Critical behavior of the de gennes elastic constants near the nematic-smectic- A transition of TBBA
We have studied the behavior of elastic constants A, B, and C deduced from ultrasound velocity anisotropies in the vicinity of the nematic-smectic- A transition of terephthal-bis- p- p(')-butylaniline. A is associated with compressibility, B with layer compression, and C with the coupling between compressibility and layer compression. We show that the exponent of A is of the preasymptotic 3D- XY type, whereas those of B and C are in between the 3D- XY values and those associated with the anisotropic fixed point. This behavior is consistent with the extended crossover regime predicted by Patton and Andereck [Phys. Rev. Lett. 69, 1556 (1992)].
Sonntag
P
Laboratoire de Dynamique des Fluides Complexes, Unite Mixte de Recherche CNRS-ULP No. 7506, Universite Louis Pasteur, 4, rue Blaise Pascal, 67070 Strasbourg Cedex, France.
Collin
D
Martinoty
P