Spontaneous helix formation in a polar smectic phase.

Area of Science:

• Soft condensed matter physics
• Ferroelectricity
• Liquid crystals

Background:

• Depolarization fields in ferroelectric materials can be mitigated by periodic polarization distortions.
• This distortion is energetically favorable in polar nematic and tilted smectic phases due to director orientation changes.

Purpose of the Study:

• To investigate the spontaneous formation of helical structures in the proper ferroelectric tilted smectic (SmCHP) phase.
• To analyze the behavior of these helical structures under varying electric fields.

Main Methods:

• Observation of spontaneous helical structure formation in the SmCHP phase.
• Analysis of helical pitch and its temperature dependence.
• Application of weak and strong electric fields to study helix reorientation and destruction.

Main Results:

• A helical structure spontaneously forms in the SmCHP phase, occurring below the heliconical polar nematic (N_TBF) phase.
• The helical pitch is approximately 600 nm and remains stable across the SmCHP phase's temperature range.
• Weak electric fields reorient the helix with minimal structural change, while strong fields destroy the helix by aligning polarization with the field.

Conclusions:

• Periodic distortion of polarization direction is an effective mechanism for reducing depolarization fields in soft ferroelectrics.
• The SmCHP phase exhibits a robust helical structure that can be manipulated by external electric fields.
• Understanding these helical structures is crucial for developing novel ferroelectric liquid crystal devices.