Smectic layering: Landau theory for a complex-tensor order parameter

Disordering to order: de Vries behavior from a Landau theory for smectic phases.

We show that Landau theory for the isotropic (I), nematic (N), smectic-A, and smectic-C phases generically, but not ubiquitously, implies "de Vries" behavior: i.e., a continuous A-C transition can occur with little layer contraction while the birefringence increases significantly once the system moves into the C phase. Our theory shows that 1st order A-C transitions are also possible. These tra...

Tensor Order Parameter inPolymeri

Landau theory of the reentrant nematic-smectic A phase transition

The reentrant, nematic to smectic A phase transition is shown to follow from the Landau theory if one assumes the existence of an optimum density for smectic ordering. The shape of the coexistence line in the P-T plane is fit exactly by this theory. The effects of concentration on reentrant behaviour are also explained. LE JOURNAL DE PHYSIQUE LETTRES TOME 40, 15 JANVIER 1979, I Classification P...

Nematic-Smectic-A-Smectic-C Polycritical Point - Experimental-Evidence and a Landau Theory

Differential-scanning-calorimetry measurements and optical-microscopy observations are reported on mixtures of two stable liquid crystalline compounds, one of which has the nematic, smectic-A and smectic-, C phases, while the other has only nematic and smectic C. The phase diagram for this system is found to have the following features: (i) a line of second-order nematic — smectic-A transitions...

Complex Landau-Ginzburg theory of the hidden order in URu2Si2

We develop a Landau-Ginzburg theory of the hidden-order phase and the local moment antiferromagnetic phase of URu2Si2. We unify the two broken symmetries in a common complex-order parameter and derive many experimentally relevant consequences such as the topology of the phase diagram in magnetic field and pressure. The theory accounts for the appearance of a moment under application of stress a...