Sub-millisecond Switching and Ferroelectric-like Polarization in a Bent Shaped Liquid Crystal Exhibiting Nematic and Twist-bend Nematic Phases

Abstract

A fast switching liquid crystal (LC), especially in its nematic (N) phase, can significantly improve the performance and properties of present-day electro-optic devices and displays. We investigated the polar nature and switching behaviour of a bent shaped liquid crystal (LC) CB7CB at different temperatures, subjected to applied voltages of varying amplitude and frequency. A threshold-dependent polarization current response, with large spontaneous polarization, was observed in the nematic (N) and in the twist-bend nematic (Ntb) phases exhibited by the LC compound. The current response was identified as ferroelectric-like in nature, and the corresponding switching time was found to lie in the range of ~ 500 {\mu}s in the N phase, which is fast compared to the usual nematic switching time (in the range of milliseconds). The nematic switching is bi-stable in nature and the nematic polarization arises from the collective reorientation of cybotactic clusters on field-reversal. At larger voltages, the twist-bend helices were observed to unwind which can be considered as the main reason for the polar response in Ntb phase. The fast, bi-stable switching nature exhibited by the compound may become useful for application in next-generation of electro-optic devices.Comment: 18 pages, 17 figures, 1 tabl