In Mott insulators the evolution of antiferromagnetic order to superconducting or charge-density-wave-like states upon chemical doping underpins the control of quantum phases. Photo-doping can induce similar transitions on the ultrafast timescale, however the response of the spin system has remained elusive. Here, we use 4D-ultrafast optical spectroscopy to extract quantitative magnetic dynamics in the spin-orbit coupled Mott insulator Sr3Ir2O7. We demonstrate that light can non-thermally melt long-range spin order. At low fluences magnetic order recovers within 1 ps despite demagnetization of roughly 50%. However, high fluences induce a crossover to a long-lived demagnetized state without increasing the lattice temperature. We show that the generation of photo-induced spin defects enables a mechanism that stabilizes the demagnetized state which could help expose new transient phases.
@article{arxiv.2104.04294,
title = {Non-thermal breaking of magnetic order via photo-generated spin defects},
author = {Ernest Pastor and David Moreno-Mencía and Maurizio Monti and Allan S. Johnson and Nina Fleischmann and Cuixiang Wang and Youguo Shi and Xuerong Liu and Daniel G. Mazzone and Mark P. M. Dean and Simon Wall},
journal= {arXiv preprint arXiv:2104.04294},
year = {2022}
}