Long-lived photoinduced response observed under extreme photoexcitation densities in a one-dimensional Peierls insulator

One-dimensional metal-halide compounds provide model systems to investigate the manner in which coupling between elementary degrees of freedom - here, electronic and vibrational - result in instabilities that give rise to both chemical and structural rearrangements. Here, we employ "single-shot" pump-probe spectroscopy to examine a one-dimensional platinum iodide compound (PtI(en)) under far-from-equilibrium conditions where repeated photoexcitation results in sample damage. It presents evidence for a distinct collective excited state lasting more than 100 ps upon self-trapped exciton generation at high densities, as measured by electronic signal amplitudes and phonon properties.