Upon excitation with an intense ultrafast laser pulse, a symmetry-broken ground state can undergo a non-equilibrium phase transition through pathways dissimilar from those in thermal equilibrium. Determining the mechanism underlying these photo-induced phase transitions (PIPTs) has been a long-standing issue in the study of condensed matter systems. To this end, we investigate the light-induced melting of a unidirectional charge density wave (CDW) material, LaTe3. Using a suite of time-resolved probes, we independently track the amplitude and phase dynamics of the CDW. We find that a quick (∼1ps) recovery of the CDW amplitude is followed by a slower reestablishment of phase coherence. This longer timescale is dictated by the presence of topological defects: long-range order (LRO) is inhibited and is only restored when the defects annihilate. Our results provide a framework for understanding other PIPTs by identifying the generation of defects as a governing mechanism.
@article{arxiv.1806.02766,
title = {Disentangling amplitude and phase dynamics of a charge density wave in a photo-induced phase transition},
author = {Alfred Zong and Anshul Kogar and Ya-Qing Bie and Timm Rohwer and Changmin Lee and Edoardo Baldini and Emre Ergeçen and Mehmet B. Yilmaz and Byron Freelon and Edbert J. Sie and Hengyun Zhou and Joshua Straquadine and Philip Walmsley and Pavel E. Dolgirev and Alexander V. Rozhkov and Ian R. Fisher and Pablo Jarillo-Herrero and Boris V. Fine and Nuh Gedik},
journal= {arXiv preprint arXiv:1806.02766},
year = {2019}
}