Criticality of bistability phenomenon in deformed helix ferroelectric liquid crystal

Abstract

The dynamics of bistability in deformed helix ferroelectric liquid crystal have been investigated by electro-optical method. The threshold value of the voltage required to switch the molecules of deformed helix ferroelectric liquid crystals (DHFLC) material has been studied by applying triangular wave pulse and texture observation under polarizing microscope. Two peaks have been observed in low and high frequency regimes on the application of triangular wave pulse to the sample. It has been proposed that the first peak is due to helix unwinding-winding process and the second is due to molecular reorientation process. The occurrence of double peak has been predicted to have close correlation with the observance of memory effect in DHFLC material, which is critically dependent on frequency and applied voltage, on the application of time delayed square wave pulse to the sample cell. The conditions for dynamic and static memory effects in DHFLC material have also been discussed in detail.

Dielectric and electro-optical studies of glycerol/ferroelectric liquid crystal mixture at room temperature

“…The deformed helix FLCs ͑DHFLCs͒, which are a special kind of FLC, are very useful and have much applications in display devices because of their low driving voltage, gray scale generation capability, easily achievable alignment, fast response, etc. 19,20 The bistability or memory effect has also been demonstrated by us [21][22][23] in DHFLCs.…”

“…The optical response of pure DHFLC material has been observed by us earlier. 23,28 In earlier reports, we mentioned that whenever we had single peak in the electrical response the complete memory effect would be there. Indeed, we were able to observe the same, i.e., single peak in electrical response ͑Fig.…”

“…We observed a single symmetric polarization peak in entire frequency range. The electrical response of pure DHFLC material has been reported elsewhere, 23 where the criticality of bistability was taken into account. In that report, we found two peaks in low ͑100-500 mHz͒ frequency and high frequency ͑40-70 Hz͒ regimes while as single peak was observed in middle frequency region ͑600 mHz-40 Hz͒.…”

Nonvolatile memory effect based on gold nanoparticles doped ferroelectric liquid crystal

“…The deformed helix FLCs ͑DHFLCs͒, which is a special kind of FLC, are very useful and have much applications in display devices because of their low driving voltage, gray scale generation capability, easily achievable alignment, fast response, etc. 24,25 The bistability or memory effect has also been demonstrated by us [26][27][28] in DHFLCs. In this letter, the long nonvolatile memory effect in GNPs doped DHFLC material has been observed which is probably due to the electric field induced charge transfer effect, and the stabilization of helix deformation process.…”

“…ported elsewhere. 28 Figure 2 shows that a complete memory effect is observed in the entire frequency range and at a fixed voltage. As seen in the figure the optical transmission changes from maximum to minimum as the applied field reverses its polarity and there is almost no change when the applied field attains its 0 V state.…”