Laser-induced transient magnons in Sr ₃ Ir ₂ O ₇ throughout the Brillouin zone

Although ultrafast manipulation of magnetism holds great promise for new physical phenomena and applications, targeting specific states is held back by our limited understanding how magnetic correlations evolve on timescales. Using resonant inelastic x-ray scattering we demonstrate that femtosecond laser pulses can excite transient magnons at large wavevectors in gapped antiferromagnets, they persist several picoseconds which opposite to what observed nearly gapless magnets. Our work suggests materials with isotropic interactions are preferred achieve rapid magnetism.