  We describe a \emph{nonthermal} magnon activation mechanism in
antiferromagnetic (AFM) systems via locally equilibrated
\emph{spin-unpolarized} hot electrons excited by an ultrafast intense laser
pulse. We employ a quantum kinetic equation that takes into account a direct
electron-magnon scattering channel in either bulk AFM metal or at the interface
of the AFM/normal-metal heterostructure. The mechanism is responsible for the
nonequilibrium population of AFM magnon modes on a subnanosecond timescale,
which are formed shortly after the local thermalization of hot electrons by
Coulomb interactions. Nonequilibrium magnon populations can be additionally
manipulated by applying an external magnetic field. Our work paves the way
toward spin dynamics control in AFM systems via the ultrafast manipulation of
out-of-equilibrium magnon excitations.
