Ultrafast light-induced softening of chalcogenide thin films above the rigidity percolation transition

摘要: Little is known about the role of network rigidity in light-induced structural rearrangements glasses due to a lack supporting experiments and theories. In this article, we demonstrate for first time ultrafast manifested as induced absorption (IA) over broad spectral range a-GexAs35-xSe65 thin films above mean-field percolation transition, quantified by mean coordination number ⟨r⟩ = 2.40. The IA spectrum arising from self-trapped excitons softening glass that strikingly reveals two relaxation mechanisms which differ one order magnitude. fast kinetics electron-lattice interaction occurs within 1 ps, exhibits weak dependence on rigidity, dominates sub-bandgap region. stark contrast, slow associated with changes bandgap region depends strongly rigidity. Our results further amplitude scales linear relationship excitation fluence provides unique way induce an over-coordinated exploit it practical purposes. modify conventional concept effects glasses, when excited laser.