Possible general behavior in smectic-A-smectic-C(chiral smectic-C) transitions in liquid crystals

Abstract

From the heat-capacity studies of several different liquid-crystal compounds, each with an isotropic ($I$)-smectic-$A$ ($\mathrm{Sm}A$)-smectic-$C$ ($\mathrm{Sm}C$) [or chiral-smectic-$C$ (${\mathrm{Sm}C}^{*}$)] transition sequence, one possible general behavior is found between $t_0$ and $\frac{T_{\mathrm{AC}}}{T_{\mathrm{IA}}}$. Here $T_{\mathrm{AC}}$ and $T_{\mathrm{IA}}$ denote the $\mathrm{Sm}A-\mathrm{Sm}C(-{\mathrm{Sm}C}^{*}$) and $I-\mathrm{S}\mathrm{m}A$ transition temperatures. The important parameter $t_0$ characterizes the full width at the half-height of the mean-field heat-capacity anomaly associated with the $\mathrm{Sm}A-\mathrm{S}\mathrm{m}C$ or $\mathrm{Sm}A-{\mathrm{Sm}C}^{*}$ transition and features the crossover from an ordinary mean-field-like behavior to a mean-field-tricritical-like behavior as the temperature of the system moves away from the transition temperature.