Manipulation of the nanoscale heliconical structure of a twist-bend nematic material with polarized purple light*

This research shows the first evidence of using polarized light to manipulate nanoscale heliconical structure of a twist bend nematic liquid crystal dimer containing both sulfur atoms and an azo linkage by tender X-ray scattering. The scattering pattern reveals two different heliconical pitch values of aligned and unaligned domains under polarized light. In addition to the bulk alignment, the value of the heliconical pitch can be tuned in two timescales by UV-violet light and recovered with a temperature dependent memory. As expected, an azo linkage group liquid crystal material with nematic (N) to nematic twist bend (NTB) transition highly sensitive to UV irradiation due to the formation of cis-isomers, which can be strongly influence in pitch. This is the first time we not only quantitatively verify this expectation, but we also show that there are two different pitch values. We also show that the pitch variation happens in two time scales and has a temperature dependent memory. In addition, we show evidence of the polarized UV-Violet light leads to a bulk metastable alignment of the heliconical axis of the NTB phase.