A Seesaw Mechanism in the Higgs Sector

In this letter we revisit the seesaw Higgs mechanism. We show how a seesaw mechanism in a two Higgs doublets model can trigger the electroweak symmetry breaking if at least one of the eigenvalues of the squared mass matrix is negative. We then consider two special cases of interest. In the decoupling scenario, there is only one scalar degree of freedom in the low energy regime. In the degenerate scenario, all five degrees of freedom are in the low energy regime and will lead to observables effects at the LHC. Furthermore, in that scenario, it is possible to impose a discrete symmetry between the doublets that makes the extra neutral degrees of freedom stable. These are thus viable dark matter candidates. We find an interesting relation between the electroweak symmetry breaking mechanism and dark matter.