Hierarchical quasiparticle dynamics in antiferromagnets revealed by time- and momentum-resolved X-ray scattering
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Updated: Oct 31, 2026

Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses
Published on: June 7, 2018
Arnau Romaguera1,2, Elizabeth Skoropata1, Yun Yen3,4,5
1PSI Center for Photon Science, Paul Scherrer Institute, Villigen-PSI, Switzerland.
Abstract:
Energy flows among coupled subsystems are essential for ultrafast dynamics and high-speed technologies. In magnetic materials, spin fluctuations -magnons- mediate these flows in ultrafast magnetism. Yet momentum-resolved access to low-energy magnons governing the microscopic dynamics has been lacking. Using time-resolved resonant diffuse scattering alongside complementary time-resolved X-ray techniques and quantum-kinetic simulations, we unveil the hierarchical energy pathways among correlated systems in the photoexcited antiferromagnet CuO. Above-bandgap excitation triggers near-instantaneous spin disorder, generating non-thermal magnons throughout reciprocal space within femtoseconds. Real-time momentum-resolved tracking reveals picosecond magnon quasi-thermalization, followed by nanosecond recovery via momentum-selective magnon-phonon scattering. The quasiparticle dispersion mismatch creates recovery bottlenecks that control non-equilibrium lifetimes. This microscopic framework transcends phenomenological models and generalizes across antiferromagnetic insulators, establishing design principles for ultrafast control of antiferromagnetic order.
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