FLUCTUATIONS DOMINATE THE PHASE-DIAGRAM OF CHIRAL NEMATIC LIQUID-CRYSTALS

Phase diagrams of the liquid-crystalline blue phases (BPs), as calcula ted by means of Landau theory, display two serious deficiencies: They contain a never-observed structure of space group O-5, and BP II does not disappear at very high chiralities. Here we prove by a first-order cumulant expansion that neglect of fluctuations is the cause. We also observe a smooth transition from a strongly to a weakly correlated is otropic phase, which vanishes at large chiralities. It indicates the e xistence of a critical point and characterizes BP III as a second isot ropic phase, in agreement with recent experiments.