Light-Induced Thermomechanical Reorientation and Helicity Flipping in Ferroelectric Nematic Phase

Director rotation and related domain wall motion induced by laser light absorption have been observed in the ferroelectric nematic (N _F ) phase of the archetypal liquid crystal DIO. The observed phenomena strongly depend on the alignment of the ferroelectric polarization on the boundary plates with respect to each other and the direction of the laser light. It is found that laser absorption in the electrodes of the cell plays an essential role in the observed phenomena. The main characteristics of the findings can be explained by a torque acting on the polar director due to a temperature gradient. These experiments provide the first demonstration of a thermomechanical effect that is a property of polar fluids and does not exist in the conventional paraelectric nematic and antiferroelectric phases.