Linear and quadratic electromechanical effects of a room temperature ferroelectric nematic liquid crystal*

The lack of centrosymmetry of the ferroelectric nematic (N_F) liquid crystal phase enables both linear (piezoelectric) and quadratic (electrostriction) electromechanical couplings. Here we report measurements of AC electric field induced mechanical vibration of a room temperature ferroelectric nematic liquid crystal mixture using a lock in amplifier and accelerometer. Mechanical vibrations were detected both at the base frequency (linear piezoelectric signals) and at double frequencies (electrostriction).  The signals are correlated with the alignment properties of the director and a theoretical model is proposed to explain the observations.