Orientational order in the splay nematic ground state

Area of Science:

• Materials Science
• Condensed Matter Physics
• Liquid Crystal Physics

Background:

• Modulated nematic liquid crystal phases exhibit periodic variations in orientational order.
• The splay nematic (NS) phase features a periodic splay deformation of orientation perpendicular to the director.
• Understanding these phases is crucial for advanced material applications.

Purpose of the Study:

• To quantitatively measure orientational order parameters in the nematic (N) and splay nematic (NS) phases of RM734.
• To characterize the orientational distribution function in the NS phase.
• To determine the implications of the splay modulation on molecular orientation and periodicity.

Main Methods:

• X-ray scattering experiments were employed to probe the liquid crystalline material RM734.
• Orientational order parameters were measured across N and NS phases.
• The orientational distribution function was reconstructed from experimental data.

Main Results:

• Orientational order is higher in the NS phase compared to the N phase.
• The orientational distribution function in the NS phase is nematic-like.
• The splay modulation involves a very small change in molecular orientation between adjacent molecules.
• This suggests a larger splay modulation period than previously anticipated.

Conclusions:

• The splay nematic phase exhibits enhanced orientational order.
• The small splay angle indicates a large modulation period, challenging prior estimations.
• The developed X-ray scattering method facilitates unambiguous identification of the splay nematic phase.