Altermagnetic polar metallic phase in ultrathin epitaxially strained RuO <sub>2</sub> films
Abstract
Altermagnetism refers to a wide class of magnetic orders featuring magnetic sublattices with opposite spins related by rotational symmetries, resulting in nontrivial spin splitting and magnetic multipoles. However, the direct observation of the altermagnetic transition remains elusive. Here, by combining theoretical analysis, electrical transport, X-ray, and optical spectroscopies, we establish a phase diagram in hybrid molecular beam epitaxy-grown RuO 2 /TiO 2 (110) films, mapping symmetries along with altermagnetic/electronic/structural phase transitions as functions of film thickness and temperature. This features an altermagnetic metallic polar phase in epitaxially strained 2 nm films, suggesting a potential link between polar metals and altermagnetic materials. Such a clear signature of a magnetic phase transition at ~500 K is observed exclusively in ultrathin strained films, unlike in bulk RuO 2 single crystals. These results highlight the power of epitaxial heterostructure engineering to induce altermagnetism in systems initially nonmagnetic, opening avenues for realizing emergent quantum phases with multifunctional properties.
Article Details
Journal Info
Proceedings of the National Academy of Sciences
National Academy of Sciences
Authors (17)
Seung Gyo Jeong
Department of Chemical Engineering and Materials Science, University of Minnesota−Twin Cities
In Hyeok Choi
Department of Physics and Photon Science, Gwangju Institute of Science and Technology
Sreejith Nair
Luca Buiarelli
Department of Chemical Engineering and Materials Science, University of Minnesota−Twin Cities
Bita Pourbahari
Canadian Centre for Electron Microscopy and Department of Materials Science and Engineering, McMaster University
Jin Young Oh
Department of Physics, Sungkyunkwan University
Bonnie Y.X. Lin
Department of Materials Science and Engineering, Massachusetts Institute of Technology
James M. LeBeau
Nabil Bassim
Canadian Centre for Electron Microscopy and Department of Materials Science and Engineering, McMaster University
Daigorou Hirai
Department of Applied Physics, Graduate School of Engineering, Nagoya University
Ambrose Seo
Department of Physics and Astronomy, University of Kentucky
Woo Seok Choi
Department of Physics
Rafael M. Fernandes
Turan Birol
Department of Chemical Engineering and Materials Science, University of Minnesota−Twin Cities
Liuyan Zhao
Department of Physics, University of Michigan
Jong Seok Lee
Department of Physics and Photon Science, Gwangju Institute of Science and Technology
Bharat Jalan
Department of Chemical Engineering and Materials Science, University of Minnesota−Twin Cities