Phase Transition Temperatures of a Nematic Liquid Crystal in the Presence of Noise and DC Fields

Thermal phase transitions from a nematic liquid-crystal phase to an isotropic phase are reported in this study. The phase transition temperature T_c under noise and DC fields was examined during continuous heating processes with different heating rates R (1–10 °C/min). T_c was determined as functions of the noise intensity V_N and the DC intensity V. Evidently, T_c shows different behavior with respect to the fields at fixed values of R. T_c decreased monotonously with V_N, whereas it exhibited nonmonotonic behavior in T_c(V). These shifts in T_c are quite different from that previously observed in the AC field. It was found that DC field-induced electroconvection is responsible for the unexpected nonmonotonic behavior. In particular, the transition between the dynamic scattering modes (i.e., DSM1 and DSM2) may be related to this behavior. The different behavior for the noise and DC fields was confirmed using various values of R. Furthermore, the present results in comparison with the previous results for the AC field were discussed.