Chiral symmetry breaking in three-dimensional smectic-C liquid-crystal domains

We report an observation of a unique type of spontaneous chiral symmetry breaking in three-dimensional domains of a smectic-C material consisting of achiral molecules. The observed helical structure clearly demonstrates the effect of an elastic coupling between the bend and the twist distortions in the c field. The sign and the magnitude of the coupling coefficient are determined experimentally. We also demonstrate that an external chiral bias field favors domains of one handedness