Non-equilibrium magnons revealed by neutrons

Egami highlight May 2026 — Comparison between the intensity with laser excitation (blue solid line) and at equilibrium (red dashed line) integrated over a short range of Q vectors (left panel). The right panel shows the Q resolved difference in intensity between the laser excited and in-equilibrium structure factor maps. Excess magnon population was created by laser excitations.

Scientific Achievement: Laser pumping combined with inelastic neutron scattering reveals long-living nonequilibrium magnons in a 2D Heisenberg antiferromagnet that break detailed balance in the structure factor and form steady states under periodic driving, analogous to driven dissipative nonequilibrium systems.

Significance and Impact: This work opens a previously unexplored frontier: momentum- and energy-resolved studies of dissipative quantum dynamics at milli-electron-volt energy and microsecond time scales.

DOI: 10.1038/s41467-026-71068-w