The discovery of the ferroelectric nematic phase has brought with it a plethora of new polar liquid crystalline phases. One in particular is the anti-ferroelectric smectic A SmA\textsubscript{AF} phase. In this letter we show via observation and analysis of satellite peaks in the X-ray scattering pattern that the structure of the SmA\textsubscript{AF} phase involves a density modulation of ≈10-20 nm lateral to the smectic layer normal. Further, we demonstrate a previously undiscovered phase where the anti-ferroelectric order is maintained into a tilted smectic phase demonstrating the robustness of the underlying frustration that leads to the modulated structure. We suggest that the modulations are only in a single dimension and appear parallel to the tilt plane. This new phase also shows a significantly different and complex response to an electric field from other discovered polar LC phases due to the ability to modulate both tilt and polarisation direction.
@article{arxiv.2602.13034,
title = {Modulated Anti-Ferroelectric Smectic Phases with Orthogonal and Tilted Structures},
author = {Jordan Hobbs and Calum J. Gibb and William C. Ogle and Peter Medle Rupnik and Natan Osterman and Nerea Sebastián and Alenka Mertelj and Richard J. Mandle},
journal= {arXiv preprint arXiv:2602.13034},
year = {2026}
}