The emergent properties of quantum materials, such as symmetry-broken phases and associated spectral gaps, can be effectively manipulated by ultrashort photon pulses. Impulsive optical excitation generally results in a complex non-equilibrium electron and lattice dynamics that involves multiple processes on distinct timescales, and a common conception is that for times shorter than about 100 fs the gap in the electronic spectrum is not seriously affected by lattice vibrations. Here, we directly monitor the photo-induced collapse of the spectral gap in a canonical charge-density-wave material, blue bronze Rb0.3MoO3. We find that ultra-fast (about 60 fs) vibrational disordering due to efficient hot-electron energy dissipation quenches the gap significantly faster than the typical structural bottleneck time corresponding to one half-cycle oscillation (about 315 fs) of the coherent charge-density-wave amplitude mode. This result not only demonstrates the importance of incoherent lattice motion in the photo-induced quenching of electronic order, but also resolves the perennial debate about the nature of the spectral gap in a coupled electron-lattice system.
@article{arxiv.2005.08523,
title = {Bypassing the structural bottleneck in the ultrafast melting of electronic order},
author = {L. X. Yang and G. Rohde and K. Hanff. A. Stange and R. Xiong and J. Shi and M. Bauer and K. Rossnagel},
journal= {arXiv preprint arXiv:2005.08523},
year = {2021}
}