Exploring CP violation and vanishing electric dipole moment of the electron in a scale-invariant general 2HDM

Abstract

We investigate a scale-invariant general two-Higgs-doublet model with explicit CP violation. Using the Gildener-Weinberg method, we analyze the Higgs mass spectrum and couplings at the one-loop level, focusing on CP violation originating from both the Higgs potential and the Yukawa sector. We show that, due to the flatness condition, both CP-even and CP-odd mixings between the 125 GeV Higgs boson and the heavier Higgs states arise only radiatively. As a result, the Higgs couplings to gauge bosons and fermions remain Standard Model-like, in agreement with current LHC constraints. We also find that the magnitude of CP violation from the Higgs potential depends on the new complex Yukawa couplings and heavy Higgs masses, due to the flatness condition. In the case where only an additional top Yukawa coupling $\rho_{tt}$ is present, the electron electric dipole moment is directly proportional to $\mathrm{Im}\rho_{tt}^2$. Furthermore, a nontrivial cancellation region can occur for a specific Higgs mass spectrum. We extend our analysis to scenarios with an additional complex electron Yukawa coupling, identifying the conditions under which the electron electric dipole moment is suppressed or vanishes.