  We propose a novel framework where baryon asymmetry of the universe can arise
due to forbidden decay of dark matter (DM) enabled by finite-temperature
effects in the vicinity of a first order phase transition (FOPT). In order to
implement this novel cogenesis mechanism, we consider the extension of the
standard model by one scalar doublet $\eta$, three right handed neutrinos
(RHN), all odd under an unbroken $Z_2$ symmetry, popularly referred to as the
scotogenic model of radiative neutrino mass. While the lightest RHN $N_1$ is
the DM candidate and stable at zero temperature, there arises a temperature
window prior to the nucleation temperature of the FOPT assisted by $\eta$,
where $N_1$ can decay into $\eta$ and leptons generating a non-zero lepton
asymmetry which gets converted into baryon asymmetry subsequently by
sphalerons. The requirement of successful cogenesis together with a first order
electroweak phase transition not only keep the mass spectrum of new particles
in sub-TeV ballpark within reach of collider experiments but also leads to
observable stochastic gravitational wave spectrum which can be discovered in
planned experiments like LISA.
