Periodic Frederiks transition in a planar ferroelectric nematic cell

Electric field-induced distortion of a thin planar nematic film, called the Frederiks transition, is a well-studied phenomenon used in modern electro-optical devices. In conventional low-molecular weight apolar nematics, the distortion is one-dimensional and homogeneous in the plane of the sample. The Frederiks transition exhibits periodic distortions in polymer nematics formed by very long molecules which cause the splay elastic constant to be much larger than its twist counterpart.

Here we demonstrate that an electric field applied to a low-molecular-weight ferroelectric nematic causes complex splay-twist periodic spatial modulation of spontaneous polarization. The patterns are either two-dimensional (splay-twist stripes) or three-dimensional (periodic lattice of +1 and -1 defects). The phenomenon is explained by a large splay modulus caused by the development of space electric charges at splay deformations of spontaneous polarization.