  We study the screened dynamics of the nonequilibrium excitonic consensate
forming in a bulk WSe$_{2}$ when illuminated by coherent light resonant with
the lowest-energy exciton. Intervalley scattering causes electron migration
from the optically populated K valley to the conduction band minimum at
$\Sigma$. Due to the electron-hole unbalance at the K point a plasma of
quasi-free holes develops, which efficiently screens the interaction of the
remaining excitons. We show that this plasma screening causes an ultrafast
melting of the nonequilibrium consensate and that during melting coherent
excitons and quasi-free electron-hole pairs coexist. The time-resolved spectral
function does exhibit a conduction and excitonic sidebands of opposite
convexity and relative spectral weight that changes in time. Both the
dependence of the time-dependent conduction density on the laser intensity and
the time-resolved spectral function agree with recent experiments.

Mesoscale and Nanoscale Physics