Published in Physical Review E, Volume 84, Issue 1, July 27, 2011.
Copyright © 2011 American Physical Society. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Physical Society. The following article appeared in Physical Review E and may be found at http://dx.doi.org/10.1103/PhysRevE.84.011708.
The biaxial smectic-A* (Sm-AB*) phase, appearing in the phase sequence Sm-A*–Sm-AB*–Sm-C*, is analyzed using Landau theory. It is found to possess a helical superstructure with a pitch that is significantly shorter than the pitch of the Sm-C* helical superstructure. The Sm-AB*–Sm-C* transition can be either first or second order, and correspondingly there will be either a jump or continuous variation in the pitch. The behaviors of the birefringence and electroclinic effect are analyzed and found to be similar to those of a Sm-Cα* phase. As such, it is possible that the Sm-AB* phase could be misidentified as a Sm-Cα* phase. Ways to distinguish the two phases are discussed.