Laser-induced transient magnons in Sr3Ir2O7 throughout the Brillouin zone

Ultrafast manipulation of magnetic states holds great promise for progress in our understanding of new quantum states and technical applications, but our current knowledge of transient magnetism is very limited. Our work elucidates the nature of transient magnetism in gapped antiferromagnets using Sr3Ir2O7 as a model material. We find that transient magnetic fluctuations are trapped throughout the entire Brillouin zone while remaining present beyond the time that is required to restore the original spin network. The results are interpreted in the context of a spin-bottleneck effect, in which the exis- tence of an explicit magnetic decay channel allows for an efficient thermalization of transient spin waves.