Ultrafast dynamics in quantum magnets

Photoinduced coherent dynamics in quantum magnets generated on ultrafast timescales have been observed over a broad range of pump photon energy scales. They reveal both the intrinsic low-energy dynamics and its connections to excitations of the materials coupled directly with the light. In this talk, I will discuss a few non-thermal mechanisms for photoinduced coherent magnon dynamics motivated by recent experiments. I show that the interplay between coherent driven dynamics and non-unitary dynamics due to dissipation plays an important role on the crossover between in transparency and on resonance driving. Proposals to observe exotic steady state in quantum magnets will also discussed.