We explore $CP$ violating aspects in the Higgs sector of models where new vectorlike quarks carry Yukawa couplings mainly to the third generation quarks of the Standard Model. We point out that in the simplest model, Higgs $CP$ violating interactions only exist in the $hWW$ channel. At low energy, we find that rare $B$ decays can place similarly strong constraints as those from electric dipole moments on the source of $CP$ violation. These observations offer a new handle to discriminate from other Higgs $CP$ violating scenarios such as scalar sector extensions of the Standard Model, and imply an interesting future interplay among limits from different experiments.

• Received 30 July 2015

DOI:https://doi.org/10.1103/PhysRevD.92.075026