A groundbreaking study from Rice University physicists and international collaborators is reshaping how scientists understand magnetism and electronic behavior in cutting-edge materials—a discovery that could drive advancements in quantum computing and high-temperature superconductors. Led by Rice researchers Zheng Ren and Ming Yi, the team explored thin films of iron-tin (FeSn), finding that this material's magnetic properties come from localized electrons, not the previously assumed mobile electrons.

Published in Nature Communications, this research challenges long-standing theories about kagome magnets—a category of materials named after a traditional basket-weaving pattern and marked by their unique lattice structure, which allows for unusual electronic behaviors due to quantum interference. This discovery could enable scientists to design materials with tailored properties, potentially advancing key technologies that rely on sophisticated magnetic behaviors.

What Makes Kagome Magnets Special?

Kagome magnets, like FeSn, have a lattice structure resembling a woven basket that creates a complex network for electron interactions. This distinctive structure can give rise to flat bands—specific energy bands where electrons’ kinetic energy is minimized, making them highly correlated. The Rice team’s research revealed that, even at higher temperatures, the flat bands of FeSn remain split, indicating that localized electrons are driving the magnetism in these materials.

The discovery upends prior theories, which posited that itinerant electrons—those that move freely within the material—were responsible for magnetic behavior. Instead, Rice’s findings show that localized electrons, which are more confined, play a crucial role, adding new insight into how magnetic properties arise in kagome metals.

Advanced Techniques Reveal Complex Interactions

The research team employed a combination of molecular beam epitaxy and angle-resolved photoemission spectroscopy to create high-quality FeSn thin films and study their electronic structure in detail. This approach allowed the team to observe electron behavior in FeSn, particularly how certain electron orbitals demonstrated selective band renormalization. This phenomenon, seen in iron-based superconductors, highlights the complex interplay of electron interactions that influence the overall behavior of kagome magnets.

“Our study highlights the complex interplay between magnetism and electron correlations in kagome magnets and suggests that these effects are non-negligible in shaping their overall behavior,” said Ren, a Rice Academy Junior Fellow.

Implications for Future Technologies

The implications of this discovery extend beyond FeSn, as the team’s insights into flat bands and electron correlations could inspire the development of new quantum technologies. In quantum computing, where the interaction between magnetism and quantum states is crucial, materials with such unique magnetic properties could be ideal for creating quantum logic gates. 

Additionally, understanding these electron interactions could aid the design of high-temperature superconductors—materials that conduct electricity without resistance at relatively high temperatures.

“This work is expected to stimulate further experimental and theoretical studies on the emergent properties of quantum materials, deepening our understanding of these enigmatic materials and their potential real-world applications,” said Yi, an associate professor of physics and astronomy and Rice Academy Senior Fellow.

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