Discovery of a novel smectic-C* liquid crystal phase with six-layer periodicity

We report the discovery of a new SmC*$_{d6 }$liquid crystal phase with six-layer periodicity by resonant x-ray diffraction. Upon cooling, the new phase appears between the SmC*$_{\alpha }$ phase having a helical structure and the SmC*$d4$ phase with four-layer periodicity. This SmC*$_{d6}$ phase was identified in two mixtures which have an unusual reversed SmC*d4-SmC$* $phase sequence. The SmC*$_{d6 }$phase shows a distorted clock structure. The existence of phases having liquid-like in-plane ordering with a ``long-range'' lock-in periodicity (now being extended to six layers) is one of the long-lasting questions in condensed matter. Major efforts are required to address the physical origin of long-range interactions and novel physical properties of the SmC*$_{d6 }$phase.