New Two-Loop Contribution to Electric Dipole Moments in Supersymmetric Theories

We calculate a new type of two-loop contribution to the electric dipole moments of the electron and neutron in supersymmetric theories. The new contributions are originated from the potential $\mathrm{CP}$ violation in the trilinear couplings of the Higgs bosons to the scalar-top or the scalar-bottom quarks. These couplings did not receive stringent constraints directly. The electric dipole moments are induced through a mechanism analogous to that due to Barr and Zee [Phys. Rev. Lett. 65, 21 (1990)]. We find observable effects for a sizable portion of the parameter space related to the third generation scalar quarks in the minimal supersymmetric standard model which cannot be excluded by earlier considerations.