Baryon asymmetry from dark matter decay in the vicinity of a phase transition

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., three right-handed neutrinos (RHNs), 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. and leptons, generating a nonzero 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 keeps the mass spectrum of new particles in the 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 the Laser Interferometer Space Antenna.