Two-component asymmetric dark matter via bound states and freeze-in decay

We propose a novel mechanism to realize two-component asymmetric dark matter of very different mass scales through bound state formation and late freeze-in decay. Assuming a particle-antiparticle asymmetry is initially shared by SM baryons and two dark matter components, we demonstrate that the existence of bound states formed by the heavy component can efficiently transfer the asymmetry from the heavy to the light component via late decay. In this case, the energy densities of the two components can be comparable, and the correct relic density is reproduced.