摘要: We study in this work a scenario that the universe undergoes a two step phase transition with the first step
happened to the dark matter sector and the second step being the transition between the dark matter and the
electroweak vacuums, where the barrier between the two vacuums, that is necessary for a strongly first order
electroweak phase transition (EWPT) as required by the electroweak baryogenesis mechanism, arises at the
tree-level. We illustrate this idea by working with the standard model (SM) augmented by a scalar singlet
dark matter and an extra scalar singlet which mixes with the SM Higgs boson. We study the conditions for
such pattern of phase transition to occur and especially for the strongly first order EWPT to take place, as
well as its compatibility with the basic requirements of a successful dark matter, such as observed relic density
and constraints of direct detections. We further explore the discovery possibility of this pattern EWPT by
searching for the gravitational waves generated during this process in spaced based interferometer, by showing
a representative benchmark point of the parameter space that the generated gravitational waves fall within the
sensitivity of eLISA, DECIGO and BBO.