Amplitude and phase fluctuation modes in the smectic C_α* phase of an antiferroelectric compound

Abstract

Dielectric measurements have been carried out on the chiral smectic C_α (SmC_α*) phase of a MHPOBC analogous compound. Two relaxation modes have been observed in this phase for planar orientation of the molecules. One process has been observed at frequency lower than that of the soft mode of the chiral smectic A (SmA*) phase. This relaxation process is connected with the helicity of the SmC_α* phase. In the high‐frequency region, another relaxation process has been observed in the SmC_α* phase for which bias field dependence is similar to that of the soft mode at the SmA*–SmC* phase transition. The experimental observations are in agreement with a recently proposed dielectric theory for the SmC_α* phase and theoretical dielectric results obtained by numerical simulations. Thus, we report here experimental verification of two theoretically predicted dielectric modes in the SmC_α* phase.

Keywords:

• dielectric relaxation
• soft mode
• chiral phases
• SmC_α* phase
• bias field dependence

Acknowledgements

MBP wishes to thank the Department of Science and Technology, Government of India, New Delhi, for financial assistance under a fast‐track project for young scientist (SR/FTP/PS‐14/2005). The authors sincerely thank to Prof. H. Prakash, Head, Physics Department, and Prof. I. M. L. Das, Physics Department, University of Allahabad, Allahabad, for their support.