Year: 2026
Type: article
Abstract: We report direct spectroscopic evidence of antimagnons, i.e., negative-energy spin waves identified by their signature inverted dispersion and left-handed precession with Brillouin light scattering (BLS) spectroscopy. We investigate an ultrathin BiYIG film with a perpendicular magnetic anisotropy that compensates the demagnetizing field. By injecting a spin-orbit torque, the magnetization is driven into auto-oscillation and eventually into a nonequilibrium reversed state above a secondary current threshold (∼1.2×10^{7} A/cm^{2}). The dispersion is measured by wave-vector-resolved BLS and exhibits a sharp change from an upward dispersion to a downward one, in agreement with theoretical predictions and micromagnetic simulations. Around the threshold current, we observe the coexistence of conventional magnons and antimagnons. Our Letter establishes antimagnons with inverted dispersion and is a first step toward exploring novel phenomena and applications due to magnon-antimagnon coupling, such as magnon amplification and magnon-antimagnon entanglement, which are part of the emerging field of antimagnonics.
Source: Physical Review Letters
DOI: 10.1103/2g7f-5dlb
Authors: Hanchen Wang, Junfeng Hu, Wenjie Song, Artim L. Bassant, Jinlong Wang, Haishen Peng, Emir Karadža, Paul Noël, William Legrand, Richard Schlitz, Jilei Chen, Song Liu, Dapeng Yu, Jean-Philippe Ansermet, Rembert A. Duine, Pietro Gambardella, Haiming Yu
Institutions: ETH Zurich, Shenzhen International Quantum Academy, Utrecht University, Beihang University, Centre National de la Recherche Scientifique, Institut de Physique et Chimie des Matériaux de Strasbourg, Université de Strasbourg, Institut Néel, Université Grenoble Alpes, University of Konstanz, École Polytechnique Fédérale de Lausanne, Eindhoven University of Technology
Language: English
Subfield: Condensed Matter Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funders: National Science Foundation, Deutsche Forschungsgemeinschaft, Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung, National Natural Science Foundation of China, Nederlandse Organisatie voor Wetenschappelijk Onderzoek, China Scholarship Council, National Key Research and Development Program of China, Shenzhen Science and Technology Innovation Program
OpenAlex ID: W7203834482