Domain patterns with paired soliton walls stabilized by polar surface interactions in a ferroelectric nematic liquid crystal

Abstract Surface interactions are responsible for many properties of condensed matter, ranging from crystal faceting to the kinetics of phase transitions. Usually, these interactions are polar along the normal to the interface and apolar within the interface. Here we demonstrate that polar in-plane surface interactions produce stable domain structures in the bulk of a ferroelectric nematic liquid crystal. Monodomains form in micron-thick cells, while thicker cells feature quasiperiodic stripes of an alternating uniform electric polarization, separated by domain walls, within which the polarization rotates by 180°. The surface polarity makes these walls paired with a total rotation by 360°. Analysis of the domain structures allows one to determine the polar contribution to the surface anchoring potential. The 360° pairs of domain walls resemble domain walls in cosmology models with biased vacuums and ferromagnets in an external magnetic field. The polarity-biased ferroelectric structures are highly susceptible to weak electric fields and could lead to applications in advanced electro-optics, sorting of polar inclusions, sensing, memory, and grating devices.