Structure and Dynamics of Isotropic Order

Abstract

“Isotropic order”. Soft condensed matter system can form the huge length scale order. SmBPIso is characterized by the simultaneous presence of the local order parameter of an helix and of a smectic layer, while being spontaneously isotropic without any characteristic discontinuity on a mesoscopic length scale. It is great advantage for the optical devices that the spectrum of the iridescent color of SmBPIso is completely equivalent by the changing the viewing angle because of the special isotropic symmetry and its wavelength can be successively controlled by changing temperature. Recently, we found the color can be tuned by shining the strong pulsed laser light. Then we can artificially design the special pattern of the “structural color” by scanning and on/off the laser light beam. Response time of the color shift is not so fast but not so slow (~200msec) in spite of the existence of the complicated inter-connected multi-lamellar structure. We also confirms experimentally that the existence of the collective fluctuation mode just around the sub second by the dynamic light scattering measurement. Relaxation time can be assigned as reorientation motion of the helical pitch, which must be correlated to the dynamics of the shrinkage/elongation of the inter-connected multi-lamellar structure through the coupling between two types of the liquid crystalline orders. Furthermore, we found that cubic SmBP reenter the SmBPIso at super cooling temperature (Tsc) in the twin poor region. Since Smectic A phase appear by applying the heating shock and is stable until Tsc where cubic SmBP reappear. So we can conclude that the re-entrant SmBPIso is super-cooled state. We also found the power law slow dynamics in the director orientation fluctuation as similar to the conven smectic-A phase, which is hidden by the super cooling of SmBP tional liquid-glass transition. However, it should be noted that