Three experimental measurements have been conducted to investigate the nature of the SmA-SmCα*-SmC* phase transitions of two liquid crystal compounds. The SmA-SmCα* transition shows a continuous transition with XY-like critical exponents. The SmC α*-SmC* transition displays a rapid variation of the incommensurate helical pitch. One of the compounds shows a small jump in the helical pitch, which signals a first order transition and is consistent with high resolution calorimetric results.
Bibliographical noteFunding Information:
This work was partially supported by the National Science Foundation under Grants No. DMR-0106122 and INT-9815859, and Grant-in-Aid for Scientific Research by the Ministry of Education and Science, No. 12129204. The research was carried out in part at the National Synchrotron Light Source, Brookhaven National Laboratory, which is supported by the U.S. Department of Energy, Division of Materials Sciences and Division of Chemical Sciences, under Contract No. DE-AC02-98CH10886.