory. The results appeared October 1, 2026 in Science Advances.
The study, led by Assistant Professor Shuolong Yang at the UChicago Pritzker School of Molecular Engineering, challenges how scientists think about magnetism in this class of materials.
What did the team actually observe?
Fe5GeTe2 — discovered about seven years ago — belongs to a family of "van der Waals" magnets. These materials stack in layers held together by weak atomic forces, and researchers can peel them down to atomically thin sheets for next-generation electronics.
Yang's group found that under specific conditions, Fe5GeTe2 enters a charge-ordered state with a flat electronic band. In solid-state physics, a band is the range of energies electrons can use for conduction. A flat band compresses that range, leaving electrons no room to pick up speed.
"We're not measuring one electron," Yang said. "We're measuring the interaction of thousands or millions of electrons, and they are all moving together in a coherent way. That's a quantum many-body phenomenon, and it's actually a very weird thing."
Yang compares the effect to water flowing over a slope. A steep slope speeds the flow; a shallow one slows it. A flat band is the shallow slope — the electrons crawl.
How did they measure it?
The team used angle-resolved photoemission spectroscopy (ARPES), which shines photons at a sample and ejects surface electrons. Tracking the energy and angle of those ejected electrons maps the material's electronic structure.
The researchers focused an ultraviolet laser onto a spot just 10 micrometers across, roughly one-tenth the width of a human hair. Postdoctoral scholars Gabriele Berruto and Qiang Gao led the experiments.
Why does this contradict theory?
Standard models predicted a different magnetic interaction for Fe5GeTe2. Instead, the team observed coherent collective motion of millions of electrons in a flat band — a quantum many-body behavior the prevailing theory does not predict for this material.
"This is a fundamental discovery that deviates from theoretical predictions," Yang said. "We now have to go back and think about the magnetic interactions of this material from scratch."
"From a scientific perspective, it suggests that the magnetic interactions within the material are totally different from what theory predicts," Berruto added.
Could it ever power a memory device?
Fe5GeTe2 can adopt several distinct magnetic states, which could in principle serve as storage for information. Yang's group has begun testing whether a tightly focused laser can switch the material between the new quantum many-body phase and other phases. Their preliminary data suggest such switching is possible, though the work remains at an early stage.
"If we eventually want to use it in a memory device, it needs to work at room temperature," said Gao, who is now a research scientist at Lawrence Berkeley National Laboratory.
The coherent behavior survives up to 100 kelvin (-173 °C). That is still far below room temperature, but unusually high for a quantum material of this type. The team's next step is to test whether the effect persists when Fe5GeTe2 is exfoliated to a single atomic layer.
What was Peter Littlewood's role in this work?
The paper is among the final scientific contributions of Peter Littlewood, a distinguished UChicago physicist who died on June 15, 2026. He was a leading theorist in quantum materials.
"He was a great theoretical physicist and a leader of quantum materials research at UChicago," Yang said. "We dedicate this paper to him."
Other co-authors include Khanh Duy Nguyen, Chaowei Hu, Paul Malinowski, Haoran Lin, Beomjoon Goh, Bo Gyu Jang, Xiaodong Xu, and Jiun-Haw Chu. Funding came from the U.S. Department of Energy (Grant No. DE-SC0022960) and the Gordon and Betty Moore Foundation (Grant No. GBMF12763).
via pme.uchicago.edu (Original)
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