Breakthrough in magnetism could transform quantum computing and superconductors

The findings, published in Nature Communications Oct. 30, reveal that FeSn's magnetic properties arise from localized electrons, not the mobile electrons scientists previously thought. This discovery challenges existing theories about magnetism in kagome metals in which itinerant electrons were assumed to drive magnetic behavior. By providing a new perspective on magnetism, the research team's work could guide the development of materials with tailored properties for advanced tech applications such as quantum computing and superconductors.

"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.

Using an advanced technique that combines molecular beam epitaxy and angle-resolved photoemission spectroscopy, the researchers created high-quality FeSn thin films and analyzed their electronic structure. They found that even at elevated temperatures, the kagome flat bands remained split, an indicator that localized electrons drive magnetism in the material. This electron correlation effect adds a new layer of complexity to understanding how electron behavior influences magnetic properties in kagome magnets.

The study also revealed that some electron orbitals showed stronger interactions than others, a phenomenon known as selective band renormalization previously observed in iron-based superconductors, offering a fresh perspective on how electron interactions influence the 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.

Beyond advancing the understanding of FeSn, the research has broader implications for materials with similar properties. Insights into flat bands and electron correlations could influence the development of new technologies such as high-temperature superconductors and topological quantum computation, where the interplay of magnetism and topological flat bands generates quantum states that can be used as quantum logic gates.

Rice researchers who collaborated on this study include Department of Physics and Astronomy postdoctoral associates and graduate students Jianwei Huang, Ananya Biswas, Yichen Zhang, Yaofeng Xie, Ziqin Yue, Lei Chen, Fang Xie, Kevin Allen, Han Wu and Qirui Ren; Junichiro Kono, the Karl F. Hasselmann Professor of Engineering and director of the Smalley-Curl Institute; Emilia Morosan, professor of physics and astronomy, chemistry and materials science and nanoengineering; Qimiao Si, the Harry C. and Olga K. Wiess Professor of Physics and Astronomy; and Pengcheng Dai, the Sam and Helen Worden Professor of Physics and Astronomy.

Collaborators from around the world include Hengxin Tan and Binghai Yan of the Department of Condensed Matter Physics at Weizmann Institute of Science; Aki Pulkkinen and Ján Minár of the New Technologies Research Center, University of West Bohemia; Anil Rajapitamahuni, Asish K. Kundu and Elio Vescovo of the National Synchrotron Light Source II, Brookhaven National Lab; and Jian-Xin Zhu of the Theoretical Division and Center for Integrated Nanotechnologies at Los Alamos National Laboratory.

The U.S. Department of Energy, Robert A. Welch Foundation, Gordon and Betty Moore Foundation's EPiQS Initiative, Rice Academy of Fellows, Air Force Office of Scientific Research and Vannevar Bush Faculty Fellowship supported this study.