Flashing flexodomains and electroconvection rolls in a nematic liquid crystal

TL;DR

This study investigates pattern-forming instabilities in nematic liquid crystals under ultralow frequency voltages, revealing distinct electroconvection and flexodomain patterns, their correlation with electrical responses, and temperature-dependent properties.

Contribution

It provides new insights into the temporal separation and characteristics of electroconvection and flexodomain patterns induced by ultralow frequency voltages in nematic liquid crystals.

Findings

EC and FD appear as time-separated flashes within each half period.

Correlation between EC flashes and nonlinear current response.

Voltage dependence of pattern contrast differs for EC and FD.

Abstract

Pattern forming instabilities induced by ultralow frequency sinusoidal voltages were studied in a rod-like nematic liquid crystal by microscopic observations and simultaneous electric current measurements. Two pattern morphologies, electroconvection (EC) and flexodomains (FD), were distinguished; both appearing as time separated flashes within each half period of driving. A correlation was found between the time instants of the EC flashes and that of the nonlinear current response. The voltage dependence of the pattern contrast C(U) for EC has a different character than that for the FD. The flattening of C(U) at reducing the frequency was described in terms of an imperfect bifurcation model. Analysing the threshold characteristics of FD the temperature dependence of the difference |e_1-e_3| of the flexoelectric coefficients were also determined by considering elastic anisotropy.