  While being extensively studied as an important physical process to alter
exciton population in nanostructures at fs time scale, carrier multiplication
has not been considered seriously as a major mechanism for phase transition.
Real-time time-dependent density functional theory study of Ge2Sb2Te5 reveals
that carrier multiplication can induce ultrafast phase transition in solid
state despite that the lattice remains cold. The results also unify the
experimental findings in other semiconductors for which the explanation remains
to be the 30-year old phenomenological plasma annealing model.
