Longitudinal Spontaneous Polarization and Longitudinal Electroclinic Effect in Achiral Smectic Phases with Bent-Shaped Molecules

The stable smectic configurations associated with achiral bent-shaped molecules are investigated theoretically. Five different configurations of the molecules within the layers are found, among which two possess a spontaneous longitudinal polarization, consistent with the $\hat{n}\to -\hat{n}$ symmetry. Under application of a longitudinal electric field these configurations can give rise to remarkable field effects, such as a three-state switching of the transverse polarization under alternating field, and a longitudinal electroclinic effect.